linux/kernel/user_namespace.c

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// SPDX-License-Identifier: GPL-2.0-only
#include <linux/export.h>
#include <linux/nsproxy.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/user_namespace.h>
#include <linux/proc_ns.h>
#include <linux/highuid.h>
User namespaces: set of cleanups (v2) The user_ns is moved from nsproxy to user_struct, so that a struct cred by itself is sufficient to determine access (which it otherwise would not be). Corresponding ecryptfs fixes (by David Howells) are here as well. Fix refcounting. The following rules now apply: 1. The task pins the user struct. 2. The user struct pins its user namespace. 3. The user namespace pins the struct user which created it. User namespaces are cloned during copy_creds(). Unsharing a new user_ns is no longer possible. (We could re-add that, but it'll cause code duplication and doesn't seem useful if PAM doesn't need to clone user namespaces). When a user namespace is created, its first user (uid 0) gets empty keyrings and a clean group_info. This incorporates a previous patch by David Howells. Here is his original patch description: >I suggest adding the attached incremental patch. It makes the following >changes: > > (1) Provides a current_user_ns() macro to wrap accesses to current's user > namespace. > > (2) Fixes eCryptFS. > > (3) Renames create_new_userns() to create_user_ns() to be more consistent > with the other associated functions and because the 'new' in the name is > superfluous. > > (4) Moves the argument and permission checks made for CLONE_NEWUSER to the > beginning of do_fork() so that they're done prior to making any attempts > at allocation. > > (5) Calls create_user_ns() after prepare_creds(), and gives it the new creds > to fill in rather than have it return the new root user. I don't imagine > the new root user being used for anything other than filling in a cred > struct. > > This also permits me to get rid of a get_uid() and a free_uid(), as the > reference the creds were holding on the old user_struct can just be > transferred to the new namespace's creator pointer. > > (6) Makes create_user_ns() reset the UIDs and GIDs of the creds under > preparation rather than doing it in copy_creds(). > >David >Signed-off-by: David Howells <dhowells@redhat.com> Changelog: Oct 20: integrate dhowells comments 1. leave thread_keyring alone 2. use current_user_ns() in set_user() Signed-off-by: Serge Hallyn <serue@us.ibm.com>
2008-10-15 21:38:45 +00:00
#include <linux/cred.h>
#include <linux/securebits.h>
security, lsm: Introduce security_create_user_ns() User namespaces are an effective tool to allow programs to run with permission without requiring the need for a program to run as root. User namespaces may also be used as a sandboxing technique. However, attackers sometimes leverage user namespaces as an initial attack vector to perform some exploit. [1,2,3] While it is not the unprivileged user namespace functionality, which causes the kernel to be exploitable, users/administrators might want to more granularly limit or at least monitor how various processes use this functionality, while vulnerable kernel subsystems are being patched. Preventing user namespace already creation comes in a few of forms in order of granularity: 1. /proc/sys/user/max_user_namespaces sysctl 2. Distro specific patch(es) 3. CONFIG_USER_NS To block a task based on its attributes, the LSM hook cred_prepare is a decent candidate for use because it provides more granular control, and it is called before create_user_ns(): cred = prepare_creds() security_prepare_creds() call_int_hook(cred_prepare, ... if (cred) create_user_ns(cred) Since security_prepare_creds() is meant for LSMs to copy and prepare credentials, access control is an unintended use of the hook. [4] Further, security_prepare_creds() will always return a ENOMEM if the hook returns any non-zero error code. This hook also does not handle the clone3 case which requires us to access a user space pointer to know if we're in the CLONE_NEW_USER call path which may be subject to a TOCTTOU attack. Lastly, cred_prepare is called in many call paths, and a targeted hook further limits the frequency of calls which is a beneficial outcome. Therefore introduce a new function security_create_user_ns() with an accompanying userns_create LSM hook. With the new userns_create hook, users will have more control over the observability and access control over user namespace creation. Users should expect that normal operation of user namespaces will behave as usual, and only be impacted when controls are implemented by users or administrators. This hook takes the prepared creds for LSM authors to write policy against. On success, the new namespace is applied to credentials, otherwise an error is returned. Links: 1. https://nvd.nist.gov/vuln/detail/CVE-2022-0492 2. https://nvd.nist.gov/vuln/detail/CVE-2022-25636 3. https://nvd.nist.gov/vuln/detail/CVE-2022-34918 4. https://lore.kernel.org/all/1c4b1c0d-12f6-6e9e-a6a3-cdce7418110c@schaufler-ca.com/ Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org> Reviewed-by: KP Singh <kpsingh@kernel.org> Signed-off-by: Frederick Lawler <fred@cloudflare.com> Signed-off-by: Paul Moore <paul@paul-moore.com>
2022-08-15 16:20:25 +00:00
#include <linux/security.h>
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
#include <linux/keyctl.h>
#include <linux/key-type.h>
#include <keys/user-type.h>
#include <linux/seq_file.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/ctype.h>
#include <linux/projid.h>
#include <linux/fs_struct.h>
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
#include <linux/bsearch.h>
#include <linux/sort.h>
static struct kmem_cache *user_ns_cachep __ro_after_init;
static DEFINE_MUTEX(userns_state_mutex);
static bool new_idmap_permitted(const struct file *file,
struct user_namespace *ns, int cap_setid,
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
struct uid_gid_map *map);
static void free_user_ns(struct work_struct *work);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
static struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
{
return inc_ucount(ns, uid, UCOUNT_USER_NAMESPACES);
}
static void dec_user_namespaces(struct ucounts *ucounts)
{
return dec_ucount(ucounts, UCOUNT_USER_NAMESPACES);
}
static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
{
/* Start with the same capabilities as init but useless for doing
* anything as the capabilities are bound to the new user namespace.
*/
cred->securebits = SECUREBITS_DEFAULT;
cred->cap_inheritable = CAP_EMPTY_SET;
cred->cap_permitted = CAP_FULL_SET;
cred->cap_effective = CAP_FULL_SET;
capabilities: ambient capabilities Credit where credit is due: this idea comes from Christoph Lameter with a lot of valuable input from Serge Hallyn. This patch is heavily based on Christoph's patch. ===== The status quo ===== On Linux, there are a number of capabilities defined by the kernel. To perform various privileged tasks, processes can wield capabilities that they hold. Each task has four capability masks: effective (pE), permitted (pP), inheritable (pI), and a bounding set (X). When the kernel checks for a capability, it checks pE. The other capability masks serve to modify what capabilities can be in pE. Any task can remove capabilities from pE, pP, or pI at any time. If a task has a capability in pP, it can add that capability to pE and/or pI. If a task has CAP_SETPCAP, then it can add any capability to pI, and it can remove capabilities from X. Tasks are not the only things that can have capabilities; files can also have capabilities. A file can have no capabilty information at all [1]. If a file has capability information, then it has a permitted mask (fP) and an inheritable mask (fI) as well as a single effective bit (fE) [2]. File capabilities modify the capabilities of tasks that execve(2) them. A task that successfully calls execve has its capabilities modified for the file ultimately being excecuted (i.e. the binary itself if that binary is ELF or for the interpreter if the binary is a script.) [3] In the capability evolution rules, for each mask Z, pZ represents the old value and pZ' represents the new value. The rules are: pP' = (X & fP) | (pI & fI) pI' = pI pE' = (fE ? pP' : 0) X is unchanged For setuid binaries, fP, fI, and fE are modified by a moderately complicated set of rules that emulate POSIX behavior. Similarly, if euid == 0 or ruid == 0, then fP, fI, and fE are modified differently (primary, fP and fI usually end up being the full set). For nonroot users executing binaries with neither setuid nor file caps, fI and fP are empty and fE is false. As an extra complication, if you execute a process as nonroot and fE is set, then the "secure exec" rules are in effect: AT_SECURE gets set, LD_PRELOAD doesn't work, etc. This is rather messy. We've learned that making any changes is dangerous, though: if a new kernel version allows an unprivileged program to change its security state in a way that persists cross execution of a setuid program or a program with file caps, this persistent state is surprisingly likely to allow setuid or file-capped programs to be exploited for privilege escalation. ===== The problem ===== Capability inheritance is basically useless. If you aren't root and you execute an ordinary binary, fI is zero, so your capabilities have no effect whatsoever on pP'. This means that you can't usefully execute a helper process or a shell command with elevated capabilities if you aren't root. On current kernels, you can sort of work around this by setting fI to the full set for most or all non-setuid executable files. This causes pP' = pI for nonroot, and inheritance works. No one does this because it's a PITA and it isn't even supported on most filesystems. If you try this, you'll discover that every nonroot program ends up with secure exec rules, breaking many things. This is a problem that has bitten many people who have tried to use capabilities for anything useful. ===== The proposed change ===== This patch adds a fifth capability mask called the ambient mask (pA). pA does what most people expect pI to do. pA obeys the invariant that no bit can ever be set in pA if it is not set in both pP and pI. Dropping a bit from pP or pI drops that bit from pA. This ensures that existing programs that try to drop capabilities still do so, with a complication. Because capability inheritance is so broken, setting KEEPCAPS, using setresuid to switch to nonroot uids, and then calling execve effectively drops capabilities. Therefore, setresuid from root to nonroot conditionally clears pA unless SECBIT_NO_SETUID_FIXUP is set. Processes that don't like this can re-add bits to pA afterwards. The capability evolution rules are changed: pA' = (file caps or setuid or setgid ? 0 : pA) pP' = (X & fP) | (pI & fI) | pA' pI' = pI pE' = (fE ? pP' : pA') X is unchanged If you are nonroot but you have a capability, you can add it to pA. If you do so, your children get that capability in pA, pP, and pE. For example, you can set pA = CAP_NET_BIND_SERVICE, and your children can automatically bind low-numbered ports. Hallelujah! Unprivileged users can create user namespaces, map themselves to a nonzero uid, and create both privileged (relative to their namespace) and unprivileged process trees. This is currently more or less impossible. Hallelujah! You cannot use pA to try to subvert a setuid, setgid, or file-capped program: if you execute any such program, pA gets cleared and the resulting evolution rules are unchanged by this patch. Users with nonzero pA are unlikely to unintentionally leak that capability. If they run programs that try to drop privileges, dropping privileges will still work. It's worth noting that the degree of paranoia in this patch could possibly be reduced without causing serious problems. Specifically, if we allowed pA to persist across executing non-pA-aware setuid binaries and across setresuid, then, naively, the only capabilities that could leak as a result would be the capabilities in pA, and any attacker *already* has those capabilities. This would make me nervous, though -- setuid binaries that tried to privilege-separate might fail to do so, and putting CAP_DAC_READ_SEARCH or CAP_DAC_OVERRIDE into pA could have unexpected side effects. (Whether these unexpected side effects would be exploitable is an open question.) I've therefore taken the more paranoid route. We can revisit this later. An alternative would be to require PR_SET_NO_NEW_PRIVS before setting ambient capabilities. I think that this would be annoying and would make granting otherwise unprivileged users minor ambient capabilities (CAP_NET_BIND_SERVICE or CAP_NET_RAW for example) much less useful than it is with this patch. ===== Footnotes ===== [1] Files that are missing the "security.capability" xattr or that have unrecognized values for that xattr end up with has_cap set to false. The code that does that appears to be complicated for no good reason. [2] The libcap capability mask parsers and formatters are dangerously misleading and the documentation is flat-out wrong. fE is *not* a mask; it's a single bit. This has probably confused every single person who has tried to use file capabilities. [3] Linux very confusingly processes both the script and the interpreter if applicable, for reasons that elude me. The results from thinking about a script's file capabilities and/or setuid bits are mostly discarded. Preliminary userspace code is here, but it needs updating: https://git.kernel.org/cgit/linux/kernel/git/luto/util-linux-playground.git/commit/?h=cap_ambient&id=7f5afbd175d2 Here is a test program that can be used to verify the functionality (from Christoph): /* * Test program for the ambient capabilities. This program spawns a shell * that allows running processes with a defined set of capabilities. * * (C) 2015 Christoph Lameter <cl@linux.com> * Released under: GPL v3 or later. * * * Compile using: * * gcc -o ambient_test ambient_test.o -lcap-ng * * This program must have the following capabilities to run properly: * Permissions for CAP_NET_RAW, CAP_NET_ADMIN, CAP_SYS_NICE * * A command to equip the binary with the right caps is: * * setcap cap_net_raw,cap_net_admin,cap_sys_nice+p ambient_test * * * To get a shell with additional caps that can be inherited by other processes: * * ./ambient_test /bin/bash * * * Verifying that it works: * * From the bash spawed by ambient_test run * * cat /proc/$$/status * * and have a look at the capabilities. */ #include <stdlib.h> #include <stdio.h> #include <errno.h> #include <cap-ng.h> #include <sys/prctl.h> #include <linux/capability.h> /* * Definitions from the kernel header files. These are going to be removed * when the /usr/include files have these defined. */ #define PR_CAP_AMBIENT 47 #define PR_CAP_AMBIENT_IS_SET 1 #define PR_CAP_AMBIENT_RAISE 2 #define PR_CAP_AMBIENT_LOWER 3 #define PR_CAP_AMBIENT_CLEAR_ALL 4 static void set_ambient_cap(int cap) { int rc; capng_get_caps_process(); rc = capng_update(CAPNG_ADD, CAPNG_INHERITABLE, cap); if (rc) { printf("Cannot add inheritable cap\n"); exit(2); } capng_apply(CAPNG_SELECT_CAPS); /* Note the two 0s at the end. Kernel checks for these */ if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, cap, 0, 0)) { perror("Cannot set cap"); exit(1); } } int main(int argc, char **argv) { int rc; set_ambient_cap(CAP_NET_RAW); set_ambient_cap(CAP_NET_ADMIN); set_ambient_cap(CAP_SYS_NICE); printf("Ambient_test forking shell\n"); if (execv(argv[1], argv + 1)) perror("Cannot exec"); return 0; } Signed-off-by: Christoph Lameter <cl@linux.com> # Original author Signed-off-by: Andy Lutomirski <luto@kernel.org> Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Aaron Jones <aaronmdjones@gmail.com> Cc: Ted Ts'o <tytso@mit.edu> Cc: Andrew G. Morgan <morgan@kernel.org> Cc: Mimi Zohar <zohar@linux.vnet.ibm.com> Cc: Austin S Hemmelgarn <ahferroin7@gmail.com> Cc: Markku Savela <msa@moth.iki.fi> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: James Morris <james.l.morris@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-04 22:42:45 +00:00
cred->cap_ambient = CAP_EMPTY_SET;
cred->cap_bset = CAP_FULL_SET;
#ifdef CONFIG_KEYS
key_put(cred->request_key_auth);
cred->request_key_auth = NULL;
#endif
/* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
cred->user_ns = user_ns;
}
static unsigned long enforced_nproc_rlimit(void)
{
unsigned long limit = RLIM_INFINITY;
/* Is RLIMIT_NPROC currently enforced? */
if (!uid_eq(current_uid(), GLOBAL_ROOT_UID) ||
(current_user_ns() != &init_user_ns))
limit = rlimit(RLIMIT_NPROC);
return limit;
}
/*
User namespaces: set of cleanups (v2) The user_ns is moved from nsproxy to user_struct, so that a struct cred by itself is sufficient to determine access (which it otherwise would not be). Corresponding ecryptfs fixes (by David Howells) are here as well. Fix refcounting. The following rules now apply: 1. The task pins the user struct. 2. The user struct pins its user namespace. 3. The user namespace pins the struct user which created it. User namespaces are cloned during copy_creds(). Unsharing a new user_ns is no longer possible. (We could re-add that, but it'll cause code duplication and doesn't seem useful if PAM doesn't need to clone user namespaces). When a user namespace is created, its first user (uid 0) gets empty keyrings and a clean group_info. This incorporates a previous patch by David Howells. Here is his original patch description: >I suggest adding the attached incremental patch. It makes the following >changes: > > (1) Provides a current_user_ns() macro to wrap accesses to current's user > namespace. > > (2) Fixes eCryptFS. > > (3) Renames create_new_userns() to create_user_ns() to be more consistent > with the other associated functions and because the 'new' in the name is > superfluous. > > (4) Moves the argument and permission checks made for CLONE_NEWUSER to the > beginning of do_fork() so that they're done prior to making any attempts > at allocation. > > (5) Calls create_user_ns() after prepare_creds(), and gives it the new creds > to fill in rather than have it return the new root user. I don't imagine > the new root user being used for anything other than filling in a cred > struct. > > This also permits me to get rid of a get_uid() and a free_uid(), as the > reference the creds were holding on the old user_struct can just be > transferred to the new namespace's creator pointer. > > (6) Makes create_user_ns() reset the UIDs and GIDs of the creds under > preparation rather than doing it in copy_creds(). > >David >Signed-off-by: David Howells <dhowells@redhat.com> Changelog: Oct 20: integrate dhowells comments 1. leave thread_keyring alone 2. use current_user_ns() in set_user() Signed-off-by: Serge Hallyn <serue@us.ibm.com>
2008-10-15 21:38:45 +00:00
* Create a new user namespace, deriving the creator from the user in the
* passed credentials, and replacing that user with the new root user for the
* new namespace.
