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/fs_context.h>
  23 #include <linux/mount.h>
  24 #include <linux/pid_namespace.h>
  25 #include <linux/fs_parser.h>
  26 #include <linux/cred.h>
  27 #include <linux/magic.h>
  28 #include <linux/slab.h>
  29
  30 #include "internal.h"
  31
  32 struct proc_fs_context {
  33         struct pid_namespace    *pid_ns;
  34         unsigned int            mask;
  35         int                     hidepid;
  36         int                     gid;
  37 };
  38
  39 enum proc_param {
  40         Opt_gid,
  41         Opt_hidepid,
  42 };
  43
  44 static const struct fs_parameter_spec proc_param_specs[] = {
  45         fsparam_u32("gid",      Opt_gid),
  46         fsparam_u32("hidepid",  Opt_hidepid),
  47         {}
  48 };
  49
  50 static const struct fs_parameter_description proc_fs_parameters = {
  51         .name           = "proc",
  52         .specs          = proc_param_specs,
  53 };
  54
  55 static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
  56 {
  57         struct proc_fs_context *ctx = fc->fs_private;
  58         struct fs_parse_result result;
  59         int opt;
  60
  61         opt = fs_parse(fc, &proc_fs_parameters, param, &result);
  62         if (opt < 0)
  63                 return opt;
  64
  65         switch (opt) {
  66         case Opt_gid:
  67                 ctx->gid = result.uint_32;
  68                 break;
  69
  70         case Opt_hidepid:
  71                 ctx->hidepid = result.uint_32;
  72                 if (ctx->hidepid < HIDEPID_OFF ||
  73                     ctx->hidepid > HIDEPID_INVISIBLE)
  74                         return invalf(fc, "proc: hidepid value must be between 0 and 2.\n");
  75                 break;
  76
  77         default:
  78                 return -EINVAL;
  79         }
  80
  81         ctx->mask |= 1 << opt;
  82         return 0;
  83 }
  84
  85 static void proc_apply_options(struct super_block *s,
  86                                struct fs_context *fc,
  87                                struct pid_namespace *pid_ns,
  88                                struct user_namespace *user_ns)
  89 {
  90         struct proc_fs_context *ctx = fc->fs_private;
  91
  92         if (ctx->mask & (1 << Opt_gid))
  93                 pid_ns->pid_gid = make_kgid(user_ns, ctx->gid);
  94         if (ctx->mask & (1 << Opt_hidepid))
  95                 pid_ns->hide_pid = ctx->hidepid;
  96 }
  97
  98 static int proc_fill_super(struct super_block *s, struct fs_context *fc)
  99 {
 100         struct pid_namespace *pid_ns = get_pid_ns(s->s_fs_info);
 101         struct inode *root_inode;
 102         int ret;
 103
 104         proc_apply_options(s, fc, pid_ns, current_user_ns());
 105
 106         /* User space would break if executables or devices appear on proc */
 107         s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
 108         s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
 109         s->s_blocksize = 1024;
 110         s->s_blocksize_bits = 10;
 111         s->s_magic = PROC_SUPER_MAGIC;
 112         s->s_op = &proc_sops;
 113         s->s_time_gran = 1;
 114
 115         /*
 116          * procfs isn't actually a stacking filesystem; however, there is
 117          * too much magic going on inside it to permit stacking things on
 118          * top of it
 119          */
 120         s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
 121
 122         /* procfs dentries and inodes don't require IO to create */
 123         s->s_shrink.seeks = 0;
 124
 125         pde_get(&proc_root);
 126         root_inode = proc_get_inode(s, &proc_root);
 127         if (!root_inode) {
 128                 pr_err("proc_fill_super: get root inode failed\n");
 129                 return -ENOMEM;
 130         }
 131
 132         s->s_root = d_make_root(root_inode);
 133         if (!s->s_root) {
 134                 pr_err("proc_fill_super: allocate dentry failed\n");
 135                 return -ENOMEM;
 136         }
 137
 138         ret = proc_setup_self(s);
 139         if (ret) {
 140                 return ret;
 141         }
 142         return proc_setup_thread_self(s);
 143 }
 144
 145 static int proc_reconfigure(struct fs_context *fc)
 146 {
 147         struct super_block *sb = fc->root->d_sb;
 148         struct pid_namespace *pid = sb->s_fs_info;
 149
 150         sync_filesystem(sb);
 151
 152         proc_apply_options(sb, fc, pid, current_user_ns());
 153         return 0;
 154 }
 155
 156 static int proc_get_tree(struct fs_context *fc)
 157 {
 158         struct proc_fs_context *ctx = fc->fs_private;
 159
 160         fc->s_fs_info = ctx->pid_ns;
 161         return vfs_get_super(fc, vfs_get_keyed_super, proc_fill_super);
 162 }
 163
 164 static void proc_fs_context_free(struct fs_context *fc)
 165 {
 166         struct proc_fs_context *ctx = fc->fs_private;
 167
 168         put_pid_ns(ctx->pid_ns);
 169         kfree(ctx);
 170 }
 171
 172 static const struct fs_context_operations proc_fs_context_ops = {
 173         .free           = proc_fs_context_free,
 174         .parse_param    = proc_parse_param,
 175         .get_tree       = proc_get_tree,
 176         .reconfigure    = proc_reconfigure,
 177 };
 178
