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058f2e4da7
syzbot found that proc_fill_super() fails before filling up sb->s_fs_info,
deactivate_locked_super() will be called and sb->s_fs_info will be NULL.
The proc_kill_sb() does not expect fs_info to be NULL which is wrong.
Link: https://lore.kernel.org/lkml/0000000000002d7ca605a7b8b1c5@google.com
Reported-by: syzbot+4abac52934a48af5ff19@syzkaller.appspotmail.com
Fixes: fa10fed30f
("proc: allow to mount many instances of proc in one pid namespace")
Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
373 lines
8.7 KiB
C
373 lines
8.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/fs/proc/root.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* proc root directory handling functions
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*/
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#include <linux/uaccess.h>
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#include <linux/errno.h>
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#include <linux/time.h>
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#include <linux/proc_fs.h>
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#include <linux/stat.h>
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#include <linux/init.h>
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#include <linux/sched.h>
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#include <linux/sched/stat.h>
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#include <linux/module.h>
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#include <linux/bitops.h>
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#include <linux/user_namespace.h>
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#include <linux/fs_context.h>
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#include <linux/mount.h>
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#include <linux/pid_namespace.h>
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#include <linux/fs_parser.h>
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#include <linux/cred.h>
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#include <linux/magic.h>
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#include <linux/slab.h>
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#include "internal.h"
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struct proc_fs_context {
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struct pid_namespace *pid_ns;
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unsigned int mask;
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enum proc_hidepid hidepid;
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int gid;
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enum proc_pidonly pidonly;
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};
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enum proc_param {
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Opt_gid,
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Opt_hidepid,
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Opt_subset,
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};
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static const struct fs_parameter_spec proc_fs_parameters[] = {
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fsparam_u32("gid", Opt_gid),
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fsparam_string("hidepid", Opt_hidepid),
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fsparam_string("subset", Opt_subset),
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{}
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};
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static inline int valid_hidepid(unsigned int value)
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{
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return (value == HIDEPID_OFF ||
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value == HIDEPID_NO_ACCESS ||
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value == HIDEPID_INVISIBLE ||
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value == HIDEPID_NOT_PTRACEABLE);
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}
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static int proc_parse_hidepid_param(struct fs_context *fc, struct fs_parameter *param)
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{
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struct proc_fs_context *ctx = fc->fs_private;
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struct fs_parameter_spec hidepid_u32_spec = fsparam_u32("hidepid", Opt_hidepid);
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struct fs_parse_result result;
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int base = (unsigned long)hidepid_u32_spec.data;
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if (param->type != fs_value_is_string)
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return invalf(fc, "proc: unexpected type of hidepid value\n");
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if (!kstrtouint(param->string, base, &result.uint_32)) {
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if (!valid_hidepid(result.uint_32))
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return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string);
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ctx->hidepid = result.uint_32;
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return 0;
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}
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if (!strcmp(param->string, "off"))
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ctx->hidepid = HIDEPID_OFF;
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else if (!strcmp(param->string, "noaccess"))
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ctx->hidepid = HIDEPID_NO_ACCESS;
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else if (!strcmp(param->string, "invisible"))
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ctx->hidepid = HIDEPID_INVISIBLE;
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else if (!strcmp(param->string, "ptraceable"))
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ctx->hidepid = HIDEPID_NOT_PTRACEABLE;
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else
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return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string);
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return 0;
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}
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static int proc_parse_subset_param(struct fs_context *fc, char *value)
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{
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struct proc_fs_context *ctx = fc->fs_private;
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while (value) {
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char *ptr = strchr(value, ',');
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if (ptr != NULL)
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*ptr++ = '\0';
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if (*value != '\0') {
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if (!strcmp(value, "pid")) {
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ctx->pidonly = PROC_PIDONLY_ON;
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} else {
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return invalf(fc, "proc: unsupported subset option - %s\n", value);
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}
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}
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value = ptr;
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}
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return 0;
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}
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static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
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{
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struct proc_fs_context *ctx = fc->fs_private;
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struct fs_parse_result result;
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int opt;
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opt = fs_parse(fc, proc_fs_parameters, param, &result);
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if (opt < 0)
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return opt;
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switch (opt) {
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case Opt_gid:
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ctx->gid = result.uint_32;
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break;
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case Opt_hidepid:
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if (proc_parse_hidepid_param(fc, param))
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return -EINVAL;
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break;
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case Opt_subset:
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if (proc_parse_subset_param(fc, param->string) < 0)
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return -EINVAL;
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break;
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default:
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return -EINVAL;
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}
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ctx->mask |= 1 << opt;
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return 0;
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}
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static void proc_apply_options(struct proc_fs_info *fs_info,
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struct fs_context *fc,
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struct user_namespace *user_ns)
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{
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struct proc_fs_context *ctx = fc->fs_private;
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if (ctx->mask & (1 << Opt_gid))
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fs_info->pid_gid = make_kgid(user_ns, ctx->gid);
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if (ctx->mask & (1 << Opt_hidepid))
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fs_info->hide_pid = ctx->hidepid;
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if (ctx->mask & (1 << Opt_subset))
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fs_info->pidonly = ctx->pidonly;
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}
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static int proc_fill_super(struct super_block *s, struct fs_context *fc)
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{
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struct proc_fs_context *ctx = fc->fs_private;
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struct inode *root_inode;
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struct proc_fs_info *fs_info;
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int ret;
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fs_info = kzalloc(sizeof(*fs_info), GFP_KERNEL);
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if (!fs_info)
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return -ENOMEM;
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fs_info->pid_ns = get_pid_ns(ctx->pid_ns);
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proc_apply_options(fs_info, fc, current_user_ns());
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/* User space would break if executables or devices appear on proc */
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s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
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s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
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s->s_blocksize = 1024;
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s->s_blocksize_bits = 10;
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s->s_magic = PROC_SUPER_MAGIC;
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s->s_op = &proc_sops;
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s->s_time_gran = 1;
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s->s_fs_info = fs_info;