*
* This is called by copy_creds(), which will finish setting the target task's
* credentials.
*/
User namespaces: set of cleanups (v2) The user_ns is moved from nsproxy to user_struct, so that a struct cred by itself is sufficient to determine access (which it otherwise would not be). Corresponding ecryptfs fixes (by David Howells) are here as well. Fix refcounting. The following rules now apply: 1. The task pins the user struct. 2. The user struct pins its user namespace. 3. The user namespace pins the struct user which created it. User namespaces are cloned during copy_creds(). Unsharing a new user_ns is no longer possible. (We could re-add that, but it'll cause code duplication and doesn't seem useful if PAM doesn't need to clone user namespaces). When a user namespace is created, its first user (uid 0) gets empty keyrings and a clean group_info. This incorporates a previous patch by David Howells. Here is his original patch description: >I suggest adding the attached incremental patch. It makes the following >changes: > > (1) Provides a current_user_ns() macro to wrap accesses to current's user > namespace. > > (2) Fixes eCryptFS. > > (3) Renames create_new_userns() to create_user_ns() to be more consistent > with the other associated functions and because the 'new' in the name is > superfluous. > > (4) Moves the argument and permission checks made for CLONE_NEWUSER to the > beginning of do_fork() so that they're done prior to making any attempts > at allocation. > > (5) Calls create_user_ns() after prepare_creds(), and gives it the new creds > to fill in rather than have it return the new root user. I don't imagine > the new root user being used for anything other than filling in a cred > struct. > > This also permits me to get rid of a get_uid() and a free_uid(), as the > reference the creds were holding on the old user_struct can just be > transferred to the new namespace's creator pointer. > > (6) Makes create_user_ns() reset the UIDs and GIDs of the creds under > preparation rather than doing it in copy_creds(). > >David >Signed-off-by: David Howells <dhowells@redhat.com> Changelog: Oct 20: integrate dhowells comments 1. leave thread_keyring alone 2. use current_user_ns() in set_user() Signed-off-by: Serge Hallyn <serue@us.ibm.com>
2008-10-15 21:38:45 +00:00
int create_user_ns(struct cred *new)
{
struct user_namespace *ns, *parent_ns = new->user_ns;
kuid_t owner = new->euid;
kgid_t group = new->egid;
struct ucounts *ucounts;
int ret, i;
ret = -ENOSPC;
if (parent_ns->level > 32)
goto fail;
ucounts = inc_user_namespaces(parent_ns, owner);
if (!ucounts)
goto fail;
/*
* Verify that we can not violate the policy of which files
* may be accessed that is specified by the root directory,
* by verifying that the root directory is at the root of the
* mount namespace which allows all files to be accessed.
*/
ret = -EPERM;
if (current_chrooted())
goto fail_dec;
/* The creator needs a mapping in the parent user namespace
* or else we won't be able to reasonably tell userspace who
* created a user_namespace.
*/
ret = -EPERM;
if (!kuid_has_mapping(parent_ns, owner) ||
!kgid_has_mapping(parent_ns, group))
goto fail_dec;
security, lsm: Introduce security_create_user_ns() User namespaces are an effective tool to allow programs to run with permission without requiring the need for a program to run as root. User namespaces may also be used as a sandboxing technique. However, attackers sometimes leverage user namespaces as an initial attack vector to perform some exploit. [1,2,3] While it is not the unprivileged user namespace functionality, which causes the kernel to be exploitable, users/administrators might want to more granularly limit or at least monitor how various processes use this functionality, while vulnerable kernel subsystems are being patched. Preventing user namespace already creation comes in a few of forms in order of granularity: 1. /proc/sys/user/max_user_namespaces sysctl 2. Distro specific patch(es) 3. CONFIG_USER_NS To block a task based on its attributes, the LSM hook cred_prepare is a decent candidate for use because it provides more granular control, and it is called before create_user_ns(): cred = prepare_creds() security_prepare_creds() call_int_hook(cred_prepare, ... if (cred) create_user_ns(cred) Since security_prepare_creds() is meant for LSMs to copy and prepare credentials, access control is an unintended use of the hook. [4] Further, security_prepare_creds() will always return a ENOMEM if the hook returns any non-zero error code. This hook also does not handle the clone3 case which requires us to access a user space pointer to know if we're in the CLONE_NEW_USER call path which may be subject to a TOCTTOU attack. Lastly, cred_prepare is called in many call paths, and a targeted hook further limits the frequency of calls which is a beneficial outcome. Therefore introduce a new function security_create_user_ns() with an accompanying userns_create LSM hook. With the new userns_create hook, users will have more control over the observability and access control over user namespace creation. Users should expect that normal operation of user namespaces will behave as usual, and only be impacted when controls are implemented by users or administrators. This hook takes the prepared creds for LSM authors to write policy against. On success, the new namespace is applied to credentials, otherwise an error is returned. Links: 1. https://nvd.nist.gov/vuln/detail/CVE-2022-0492 2. https://nvd.nist.gov/vuln/detail/CVE-2022-25636 3. https://nvd.nist.gov/vuln/detail/CVE-2022-34918 4. https://lore.kernel.org/all/1c4b1c0d-12f6-6e9e-a6a3-cdce7418110c@schaufler-ca.com/ Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org> Reviewed-by: KP Singh <kpsingh@kernel.org> Signed-off-by: Frederick Lawler <fred@cloudflare.com> Signed-off-by: Paul Moore <paul@paul-moore.com>
2022-08-15 16:20:25 +00:00
ret = security_create_user_ns(new);
if (ret < 0)
goto fail_dec;
ret = -ENOMEM;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
if (!ns)
goto fail_dec;
capabilities: require CAP_SETFCAP to map uid 0 cap_setfcap is required to create file capabilities. Since commit 8db6c34f1dbc ("Introduce v3 namespaced file capabilities"), a process running as uid 0 but without cap_setfcap is able to work around this as follows: unshare a new user namespace which maps parent uid 0 into the child namespace. While this task will not have new capabilities against the parent namespace, there is a loophole due to the way namespaced file capabilities are represented as xattrs. File capabilities valid in userns 1 are distinguished from file capabilities valid in userns 2 by the kuid which underlies uid 0. Therefore the restricted root process can unshare a new self-mapping namespace, add a namespaced file capability onto a file, then use that file capability in the parent namespace. To prevent that, do not allow mapping parent uid 0 if the process which opened the uid_map file does not have CAP_SETFCAP, which is the capability for setting file capabilities. As a further wrinkle: a task can unshare its user namespace, then open its uid_map file itself, and map (only) its own uid. In this case we do not have the credential from before unshare, which was potentially more restricted. So, when creating a user namespace, we record whether the creator had CAP_SETFCAP. Then we can use that during map_write(). With this patch: 1. Unprivileged user can still unshare -Ur ubuntu@caps:~$ unshare -Ur root@caps:~# logout 2. Root user can still unshare -Ur ubuntu@caps:~$ sudo bash root@caps:/home/ubuntu# unshare -Ur root@caps:/home/ubuntu# logout 3. Root user without CAP_SETFCAP cannot unshare -Ur: root@caps:/home/ubuntu# /sbin/capsh --drop=cap_setfcap -- root@caps:/home/ubuntu# /sbin/setcap cap_setfcap=p /sbin/setcap unable to set CAP_SETFCAP effective capability: Operation not permitted root@caps:/home/ubuntu# unshare -Ur unshare: write failed /proc/self/uid_map: Operation not permitted Note: an alternative solution would be to allow uid 0 mappings by processes without CAP_SETFCAP, but to prevent such a namespace from writing any file capabilities. This approach can be seen at [1]. Background history: commit 95ebabde382 ("capabilities: Don't allow writing ambiguous v3 file capabilities") tried to fix the issue by preventing v3 fscaps to be written to disk when the root uid would map to the same uid in nested user namespaces. This led to regressions for various workloads. For example, see [2]. Ultimately this is a valid use-case we have to support meaning we had to revert this change in 3b0c2d3eaa83 ("Revert 95ebabde382c ("capabilities: Don't allow writing ambiguous v3 file capabilities")"). Link: https://git.kernel.org/pub/scm/linux/kernel/git/sergeh/linux.git/log/?h=2021-04-15/setfcap-nsfscaps-v4 [1] Link: https://github.com/containers/buildah/issues/3071 [2] Signed-off-by: Serge Hallyn <serge@hallyn.com> Reviewed-by: Andrew G. Morgan <morgan@kernel.org> Tested-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com> Tested-by: Giuseppe Scrivano <gscrivan@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-04-20 13:43:34 +00:00
ns->parent_could_setfcap = cap_raised(new->cap_effective, CAP_SETFCAP);
ret = ns_alloc_inum(&ns->ns);
if (ret)
goto fail_free;
ns->ns.ops = &userns_operations;
user: Use generic ns_common::count Switch over user namespaces to use the newly introduced common lifetime counter. Currently every namespace type has its own lifetime counter which is stored in the specific namespace struct. The lifetime counters are used identically for all namespaces types. Namespaces may of course have additional unrelated counters and these are not altered. This introduces a common lifetime counter into struct ns_common. The ns_common struct encompasses information that all namespaces share. That should include the lifetime counter since its common for all of them. It also allows us to unify the type of the counters across all namespaces. Most of them use refcount_t but one uses atomic_t and at least one uses kref. Especially the last one doesn't make much sense since it's just a wrapper around refcount_t since 2016 and actually complicates cleanup operations by having to use container_of() to cast the correct namespace struct out of struct ns_common. Having the lifetime counter for the namespaces in one place reduces maintenance cost. Not just because after switching all namespaces over we will have removed more code than we added but also because the logic is more easily understandable and we indicate to the user that the basic lifetime requirements for all namespaces are currently identical. Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Link: https://lore.kernel.org/r/159644979754.604812.601625186726406922.stgit@localhost.localdomain Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2020-08-03 10:16:37 +00:00
refcount_set(&ns->ns.count, 1);
/* Leave the new->user_ns reference with the new user namespace. */
ns->parent = parent_ns;
ns->level = parent_ns->level + 1;
ns->owner = owner;
ns->group = group;
INIT_WORK(&ns->work, free_user_ns);
for (i = 0; i < UCOUNT_COUNTS; i++) {
ns->ucount_max[i] = INT_MAX;
}
set_userns_rlimit_max(ns, UCOUNT_RLIMIT_NPROC, enforced_nproc_rlimit());
set_userns_rlimit_max(ns, UCOUNT_RLIMIT_MSGQUEUE, rlimit(RLIMIT_MSGQUEUE));
set_userns_rlimit_max(ns, UCOUNT_RLIMIT_SIGPENDING, rlimit(RLIMIT_SIGPENDING));
set_userns_rlimit_max(ns, UCOUNT_RLIMIT_MEMLOCK, rlimit(RLIMIT_MEMLOCK));
ns->ucounts = ucounts;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
2014-12-02 18:27:26 +00:00
/* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
mutex_lock(&userns_state_mutex);
ns->flags = parent_ns->flags;
mutex_unlock(&userns_state_mutex);
#ifdef CONFIG_KEYS
INIT_LIST_HEAD(&ns->keyring_name_list);
init_rwsem(&ns->keyring_sem);