 179 static int proc_init_fs_context(struct fs_context *fc)
 180 {
 181         struct proc_fs_context *ctx;
 182
 183         ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL);
 184         if (!ctx)
 185                 return -ENOMEM;
 186
 187         ctx->pid_ns = get_pid_ns(task_active_pid_ns(current));
 188         put_user_ns(fc->user_ns);
 189         fc->user_ns = get_user_ns(ctx->pid_ns->user_ns);
 190         fc->fs_private = ctx;
 191         fc->ops = &proc_fs_context_ops;
 192         return 0;
 193 }
 194
 195 static void proc_kill_sb(struct super_block *sb)
 196 {
 197         struct pid_namespace *ns;
 198
 199         ns = (struct pid_namespace *)sb->s_fs_info;
 200         if (ns->proc_self)
 201                 dput(ns->proc_self);
 202         if (ns->proc_thread_self)
 203                 dput(ns->proc_thread_self);
 204         kill_anon_super(sb);
 205         put_pid_ns(ns);
 206 }
 207
 208 static struct file_system_type proc_fs_type = {
 209         .name                   = "proc",
 210         .init_fs_context        = proc_init_fs_context,
 211         .parameters             = &proc_fs_parameters,
 212         .kill_sb                = proc_kill_sb,
 213         .fs_flags               = FS_USERNS_MOUNT | FS_DISALLOW_NOTIFY_PERM,
 214 };
 215
 216 void __init proc_root_init(void)
 217 {
 218         proc_init_kmemcache();
 219         set_proc_pid_nlink();
 220         proc_self_init();
 221         proc_thread_self_init();
 222         proc_symlink("mounts", NULL, "self/mounts");
 223
 224         proc_net_init();
 225         proc_mkdir("fs", NULL);
 226         proc_mkdir("driver", NULL);
 227         proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
 228 #if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
 229         /* just give it a mountpoint */
 230         proc_create_mount_point("openprom");
 231 #endif
 232         proc_tty_init();
 233         proc_mkdir("bus", NULL);
 234         proc_sys_init();
 235
 236         register_filesystem(&proc_fs_type);
 237 }
 238
 239 static int proc_root_getattr(const struct path *path, struct kstat *stat,
 240                              u32 request_mask, unsigned int query_flags)
 241 {
 242         generic_fillattr(d_inode(path->dentry), stat);
 243         stat->nlink = proc_root.nlink + nr_processes();
 244         return 0;
 245 }
 246
 247 static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
 248 {
 249         if (!proc_pid_lookup(dentry, flags))
 250                 return NULL;
 251
 252         return proc_lookup(dir, dentry, flags);
 253 }
 254
 255 static int proc_root_readdir(struct file *file, struct dir_context *ctx)
 256 {
 257         if (ctx->pos < FIRST_PROCESS_ENTRY) {
 258                 int error = proc_readdir(file, ctx);
 259                 if (unlikely(error <= 0))
 260                         return error;
 261                 ctx->pos = FIRST_PROCESS_ENTRY;
 262         }
 263
 264         return proc_pid_readdir(file, ctx);
 265 }
 266
 267 /*
 268  * The root /proc directory is special, as it has the
 269  * <pid> directories. Thus we don't use the generic
 270  * directory handling functions for that..
 271  */
 272 static const struct file_operations proc_root_operations = {
 273         .read            = generic_read_dir,
 274         .iterate_shared  = proc_root_readdir,
 275         .llseek         = generic_file_llseek,
 276 };
 277
 278 /*
 279  * proc root can do almost nothing..
 280  */
 281 static const struct inode_operations proc_root_inode_operations = {
 282         .lookup         = proc_root_lookup,
 283         .getattr        = proc_root_getattr,
 284 };
 285
 286 /*
 287  * This is the root "inode" in the /proc tree..
 288  */
 289 struct proc_dir_entry proc_root = {
 290         .low_ino        = PROC_ROOT_INO,
 291         .namelen        = 5,
 292         .mode           = S_IFDIR | S_IRUGO | S_IXUGO,
 293         .nlink          = 2,
 294         .refcnt         = REFCOUNT_INIT(1),
 295         .proc_iops      = &proc_root_inode_operations,
 296         .proc_fops      = &proc_root_operations,
 297         .parent         = &proc_root,
 298         .subdir         = RB_ROOT,
 299         .name           = "/proc",
 300 };
 301
 302 int pid_ns_prepare_proc(struct pid_namespace *ns)
 303 {
 304         struct proc_fs_context *ctx;
 305         struct fs_context *fc;
 306         struct vfsmount *mnt;
 307
 308         fc = fs_context_for_mount(&proc_fs_type, SB_KERNMOUNT);
 309         if (IS_ERR(fc))
 310                 return PTR_ERR(fc);
 311
 312         if (fc->user_ns != ns->user_ns) {
 313                 put_user_ns(fc->user_ns);
 314                 fc->user_ns = get_user_ns(ns->user_ns);
 315         }
 316
 317         ctx = fc->fs_private;
 318         if (ctx->pid_ns != ns) {
 319                 put_pid_ns(ctx->pid_ns);
 320                 get_pid_ns(ns);
 321                 ctx->pid_ns = ns;
 322         }
 323
 324         mnt = fc_mount(fc);
 325         put_fs_context(fc);
 326         if (IS_ERR(mnt))
 327                 return PTR_ERR(mnt);
 328
 329         ns->proc_mnt = mnt;
 330         return 0;
 331 }
 332
 333 void pid_ns_release_proc(struct pid_namespace *ns)
 334 {
 335         kern_unmount(ns->proc_mnt);
 336 }