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/*
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* procfs isn't actually a stacking filesystem; however, there is
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* too much magic going on inside it to permit stacking things on
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* top of it
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*/
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s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
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/* procfs dentries and inodes don't require IO to create */
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s->s_shrink.seeks = 0;
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pde_get(&proc_root);
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root_inode = proc_get_inode(s, &proc_root);
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if (!root_inode) {
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pr_err("proc_fill_super: get root inode failed\n");
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return -ENOMEM;
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}
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s->s_root = d_make_root(root_inode);
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if (!s->s_root) {
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pr_err("proc_fill_super: allocate dentry failed\n");
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return -ENOMEM;
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}
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ret = proc_setup_self(s);
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if (ret) {
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return ret;
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}
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return proc_setup_thread_self(s);
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}
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static int proc_reconfigure(struct fs_context *fc)
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{
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struct super_block *sb = fc->root->d_sb;
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struct proc_fs_info *fs_info = proc_sb_info(sb);
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sync_filesystem(sb);
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proc_apply_options(fs_info, fc, current_user_ns());
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return 0;
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}
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static int proc_get_tree(struct fs_context *fc)
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{
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return get_tree_nodev(fc, proc_fill_super);
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}
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static void proc_fs_context_free(struct fs_context *fc)
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{
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struct proc_fs_context *ctx = fc->fs_private;
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put_pid_ns(ctx->pid_ns);
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kfree(ctx);
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}
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static const struct fs_context_operations proc_fs_context_ops = {
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.free = proc_fs_context_free,
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.parse_param = proc_parse_param,
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.get_tree = proc_get_tree,
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.reconfigure = proc_reconfigure,
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};
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static int proc_init_fs_context(struct fs_context *fc)
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{
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struct proc_fs_context *ctx;
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ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL);
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if (!ctx)
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return -ENOMEM;
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ctx->pid_ns = get_pid_ns(task_active_pid_ns(current));
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put_user_ns(fc->user_ns);
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fc->user_ns = get_user_ns(ctx->pid_ns->user_ns);
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fc->fs_private = ctx;
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fc->ops = &proc_fs_context_ops;
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return 0;
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}
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static void proc_kill_sb(struct super_block *sb)
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{
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struct proc_fs_info *fs_info = proc_sb_info(sb);
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if (!fs_info) {
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kill_anon_super(sb);
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return;
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}
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dput(fs_info->proc_self);
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dput(fs_info->proc_thread_self);
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kill_anon_super(sb);
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put_pid_ns(fs_info->pid_ns);
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kfree(fs_info);
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}
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static struct file_system_type proc_fs_type = {
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.name = "proc",
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.init_fs_context = proc_init_fs_context,
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.parameters = proc_fs_parameters,
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.kill_sb = proc_kill_sb,
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.fs_flags = FS_USERNS_MOUNT | FS_DISALLOW_NOTIFY_PERM,
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};
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void __init proc_root_init(void)
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{
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proc_init_kmemcache();
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set_proc_pid_nlink();
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proc_self_init();
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proc_thread_self_init();
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proc_symlink("mounts", NULL, "self/mounts");
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proc_net_init();
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proc_mkdir("fs", NULL);
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proc_mkdir("driver", NULL);
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proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
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#if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
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/* just give it a mountpoint */
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proc_create_mount_point("openprom");
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#endif
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proc_tty_init();
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proc_mkdir("bus", NULL);
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proc_sys_init();
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register_filesystem(&proc_fs_type);
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}
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static int proc_root_getattr(const struct path *path, struct kstat *stat,
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u32 request_mask, unsigned int query_flags)
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{
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generic_fillattr(d_inode(path->dentry), stat);
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stat->nlink = proc_root.nlink + nr_processes();
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return 0;
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}
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static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
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{
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if (!proc_pid_lookup(dentry, flags))
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return NULL;
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return proc_lookup(dir, dentry, flags);
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}
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static int proc_root_readdir(struct file *file, struct dir_context *ctx)
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{
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if (ctx->pos < FIRST_PROCESS_ENTRY) {
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int error = proc_readdir(file, ctx);
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if (unlikely(error <= 0))
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return error;
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ctx->pos = FIRST_PROCESS_ENTRY;
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}
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return proc_pid_readdir(file, ctx);
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}
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/*
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* The root /proc directory is special, as it has the
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* <pid> directories. Thus we don't use the generic
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* directory handling functions for that..
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*/
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static const struct file_operations proc_root_operations = {
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.read = generic_read_dir,
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.iterate_shared = proc_root_readdir,
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.llseek = generic_file_llseek,
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};
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/*
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* proc root can do almost nothing..
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*/
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static const struct inode_operations proc_root_inode_operations = {
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.lookup = proc_root_lookup,
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.getattr = proc_root_getattr,
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};
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/*
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* This is the root "inode" in the /proc tree..
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*/
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struct proc_dir_entry proc_root = {
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.low_ino = PROC_ROOT_INO,
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.namelen = 5,
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.mode = S_IFDIR | S_IRUGO | S_IXUGO,
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.nlink = 2,
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.refcnt = REFCOUNT_INIT(1),
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.proc_iops = &proc_root_inode_operations,
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.proc_dir_ops = &proc_root_operations,
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.parent = &proc_root,
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.subdir = RB_ROOT,
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.name = "/proc",
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};
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