KEYS: Add per-user_namespace registers for persistent per-UID kerberos caches Add support for per-user_namespace registers of persistent per-UID kerberos caches held within the kernel. This allows the kerberos cache to be retained beyond the life of all a user's processes so that the user's cron jobs can work. The kerberos cache is envisioned as a keyring/key tree looking something like: struct user_namespace \___ .krb_cache keyring - The register \___ _krb.0 keyring - Root's Kerberos cache \___ _krb.5000 keyring - User 5000's Kerberos cache \___ _krb.5001 keyring - User 5001's Kerberos cache \___ tkt785 big_key - A ccache blob \___ tkt12345 big_key - Another ccache blob Or possibly: struct user_namespace \___ .krb_cache keyring - The register \___ _krb.0 keyring - Root's Kerberos cache \___ _krb.5000 keyring - User 5000's Kerberos cache \___ _krb.5001 keyring - User 5001's Kerberos cache \___ tkt785 keyring - A ccache \___ krbtgt/REDHAT.COM@REDHAT.COM big_key \___ http/REDHAT.COM@REDHAT.COM user \___ afs/REDHAT.COM@REDHAT.COM user \___ nfs/REDHAT.COM@REDHAT.COM user \___ krbtgt/KERNEL.ORG@KERNEL.ORG big_key \___ http/KERNEL.ORG@KERNEL.ORG big_key What goes into a particular Kerberos cache is entirely up to userspace. Kernel support is limited to giving you the Kerberos cache keyring that you want. The user asks for their Kerberos cache by: krb_cache = keyctl_get_krbcache(uid, dest_keyring); The uid is -1 or the user's own UID for the user's own cache or the uid of some other user's cache (requires CAP_SETUID). This permits rpc.gssd or whatever to mess with the cache. The cache returned is a keyring named "_krb.<uid>" that the possessor can read, search, clear, invalidate, unlink from and add links to. Active LSMs get a chance to rule on whether the caller is permitted to make a link. Each uid's cache keyring is created when it first accessed and is given a timeout that is extended each time this function is called so that the keyring goes away after a while. The timeout is configurable by sysctl but defaults to three days. Each user_namespace struct gets a lazily-created keyring that serves as the register. The cache keyrings are added to it. This means that standard key search and garbage collection facilities are available. The user_namespace struct's register goes away when it does and anything left in it is then automatically gc'd. Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Simo Sorce <simo@redhat.com> cc: Serge E. Hallyn <serge.hallyn@ubuntu.com> cc: Eric W. Biederman <ebiederm@xmission.com>
2013-09-24 09:35:19 +00:00
#endif
ret = -ENOMEM;
if (!setup_userns_sysctls(ns))
goto fail_keyring;
set_cred_user_ns(new, ns);
User namespaces: set of cleanups (v2) The user_ns is moved from nsproxy to user_struct, so that a struct cred by itself is sufficient to determine access (which it otherwise would not be). Corresponding ecryptfs fixes (by David Howells) are here as well. Fix refcounting. The following rules now apply: 1. The task pins the user struct. 2. The user struct pins its user namespace. 3. The user namespace pins the struct user which created it. User namespaces are cloned during copy_creds(). Unsharing a new user_ns is no longer possible. (We could re-add that, but it'll cause code duplication and doesn't seem useful if PAM doesn't need to clone user namespaces). When a user namespace is created, its first user (uid 0) gets empty keyrings and a clean group_info. This incorporates a previous patch by David Howells. Here is his original patch description: >I suggest adding the attached incremental patch. It makes the following >changes: > > (1) Provides a current_user_ns() macro to wrap accesses to current's user > namespace. > > (2) Fixes eCryptFS. > > (3) Renames create_new_userns() to create_user_ns() to be more consistent > with the other associated functions and because the 'new' in the name is > superfluous. > > (4) Moves the argument and permission checks made for CLONE_NEWUSER to the > beginning of do_fork() so that they're done prior to making any attempts > at allocation. > > (5) Calls create_user_ns() after prepare_creds(), and gives it the new creds > to fill in rather than have it return the new root user. I don't imagine > the new root user being used for anything other than filling in a cred > struct. > > This also permits me to get rid of a get_uid() and a free_uid(), as the > reference the creds were holding on the old user_struct can just be > transferred to the new namespace's creator pointer. > > (6) Makes create_user_ns() reset the UIDs and GIDs of the creds under > preparation rather than doing it in copy_creds(). > >David >Signed-off-by: David Howells <dhowells@redhat.com> Changelog: Oct 20: integrate dhowells comments 1. leave thread_keyring alone 2. use current_user_ns() in set_user() Signed-off-by: Serge Hallyn <serue@us.ibm.com>
2008-10-15 21:38:45 +00:00
return 0;
fail_keyring:
#ifdef CONFIG_PERSISTENT_KEYRINGS
key_put(ns->persistent_keyring_register);
#endif
ns_free_inum(&ns->ns);
fail_free:
kmem_cache_free(user_ns_cachep, ns);
fail_dec:
dec_user_namespaces(ucounts);
fail:
return ret;
}
int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
{
struct cred *cred;
int err = -ENOMEM;
if (!(unshare_flags & CLONE_NEWUSER))
return 0;
cred = prepare_creds();
if (cred) {
err = create_user_ns(cred);
if (err)
put_cred(cred);
else
*new_cred = cred;
}
return err;
}
static void free_user_ns(struct work_struct *work)
{
struct user_namespace *parent, *ns =
container_of(work, struct user_namespace, work);
do {
struct ucounts *ucounts = ns->ucounts;
parent = ns->parent;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if (ns->gid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
kfree(ns->gid_map.forward);
kfree(ns->gid_map.reverse);
}
if (ns->uid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
kfree(ns->uid_map.forward);
kfree(ns->uid_map.reverse);
}
if (ns->projid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
kfree(ns->projid_map.forward);
kfree(ns->projid_map.reverse);
}
binfmt_misc: enable sandboxed mounts Enable unprivileged sandboxes to create their own binfmt_misc mounts. This is based on Laurent's work in [1] but has been significantly reworked to fix various issues we identified in earlier versions. While binfmt_misc can currently only be mounted in the initial user namespace, binary types registered in this binfmt_misc instance are available to all sandboxes (Either by having them installed in the sandbox or by registering the binary type with the F flag causing the interpreter to be opened right away). So binfmt_misc binary types are already delegated to sandboxes implicitly. However, while a sandbox has access to all registered binary types in binfmt_misc a sandbox cannot currently register its own binary types in binfmt_misc. This has prevented various use-cases some of which were already outlined in [1] but we have a range of issues associated with this (cf. [3]-[5] below which are just a small sample). Extend binfmt_misc to be mountable in non-initial user namespaces. Similar to other filesystem such as nfsd, mqueue, and sunrpc we use keyed superblock management. The key determines whether we need to create a new superblock or can reuse an already existing one. We use the user namespace of the mount as key. This means a new binfmt_misc superblock is created once per user namespace creation. Subsequent mounts of binfmt_misc in the same user namespace will mount the same binfmt_misc instance. We explicitly do not create a new binfmt_misc superblock on every binfmt_misc mount as the semantics for load_misc_binary() line up with the keying model. This also allows us to retrieve the relevant binfmt_misc instance based on the caller's user namespace which can be done in a simple (bounded to 32 levels) loop. Similar to the current binfmt_misc semantics allowing access to the binary types in the initial binfmt_misc instance we do allow sandboxes access to their parent's binfmt_misc mounts if they do not have created a separate binfmt_misc instance. Overall, this will unblock the use-cases mentioned below and in general will also allow to support and harden execution of another architecture's binaries in tight sandboxes. For instance, using the unshare binary it possible to start a chroot of another architecture and configure the binfmt_misc interpreter without being root to run the binaries in this chroot and without requiring the host to modify its binary type handlers. Henning had already posted a few experiments in the cover letter at [1]. But here's an additional example where an unprivileged container registers qemu-user-static binary handlers for various binary types in its separate binfmt_misc mount and is then seamlessly able to start containers with a different architecture without affecting the host: root [lxc monitor] /var/snap/lxd/common/lxd/containers f1 1000000 \_ /sbin/init 1000000 \_ /lib/systemd/systemd-journald 1000000 \_ /lib/systemd/systemd-udevd 1000100 \_ /lib/systemd/systemd-networkd 1000101 \_ /lib/systemd/systemd-resolved 1000000 \_ /usr/sbin/cron -f 1000103 \_ /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only 1000000 \_ /usr/bin/python3 /usr/bin/networkd-dispatcher --run-startup-triggers 1000104 \_ /usr/sbin/rsyslogd -n -iNONE 1000000 \_ /lib/systemd/systemd-logind 1000000 \_ /sbin/agetty -o -p -- \u --noclear --keep-baud console 115200,38400,9600 vt220 1000107 \_ dnsmasq --conf-file=/dev/null -u lxc-dnsmasq --strict-order --bind-interfaces --pid-file=/run/lxc/dnsmasq.pid --liste 1000000 \_ [lxc monitor] /var/lib/lxc f1-s390x 1100000 \_ /usr/bin/qemu-s390x-static /sbin/init 1100000 \_ /usr/bin/qemu-s390x-static /lib/systemd/systemd-journald 1100000 \_ /usr/bin/qemu-s390x-static /usr/sbin/cron -f 1100103 \_ /usr/bin/qemu-s390x-static /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-ac 1100000 \_ /usr/bin/qemu-s390x-static /usr/bin/python3 /usr/bin/networkd-dispatcher --run-startup-triggers 1100104 \_ /usr/bin/qemu-s390x-static /usr/sbin/rsyslogd -n -iNONE 1100000 \_ /usr/bin/qemu-s390x-static /lib/systemd/systemd-logind 1100000 \_ /usr/bin/qemu-s390x-static /sbin/agetty -o -p -- \u --noclear --keep-baud console 115200,38400,9600 vt220 1100000 \_ /usr/bin/qemu-s390x-static /sbin/agetty -o -p -- \u --noclear --keep-baud pts/0 115200,38400,9600 vt220 1100000 \_ /usr/bin/qemu-s390x-static /sbin/agetty -o -p -- \u --noclear --keep-baud pts/1 115200,38400,9600 vt220 1100000 \_ /usr/bin/qemu-s390x-static /sbin/agetty -o -p -- \u --noclear --keep-baud pts/2 115200,38400,9600 vt220 1100000 \_ /usr/bin/qemu-s390x-static /sbin/agetty -o -p -- \u --noclear --keep-baud pts/3 115200,38400,9600 vt220 1100000 \_ /usr/bin/qemu-s390x-static /lib/systemd/systemd-udevd [1]: https://lore.kernel.org/all/20191216091220.465626-1-laurent@vivier.eu [2]: https://discuss.linuxcontainers.org/t/binfmt-misc-permission-denied [3]: https://discuss.linuxcontainers.org/t/lxd-binfmt-support-for-qemu-static-interpreters [4]: https://discuss.linuxcontainers.org/t/3-1-0-binfmt-support-service-in-unprivileged-guest-requires-write-access-on-hosts-proc-sys-fs-binfmt-misc [5]: https://discuss.linuxcontainers.org/t/qemu-user-static-not-working-4-11 Link: https://lore.kernel.org/r/20191216091220.465626-2-laurent@vivier.eu (origin) Link: https://lore.kernel.org/r/20211028103114.2849140-2-brauner@kernel.org (v1) Cc: Sargun Dhillon <sargun@sargun.me> Cc: Serge Hallyn <serge@hallyn.com> Cc: Jann Horn <jannh@google.com> Cc: Henning Schild <henning.schild@siemens.com> Cc: Andrei Vagin <avagin@gmail.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Laurent Vivier <laurent@vivier.eu> Cc: linux-fsdevel@vger.kernel.org Signed-off-by: Laurent Vivier <laurent@vivier.eu> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Kees Cook <keescook@chromium.org> --- /* v2 */ - Serge Hallyn <serge@hallyn.com>: - Use GFP_KERNEL_ACCOUNT for userspace triggered allocations when a new binary type handler is registered. - Christian Brauner <christian.brauner@ubuntu.com>: - Switch authorship to me. I refused to do that earlier even though Laurent said I should do so because I think it's genuinely bad form. But by now I have changed so many things that it'd be unfair to blame Laurent for any potential bugs in here. - Add more comments that explain what's going on. - Rename functions while changing them to better reflect what they are doing to make the code easier to understand. - In the first version when a specific binary type handler was removed either through a write to the entry's file or all binary type handlers were removed by a write to the binfmt_misc mount's status file all cleanup work happened during inode eviction. That includes removal of the relevant entries from entry list. While that works fine I disliked that model after thinking about it for a bit. Because it means that there was a window were someone has already removed a or all binary handlers but they could still be safely reached from load_misc_binary() when it has managed to take the read_lock() on the entries list while inode eviction was already happening. Again, that perfectly benign but it's cleaner to remove the binary handler from the list immediately meaning that ones the write to then entry's file or the binfmt_misc status file returns the binary type cannot be executed anymore. That gives stronger guarantees to the user.
