linux/fs/proc/root.c
Al Viro e31f0a57ae procfs: make freeing proc_fs_info rcu-delayed
makes proc_pid_ns() safe from rcu pathwalk (put_pid_ns()
is still synchronous, but that's not a problem - it does
rcu-delay everything that needs to be)

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-02-25 02:10:32 -05:00

377 lines
8.9 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* linux/fs/proc/root.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* proc root directory handling functions
*/
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/sched/stat.h>
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/user_namespace.h>
#include <linux/fs_context.h>
#include <linux/mount.h>
#include <linux/pid_namespace.h>
#include <linux/fs_parser.h>
#include <linux/cred.h>
#include <linux/magic.h>
#include <linux/slab.h>
#include "internal.h"
struct proc_fs_context {
struct pid_namespace *pid_ns;
unsigned int mask;
enum proc_hidepid hidepid;
int gid;
enum proc_pidonly pidonly;
};
enum proc_param {
Opt_gid,
Opt_hidepid,
Opt_subset,
};
static const struct fs_parameter_spec proc_fs_parameters[] = {
fsparam_u32("gid", Opt_gid),
fsparam_string("hidepid", Opt_hidepid),
fsparam_string("subset", Opt_subset),
{}
};
static inline int valid_hidepid(unsigned int value)
{
return (value == HIDEPID_OFF ||
value == HIDEPID_NO_ACCESS ||
value == HIDEPID_INVISIBLE ||
value == HIDEPID_NOT_PTRACEABLE);
}
static int proc_parse_hidepid_param(struct fs_context *fc, struct fs_parameter *param)
{
struct proc_fs_context *ctx = fc->fs_private;
struct fs_parameter_spec hidepid_u32_spec = fsparam_u32("hidepid", Opt_hidepid);
struct fs_parse_result result;
int base = (unsigned long)hidepid_u32_spec.data;
if (param->type != fs_value_is_string)
return invalf(fc, "proc: unexpected type of hidepid value\n");
if (!kstrtouint(param->string, base, &result.uint_32)) {
if (!valid_hidepid(result.uint_32))
return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string);
ctx->hidepid = result.uint_32;
return 0;
}
if (!strcmp(param->string, "off"))
ctx->hidepid = HIDEPID_OFF;
else if (!strcmp(param->string, "noaccess"))
ctx->hidepid = HIDEPID_NO_ACCESS;
else if (!strcmp(param->string, "invisible"))
ctx->hidepid = HIDEPID_INVISIBLE;
else if (!strcmp(param->string, "ptraceable"))
ctx->hidepid = HIDEPID_NOT_PTRACEABLE;
else
return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string);
return 0;
}
static int proc_parse_subset_param(struct fs_context *fc, char *value)
{
struct proc_fs_context *ctx = fc->fs_private;
while (value) {
char *ptr = strchr(value, ',');
if (ptr != NULL)
*ptr++ = '\0';
if (*value != '\0') {
if (!strcmp(value, "pid")) {
ctx->pidonly = PROC_PIDONLY_ON;
} else {
return invalf(fc, "proc: unsupported subset option - %s\n", value);
}
}
value = ptr;
}
return 0;
}
static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
struct proc_fs_context *ctx = fc->fs_private;
struct fs_parse_result result;
int opt;
opt = fs_parse(fc, proc_fs_parameters, param, &result);
if (opt < 0)
return opt;
switch (opt) {
case Opt_gid:
ctx->gid = result.uint_32;
break;
case Opt_hidepid:
if (proc_parse_hidepid_param(fc, param))
return -EINVAL;
break;
case Opt_subset:
if (proc_parse_subset_param(fc, param->string) < 0)
return -EINVAL;
break;
default:
return -EINVAL;
}
ctx->mask |= 1 << opt;
return 0;
}
static void proc_apply_options(struct proc_fs_info *fs_info,
struct fs_context *fc,
struct user_namespace *user_ns)
{
struct proc_fs_context *ctx = fc->fs_private;
if (ctx->mask & (1 << Opt_gid))
fs_info->pid_gid = make_kgid(user_ns, ctx->gid);
if (ctx->mask & (1 << Opt_hidepid))
fs_info->hide_pid = ctx->hidepid;
if (ctx->mask & (1 << Opt_subset))
fs_info->pidonly = ctx->pidonly;
}
static int proc_fill_super(struct super_block *s, struct fs_context *fc)
{
struct proc_fs_context *ctx = fc->fs_private;
struct inode *root_inode;
struct proc_fs_info *fs_info;
int ret;
fs_info = kzalloc(sizeof(*fs_info), GFP_KERNEL);
if (!fs_info)
return -ENOMEM;
fs_info->pid_ns = get_pid_ns(ctx->pid_ns);
proc_apply_options(fs_info, fc, current_user_ns());
/* User space would break if executables or devices appear on proc */
s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
s->s_blocksize = 1024;
s->s_blocksize_bits = 10;
s->s_magic = PROC_SUPER_MAGIC;
s->s_op = &proc_sops;
s->s_time_gran = 1;
s->s_fs_info = fs_info;
/*
