fs/proc/root.c

   1 /*
   2  *  linux/fs/proc/root.c
   3  *
   4  *  Copyright (C) 1991, 1992 Linus Torvalds
   5  *
   6  *  proc root directory handling functions
   7  */
   8
   9 #include <asm/uaccess.h>
  10
  11 #include <linux/errno.h>
  12 #include <linux/time.h>
  13 #include <linux/proc_fs.h>
  14 #include <linux/stat.h>
  15 #include <linux/init.h>
  16 #include <linux/sched.h>
  17 #include <linux/module.h>
  18 #include <linux/bitops.h>
  19 #include <linux/user_namespace.h>
  20 #include <linux/mount.h>
  21 #include <linux/pid_namespace.h>
  22 #include <linux/parser.h>
  23
  24 #include "internal.h"
  25
  26 static int proc_test_super(struct super_block *sb, void *data)
  27 {
  28         return sb->s_fs_info == data;
  29 }
  30
  31 static int proc_set_super(struct super_block *sb, void *data)
  32 {
  33         int err = set_anon_super(sb, NULL);
  34         if (!err) {
  35                 struct pid_namespace *ns = (struct pid_namespace *)data;
  36                 sb->s_fs_info = get_pid_ns(ns);
  37         }
  38         return err;
  39 }
  40
  41 enum {
  42         Opt_gid, Opt_hidepid, Opt_err,
  43 };
  44
  45 static const match_table_t tokens = {
  46         {Opt_hidepid, "hidepid=%u"},
  47         {Opt_gid, "gid=%u"},
  48         {Opt_err, NULL},
  49 };
  50
  51 static int proc_parse_options(char *options, struct pid_namespace *pid)
  52 {
  53         char *p;
  54         substring_t args[MAX_OPT_ARGS];
  55         int option;
  56
  57         if (!options)
  58                 return 1;
  59
  60         while ((p = strsep(&options, ",")) != NULL) {
  61                 int token;
  62                 if (!*p)
  63                         continue;
  64
  65                 args[0].to = args[0].from = NULL;
  66                 token = match_token(p, tokens, args);
  67                 switch (token) {
  68                 case Opt_gid:
  69                         if (match_int(&args[0], &option))
  70                                 return 0;
  71                         pid->pid_gid = make_kgid(current_user_ns(), option);
  72                         break;
  73                 case Opt_hidepid:
  74                         if (match_int(&args[0], &option))
  75                                 return 0;
  76                         if (option < 0 || option > 2) {
  77                                 pr_err("proc: hidepid value must be between 0 and 2.\n");
  78                                 return 0;
  79                         }
  80                         pid->hide_pid = option;
  81                         break;
  82                 default:
  83                         pr_err("proc: unrecognized mount option \"%s\" "
  84                                "or missing value\n", p);
  85                         return 0;
  86                 }
  87         }
  88
  89         return 1;
  90 }
  91
  92 int proc_remount(struct super_block *sb, int *flags, char *data)
  93 {
  94         struct pid_namespace *pid = sb->s_fs_info;
  95
  96         sync_filesystem(sb);
  97         return !proc_parse_options(data, pid);
  98 }
  99
 100 static struct dentry *proc_mount(struct file_system_type *fs_type,
 101         int flags, const char *dev_name, void *data)
 102 {
 103         int err;
 104         struct super_block *sb;
 105         struct pid_namespace *ns;
 106         char *options;
 107
 108         if (flags & MS_KERNMOUNT) {
 109                 ns = (struct pid_namespace *)data;
 110                 options = NULL;
 111         } else {
 112                 ns = task_active_pid_ns(current);
 113                 options = data;
 114
 115                 /* Does the mounter have privilege over the pid namespace? */
 116                 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
 117                         return ERR_PTR(-EPERM);
 118         }
 119
 120         sb = sget(fs_type, proc_test_super, proc_set_super, flags, ns);
 121         if (IS_ERR(sb))
 122                 return ERR_CAST(sb);
 123
 124         /*
 125          * procfs isn't actually a stacking filesystem; however, there is
 126          * too much magic going on inside it to permit stacking things on
 127          * top of it
 128          */
 129         sb->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
 130
 131         if (!proc_parse_options(options, ns)) {
 132                 deactivate_locked_super(sb);
 133                 return ERR_PTR(-EINVAL);
 134         }
 135
 136         if (!sb->s_root) {