2021-10-28 10:31:14 +00:00
#if IS_ENABLED(CONFIG_BINFMT_MISC)
kfree(ns->binfmt_misc);
#endif
retire_userns_sysctls(ns);
key_free_user_ns(ns);
ns_free_inum(&ns->ns);
kmem_cache_free(user_ns_cachep, ns);
dec_user_namespaces(ucounts);
ns = parent;
user: Use generic ns_common::count Switch over user namespaces to use the newly introduced common lifetime counter. Currently every namespace type has its own lifetime counter which is stored in the specific namespace struct. The lifetime counters are used identically for all namespaces types. Namespaces may of course have additional unrelated counters and these are not altered. This introduces a common lifetime counter into struct ns_common. The ns_common struct encompasses information that all namespaces share. That should include the lifetime counter since its common for all of them. It also allows us to unify the type of the counters across all namespaces. Most of them use refcount_t but one uses atomic_t and at least one uses kref. Especially the last one doesn't make much sense since it's just a wrapper around refcount_t since 2016 and actually complicates cleanup operations by having to use container_of() to cast the correct namespace struct out of struct ns_common. Having the lifetime counter for the namespaces in one place reduces maintenance cost. Not just because after switching all namespaces over we will have removed more code than we added but also because the logic is more easily understandable and we indicate to the user that the basic lifetime requirements for all namespaces are currently identical. Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Link: https://lore.kernel.org/r/159644979754.604812.601625186726406922.stgit@localhost.localdomain Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2020-08-03 10:16:37 +00:00
} while (refcount_dec_and_test(&parent->ns.count));
}
void __put_user_ns(struct user_namespace *ns)
{
schedule_work(&ns->work);
}
EXPORT_SYMBOL(__put_user_ns);
/*
* struct idmap_key - holds the information necessary to find an idmapping in a
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
* sorted idmap array. It is passed to cmp_map_id() as first argument.
*/
struct idmap_key {
bool map_up; /* true -> id from kid; false -> kid from id */
u32 id; /* id to find */
u32 count; /* == 0 unless used with map_id_range_down() */
};
/*
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
* cmp_map_id - Function to be passed to bsearch() to find the requested
* idmapping. Expects struct idmap_key to be passed via @k.
*/
static int cmp_map_id(const void *k, const void *e)
{
u32 first, last, id2;
const struct idmap_key *key = k;
const struct uid_gid_extent *el = e;
id2 = key->id + key->count - 1;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
/* handle map_id_{down,up}() */
if (key->map_up)
first = el->lower_first;
else
first = el->first;
last = first + el->count - 1;
if (key->id >= first && key->id <= last &&
(id2 >= first && id2 <= last))
return 0;
if (key->id < first || id2 < first)
return -1;
return 1;
}
/*
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
* map_id_range_down_max - Find idmap via binary search in ordered idmap array.
* Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
*/
static struct uid_gid_extent *
map_id_range_down_max(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
{
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
struct idmap_key key;
key.map_up = false;
key.count = count;
key.id = id;
return bsearch(&key, map->forward, extents,
sizeof(struct uid_gid_extent), cmp_map_id);
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
}
/*
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
* map_id_range_down_base - Find idmap via binary search in static extent array.
* Can only be called if number of mappings is equal or less than
* UID_GID_MAP_MAX_BASE_EXTENTS.
*/
static struct uid_gid_extent *
map_id_range_down_base(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
{
unsigned idx;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
u32 first, last, id2;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
id2 = id + count - 1;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
/* Find the matching extent */
for (idx = 0; idx < extents; idx++) {
first = map->extent[idx].first;
last = first + map->extent[idx].count - 1;
if (id >= first && id <= last &&
(id2 >= first && id2 <= last))
return &map->extent[idx];
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
}
return NULL;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
}
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
{
struct uid_gid_extent *extent;
unsigned extents = map->nr_extents;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
smp_rmb();
if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
extent = map_id_range_down_base(extents, map, id, count);
else
extent = map_id_range_down_max(extents, map, id, count);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
/* Map the id or note failure */
if (extent)
id = (id - extent->first) + extent->lower_first;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
else
id = (u32) -1;
return id;
}
u32 map_id_down(struct uid_gid_map *map, u32 id)
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
{
return map_id_range_down(map, id, 1);
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
}
/*
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
* map_id_up_base - Find idmap via binary search in static extent array.
* Can only be called if number of mappings is equal or less than
* UID_GID_MAP_MAX_BASE_EXTENTS.
*/
static struct uid_gid_extent *
map_id_up_base(unsigned extents, struct uid_gid_map *map, u32 id)
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
{
unsigned idx;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
u32 first, last;
/* Find the matching extent */
for (idx = 0; idx < extents; idx++) {
first = map->extent[idx].lower_first;
last = first + map->extent[idx].count - 1;
if (id >= first && id <= last)
return &map->extent[idx];
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
}
return NULL;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
}
/*
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
* map_id_up_max - Find idmap via binary search in ordered idmap array.
* Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
*/
static struct uid_gid_extent *
map_id_up_max(unsigned extents, struct uid_gid_map *map, u32 id)
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
{
struct idmap_key key;
key.map_up = true;
key.count = 1;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
key.id = id;
return bsearch(&key, map->reverse, extents,
sizeof(struct uid_gid_extent), cmp_map_id);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
}
u32 map_id_up(struct uid_gid_map *map, u32 id)
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
{
struct uid_gid_extent *extent;
unsigned extents = map->nr_extents;
smp_rmb();
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
extent = map_id_up_base(extents, map, id);
else
extent = map_id_up_max(extents, map, id);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
/* Map the id or note failure */
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if (extent)
id = (id - extent->lower_first) + extent->first;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
else
id = (u32) -1;
return id;
}
/**
* make_kuid - Map a user-namespace uid pair into a kuid.
* @ns: User namespace that the uid is in
* @uid: User identifier
*
* Maps a user-namespace uid pair into a kernel internal kuid,
* and returns that kuid.
*
* When there is no mapping defined for the user-namespace uid
* pair INVALID_UID is returned. Callers are expected to test
* for and handle INVALID_UID being returned. INVALID_UID
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
* may be tested for using uid_valid().
*/
kuid_t make_kuid(struct user_namespace *ns, uid_t uid)
{
/* Map the uid to a global kernel uid */
return KUIDT_INIT(map_id_down(&ns->uid_map, uid));
}
EXPORT_SYMBOL(make_kuid);
/**
* from_kuid - Create a uid from a kuid user-namespace pair.
* @targ: The user namespace we want a uid in.
* @kuid: The kernel internal uid to start with.
*
* Map @kuid into the user-namespace specified by @targ and
* return the resulting uid.
*
* There is always a mapping into the initial user_namespace.
*
* If @kuid has no mapping in @targ (uid_t)-1 is returned.
*/
uid_t from_kuid(struct user_namespace *targ, kuid_t kuid)
{
/* Map the uid from a global kernel uid */
return map_id_up(&targ->uid_map, __kuid_val(kuid));
}
EXPORT_SYMBOL(from_kuid);
/**
* from_kuid_munged - Create a uid from a kuid user-namespace pair.
* @targ: The user namespace we want a uid in.
* @kuid: The kernel internal uid to start with.
*
* Map @kuid into the user-namespace specified by @targ and
* return the resulting uid.
*
* There is always a mapping into the initial user_namespace.
*
* Unlike from_kuid from_kuid_munged never fails and always
* returns a valid uid. This makes from_kuid_munged appropriate
* for use in syscalls like stat and getuid where failing the
* system call and failing to provide a valid uid are not an
* options.
*
* If @kuid has no mapping in @targ overflowuid is returned.
*/
uid_t from_kuid_munged(struct user_namespace *targ, kuid_t kuid)
{
uid_t uid;
uid = from_kuid(targ, kuid);
if (uid == (uid_t) -1)
uid = overflowuid;
return uid;
}
EXPORT_SYMBOL(from_kuid_munged);
/**
* make_kgid - Map a user-namespace gid pair into a kgid.
* @ns: User namespace that the gid is in
* @gid: group identifier
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
*
* Maps a user-namespace gid pair into a kernel internal kgid,
* and returns that kgid.
*
* When there is no mapping defined for the user-namespace gid
* pair INVALID_GID is returned. Callers are expected to test
* for and handle INVALID_GID being returned. INVALID_GID may be
* tested for using gid_valid().
*/
kgid_t make_kgid(struct user_namespace *ns, gid_t gid)
{
/* Map the gid to a global kernel gid */
return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
}
EXPORT_SYMBOL(make_kgid);
/**
* from_kgid - Create a gid from a kgid user-namespace pair.
* @targ: The user namespace we want a gid in.
* @kgid: The kernel internal gid to start with.
*
* Map @kgid into the user-namespace specified by @targ and
* return the resulting gid.
*
* There is always a mapping into the initial user_namespace.
*
* If @kgid has no mapping in @targ (gid_t)-1 is returned.
*/
gid_t from_kgid(struct user_namespace *targ, kgid_t kgid)
{
/* Map the gid from a global kernel gid */
return map_id_up(&targ->gid_map, __kgid_val(kgid));
}
EXPORT_SYMBOL(from_kgid);
/**
* from_kgid_munged - Create a gid from a kgid user-namespace pair.
* @targ: The user namespace we want a gid in.
* @kgid: The kernel internal gid to start with.
*
* Map @kgid into the user-namespace specified by @targ and
* return the resulting gid.
*
* There is always a mapping into the initial user_namespace.
*
* Unlike from_kgid from_kgid_munged never fails and always
* returns a valid gid. This makes from_kgid_munged appropriate
* for use in syscalls like stat and getgid where failing the
* system call and failing to provide a valid gid are not options.
*
* If @kgid has no mapping in @targ overflowgid is returned.
*/
gid_t from_kgid_munged(struct user_namespace *targ, kgid_t kgid)
{
gid_t gid;
gid = from_kgid(targ, kgid);
if (gid == (gid_t) -1)
gid = overflowgid;
return gid;
}
EXPORT_SYMBOL(from_kgid_munged);
/**
* make_kprojid - Map a user-namespace projid pair into a kprojid.
* @ns: User namespace that the projid is in
* @projid: Project identifier
*
* Maps a user-namespace uid pair into a kernel internal kuid,
* and returns that kuid.
*
* When there is no mapping defined for the user-namespace projid
* pair INVALID_PROJID is returned. Callers are expected to test
* for and handle INVALID_PROJID being returned. INVALID_PROJID
* may be tested for using projid_valid().
*/
kprojid_t make_kprojid(struct user_namespace *ns, projid_t projid)
{
/* Map the uid to a global kernel uid */
return KPROJIDT_INIT(map_id_down(&ns->projid_map, projid));
}
EXPORT_SYMBOL(make_kprojid);
/**
* from_kprojid - Create a projid from a kprojid user-namespace pair.
* @targ: The user namespace we want a projid in.
* @kprojid: The kernel internal project identifier to start with.
*
* Map @kprojid into the user-namespace specified by @targ and
* return the resulting projid.
*
* There is always a mapping into the initial user_namespace.
*
* If @kprojid has no mapping in @targ (projid_t)-1 is returned.
*/
projid_t from_kprojid(struct user_namespace *targ, kprojid_t kprojid)
{
/* Map the uid from a global kernel uid */
return map_id_up(&targ->projid_map, __kprojid_val(kprojid));
}
EXPORT_SYMBOL(from_kprojid);
/**
* from_kprojid_munged - Create a projiid from a kprojid user-namespace pair.
* @targ: The user namespace we want a projid in.
* @kprojid: The kernel internal projid to start with.
*
* Map @kprojid into the user-namespace specified by @targ and
* return the resulting projid.
*
* There is always a mapping into the initial user_namespace.
*
* Unlike from_kprojid from_kprojid_munged never fails and always
* returns a valid projid. This makes from_kprojid_munged
* appropriate for use in syscalls like stat and where
* failing the system call and failing to provide a valid projid are
* not an options.
*
* If @kprojid has no mapping in @targ OVERFLOW_PROJID is returned.
