linux/fs/hfs/super.c

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/*
* linux/fs/hfs/super.c
*
* Copyright (C) 1995-1997 Paul H. Hargrove
* (C) 2003 Ardis Technologies <roman@ardistech.com>
* This file may be distributed under the terms of the GNU General Public License.
*
* This file contains hfs_read_super(), some of the super_ops and
* init_hfs_fs() and exit_hfs_fs(). The remaining super_ops are in
* inode.c since they deal with inodes.
*
* Based on the minix file system code, (C) 1991, 1992 by Linus Torvalds
*/
#include <linux/module.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/mount.h>
#include <linux/init.h>
#include <linux/nls.h>
#include <linux/parser.h>
#include <linux/seq_file.h>
include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-24 08:04:11 +00:00
#include <linux/slab.h>
#include <linux/vfs.h>
#include "hfs_fs.h"
#include "btree.h"
static struct kmem_cache *hfs_inode_cachep;
MODULE_LICENSE("GPL");
static int hfs_sync_fs(struct super_block *sb, int wait)
{
hfs_mdb_commit(sb);
return 0;
}
/*
* hfs_put_super()
*
* This is the put_super() entry in the super_operations structure for
* HFS filesystems. The purpose is to release the resources
* associated with the superblock sb.
*/
static void hfs_put_super(struct super_block *sb)
{
cancel_delayed_work_sync(&HFS_SB(sb)->mdb_work);
hfs_mdb_close(sb);
/* release the MDB's resources */
hfs_mdb_put(sb);
}
static void flush_mdb(struct work_struct *work)
{
struct hfs_sb_info *sbi;
struct super_block *sb;
sbi = container_of(work, struct hfs_sb_info, mdb_work.work);
sb = sbi->sb;
spin_lock(&sbi->work_lock);
sbi->work_queued = 0;
spin_unlock(&sbi->work_lock);
hfs_mdb_commit(sb);
}
void hfs_mark_mdb_dirty(struct super_block *sb)
{
struct hfs_sb_info *sbi = HFS_SB(sb);
unsigned long delay;
if (sb->s_flags & MS_RDONLY)
return;
spin_lock(&sbi->work_lock);
if (!sbi->work_queued) {
delay = msecs_to_jiffies(dirty_writeback_interval * 10);
queue_delayed_work(system_long_wq, &sbi->mdb_work, delay);
sbi->work_queued = 1;
}
spin_unlock(&sbi->work_lock);
}
/*
* hfs_statfs()
*
* This is the statfs() entry in the super_operations structure for
* HFS filesystems. The purpose is to return various data about the
* filesystem.
*
* changed f_files/f_ffree to reflect the fs_ablock/free_ablocks.
*/
static int hfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct super_block *sb = dentry->d_sb;
u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
buf->f_type = HFS_SUPER_MAGIC;
buf->f_bsize = sb->s_blocksize;
buf->f_blocks = (u32)HFS_SB(sb)->fs_ablocks * HFS_SB(sb)->fs_div;
buf->f_bfree = (u32)HFS_SB(sb)->free_ablocks * HFS_SB(sb)->fs_div;
buf->f_bavail = buf->f_bfree;
buf->f_files = HFS_SB(sb)->fs_ablocks;
buf->f_ffree = HFS_SB(sb)->free_ablocks;
buf->f_fsid.val[0] = (u32)id;
buf->f_fsid.val[1] = (u32)(id >> 32);
buf->f_namelen = HFS_NAMELEN;
return 0;
}
static int hfs_remount(struct super_block *sb, int *flags, char *data)
{