 137                 err = proc_fill_super(sb);
 138                 if (err) {
 139                         deactivate_locked_super(sb);
 140                         return ERR_PTR(err);
 141                 }
 142
 143                 sb->s_flags |= MS_ACTIVE;
 144                 /* User space would break if executables appear on proc */
 145                 sb->s_iflags |= SB_I_NOEXEC;
 146         }
 147
 148         return dget(sb->s_root);
 149 }
 150
 151 static void proc_kill_sb(struct super_block *sb)
 152 {
 153         struct pid_namespace *ns;
 154
 155         ns = (struct pid_namespace *)sb->s_fs_info;
 156         if (ns->proc_self)
 157                 dput(ns->proc_self);
 158         if (ns->proc_thread_self)
 159                 dput(ns->proc_thread_self);
 160         kill_anon_super(sb);
 161         put_pid_ns(ns);
 162 }
 163
 164 static struct file_system_type proc_fs_type = {
 165         .name           = "proc",
 166         .mount          = proc_mount,
 167         .kill_sb        = proc_kill_sb,
 168         .fs_flags       = FS_USERNS_VISIBLE | FS_USERNS_MOUNT,
 169 };
 170
 171 void __init proc_root_init(void)
 172 {
 173         int err;
 174
 175         proc_init_inodecache();
 176         err = register_filesystem(&proc_fs_type);
 177         if (err)
 178                 return;
 179
 180         proc_self_init();
 181         proc_thread_self_init();
 182         proc_symlink("mounts", NULL, "self/mounts");
 183
 184         proc_net_init();
 185
 186 #ifdef CONFIG_SYSVIPC
 187         proc_mkdir("sysvipc", NULL);
 188 #endif
 189         proc_mkdir("fs", NULL);
 190         proc_mkdir("driver", NULL);
 191         proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
 192 #if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
 193         /* just give it a mountpoint */
 194         proc_create_mount_point("openprom");
 195 #endif
 196         proc_tty_init();
 197         proc_mkdir("bus", NULL);
 198         proc_sys_init();
 199 }
 200
 201 static int proc_root_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat
 202 )
 203 {
 204         generic_fillattr(d_inode(dentry), stat);
 205         stat->nlink = proc_root.nlink + nr_processes();
 206         return 0;
 207 }
 208
 209 static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
 210 {
 211         if (!proc_pid_lookup(dir, dentry, flags))
 212                 return NULL;
 213
 214         return proc_lookup(dir, dentry, flags);
 215 }
 216
 217 static int proc_root_readdir(struct file *file, struct dir_context *ctx)
 218 {
 219         if (ctx->pos < FIRST_PROCESS_ENTRY) {
 220                 int error = proc_readdir(file, ctx);
 221                 if (unlikely(error <= 0))
 222                         return error;
 223                 ctx->pos = FIRST_PROCESS_ENTRY;
 224         }
 225
 226         return proc_pid_readdir(file, ctx);
 227 }
 228
 229 /*
 230  * The root /proc directory is special, as it has the
 231  * <pid> directories. Thus we don't use the generic
 232  * directory handling functions for that..
 233  */
 234 static const struct file_operations proc_root_operations = {
 235         .read            = generic_read_dir,
 236         .iterate         = proc_root_readdir,
 237         .llseek         = default_llseek,
 238 };
 239
 240 /*
 241  * proc root can do almost nothing..
 242  */
 243 static const struct inode_operations proc_root_inode_operations = {
 244         .lookup         = proc_root_lookup,
 245         .getattr        = proc_root_getattr,
 246 };
 247
 248 /*
 249  * This is the root "inode" in the /proc tree..
 250  */
 251 struct proc_dir_entry proc_root = {
 252         .low_ino        = PROC_ROOT_INO,
 253         .namelen        = 5,
 254         .mode           = S_IFDIR | S_IRUGO | S_IXUGO,
 255         .nlink          = 2,
 256         .count          = ATOMIC_INIT(1),
 257         .proc_iops      = &proc_root_inode_operations,
 258         .proc_fops      = &proc_root_operations,
 259         .parent         = &proc_root,
 260         .subdir         = RB_ROOT,
 261         .name           = "/proc",
 262 };
 263
 264 int pid_ns_prepare_proc(struct pid_namespace *ns)
 265 {
 266         struct vfsmount *mnt;
 267
 268         mnt = kern_mount_data(&proc_fs_type, ns);
 269         if (IS_ERR(mnt))
 270                 return PTR_ERR(mnt);
 271
 272         ns->proc_mnt = mnt;
 273         return 0;
 274 }
 275
 276 void pid_ns_release_proc(struct pid_namespace *ns)
 277 {
 278         kern_unmount(ns->proc_mnt);
 279 }