*/
projid_t from_kprojid_munged(struct user_namespace *targ, kprojid_t kprojid)
{
projid_t projid;
projid = from_kprojid(targ, kprojid);
if (projid == (projid_t) -1)
projid = OVERFLOW_PROJID;
return projid;
}
EXPORT_SYMBOL(from_kprojid_munged);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
static int uid_m_show(struct seq_file *seq, void *v)
{
struct user_namespace *ns = seq->private;
struct uid_gid_extent *extent = v;
struct user_namespace *lower_ns;
uid_t lower;
lower_ns = seq_user_ns(seq);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
if ((lower_ns == ns) && lower_ns->parent)
lower_ns = lower_ns->parent;
lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first));
seq_printf(seq, "%10u %10u %10u\n",
extent->first,
lower,
extent->count);
return 0;
}
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
static int gid_m_show(struct seq_file *seq, void *v)
{
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
struct user_namespace *ns = seq->private;
struct uid_gid_extent *extent = v;
struct user_namespace *lower_ns;
gid_t lower;
lower_ns = seq_user_ns(seq);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
if ((lower_ns == ns) && lower_ns->parent)
lower_ns = lower_ns->parent;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first));
seq_printf(seq, "%10u %10u %10u\n",
extent->first,
lower,
extent->count);
return 0;
}
static int projid_m_show(struct seq_file *seq, void *v)
{
struct user_namespace *ns = seq->private;
struct uid_gid_extent *extent = v;
struct user_namespace *lower_ns;
projid_t lower;
lower_ns = seq_user_ns(seq);
if ((lower_ns == ns) && lower_ns->parent)
lower_ns = lower_ns->parent;
lower = from_kprojid(lower_ns, KPROJIDT_INIT(extent->lower_first));
seq_printf(seq, "%10u %10u %10u\n",
extent->first,
lower,
extent->count);
return 0;
}
static void *m_start(struct seq_file *seq, loff_t *ppos,
struct uid_gid_map *map)
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
{
loff_t pos = *ppos;
unsigned extents = map->nr_extents;
smp_rmb();
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
if (pos >= extents)
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
return NULL;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
return &map->extent[pos];
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
return &map->forward[pos];
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
}
static void *uid_m_start(struct seq_file *seq, loff_t *ppos)
{
struct user_namespace *ns = seq->private;
return m_start(seq, ppos, &ns->uid_map);
}
static void *gid_m_start(struct seq_file *seq, loff_t *ppos)
{
struct user_namespace *ns = seq->private;
return m_start(seq, ppos, &ns->gid_map);
}
static void *projid_m_start(struct seq_file *seq, loff_t *ppos)
{
struct user_namespace *ns = seq->private;
return m_start(seq, ppos, &ns->projid_map);
}
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
static void *m_next(struct seq_file *seq, void *v, loff_t *pos)
{
(*pos)++;
return seq->op->start(seq, pos);
}
static void m_stop(struct seq_file *seq, void *v)
{
return;
}
const struct seq_operations proc_uid_seq_operations = {
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
.start = uid_m_start,
.stop = m_stop,
.next = m_next,
.show = uid_m_show,
};
const struct seq_operations proc_gid_seq_operations = {
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
.start = gid_m_start,
.stop = m_stop,
.next = m_next,
.show = gid_m_show,
};
const struct seq_operations proc_projid_seq_operations = {
.start = projid_m_start,
.stop = m_stop,
.next = m_next,
.show = projid_m_show,
};
static bool mappings_overlap(struct uid_gid_map *new_map,
struct uid_gid_extent *extent)
{
u32 upper_first, lower_first, upper_last, lower_last;
unsigned idx;
upper_first = extent->first;
lower_first = extent->lower_first;
upper_last = upper_first + extent->count - 1;
lower_last = lower_first + extent->count - 1;
for (idx = 0; idx < new_map->nr_extents; idx++) {
u32 prev_upper_first, prev_lower_first;
u32 prev_upper_last, prev_lower_last;
struct uid_gid_extent *prev;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
prev = &new_map->extent[idx];
else
prev = &new_map->forward[idx];
prev_upper_first = prev->first;
prev_lower_first = prev->lower_first;
prev_upper_last = prev_upper_first + prev->count - 1;
prev_lower_last = prev_lower_first + prev->count - 1;
/* Does the upper range intersect a previous extent? */
if ((prev_upper_first <= upper_last) &&
(prev_upper_last >= upper_first))
return true;
/* Does the lower range intersect a previous extent? */
if ((prev_lower_first <= lower_last) &&
(prev_lower_last >= lower_first))
return true;
}
return false;
}
/*
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
* insert_extent - Safely insert a new idmap extent into struct uid_gid_map.
* Takes care to allocate a 4K block of memory if the number of mappings exceeds
* UID_GID_MAP_MAX_BASE_EXTENTS.
*/
static int insert_extent(struct uid_gid_map *map, struct uid_gid_extent *extent)
{
struct uid_gid_extent *dest;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if (map->nr_extents == UID_GID_MAP_MAX_BASE_EXTENTS) {
struct uid_gid_extent *forward;
/* Allocate memory for 340 mappings. */
treewide: kmalloc() -> kmalloc_array() The kmalloc() function has a 2-factor argument form, kmalloc_array(). This patch replaces cases of: kmalloc(a * b, gfp) with: kmalloc_array(a * b, gfp) as well as handling cases of: kmalloc(a * b * c, gfp) with: kmalloc(array3_size(a, b, c), gfp) as it's slightly less ugly than: kmalloc_array(array_size(a, b), c, gfp) This does, however, attempt to ignore constant size factors like: kmalloc(4 * 1024, gfp) though any constants defined via macros get caught up in the conversion. Any factors with a sizeof() of "unsigned char", "char", and "u8" were dropped, since they're redundant. The tools/ directory was manually excluded, since it has its own implementation of kmalloc(). The Coccinelle script used for this was: // Fix redundant parens around sizeof(). @@ type TYPE; expression THING, E; @@ ( kmalloc( - (sizeof(TYPE)) * E + sizeof(TYPE) * E , ...) | kmalloc( - (sizeof(THING)) * E + sizeof(THING) * E , ...) ) // Drop single-byte sizes and redundant parens. @@ expression COUNT; typedef u8; typedef __u8; @@ ( kmalloc( - sizeof(u8) * (COUNT) + COUNT , ...) | kmalloc( - sizeof(__u8) * (COUNT) + COUNT , ...) | kmalloc( - sizeof(char) * (COUNT) + COUNT , ...) | kmalloc( - sizeof(unsigned char) * (COUNT) + COUNT , ...) | kmalloc( - sizeof(u8) * COUNT + COUNT , ...) | kmalloc( - sizeof(__u8) * COUNT + COUNT , ...) | kmalloc( - sizeof(char) * COUNT + COUNT , ...) | kmalloc( - sizeof(unsigned char) * COUNT + COUNT , ...) ) // 2-factor product with sizeof(type/expression) and identifier or constant. @@ type TYPE; expression THING; identifier COUNT_ID; constant COUNT_CONST; @@ ( - kmalloc + kmalloc_array ( - sizeof(TYPE) * (COUNT_ID) + COUNT_ID, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * COUNT_ID + COUNT_ID, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * (COUNT_CONST) + COUNT_CONST, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * COUNT_CONST + COUNT_CONST, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * (COUNT_ID) + COUNT_ID, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * COUNT_ID + COUNT_ID, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * (COUNT_CONST) + COUNT_CONST, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * COUNT_CONST + COUNT_CONST, sizeof(THING) , ...) ) // 2-factor product, only identifiers. @@ identifier SIZE, COUNT; @@ - kmalloc + kmalloc_array ( - SIZE * COUNT + COUNT, SIZE , ...) // 3-factor product with 1 sizeof(type) or sizeof(expression), with // redundant parens removed. @@ expression THING; identifier STRIDE, COUNT; type TYPE; @@ ( kmalloc( - sizeof(TYPE) * (COUNT) * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kmalloc( - sizeof(TYPE) * (COUNT) * STRIDE + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kmalloc( - sizeof(TYPE) * COUNT * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kmalloc( - sizeof(TYPE) * COUNT * STRIDE + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kmalloc( - sizeof(THING) * (COUNT) * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kmalloc( - sizeof(THING) * (COUNT) * STRIDE + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kmalloc( - sizeof(THING) * COUNT * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kmalloc( - sizeof(THING) * COUNT * STRIDE + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) ) // 3-factor product with 2 sizeof(variable), with redundant parens removed. @@ expression THING1, THING2; identifier COUNT; type TYPE1, TYPE2; @@ ( kmalloc( - sizeof(TYPE1) * sizeof(TYPE2) * COUNT + array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2)) , ...) | kmalloc( - sizeof(TYPE1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2)) , ...) | kmalloc( - sizeof(THING1) * sizeof(THING2) * COUNT + array3_size(COUNT, sizeof(THING1), sizeof(THING2)) , ...) | kmalloc( - sizeof(THING1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(THING1), sizeof(THING2)) , ...) | kmalloc( - sizeof(TYPE1) * sizeof(THING2) * COUNT + array3_size(COUNT, sizeof(TYPE1), sizeof(THING2)) , ...) | kmalloc( - sizeof(TYPE1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(TYPE1), sizeof(THING2)) , ...) ) // 3-factor product, only identifiers, with redundant parens removed. @@ identifier STRIDE, SIZE, COUNT; @@ ( kmalloc( - (COUNT) * STRIDE * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - COUNT * (STRIDE) * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - COUNT * STRIDE * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - (COUNT) * (STRIDE) * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - COUNT * (STRIDE) * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - (COUNT) * STRIDE * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - (COUNT) * (STRIDE) * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - COUNT * STRIDE * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) ) // Any remaining multi-factor products, first at least 3-factor products, // when they're not all constants... @@ expression E1, E2, E3; constant C1, C2, C3; @@ ( kmalloc(C1 * C2 * C3, ...) | kmalloc( - (E1) * E2 * E3 + array3_size(E1, E2, E3) , ...) | kmalloc( - (E1) * (E2) * E3 + array3_size(E1, E2, E3) , ...) | kmalloc( - (E1) * (E2) * (E3) + array3_size(E1, E2, E3) , ...) | kmalloc( - E1 * E2 * E3 + array3_size(E1, E2, E3) , ...) ) // And then all remaining 2 factors products when they're not all constants, // keeping sizeof() as the second factor argument. @@ expression THING, E1, E2; type TYPE; constant C1, C2, C3; @@ ( kmalloc(sizeof(THING) * C2, ...) | kmalloc(sizeof(TYPE) * C2, ...) | kmalloc(C1 * C2 * C3, ...) | kmalloc(C1 * C2, ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * (E2) + E2, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * E2 + E2, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * (E2) + E2, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * E2 + E2, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - (E1) * E2 + E1, E2 , ...) | - kmalloc + kmalloc_array ( - (E1) * (E2) + E1, E2 , ...) | - kmalloc + kmalloc_array ( - E1 * E2 + E1, E2 , ...) ) Signed-off-by: Kees Cook <keescook@chromium.org>
2018-06-12 20:55:00 +00:00
forward = kmalloc_array(UID_GID_MAP_MAX_EXTENTS,
sizeof(struct uid_gid_extent),
GFP_KERNEL);
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if (!forward)
return -ENOMEM;
/* Copy over memory. Only set up memory for the forward pointer.
* Defer the memory setup for the reverse pointer.
*/
memcpy(forward, map->extent,
map->nr_extents * sizeof(map->extent[0]));
map->forward = forward;
map->reverse = NULL;
}
if (map->nr_extents < UID_GID_MAP_MAX_BASE_EXTENTS)
dest = &map->extent[map->nr_extents];
else
dest = &map->forward[map->nr_extents];
*dest = *extent;
map->nr_extents++;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
return 0;
}
/* cmp function to sort() forward mappings */
static int cmp_extents_forward(const void *a, const void *b)
{
const struct uid_gid_extent *e1 = a;
const struct uid_gid_extent *e2 = b;
if (e1->first < e2->first)
return -1;
if (e1->first > e2->first)
return 1;
return 0;
}
/* cmp function to sort() reverse mappings */
static int cmp_extents_reverse(const void *a, const void *b)
{
const struct uid_gid_extent *e1 = a;
const struct uid_gid_extent *e2 = b;
if (e1->lower_first < e2->lower_first)
return -1;
if (e1->lower_first > e2->lower_first)
return 1;
return 0;
}
/*
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
* sort_idmaps - Sorts an array of idmap entries.
* Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
*/
static int sort_idmaps(struct uid_gid_map *map)
{
if (map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
return 0;
/* Sort forward array. */
sort(map->forward, map->nr_extents, sizeof(struct uid_gid_extent),
cmp_extents_forward, NULL);
/* Only copy the memory from forward we actually need. */
map->reverse = kmemdup(map->forward,
map->nr_extents * sizeof(struct uid_gid_extent),
GFP_KERNEL);
if (!map->reverse)
return -ENOMEM;
/* Sort reverse array. */
sort(map->reverse, map->nr_extents, sizeof(struct uid_gid_extent),
cmp_extents_reverse, NULL);
return 0;
}
capabilities: require CAP_SETFCAP to map uid 0 cap_setfcap is required to create file capabilities. Since commit 8db6c34f1dbc ("Introduce v3 namespaced file capabilities"), a process running as uid 0 but without cap_setfcap is able to work around this as follows: unshare a new user namespace which maps parent uid 0 into the child namespace. While this task will not have new capabilities against the parent namespace, there is a loophole due to the way namespaced file capabilities are represented as xattrs. File capabilities valid in userns 1 are distinguished from file capabilities valid in userns 2 by the kuid which underlies uid 0. Therefore the restricted root process can unshare a new self-mapping namespace, add a namespaced file capability onto a file, then use that file capability in the parent namespace. To prevent that, do not allow mapping parent uid 0 if the process which opened the uid_map file does not have CAP_SETFCAP, which is the capability for setting file capabilities. As a further wrinkle: a task can unshare its user namespace, then open its uid_map file itself, and map (only) its own uid. In this case we do not have the credential from before unshare, which was potentially more restricted. So, when creating a user namespace, we record whether the creator had CAP_SETFCAP. Then we can use that during map_write(). With this patch: 1. Unprivileged user can still unshare -Ur ubuntu@caps:~$ unshare -Ur root@caps:~# logout 2. Root user can still unshare -Ur ubuntu@caps:~$ sudo bash root@caps:/home/ubuntu# unshare -Ur root@caps:/home/ubuntu# logout 3. Root user without CAP_SETFCAP cannot unshare -Ur: root@caps:/home/ubuntu# /sbin/capsh --drop=cap_setfcap -- root@caps:/home/ubuntu# /sbin/setcap cap_setfcap=p /sbin/setcap unable to set CAP_SETFCAP effective capability: Operation not permitted root@caps:/home/ubuntu# unshare -Ur unshare: write failed /proc/self/uid_map: Operation not permitted Note: an alternative solution would be to allow uid 0 mappings by processes without CAP_SETFCAP, but to prevent such a namespace from writing any file capabilities. This approach can be seen at [1]. Background history: commit 95ebabde382 ("capabilities: Don't allow writing ambiguous v3 file capabilities") tried to fix the issue by preventing v3 fscaps to be written to disk when the root uid would map to the same uid in nested user namespaces. This led to regressions for various workloads. For example, see [2]. Ultimately this is a valid use-case we have to support meaning we had to revert this change in 3b0c2d3eaa83 ("Revert 95ebabde382c ("capabilities: Don't allow writing ambiguous v3 file capabilities")"). Link: https://git.kernel.org/pub/scm/linux/kernel/git/sergeh/linux.git/log/?h=2021-04-15/setfcap-nsfscaps-v4 [1] Link: https://github.com/containers/buildah/issues/3071 [2] Signed-off-by: Serge Hallyn <serge@hallyn.com> Reviewed-by: Andrew G. Morgan <morgan@kernel.org> Tested-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com> Tested-by: Giuseppe Scrivano <gscrivan@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-04-20 13:43:34 +00:00
/**
* verify_root_map() - check the uid 0 mapping
* @file: idmapping file
* @map_ns: user namespace of the target process
* @new_map: requested idmap
*
* If a process requests mapping parent uid 0 into the new ns, verify that the
* process writing the map had the CAP_SETFCAP capability as the target process
* will be able to write fscaps that are valid in ancestor user namespaces.