fs: push sync_filesystem() down to the file system's remount_fs() Previously, the no-op "mount -o mount /dev/xxx" operation when the file system is already mounted read-write causes an implied, unconditional syncfs(). This seems pretty stupid, and it's certainly documented or guaraunteed to do this, nor is it particularly useful, except in the case where the file system was mounted rw and is getting remounted read-only. However, it's possible that there might be some file systems that are actually depending on this behavior. In most file systems, it's probably fine to only call sync_filesystem() when transitioning from read-write to read-only, and there are some file systems where this is not needed at all (for example, for a pseudo-filesystem or something like romfs). Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: linux-fsdevel@vger.kernel.org Cc: Christoph Hellwig <hch@infradead.org> Cc: Artem Bityutskiy <dedekind1@gmail.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Evgeniy Dushistov <dushistov@mail.ru> Cc: Jan Kara <jack@suse.cz> Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Cc: Anders Larsen <al@alarsen.net> Cc: Phillip Lougher <phillip@squashfs.org.uk> Cc: Kees Cook <keescook@chromium.org> Cc: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz> Cc: Petr Vandrovec <petr@vandrovec.name> Cc: xfs@oss.sgi.com Cc: linux-btrfs@vger.kernel.org Cc: linux-cifs@vger.kernel.org Cc: samba-technical@lists.samba.org Cc: codalist@coda.cs.cmu.edu Cc: linux-ext4@vger.kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net Cc: fuse-devel@lists.sourceforge.net Cc: cluster-devel@redhat.com Cc: linux-mtd@lists.infradead.org Cc: jfs-discussion@lists.sourceforge.net Cc: linux-nfs@vger.kernel.org Cc: linux-nilfs@vger.kernel.org Cc: linux-ntfs-dev@lists.sourceforge.net Cc: ocfs2-devel@oss.oracle.com Cc: reiserfs-devel@vger.kernel.org
2014-03-13 14:14:33 +00:00
sync_filesystem(sb);
*flags |= MS_NODIRATIME;
if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
return 0;
if (!(*flags & MS_RDONLY)) {
if (!(HFS_SB(sb)->mdb->drAtrb & cpu_to_be16(HFS_SB_ATTRIB_UNMNT))) {
pr_warn("filesystem was not cleanly unmounted, running fsck.hfs is recommended. leaving read-only.\n");
sb->s_flags |= MS_RDONLY;
*flags |= MS_RDONLY;
} else if (HFS_SB(sb)->mdb->drAtrb & cpu_to_be16(HFS_SB_ATTRIB_SLOCK)) {
pr_warn("filesystem is marked locked, leaving read-only.\n");
sb->s_flags |= MS_RDONLY;
*flags |= MS_RDONLY;
}
}
return 0;
}
static int hfs_show_options(struct seq_file *seq, struct dentry *root)
{
struct hfs_sb_info *sbi = HFS_SB(root->d_sb);
if (sbi->s_creator != cpu_to_be32(0x3f3f3f3f))
fs: create and use seq_show_option for escaping Many file systems that implement the show_options hook fail to correctly escape their output which could lead to unescaped characters (e.g. new lines) leaking into /proc/mounts and /proc/[pid]/mountinfo files. This could lead to confusion, spoofed entries (resulting in things like systemd issuing false d-bus "mount" notifications), and who knows what else. This looks like it would only be the root user stepping on themselves, but it's possible weird things could happen in containers or in other situations with delegated mount privileges. Here's an example using overlay with setuid fusermount trusting the contents of /proc/mounts (via the /etc/mtab symlink). Imagine the use of "sudo" is something more sneaky: $ BASE="ovl" $ MNT="$BASE/mnt" $ LOW="$BASE/lower" $ UP="$BASE/upper" $ WORK="$BASE/work/ 0 0 none /proc fuse.pwn user_id=1000" $ mkdir -p "$LOW" "$UP" "$WORK" $ sudo mount -t overlay -o "lowerdir=$LOW,upperdir=$UP,workdir=$WORK" none /mnt $ cat /proc/mounts none /root/ovl/mnt overlay rw,relatime,lowerdir=ovl/lower,upperdir=ovl/upper,workdir=ovl/work/ 