* procfs isn't actually a stacking filesystem; however, there is
* too much magic going on inside it to permit stacking things on
* top of it
*/
s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
/* procfs dentries and inodes don't require IO to create */
s->s_shrink->seeks = 0;
pde_get(&proc_root);
root_inode = proc_get_inode(s, &proc_root);
if (!root_inode) {
pr_err("proc_fill_super: get root inode failed\n");
return -ENOMEM;
}
s->s_root = d_make_root(root_inode);
if (!s->s_root) {
pr_err("proc_fill_super: allocate dentry failed\n");
return -ENOMEM;
}
ret = proc_setup_self(s);
if (ret) {
return ret;
}
return proc_setup_thread_self(s);
}
static int proc_reconfigure(struct fs_context *fc)
{
struct super_block *sb = fc->root->d_sb;
struct proc_fs_info *fs_info = proc_sb_info(sb);
sync_filesystem(sb);
proc_apply_options(fs_info, fc, current_user_ns());
return 0;
}
static int proc_get_tree(struct fs_context *fc)
{
return get_tree_nodev(fc, proc_fill_super);
}
static void proc_fs_context_free(struct fs_context *fc)
{
struct proc_fs_context *ctx = fc->fs_private;
put_pid_ns(ctx->pid_ns);
kfree(ctx);
}
static const struct fs_context_operations proc_fs_context_ops = {
.free = proc_fs_context_free,
.parse_param = proc_parse_param,
.get_tree = proc_get_tree,
.reconfigure = proc_reconfigure,
};
static int proc_init_fs_context(struct fs_context *fc)
{
struct proc_fs_context *ctx;
ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL);
if (!ctx)
return -ENOMEM;
ctx->pid_ns = get_pid_ns(task_active_pid_ns(current));
put_user_ns(fc->user_ns);
fc->user_ns = get_user_ns(ctx->pid_ns->user_ns);
fc->fs_private = ctx;
fc->ops = &proc_fs_context_ops;
return 0;
}
static void proc_kill_sb(struct super_block *sb)
{
struct proc_fs_info *fs_info = proc_sb_info(sb);
if (!fs_info) {
kill_anon_super(sb);
return;
}
dput(fs_info->proc_self);
dput(fs_info->proc_thread_self);
kill_anon_super(sb);
put_pid_ns(fs_info->pid_ns);
kfree_rcu(fs_info, rcu);
}
static struct file_system_type proc_fs_type = {
.name = "proc",
.init_fs_context = proc_init_fs_context,
.parameters = proc_fs_parameters,
.kill_sb = proc_kill_sb,
.fs_flags = FS_USERNS_MOUNT | FS_DISALLOW_NOTIFY_PERM,
};
void __init proc_root_init(void)
{
proc_init_kmemcache();
set_proc_pid_nlink();
proc_self_init();
proc_thread_self_init();
proc_symlink("mounts", NULL, "self/mounts");
proc_net_init();
proc_mkdir("fs", NULL);
proc_mkdir("driver", NULL);
proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
#if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
/* just give it a mountpoint */
proc_create_mount_point("openprom");
#endif
proc_tty_init();
proc_mkdir("bus", NULL);
proc_sys_init();
/*
* Last things last. It is not like userspace processes eager
* to open /proc files exist at this point but register last
* anyway.
*/
register_filesystem(&proc_fs_type);
}
static int proc_root_getattr(struct mnt_idmap *idmap,
const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int query_flags)
{
generic_fillattr(&nop_mnt_idmap, request_mask, d_inode(path->dentry),
stat);
stat->nlink = proc_root.nlink + nr_processes();
return 0;
}
static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
{
if (!proc_pid_lookup(dentry, flags))
return NULL;
return proc_lookup(dir, dentry, flags);
}
static int proc_root_readdir(struct file *file, struct dir_context *ctx)
{
if (ctx->pos < FIRST_PROCESS_ENTRY) {
int error = proc_readdir(file, ctx);
if (unlikely(error <= 0))
return error;
ctx->pos = FIRST_PROCESS_ENTRY;
}
return proc_pid_readdir(file, ctx);
}
/*
* The root /proc directory is special, as it has the
* <pid> directories. Thus we don't use the generic
* directory handling functions for that..
*/
static const struct file_operations proc_root_operations = {
.read = generic_read_dir,
.iterate_shared = proc_root_readdir,
.llseek = generic_file_llseek,
};
/*
* proc root can do almost nothing..
*/
static const struct inode_operations proc_root_inode_operations = {
.lookup = proc_root_lookup,
.getattr = proc_root_getattr,
};
/*
* This is the root "inode" in the /proc tree..
*/
struct proc_dir_entry proc_root = {
.low_ino = PROC_ROOT_INO,
.namelen = 5,
.mode = S_IFDIR | S_IRUGO | S_IXUGO,
.nlink = 2,
.refcnt = REFCOUNT_INIT(1),
.proc_iops = &proc_root_inode_operations,
.proc_dir_ops = &proc_root_operations,
.parent = &proc_root,
.subdir = RB_ROOT,
.name = "/proc",
};