*
* Return: true if the mapping is allowed, false if not.
*/
static bool verify_root_map(const struct file *file,
struct user_namespace *map_ns,
struct uid_gid_map *new_map)
{
int idx;
const struct user_namespace *file_ns = file->f_cred->user_ns;
struct uid_gid_extent *extent0 = NULL;
for (idx = 0; idx < new_map->nr_extents; idx++) {
if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
extent0 = &new_map->extent[idx];
else
extent0 = &new_map->forward[idx];
if (extent0->lower_first == 0)
break;
extent0 = NULL;
}
if (!extent0)
return true;
if (map_ns == file_ns) {
/* The process unshared its ns and is writing to its own
* /proc/self/uid_map. User already has full capabilites in
* the new namespace. Verify that the parent had CAP_SETFCAP
* when it unshared.
* */
if (!file_ns->parent_could_setfcap)
return false;
} else {
/* Process p1 is writing to uid_map of p2, who is in a child
* user namespace to p1's. Verify that the opener of the map
* file has CAP_SETFCAP against the parent of the new map
* namespace */
if (!file_ns_capable(file, map_ns->parent, CAP_SETFCAP))
return false;
}
return true;
}
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
static ssize_t map_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos,
int cap_setid,
struct uid_gid_map *map,
struct uid_gid_map *parent_map)
{
struct seq_file *seq = file->private_data;
capabilities: require CAP_SETFCAP to map uid 0 cap_setfcap is required to create file capabilities. Since commit 8db6c34f1dbc ("Introduce v3 namespaced file capabilities"), a process running as uid 0 but without cap_setfcap is able to work around this as follows: unshare a new user namespace which maps parent uid 0 into the child namespace. While this task will not have new capabilities against the parent namespace, there is a loophole due to the way namespaced file capabilities are represented as xattrs. File capabilities valid in userns 1 are distinguished from file capabilities valid in userns 2 by the kuid which underlies uid 0. Therefore the restricted root process can unshare a new self-mapping namespace, add a namespaced file capability onto a file, then use that file capability in the parent namespace. To prevent that, do not allow mapping parent uid 0 if the process which opened the uid_map file does not have CAP_SETFCAP, which is the capability for setting file capabilities. As a further wrinkle: a task can unshare its user namespace, then open its uid_map file itself, and map (only) its own uid. In this case we do not have the credential from before unshare, which was potentially more restricted. So, when creating a user namespace, we record whether the creator had CAP_SETFCAP. Then we can use that during map_write(). With this patch: 1. Unprivileged user can still unshare -Ur ubuntu@caps:~$ unshare -Ur root@caps:~# logout 2. Root user can still unshare -Ur ubuntu@caps:~$ sudo bash root@caps:/home/ubuntu# unshare -Ur root@caps:/home/ubuntu# logout 3. Root user without CAP_SETFCAP cannot unshare -Ur: root@caps:/home/ubuntu# /sbin/capsh --drop=cap_setfcap -- root@caps:/home/ubuntu# /sbin/setcap cap_setfcap=p /sbin/setcap unable to set CAP_SETFCAP effective capability: Operation not permitted root@caps:/home/ubuntu# unshare -Ur unshare: write failed /proc/self/uid_map: Operation not permitted Note: an alternative solution would be to allow uid 0 mappings by processes without CAP_SETFCAP, but to prevent such a namespace from writing any file capabilities. This approach can be seen at [1]. Background history: commit 95ebabde382 ("capabilities: Don't allow writing ambiguous v3 file capabilities") tried to fix the issue by preventing v3 fscaps to be written to disk when the root uid would map to the same uid in nested user namespaces. This led to regressions for various workloads. For example, see [2]. Ultimately this is a valid use-case we have to support meaning we had to revert this change in 3b0c2d3eaa83 ("Revert 95ebabde382c ("capabilities: Don't allow writing ambiguous v3 file capabilities")"). Link: https://git.kernel.org/pub/scm/linux/kernel/git/sergeh/linux.git/log/?h=2021-04-15/setfcap-nsfscaps-v4 [1] Link: https://github.com/containers/buildah/issues/3071 [2] Signed-off-by: Serge Hallyn <serge@hallyn.com> Reviewed-by: Andrew G. Morgan <morgan@kernel.org> Tested-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com> Tested-by: Giuseppe Scrivano <gscrivan@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-04-20 13:43:34 +00:00
struct user_namespace *map_ns = seq->private;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
struct uid_gid_map new_map;
unsigned idx;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
struct uid_gid_extent extent;
char *kbuf, *pos, *next_line;
ssize_t ret;
/* Only allow < page size writes at the beginning of the file */
if ((*ppos != 0) || (count >= PAGE_SIZE))
return -EINVAL;
/* Slurp in the user data */
kbuf = memdup_user_nul(buf, count);
if (IS_ERR(kbuf))
return PTR_ERR(kbuf);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
/*
* The userns_state_mutex serializes all writes to any given map.
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
*
* Any map is only ever written once.
*
* An id map fits within 1 cache line on most architectures.
*
* On read nothing needs to be done unless you are on an
* architecture with a crazy cache coherency model like alpha.
*
* There is a one time data dependency between reading the
* count of the extents and the values of the extents. The
* desired behavior is to see the values of the extents that
* were written before the count of the extents.
*
* To achieve this smp_wmb() is used on guarantee the write
* order and smp_rmb() is guaranteed that we don't have crazy
* architectures returning stale data.
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
*/
mutex_lock(&userns_state_mutex);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
memset(&new_map, 0, sizeof(struct uid_gid_map));
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
ret = -EPERM;
/* Only allow one successful write to the map */
if (map->nr_extents != 0)
goto out;
/*
* Adjusting namespace settings requires capabilities on the target.
*/
capabilities: require CAP_SETFCAP to map uid 0 cap_setfcap is required to create file capabilities. Since commit 8db6c34f1dbc ("Introduce v3 namespaced file capabilities"), a process running as uid 0 but without cap_setfcap is able to work around this as follows: unshare a new user namespace which maps parent uid 0 into the child namespace. While this task will not have new capabilities against the parent namespace, there is a loophole due to the way namespaced file capabilities are represented as xattrs. File capabilities valid in userns 1 are distinguished from file capabilities valid in userns 2 by the kuid which underlies uid 0. Therefore the restricted root process can unshare a new self-mapping namespace, add a namespaced file capability onto a file, then use that file capability in the parent namespace. To prevent that, do not allow mapping parent uid 0 if the process which opened the uid_map file does not have CAP_SETFCAP, which is the capability for setting file capabilities. As a further wrinkle: a task can unshare its user namespace, then open its uid_map file itself, and map (only) its own uid. In this case we do not have the credential from before unshare, which was potentially more restricted. So, when creating a user namespace, we record whether the creator had CAP_SETFCAP. Then we can use that during map_write(). With this patch: 1. Unprivileged user can still unshare -Ur ubuntu@caps:~$ unshare -Ur root@caps:~# logout 2. Root user can still unshare -Ur ubuntu@caps:~$ sudo bash root@caps:/home/ubuntu# unshare -Ur root@caps:/home/ubuntu# logout 3. Root user without CAP_SETFCAP cannot unshare -Ur: root@caps:/home/ubuntu# /sbin/capsh --drop=cap_setfcap -- root@caps:/home/ubuntu# /sbin/setcap cap_setfcap=p /sbin/setcap unable to set CAP_SETFCAP effective capability: Operation not permitted root@caps:/home/ubuntu# unshare -Ur unshare: write failed /proc/self/uid_map: Operation not permitted Note: an alternative solution would be to allow uid 0 mappings by processes without CAP_SETFCAP, but to prevent such a namespace from writing any file capabilities. This approach can be seen at [1]. Background history: commit 95ebabde382 ("capabilities: Don't allow writing ambiguous v3 file capabilities") tried to fix the issue by preventing v3 fscaps to be written to disk when the root uid would map to the same uid in nested user namespaces. This led to regressions for various workloads. For example, see [2]. Ultimately this is a valid use-case we have to support meaning we had to revert this change in 3b0c2d3eaa83 ("Revert 95ebabde382c ("capabilities: Don't allow writing ambiguous v3 file capabilities")"). Link: https://git.kernel.org/pub/scm/linux/kernel/git/sergeh/linux.git/log/?h=2021-04-15/setfcap-nsfscaps-v4 [1] Link: https://github.com/containers/buildah/issues/3071 [2] Signed-off-by: Serge Hallyn <serge@hallyn.com> Reviewed-by: Andrew G. Morgan <morgan@kernel.org> Tested-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com> Tested-by: Giuseppe Scrivano <gscrivan@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-04-20 13:43:34 +00:00
if (cap_valid(cap_setid) && !file_ns_capable(file, map_ns, CAP_SYS_ADMIN))
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
goto out;
/* Parse the user data */
ret = -EINVAL;
pos = kbuf;
for (; pos; pos = next_line) {
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
/* Find the end of line and ensure I don't look past it */
next_line = strchr(pos, '\n');
if (next_line) {
*next_line = '\0';
next_line++;
if (*next_line == '\0')
next_line = NULL;
}
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
pos = skip_spaces(pos);
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
extent.first = simple_strtoul(pos, &pos, 10);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
if (!isspace(*pos))
goto out;
pos = skip_spaces(pos);
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
extent.lower_first = simple_strtoul(pos, &pos, 10);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
if (!isspace(*pos))
goto out;
pos = skip_spaces(pos);
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
extent.count = simple_strtoul(pos, &pos, 10);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
if (*pos && !isspace(*pos))
goto out;
/* Verify there is not trailing junk on the line */
pos = skip_spaces(pos);
if (*pos != '\0')
goto out;
/* Verify we have been given valid starting values */
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if ((extent.first == (u32) -1) ||
(extent.lower_first == (u32) -1))
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
goto out;
/* Verify count is not zero and does not cause the
* extent to wrap
*/
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if ((extent.first + extent.count) <= extent.first)
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
goto out;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if ((extent.lower_first + extent.count) <=
extent.lower_first)
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
goto out;
/* Do the ranges in extent overlap any previous extents? */
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if (mappings_overlap(&new_map, &extent))
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
goto out;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if ((new_map.nr_extents + 1) == UID_GID_MAP_MAX_EXTENTS &&
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
(next_line != NULL))
goto out;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
ret = insert_extent(&new_map, &extent);
if (ret < 0)
goto out;
ret = -EINVAL;
}
/* Be very certain the new map actually exists */
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
if (new_map.nr_extents == 0)
goto out;
ret = -EPERM;
/* Validate the user is allowed to use user id's mapped to. */
capabilities: require CAP_SETFCAP to map uid 0 cap_setfcap is required to create file capabilities. Since commit 8db6c34f1dbc ("Introduce v3 namespaced file capabilities"), a process running as uid 0 but without cap_setfcap is able to work around this as follows: unshare a new user namespace which maps parent uid 0 into the child namespace. While this task will not have new capabilities against the parent namespace, there is a loophole due to the way namespaced file capabilities are represented as xattrs. File capabilities valid in userns 1 are distinguished from file capabilities valid in userns 2 by the kuid which underlies uid 0. Therefore the restricted root process can unshare a new self-mapping namespace, add a namespaced file capability onto a file, then use that file capability in the parent namespace. To prevent that, do not allow mapping parent uid 0 if the process which opened the uid_map file does not have CAP_SETFCAP, which is the capability for setting file capabilities. As a further wrinkle: a task can unshare its user namespace, then open its uid_map file itself, and map (only) its own uid. In this case we do not have the credential from before unshare, which was potentially more restricted. So, when creating a user namespace, we record whether the creator had CAP_SETFCAP. Then we can use that during map_write(). With this patch: 1. Unprivileged user can still unshare -Ur ubuntu@caps:~$ unshare -Ur root@caps:~# logout 2. Root user can still unshare -Ur ubuntu@caps:~$ sudo bash root@caps:/home/ubuntu# unshare -Ur root@caps:/home/ubuntu# logout 3. Root user without CAP_SETFCAP cannot unshare -Ur: root@caps:/home/ubuntu# /sbin/capsh --drop=cap_setfcap -- root@caps:/home/ubuntu# /sbin/setcap cap_setfcap=p /sbin/setcap unable to set CAP_SETFCAP effective capability: Operation not permitted root@caps:/home/ubuntu# unshare -Ur unshare: write failed /proc/self/uid_map: Operation not permitted Note: an alternative solution would be to allow uid 0 mappings by processes without CAP_SETFCAP, but to prevent such a namespace from writing any file capabilities. This approach can be seen at [1]. Background history: commit 95ebabde382 ("capabilities: Don't allow writing ambiguous v3 file capabilities") tried to fix the issue by preventing v3 fscaps to be written to disk when the root uid would map to the same uid in nested user namespaces. This led to regressions for various workloads. For example, see [2]. Ultimately this is a valid use-case we have to support meaning we had to revert this change in 3b0c2d3eaa83 ("Revert 95ebabde382c ("capabilities: Don't allow writing ambiguous v3 file capabilities")"). Link: https://git.kernel.org/pub/scm/linux/kernel/git/sergeh/linux.git/log/?h=2021-04-15/setfcap-nsfscaps-v4 [1] Link: https://github.com/containers/buildah/issues/3071 [2] Signed-off-by: Serge Hallyn <serge@hallyn.com> Reviewed-by: Andrew G. Morgan <morgan@kernel.org> Tested-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com> Tested-by: Giuseppe Scrivano <gscrivan@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-04-20 13:43:34 +00:00
if (!new_idmap_permitted(file, map_ns, cap_setid, &new_map))
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
goto out;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
ret = -EPERM;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
/* Map the lower ids from the parent user namespace to the
* kernel global id space.