0 0 none /proc fuse.pwn user_id=1000 0 0 $ fusermount -u /proc $ cat /proc/mounts cat: /proc/mounts: No such file or directory This fixes the problem by adding new seq_show_option and seq_show_option_n helpers, and updating the vulnerable show_option handlers to use them as needed. Some, like SELinux, need to be open coded due to unusual existing escape mechanisms. [akpm@linux-foundation.org: add lost chunk, per Kees] [keescook@chromium.org: seq_show_option should be using const parameters] Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Acked-by: Jan Kara <jack@suse.com> Acked-by: Paul Moore <paul@paul-moore.com> Cc: J. R. Okajima <hooanon05g@gmail.com> Signed-off-by: Kees Cook <keescook@chromium.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-04 22:44:57 +00:00
seq_show_option_n(seq, "creator", (char *)&sbi->s_creator, 4);
if (sbi->s_type != cpu_to_be32(0x3f3f3f3f))
fs: create and use seq_show_option for escaping Many file systems that implement the show_options hook fail to correctly escape their output which could lead to unescaped characters (e.g. new lines) leaking into /proc/mounts and /proc/[pid]/mountinfo files. This could lead to confusion, spoofed entries (resulting in things like systemd issuing false d-bus "mount" notifications), and who knows what else. This looks like it would only be the root user stepping on themselves, but it's possible weird things could happen in containers or in other situations with delegated mount privileges. Here's an example using overlay with setuid fusermount trusting the contents of /proc/mounts (via the /etc/mtab symlink). Imagine the use of "sudo" is something more sneaky: $ BASE="ovl" $ MNT="$BASE/mnt" $ LOW="$BASE/lower" $ UP="$BASE/upper" $ WORK="$BASE/work/ 0 0 none /proc fuse.pwn user_id=1000" $ mkdir -p "$LOW" "$UP" "$WORK" $ sudo mount -t overlay -o "lowerdir=$LOW,upperdir=$UP,workdir=$WORK" none /mnt $ cat /proc/mounts none /root/ovl/mnt overlay rw,relatime,lowerdir=ovl/lower,upperdir=ovl/upper,workdir=ovl/work/ 0 0 none /proc fuse.pwn user_id=1000 0 0 $ fusermount -u /proc $ cat /proc/mounts cat: /proc/mounts: No such file or directory This fixes the problem by adding new seq_show_option and seq_show_option_n helpers, and updating the vulnerable show_option handlers to use them as needed. Some, like SELinux, need to be open coded due to unusual existing escape mechanisms. [akpm@linux-foundation.org: add lost chunk, per Kees] [keescook@chromium.org: seq_show_option should be using const parameters] Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Acked-by: Jan Kara <jack@suse.com> Acked-by: Paul Moore <paul@paul-moore.com> Cc: J. R. Okajima <hooanon05g@gmail.com> Signed-off-by: Kees Cook <keescook@chromium.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-09-04 22:44:57 +00:00
seq_show_option_n(seq, "type", (char *)&sbi->s_type, 4);
seq_printf(seq, ",uid=%u,gid=%u",
from_kuid_munged(&init_user_ns, sbi->s_uid),
from_kgid_munged(&init_user_ns, sbi->s_gid));
if (sbi->s_file_umask != 0133)
seq_printf(seq, ",file_umask=%o", sbi->s_file_umask);
if (sbi->s_dir_umask != 0022)
seq_printf(seq, ",dir_umask=%o", sbi->s_dir_umask);
if (sbi->part >= 0)
seq_printf(seq, ",part=%u", sbi->part);
if (sbi->session >= 0)
seq_printf(seq, ",session=%u", sbi->session);
if (sbi->nls_disk)
