fs/proc/root.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/fs/proc/root.c
   4  *
   5  *  Copyright (C) 1991, 1992 Linus Torvalds
   6  *
   7  *  proc root directory handling functions
   8  */
   9
  10 #include <linux/uaccess.h>
  11
  12 #include <linux/errno.h>
  13 #include <linux/time.h>
  14 #include <linux/proc_fs.h>
  15 #include <linux/stat.h>
  16 #include <linux/init.h>
  17 #include <linux/sched.h>
  18 #include <linux/sched/stat.h>
  19 #include <linux/module.h>
  20 #include <linux/bitops.h>
  21 #include <linux/user_namespace.h>
  22 #include <linux/mount.h>
  23 #include <linux/pid_namespace.h>
  24 #include <linux/parser.h>
  25 #include <linux/cred.h>
  26
  27 #include "internal.h"
  28
  29 enum {
  30         Opt_gid, Opt_hidepid, Opt_err,
  31 };
  32
  33 static const match_table_t tokens = {
  34         {Opt_hidepid, "hidepid=%u"},
  35         {Opt_gid, "gid=%u"},
  36         {Opt_err, NULL},
  37 };
  38
  39 int proc_parse_options(char *options, struct pid_namespace *pid)
  40 {
  41         char *p;
  42         substring_t args[MAX_OPT_ARGS];
  43         int option;
  44
  45         if (!options)
  46                 return 1;
  47
  48         while ((p = strsep(&options, ",")) != NULL) {
  49                 int token;
  50                 if (!*p)
  51                         continue;
  52
  53                 args[0].to = args[0].from = NULL;
  54                 token = match_token(p, tokens, args);
  55                 switch (token) {
  56                 case Opt_gid:
  57                         if (match_int(&args[0], &option))
  58                                 return 0;
  59                         pid->pid_gid = make_kgid(current_user_ns(), option);
  60                         break;
  61                 case Opt_hidepid:
  62                         if (match_int(&args[0], &option))
  63                                 return 0;
  64                         if (option < HIDEPID_OFF ||
  65                             option > HIDEPID_INVISIBLE) {
  66                                 pr_err("proc: hidepid value must be between 0 and 2.\n");
  67                                 return 0;
  68                         }
  69                         pid->hide_pid = option;
  70                         break;
  71                 default:
  72                         pr_err("proc: unrecognized mount option \"%s\" "
  73                                "or missing value\n", p);
  74                         return 0;
  75                 }
  76         }
  77
  78         return 1;
  79 }
  80
  81 int proc_remount(struct super_block *sb, int *flags, char *data)
  82 {
  83         struct pid_namespace *pid = sb->s_fs_info;
  84
  85         sync_filesystem(sb);
  86         return !proc_parse_options(data, pid);
  87 }
  88
  89 static struct dentry *proc_mount(struct file_system_type *fs_type,
  90         int flags, const char *dev_name, void *data)
  91 {
  92         struct pid_namespace *ns;
  93
  94         if (flags & MS_KERNMOUNT) {
  95                 ns = data;
  96                 data = NULL;
  97         } else {
  98                 ns = task_active_pid_ns(current);
  99         }
 100
 101         return mount_ns(fs_type, flags, data, ns, ns->user_ns, proc_fill_super);
 102 }
 103
 104 static void proc_kill_sb(struct super_block *sb)
 105 {
 106         struct pid_namespace *ns;
 107
 108         ns = (struct pid_namespace *)sb->s_fs_info;
 109         if (ns->proc_self)
 110                 dput(ns->proc_self);
 111         if (ns->proc_thread_self)
 112                 dput(ns->proc_thread_self);
 113         kill_anon_super(sb);
 114         put_pid_ns(ns);
 115 }
 116
 117 static struct file_system_type proc_fs_type = {
 118         .name           = "proc",
 119         .mount          = proc_mount,
 120         .kill_sb        = proc_kill_sb,
 121         .fs_flags       = FS_USERNS_MOUNT,
 122 };
 123
 124 void __init proc_root_init(void)
 125 {
 126         int err;
 127
 128         proc_init_inodecache();
 129         set_proc_pid_nlink();
 130         err = register_filesystem(&proc_fs_type);
 131         if (err)
 132                 return;
 133
 134         proc_self_init();
 135         proc_thread_self_init();
 136         proc_symlink("mounts", NULL, "self/mounts");
 137
 138         proc_net_init();
 139
 140 #ifdef CONFIG_SYSVIPC
 141         proc_mkdir("sysvipc", NULL);
 142 #endif
 143         proc_mkdir("fs", NULL);
 144         proc_mkdir("driver", NULL);
 145         proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
 146 #if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
 147         /* just give it a mountpoint */
 148         proc_create_mount_point("openprom");
 149 #endif
 150         proc_tty_init();
 151         proc_mkdir("bus", NULL);
 152         proc_sys_init();
 153 }
 154
 155 static int proc_root_getattr(const struct path *path, struct kstat *stat,
 156                              u32 request_mask, unsigned int query_flags)
 157 {
 158         generic_fillattr(d_inode(path->dentry), stat);
 159         stat->nlink = proc_root.nlink + nr_processes();
 160         return 0;
 161 }
 162
 163 static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
 164 {
 165         if (!proc_pid_lookup(dir, dentry, flags))
 166                 return NULL;
 167
 168         return proc_lookup(dir, dentry, flags);
 169 }
 170
 171 static int proc_root_readdir(struct file *file, struct dir_context *ctx)
 172 {
 173         if (ctx->pos < FIRST_PROCESS_ENTRY) {
 174                 int error = proc_readdir(file, ctx);
 175                 if (unlikely(error <= 0))
 176                         return error;
 177                 ctx->pos = FIRST_PROCESS_ENTRY;
 178         }
 179
 180         return proc_pid_readdir(file, ctx);
 181 }
 182
 183 /*
 184  * The root /proc directory is special, as it has the
 185  * <pid> directories. Thus we don't use the generic
 186  * directory handling functions for that..
 187  */
 188 static const struct file_operations proc_root_operations = {
 189         .read            = generic_read_dir,
 190         .iterate_shared  = proc_root_readdir,
 191         .llseek         = generic_file_llseek,
 192 };
 193
 194 /*
 195  * proc root can do almost nothing..
 196  */
 197 static const struct inode_operations proc_root_inode_operations = {
 198         .lookup         = proc_root_lookup,
 199         .getattr        = proc_root_getattr,
 200 };
 201
 202 /*
 203  * This is the root "inode" in the /proc tree..
 204  */
 205 struct proc_dir_entry proc_root = {
 206         .low_ino        = PROC_ROOT_INO,
 207         .namelen        = 5,
 208         .mode           = S_IFDIR | S_IRUGO | S_IXUGO,
 209         .nlink          = 2,
 210         .count          = ATOMIC_INIT(1),
 211         .proc_iops      = &proc_root_inode_operations,
 212         .proc_fops      = &proc_root_operations,
 213         .parent         = &proc_root,
 214         .subdir         = RB_ROOT_CACHED,
 215         .name           = "/proc",
 216 };
 217
 218 int pid_ns_prepare_proc(struct pid_namespace *ns)
 219 {
 220         struct vfsmount *mnt;
 221
 222         mnt = kern_mount_data(&proc_fs_type, ns);
 223         if (IS_ERR(mnt))
 224                 return PTR_ERR(mnt);
 225
 226         ns->proc_mnt = mnt;
 227         return 0;
 228 }
 229
 230 void pid_ns_release_proc(struct pid_namespace *ns)
 231 {
 232         kern_unmount(ns->proc_mnt);
 233 }