*/
for (idx = 0; idx < new_map.nr_extents; idx++) {
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
struct uid_gid_extent *e;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
u32 lower_first;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
e = &new_map.extent[idx];
else
e = &new_map.forward[idx];
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
lower_first = map_id_range_down(parent_map,
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
e->lower_first,
e->count);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
/* Fail if we can not map the specified extent to
* the kernel global id space.
*/
if (lower_first == (u32) -1)
goto out;
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
e->lower_first = lower_first;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
}
/*
* If we want to use binary search for lookup, this clones the extent
* array and sorts both copies.
*/
ret = sort_idmaps(&new_map);
if (ret < 0)
goto out;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
/* Install the map */
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) {
memcpy(map->extent, new_map.extent,
new_map.nr_extents * sizeof(new_map.extent[0]));
} else {
map->forward = new_map.forward;
map->reverse = new_map.reverse;
}
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
smp_wmb();
map->nr_extents = new_map.nr_extents;
*ppos = count;
ret = count;
out:
userns: bump idmap limits to 340 There are quite some use cases where users run into the current limit for {g,u}id mappings. Consider a user requesting us to map everything but 999, and 1001 for a given range of 1000000000 with a sub{g,u}id layout of: some-user:100000:1000000000 some-user:999:1 some-user:1000:1 some-user:1001:1 some-user:1002:1 This translates to: MAPPING-TYPE | CONTAINER | HOST | RANGE | -------------|-----------|---------|-----------| uid | 999 | 999 | 1 | uid | 1001 | 1001 | 1 | uid | 0 | 1000000 | 999 | uid | 1000 | 1001000 | 1 | uid | 1002 | 1001002 | 999998998 | ------------------------------------------------ gid | 999 | 999 | 1 | gid | 1001 | 1001 | 1 | gid | 0 | 1000000 | 999 | gid | 1000 | 1001000 | 1 | gid | 1002 | 1001002 | 999998998 | which is already the current limit. As discussed at LPC simply bumping the number of limits is not going to work since this would mean that struct uid_gid_map won't fit into a single cache-line anymore thereby regressing performance for the base-cases. The same problem seems to arise when using a single pointer. So the idea is to use struct uid_gid_extent { u32 first; u32 lower_first; u32 count; }; struct uid_gid_map { /* 64 bytes -- 1 cache line */ u32 nr_extents; union { struct uid_gid_extent extent[UID_GID_MAP_MAX_BASE_EXTENTS]; struct { struct uid_gid_extent *forward; struct uid_gid_extent *reverse; }; }; }; For the base cases we will only use the struct uid_gid_extent extent member. If we go over UID_GID_MAP_MAX_BASE_EXTENTS mappings we perform a single 4k kmalloc() which means we can have a maximum of 340 mappings (340 * size(struct uid_gid_extent) = 4080). For the latter case we use two pointers "forward" and "reverse". The forward pointer points to an array sorted by "first" and the reverse pointer points to an array sorted by "lower_first". We can then perform binary search on those arrays. Performance Testing: When Eric introduced the extent-based struct uid_gid_map approach he measured the performanc impact of his idmap changes: > My benchmark consisted of going to single user mode where nothing else was > running. On an ext4 filesystem opening 1,000,000 files and looping through all > of the files 1000 times and calling fstat on the individuals files. This was > to ensure I was benchmarking stat times where the inodes were in the kernels > cache, but the inode values were not in the processors cache. My results: > v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) > v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) > v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) I used an identical approach on my laptop. Here's a thorough description of what I did. I built a 4.14.0-rc4 mainline kernel with my new idmap patches applied. I booted into single user mode and used an ext4 filesystem to open/create 1,000,000 files. Then I looped through all of the files calling fstat() on each of them 1000 times and calculated the mean fstat() time for a single file. (The test program can be found below.) Here are the results. For fun, I compared the first version of my patch which scaled linearly with the new version of the patch: | # MAPPINGS | PATCH-V1 | PATCH-NEW | |--------------|------------|-----------| | 0 mappings | 158 ns | 158 ns | | 1 mappings | 164 ns | 157 ns | | 2 mappings | 170 ns | 158 ns | | 3 mappings | 175 ns | 161 ns | | 5 mappings | 187 ns | 165 ns | | 10 mappings | 218 ns | 199 ns | | 50 mappings | 528 ns | 218 ns | | 100 mappings | 980 ns | 229 ns | | 200 mappings | 1880 ns | 239 ns | | 300 mappings | 2760 ns | 240 ns | | 340 mappings | not tested | 248 ns | Here's the test program I used. I asked Eric what he did and this is a more "advanced" implementation of the idea. It's pretty straight-forward: #define __GNU_SOURCE #define __STDC_FORMAT_MACROS #include <errno.h> #include <dirent.h> #include <fcntl.h> #include <inttypes.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> int main(int argc, char *argv[]) { int ret; size_t i, k; int fd[1000000]; int times[1000]; char pathname[4096]; struct stat st; struct timeval t1, t2; uint64_t time_in_mcs; uint64_t sum = 0; if (argc != 2) { fprintf(stderr, "Please specify a directory where to create " "the test files\n"); exit(EXIT_FAILURE); } for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { sprintf(pathname, "%s/idmap_test_%zu", argv[1], i); fd[i]= open(pathname, O_RDWR | O_CREAT, S_IXUSR | S_IXGRP | S_IXOTH); if (fd[i] < 0) { ssize_t j; for (j = i; j >= 0; j--) close(fd[j]); exit(EXIT_FAILURE); } } for (k = 0; k < 1000; k++) { ret = gettimeofday(&t1, NULL); if (ret < 0) goto close_all; for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) { ret = fstat(fd[i], &st); if (ret < 0) goto close_all; } ret = gettimeofday(&t2, NULL); if (ret < 0) goto close_all; time_in_mcs = (1000000 * t2.tv_sec + t2.tv_usec) - (1000000 * t1.tv_sec + t1.tv_usec); printf("Total time in micro seconds: %" PRIu64 "\n", time_in_mcs); printf("Total time in nanoseconds: %" PRIu64 "\n", time_in_mcs * 1000); printf("Time per file in nanoseconds: %" PRIu64 "\n", (time_in_mcs * 1000) / 1000000); times[k] = (time_in_mcs * 1000) / 1000000; } close_all: for (i = 0; i < sizeof(fd) / sizeof(fd[0]); i++) close(fd[i]); if (ret < 0) exit(EXIT_FAILURE); for (k = 0; k < 1000; k++) { sum += times[k]; } printf("Mean time per file in nanoseconds: %" PRIu64 "\n", sum / 1000); exit(EXIT_SUCCESS);; } Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> CC: Serge Hallyn <serge@hallyn.com> CC: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-10-24 22:04:41 +00:00
if (ret < 0 && new_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
kfree(new_map.forward);
kfree(new_map.reverse);
map->forward = NULL;
map->reverse = NULL;
map->nr_extents = 0;
}
mutex_unlock(&userns_state_mutex);
kfree(kbuf);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
return ret;
}
ssize_t proc_uid_map_write(struct file *file, const char __user *buf,
size_t size, loff_t *ppos)
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
{
struct seq_file *seq = file->private_data;
struct user_namespace *ns = seq->private;
struct user_namespace *seq_ns = seq_user_ns(seq);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
if (!ns->parent)
return -EPERM;
if ((seq_ns != ns) && (seq_ns != ns->parent))
return -EPERM;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
return map_write(file, buf, size, ppos, CAP_SETUID,
&ns->uid_map, &ns->parent->uid_map);
}
ssize_t proc_gid_map_write(struct file *file, const char __user *buf,
size_t size, loff_t *ppos)
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
{
struct seq_file *seq = file->private_data;
struct user_namespace *ns = seq->private;
struct user_namespace *seq_ns = seq_user_ns(seq);
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
if (!ns->parent)
return -EPERM;
if ((seq_ns != ns) && (seq_ns != ns->parent))
return -EPERM;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
return map_write(file, buf, size, ppos, CAP_SETGID,
&ns->gid_map, &ns->parent->gid_map);
}
ssize_t proc_projid_map_write(struct file *file, const char __user *buf,
size_t size, loff_t *ppos)
{
struct seq_file *seq = file->private_data;
struct user_namespace *ns = seq->private;
struct user_namespace *seq_ns = seq_user_ns(seq);
if (!ns->parent)
return -EPERM;
if ((seq_ns != ns) && (seq_ns != ns->parent))
return -EPERM;
/* Anyone can set any valid project id no capability needed */
return map_write(file, buf, size, ppos, -1,
&ns->projid_map, &ns->parent->projid_map);
}
static bool new_idmap_permitted(const struct file *file,
struct user_namespace *ns, int cap_setid,
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
struct uid_gid_map *new_map)
{
const struct cred *cred = file->f_cred;
capabilities: require CAP_SETFCAP to map uid 0 cap_setfcap is required to create file capabilities. Since commit 8db6c34f1dbc ("Introduce v3 namespaced file capabilities"), a process running as uid 0 but without cap_setfcap is able to work around this as follows: unshare a new user namespace which maps parent uid 0 into the child namespace. While this task will not have new capabilities against the parent namespace, there is a loophole due to the way namespaced file capabilities are represented as xattrs. File capabilities valid in userns 1 are distinguished from file capabilities valid in userns 2 by the kuid which underlies uid 0. Therefore the restricted root process can unshare a new self-mapping namespace, add a namespaced file capability onto a file, then use that file capability in the parent namespace. To prevent that, do not allow mapping parent uid 0 if the process which opened the uid_map file does not have CAP_SETFCAP, which is the capability for setting file capabilities. As a further wrinkle: a task can unshare its user namespace, then open its uid_map file itself, and map (only) its own uid. In this case we do not have the credential from before unshare, which was potentially more restricted. So, when creating a user namespace, we record whether the creator had CAP_SETFCAP. Then we can use that during map_write(). With this patch: 1. Unprivileged user can still unshare -Ur ubuntu@caps:~$ unshare -Ur root@caps:~# logout 2. Root user can still unshare -Ur ubuntu@caps:~$ sudo bash root@caps:/home/ubuntu# unshare -Ur root@caps:/home/ubuntu# logout 3. Root user without CAP_SETFCAP cannot unshare -Ur: root@caps:/home/ubuntu# /sbin/capsh --drop=cap_setfcap -- root@caps:/home/ubuntu# /sbin/setcap cap_setfcap=p /sbin/setcap unable to set CAP_SETFCAP effective capability: Operation not permitted root@caps:/home/ubuntu# unshare -Ur unshare: write failed /proc/self/uid_map: Operation not permitted Note: an alternative solution would be to allow uid 0 mappings by processes without CAP_SETFCAP, but to prevent such a namespace from writing any file capabilities. This approach can be seen at [1]. Background history: commit 95ebabde382 ("capabilities: Don't allow writing ambiguous v3 file capabilities") tried to fix the issue by preventing v3 fscaps to be written to disk when the root uid would map to the same uid in nested user namespaces. This led to regressions for various workloads. For example, see [2]. Ultimately this is a valid use-case we have to support meaning we had to revert this change in 3b0c2d3eaa83 ("Revert 95ebabde382c ("capabilities: Don't allow writing ambiguous v3 file capabilities")"). Link: https://git.kernel.org/pub/scm/linux/kernel/git/sergeh/linux.git/log/?h=2021-04-15/setfcap-nsfscaps-v4 [1] Link: https://github.com/containers/buildah/issues/3071 [2] Signed-off-by: Serge Hallyn <serge@hallyn.com> Reviewed-by: Andrew G. Morgan <morgan@kernel.org> Tested-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com> Tested-by: Giuseppe Scrivano <gscrivan@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-04-20 13:43:34 +00:00
if (cap_setid == CAP_SETUID && !verify_root_map(file, ns, new_map))
return false;
/* Don't allow mappings that would allow anything that wouldn't
* be allowed without the establishment of unprivileged mappings.
*/
if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1) &&
uid_eq(ns->owner, cred->euid)) {
u32 id = new_map->extent[0].lower_first;
if (cap_setid == CAP_SETUID) {
kuid_t uid = make_kuid(ns->parent, id);
if (uid_eq(uid, cred->euid))
return true;
} else if (cap_setid == CAP_SETGID) {
kgid_t gid = make_kgid(ns->parent, id);
if (!(ns->flags & USERNS_SETGROUPS_ALLOWED) &&
gid_eq(gid, cred->egid))
return true;
}
}
/* Allow anyone to set a mapping that doesn't require privilege */
if (!cap_valid(cap_setid))
return true;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
/* Allow the specified ids if we have the appropriate capability
* (CAP_SETUID or CAP_SETGID) over the parent user namespace.
* And the opener of the id file also has the appropriate capability.