seq_printf(seq, ",codepage=%s", sbi->nls_disk->charset);
if (sbi->nls_io)
seq_printf(seq, ",iocharset=%s", sbi->nls_io->charset);
if (sbi->s_quiet)
seq_printf(seq, ",quiet");
return 0;
}
static struct inode *hfs_alloc_inode(struct super_block *sb)
{
struct hfs_inode_info *i;
i = kmem_cache_alloc(hfs_inode_cachep, GFP_KERNEL);
return i ? &i->vfs_inode : NULL;
}
2011-01-07 06:49:49 +00:00
static void hfs_i_callback(struct rcu_head *head)
{
2011-01-07 06:49:49 +00:00
struct inode *inode = container_of(head, struct inode, i_rcu);
kmem_cache_free(hfs_inode_cachep, HFS_I(inode));
}
2011-01-07 06:49:49 +00:00
static void hfs_destroy_inode(struct inode *inode)
{
call_rcu(&inode->i_rcu, hfs_i_callback);
}
static const struct super_operations hfs_super_operations = {
.alloc_inode = hfs_alloc_inode,
.destroy_inode = hfs_destroy_inode,
.write_inode = hfs_write_inode,
.evict_inode = hfs_evict_inode,
.put_super = hfs_put_super,
.sync_fs = hfs_sync_fs,
.statfs = hfs_statfs,
.remount_fs = hfs_remount,
.show_options = hfs_show_options,
};
enum {
opt_uid, opt_gid, opt_umask, opt_file_umask, opt_dir_umask,
opt_part, opt_session, opt_type, opt_creator, opt_quiet,
opt_codepage, opt_iocharset,
opt_err
};
static const match_table_t tokens = {
{ opt_uid, "uid=%u" },
{ opt_gid, "gid=%u" },
{ opt_umask, "umask=%o" },
{ opt_file_umask, "file_umask=%o" },
{ opt_dir_umask, "dir_umask=%o" },
{ opt_part, "part=%u" },
{ opt_session, "session=%u" },
{ opt_type, "type=%s" },
{ opt_creator, "creator=%s" },
{ opt_quiet, "quiet" },
{ opt_codepage, "codepage=%s" },
{ opt_iocharset, "iocharset=%s" },
{ opt_err, NULL }
};
static inline int match_fourchar(substring_t *arg, u32 *result)
{
if (arg->to - arg->from != 4)
return -EINVAL;
memcpy(result, arg->from, 4);
return 0;
}
/*
* parse_options()
*
* adapted from linux/fs/msdos/inode.c written 1992,93 by Werner Almesberger
* This function is called by hfs_read_super() to parse the mount options.
*/
static int parse_options(char *options, struct hfs_sb_info *hsb)
{
char *p;
substring_t args[MAX_OPT_ARGS];
int tmp, token;
/* initialize the sb with defaults */
hsb->s_uid = current_uid();
hsb->s_gid = current_gid();
hsb->s_file_umask = 0133;
hsb->s_dir_umask = 0022;
hsb->s_type = hsb->s_creator = cpu_to_be32(0x3f3f3f3f); /* == '????' */
hsb->s_quiet = 0;
hsb->part = -1;
hsb->session = -1;
if (!options)
return 1;
while ((p = strsep(&options, ",")) != NULL) {
if (!*p)
continue;
token = match_token(p, tokens, args);
switch (token) {
case opt_uid:
if (match_int(&args[0], &tmp)) {
pr_err("uid requires an argument\n");
return 0;
}
hsb->s_uid = make_kuid(current_user_ns(), (uid_t)tmp);
if (!uid_valid(hsb->s_uid)) {
pr_err("invalid uid %d\n", tmp);
return 0;
}
break;
case opt_gid:
if (match_int(&args[0], &tmp)) {
pr_err("gid requires an argument\n");
return 0;
}
hsb->s_gid = make_kgid(current_user_ns(), (gid_t)tmp);
if (!gid_valid(hsb->s_gid)) {
pr_err("invalid gid %d\n", tmp);
return 0;
}
break;
case opt_umask:
if (match_octal(&args[0], &tmp)) {
pr_err("umask requires a value\n");
return 0;
}
hsb->s_file_umask = (umode_t)tmp;
hsb->s_dir_umask = (umode_t)tmp;
break;
case opt_file_umask:
if (match_octal(&args[0], &tmp)) {
pr_err("file_umask requires a value\n");
return 0;
}
hsb->s_file_umask = (umode_t)tmp;
break;
case opt_dir_umask:
if (match_octal(&args[0], &tmp)) {
pr_err("dir_umask requires a value\n");
return 0;
}
hsb->s_dir_umask = (umode_t)tmp;
break;
case opt_part:
if (match_int(&args[0], &hsb->part)) {
pr_err("part requires an argument\n");
return 0;
}
break;
case opt_session:
if (match_int(&args[0], &hsb->session)) {
pr_err("session requires an argument\n");
return 0;
}
break;
case opt_type:
if (match_fourchar(&args[0], &hsb->s_type)) {
pr_err("type requires a 4 character value\n");
return 0;
}
break;
case opt_creator:
if (match_fourchar(&args[0], &hsb->s_creator)) {
pr_err("creator requires a 4 character value\n");
return 0;
}
break;
case opt_quiet:
hsb->s_quiet = 1;
break;
case opt_codepage:
if (hsb->nls_disk) {
pr_err("unable to change codepage\n");
return 0;
}
p = match_strdup(&args[0]);
if (p)
hsb->nls_disk = load_nls(p);
if (!hsb->nls_disk) {
pr_err("unable to load codepage \"%s\"\n", p);
kfree(p);
return 0;
}
kfree(p);
break;
case opt_iocharset:
if (hsb->nls_io) {
pr_err("unable to change iocharset\n");
return 0;
}
p = match_strdup(&args[0]);
if (p)
hsb->nls_io = load_nls(p);
if (!hsb->nls_io) {
pr_err("unable to load iocharset \"%s\"\n", p);
kfree(p);
return 0;
}
kfree(p);
break;
default:
return 0;
}
}
if (hsb->nls_disk && !hsb->nls_io) {
hsb->nls_io = load_nls_default();
if (!hsb->nls_io) {
pr_err("unable to load default iocharset\n");
return 0;
}
}
hsb->s_dir_umask &= 0777;
hsb->s_file_umask &= 0577;
return 1;
}
/*
* hfs_read_super()
*
* This is the function that is responsible for mounting an HFS
* filesystem. It performs all the tasks necessary to get enough data
* from the disk to read the root inode. This includes parsing the
* mount options, dealing with Macintosh partitions, reading the
* superblock and the allocation bitmap blocks, calling
* hfs_btree_init() to get the necessary data about the extents and
* catalog B-trees and, finally, reading the root inode into memory.
*/
static int hfs_fill_super(struct super_block *sb, void *data, int silent)
{
struct hfs_sb_info *sbi;
struct hfs_find_data fd;
hfs_cat_rec rec;
struct inode *root_inode;
int res;
sbi = kzalloc(sizeof(struct hfs_sb_info), GFP_KERNEL);
if (!sbi)
return -ENOMEM;
sbi->sb = sb;
sb->s_fs_info = sbi;
spin_lock_init(&sbi->work_lock);
INIT_DELAYED_WORK(&sbi->mdb_work, flush_mdb);
res = -EINVAL;
if (!parse_options((char *)data, sbi)) {
pr_err("unable to parse mount options\n");
goto bail;
}
sb->s_op = &hfs_super_operations;
sb->s_xattr = hfs_xattr_handlers;
sb->s_flags |= MS_NODIRATIME;
mutex_init(&sbi->bitmap_lock);
res = hfs_mdb_get(sb);
if (res) {
if (!silent)
pr_warn("can't find a HFS filesystem on dev %s\n",
hfs_mdb_name(sb));
res = -EINVAL;
goto bail;
}
/* try to get the root inode */
res = hfs_find_init(HFS_SB(sb)->cat_tree, &fd);
if (res)
goto bail_no_root;
res = hfs_cat_find_brec(sb, HFS_ROOT_CNID, &fd);
if (!res) {
if (fd.entrylength > sizeof(rec) || fd.entrylength < 0) {
res = -EIO;
goto bail;
}
hfs_bnode_read(fd.bnode, &rec, fd.entryoffset, fd.entrylength);
}
if (res) {
hfs_find_exit(&fd);
goto bail_no_root;
}
res = -EINVAL;
root_inode = hfs_iget(sb, &fd.search_key->cat, &rec);
hfs_find_exit(&fd);
if (!root_inode)
goto bail_no_root;
sb->s_d_op = &hfs_dentry_operations;
res = -ENOMEM;
sb->s_root = d_make_root(root_inode);
if (!sb->s_root)
goto bail_no_root;
/* everything's okay */
return 0;
bail_no_root:
pr_err("get root inode failed\n");
bail:
hfs_mdb_put(sb);
return res;
}
static struct dentry *hfs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
return mount_bdev(fs_type, flags, dev_name, data, hfs_fill_super);
}
static struct file_system_type hfs_fs_type = {
.owner = THIS_MODULE,
.name = "hfs",
.mount = hfs_mount,
.kill_sb = kill_block_super,
.fs_flags = FS_REQUIRES_DEV,
};
fs: Limit sys_mount to only request filesystem modules. Modify the request_module to prefix the file system type with "fs-" and add aliases to all of the filesystems that can be built as modules to match. A common practice is to build all of the kernel code and leave code that is not commonly needed as modules, with the result that many users are exposed to any bug anywhere in the kernel. Looking for filesystems with a fs- prefix limits the pool of possible modules that can be loaded by mount to just filesystems trivially making things safer with no real cost. Using aliases means user space can control the policy of which filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf with blacklist and alias directives. Allowing simple, safe, well understood work-arounds to known problematic software. This also addresses a rare but unfortunate problem where the filesystem name is not the same as it's module name and module auto-loading would not work. While writing this patch I saw a handful of such cases. The most significant being autofs that lives in the module autofs4. This is relevant to user namespaces because we can reach the request module in get_fs_type() without having any special permissions, and people get uncomfortable when a user specified string (in this case the filesystem type) goes all of the way to request_module. After having looked at this issue I don't think there is any particular reason to perform any filtering or permission checks beyond making it clear in the module request that we want a filesystem module. The common pattern in the kernel is to call request_module() without regards to the users permissions. In general all a filesystem module does once loaded is call register_filesystem() and go to sleep. Which means there is not much attack surface exposed by loading a filesytem module unless the filesystem is mounted. In a user namespace filesystems are not mounted unless .fs_flags = FS_USERNS_MOUNT, which most filesystems do not set today. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Acked-by: Kees Cook <keescook@chromium.org> Reported-by: Kees Cook <keescook@google.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-03-03 03:39:14 +00:00
MODULE_ALIAS_FS("hfs");
static void hfs_init_once(void *p)
{
struct hfs_inode_info *i = p;
inode_init_once(&i->vfs_inode);
}
static int __init init_hfs_fs(void)
{
int err;
hfs_inode_cachep = kmem_cache_create("hfs_inode_cache",
2016-01-14 23:18:21 +00:00
sizeof(struct hfs_inode_info), 0,
SLAB_HWCACHE_ALIGN|SLAB_ACCOUNT, hfs_init_once);
if (!hfs_inode_cachep)
return -ENOMEM;
err = register_filesystem(&hfs_fs_type);
if (err)
kmem_cache_destroy(hfs_inode_cachep);
return err;
}
static void __exit exit_hfs_fs(void)
{
unregister_filesystem(&hfs_fs_type);
/*
* Make sure all delayed rcu free inodes are flushed before we
* destroy cache.
*/
rcu_barrier();
kmem_cache_destroy(hfs_inode_cachep);
}
module_init(init_hfs_fs)
module_exit(exit_hfs_fs)