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
*/
if (ns_capable(ns->parent, cap_setid) &&
file_ns_capable(file, ns->parent, cap_setid))
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
return true;
userns: Rework the user_namespace adding uid/gid mapping support - Convert the old uid mapping functions into compatibility wrappers - Add a uid/gid mapping layer from user space uid and gids to kernel internal uids and gids that is extent based for simplicty and speed. * Working with number space after mapping uids/gids into their kernel internal version adds only mapping complexity over what we have today, leaving the kernel code easy to understand and test. - Add proc files /proc/self/uid_map /proc/self/gid_map These files display the mapping and allow a mapping to be added if a mapping does not exist. - Allow entering the user namespace without a uid or gid mapping. Since we are starting with an existing user our uids and gids still have global mappings so are still valid and useful they just don't have local mappings. The requirement for things to work are global uid and gid so it is odd but perfectly fine not to have a local uid and gid mapping. Not requiring global uid and gid mappings greatly simplifies the logic of setting up the uid and gid mappings by allowing the mappings to be set after the namespace is created which makes the slight weirdness worth it. - Make the mappings in the initial user namespace to the global uid/gid space explicit. Today it is an identity mapping but in the future we may want to twist this for debugging, similar to what we do with jiffies. - Document the memory ordering requirements of setting the uid and gid mappings. We only allow the mappings to be set once and there are no pointers involved so the requirments are trivial but a little atypical. Performance: In this scheme for the permission checks the performance is expected to stay the same as the actuall machine instructions should remain the same. The worst case I could think of is ls -l on a large directory where all of the stat results need to be translated with from kuids and kgids to uids and gids. So I benchmarked that case on my laptop with a dual core hyperthread Intel i5-2520M cpu with 3M of cpu cache. My benchmark consisted of going to single user mode where nothing else was running. On an ext4 filesystem opening 1,000,000 files and looping through all of the files 1000 times and calling fstat on the individuals files. This was to ensure I was benchmarking stat times where the inodes were in the kernels cache, but the inode values were not in the processors cache. My results: v3.4-rc1: ~= 156ns (unmodified v3.4-rc1 with user namespace support disabled) v3.4-rc1-userns-: ~= 155ns (v3.4-rc1 with my user namespace patches and user namespace support disabled) v3.4-rc1-userns+: ~= 164ns (v3.4-rc1 with my user namespace patches and user namespace support enabled) All of the configurations ran in roughly 120ns when I performed tests that ran in the cpu cache. So in summary the performance impact is: 1ns improvement in the worst case with user namespace support compiled out. 8ns aka 5% slowdown in the worst case with user namespace support compiled in. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2011-11-17 08:11:58 +00:00
return false;
}
2014-12-02 18:27:26 +00:00
int proc_setgroups_show(struct seq_file *seq, void *v)
{
struct user_namespace *ns = seq->private;
locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE() Please do not apply this to mainline directly, instead please re-run the coccinelle script shown below and apply its output. For several reasons, it is desirable to use {READ,WRITE}_ONCE() in preference to ACCESS_ONCE(), and new code is expected to use one of the former. So far, there's been no reason to change most existing uses of ACCESS_ONCE(), as these aren't harmful, and changing them results in churn. However, for some features, the read/write distinction is critical to correct operation. To distinguish these cases, separate read/write accessors must be used. This patch migrates (most) remaining ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following coccinelle script: ---- // Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and // WRITE_ONCE() // $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch virtual patch @ depends on patch @ expression E1, E2; @@ - ACCESS_ONCE(E1) = E2 + WRITE_ONCE(E1, E2) @ depends on patch @ expression E; @@ - ACCESS_ONCE(E) + READ_ONCE(E) ---- Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: davem@davemloft.net Cc: linux-arch@vger.kernel.org Cc: mpe@ellerman.id.au Cc: shuah@kernel.org Cc: snitzer@redhat.com Cc: thor.thayer@linux.intel.com Cc: tj@kernel.org Cc: viro@zeniv.linux.org.uk Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-10-23 21:07:29 +00:00
unsigned long userns_flags = READ_ONCE(ns->flags);
2014-12-02 18:27:26 +00:00
seq_printf(seq, "%s\n",
(userns_flags & USERNS_SETGROUPS_ALLOWED) ?
"allow" : "deny");
return 0;
}
ssize_t proc_setgroups_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
struct seq_file *seq = file->private_data;
struct user_namespace *ns = seq->private;
char kbuf[8], *pos;
bool setgroups_allowed;
ssize_t ret;
/* Only allow a very narrow range of strings to be written */
ret = -EINVAL;
if ((*ppos != 0) || (count >= sizeof(kbuf)))
goto out;
/* What was written? */
ret = -EFAULT;
if (copy_from_user(kbuf, buf, count))
goto out;
kbuf[count] = '\0';
pos = kbuf;
/* What is being requested? */
ret = -EINVAL;
if (strncmp(pos, "allow", 5) == 0) {
pos += 5;
setgroups_allowed = true;
}
else if (strncmp(pos, "deny", 4) == 0) {
pos += 4;
setgroups_allowed = false;
}
else
goto out;
/* Verify there is not trailing junk on the line */
pos = skip_spaces(pos);
if (*pos != '\0')
goto out;
ret = -EPERM;
mutex_lock(&userns_state_mutex);
if (setgroups_allowed) {
/* Enabling setgroups after setgroups has been disabled
* is not allowed.
*/
if (!(ns->flags & USERNS_SETGROUPS_ALLOWED))
goto out_unlock;
} else {
/* Permanently disabling setgroups after setgroups has
* been enabled by writing the gid_map is not allowed.
*/
if (ns->gid_map.nr_extents != 0)
goto out_unlock;
ns->flags &= ~USERNS_SETGROUPS_ALLOWED;
}
mutex_unlock(&userns_state_mutex);
/* Report a successful write */
*ppos = count;
ret = count;
out:
return ret;
out_unlock:
mutex_unlock(&userns_state_mutex);
goto out;
}
bool userns_may_setgroups(const struct user_namespace *ns)
{
bool allowed;
mutex_lock(&userns_state_mutex);
/* It is not safe to use setgroups until a gid mapping in
* the user namespace has been established.
*/
allowed = ns->gid_map.nr_extents != 0;
2014-12-02 18:27:26 +00:00
/* Is setgroups allowed? */
allowed = allowed && (ns->flags & USERNS_SETGROUPS_ALLOWED);
mutex_unlock(&userns_state_mutex);
return allowed;
}
/*
* Returns true if @child is the same namespace or a descendant of
* @ancestor.
*/
bool in_userns(const struct user_namespace *ancestor,
const struct user_namespace *child)
{
const struct user_namespace *ns;
for (ns = child; ns->level > ancestor->level; ns = ns->parent)
;
return (ns == ancestor);
}
bool current_in_userns(const struct user_namespace *target_ns)
{
return in_userns(target_ns, current_user_ns());
}
EXPORT_SYMBOL(current_in_userns);
static inline struct user_namespace *to_user_ns(struct ns_common *ns)
{
return container_of(ns, struct user_namespace, ns);
}
static struct ns_common *userns_get(struct task_struct *task)
{
struct user_namespace *user_ns;
rcu_read_lock();
user_ns = get_user_ns(__task_cred(task)->user_ns);
rcu_read_unlock();
return user_ns ? &user_ns->ns : NULL;
}
static void userns_put(struct ns_common *ns)
{
put_user_ns(to_user_ns(ns));
}
nsproxy: add struct nsset Add a simple struct nsset. It holds all necessary pieces to switch to a new set of namespaces without leaving a task in a half-switched state which we will make use of in the next patch. This patch switches the existing setns logic over without causing a change in setns() behavior. This brings setns() closer to how unshare() works(). The prepare_ns() function is responsible to prepare all necessary information. This has two reasons. First it minimizes dependencies between individual namespaces, i.e. all install handler can expect that all fields are properly initialized independent in what order they are called in. Second, this makes the code easier to maintain and easier to follow if it needs to be changed. The prepare_ns() helper will only be switched over to use a flags argument in the next patch. Here it will still use nstype as a simple integer argument which was argued would be clearer. I'm not particularly opinionated about this if it really helps or not. The struct nsset itself already contains the flags field since its name already indicates that it can contain information required by different namespaces. None of this should have functional consequences. Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Serge Hallyn <serge@hallyn.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Serge Hallyn <serge@hallyn.com> Cc: Jann Horn <jannh@google.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Aleksa Sarai <cyphar@cyphar.com> Link: https://lore.kernel.org/r/20200505140432.181565-2-christian.brauner@ubuntu.com
2020-05-05 14:04:30 +00:00
static int userns_install(struct nsset *nsset, struct ns_common *ns)
{
struct user_namespace *user_ns = to_user_ns(ns);
struct cred *cred;
/* Don't allow gaining capabilities by reentering
* the same user namespace.
*/
if (user_ns == current_user_ns())
return -EINVAL;
/* Tasks that share a thread group must share a user namespace */
if (!thread_group_empty(current))
return -EINVAL;
if (current->fs->users != 1)
return -EINVAL;
if (!ns_capable(user_ns, CAP_SYS_ADMIN))
return -EPERM;
nsproxy: add struct nsset Add a simple struct nsset. It holds all necessary pieces to switch to a new set of namespaces without leaving a task in a half-switched state which we will make use of in the next patch. This patch switches the existing setns logic over without causing a change in setns() behavior. This brings setns() closer to how unshare() works(). The prepare_ns() function is responsible to prepare all necessary information. This has two reasons. First it minimizes dependencies between individual namespaces, i.e. all install handler can expect that all fields are properly initialized independent in what order they are called in. Second, this makes the code easier to maintain and easier to follow if it needs to be changed. The prepare_ns() helper will only be switched over to use a flags argument in the next patch. Here it will still use nstype as a simple integer argument which was argued would be clearer. I'm not particularly opinionated about this if it really helps or not. The struct nsset itself already contains the flags field since its name already indicates that it can contain information required by different namespaces. None of this should have functional consequences. Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Serge Hallyn <serge@hallyn.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Serge Hallyn <serge@hallyn.com> Cc: Jann Horn <jannh@google.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Aleksa Sarai <cyphar@cyphar.com> Link: https://lore.kernel.org/r/20200505140432.181565-2-christian.brauner@ubuntu.com
2020-05-05 14:04:30 +00:00
cred = nsset_cred(nsset);
if (!cred)
nsproxy: add struct nsset Add a simple struct nsset. It holds all necessary pieces to switch to a new set of namespaces without leaving a task in a half-switched state which we will make use of in the next patch. This patch switches the existing setns logic over without causing a change in setns() behavior. This brings setns() closer to how unshare() works(). The prepare_ns() function is responsible to prepare all necessary information. This has two reasons. First it minimizes dependencies between individual namespaces, i.e. all install handler can expect that all fields are properly initialized independent in what order they are called in. Second, this makes the code easier to maintain and easier to follow if it needs to be changed. The prepare_ns() helper will only be switched over to use a flags argument in the next patch. Here it will still use nstype as a simple integer argument which was argued would be clearer. I'm not particularly opinionated about this if it really helps or not. The struct nsset itself already contains the flags field since its name already indicates that it can contain information required by different namespaces. None of this should have functional consequences. Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Serge Hallyn <serge@hallyn.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Serge Hallyn <serge@hallyn.com> Cc: Jann Horn <jannh@google.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Aleksa Sarai <cyphar@cyphar.com> Link: https://lore.kernel.org/r/20200505140432.181565-2-christian.brauner@ubuntu.com
2020-05-05 14:04:30 +00:00
return -EINVAL;
put_user_ns(cred->user_ns);
set_cred_user_ns(cred, get_user_ns(user_ns));
if (set_cred_ucounts(cred) < 0)
return -EINVAL;
nsproxy: add struct nsset Add a simple struct nsset. It holds all necessary pieces to switch to a new set of namespaces without leaving a task in a half-switched state which we will make use of in the next patch. This patch switches the existing setns logic over without causing a change in setns() behavior. This brings setns() closer to how unshare() works(). The prepare_ns() function is responsible to prepare all necessary information. This has two reasons. First it minimizes dependencies between individual namespaces, i.e. all install handler can expect that all fields are properly initialized independent in what order they are called in. Second, this makes the code easier to maintain and easier to follow if it needs to be changed. The prepare_ns() helper will only be switched over to use a flags argument in the next patch. Here it will still use nstype as a simple integer argument which was argued would be clearer. I'm not particularly opinionated about this if it really helps or not. The struct nsset itself already contains the flags field since its name already indicates that it can contain information required by different namespaces. None of this should have functional consequences. Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Serge Hallyn <serge@hallyn.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Serge Hallyn <serge@hallyn.com> Cc: Jann Horn <jannh@google.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Aleksa Sarai <cyphar@cyphar.com> Link: https://lore.kernel.org/r/20200505140432.181565-2-christian.brauner@ubuntu.com
2020-05-05 14:04:30 +00:00
return 0;
}
struct ns_common *ns_get_owner(struct ns_common *ns)
{
struct user_namespace *my_user_ns = current_user_ns();
struct user_namespace *owner, *p;
/* See if the owner is in the current user namespace */
owner = p = ns->ops->owner(ns);
for (;;) {
if (!p)
return ERR_PTR(-EPERM);
if (p == my_user_ns)
break;
p = p->parent;
}
return &get_user_ns(owner)->ns;
}
static struct user_namespace *userns_owner(struct ns_common *ns)
{
return to_user_ns(ns)->parent;
}
const struct proc_ns_operations userns_operations = {
.name = "user",
.type = CLONE_NEWUSER,
.get = userns_get,
.put = userns_put,
.install = userns_install,
.owner = userns_owner,
.get_parent = ns_get_owner,
};
static __init int user_namespaces_init(void)
{
memcg: enable accounting for new namesapces and struct nsproxy Container admin can create new namespaces and force kernel to allocate up to several pages of memory for the namespaces and its associated structures. Net and uts namespaces have enabled accounting for such allocations. It makes sense to account for rest ones to restrict the host's memory consumption from inside the memcg-limited container. Link: https://lkml.kernel.org/r/5525bcbf-533e-da27-79b7-158686c64e13@virtuozzo.com Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Acked-by: Serge Hallyn <serge@hallyn.com> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com> Reviewed-by: Shakeel Butt <shakeelb@google.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Andrei Vagin <avagin@gmail.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bp@suse.de> Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: "J. Bruce Fields" <bfields@fieldses.org> Cc: Jeff Layton <jlayton@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jiri Slaby <jirislaby@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Roman Gushchin <guro@fb.com> Cc: Tejun Heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Yutian Yang <nglaive@gmail.com> Cc: Zefan Li <lizefan.x@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-02 21:55:27 +00:00
user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC | SLAB_ACCOUNT);
return 0;
}
2014-04-03 21:48:35 +00:00
subsys_initcall(user_namespaces_init);