linux/fs/proc/root.c
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   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
  32struct proc_fs_context {
  33        struct pid_namespace    *pid_ns;
  34        unsigned int            mask;
  35        enum proc_hidepid       hidepid;
  36        int                     gid;
  37        enum proc_pidonly       pidonly;
  38};
  39
  40enum proc_param {
  41        Opt_gid,
  42        Opt_hidepid,
  43        Opt_subset,
  44};
  45
  46static const struct fs_parameter_spec proc_fs_parameters[] = {
  47        fsparam_u32("gid",      Opt_gid),
  48        fsparam_string("hidepid",       Opt_hidepid),
  49        fsparam_string("subset",        Opt_subset),
  50        {}
  51};
  52
  53static inline int valid_hidepid(unsigned int value)
  54{
  55        return (value == HIDEPID_OFF ||
  56                value == HIDEPID_NO_ACCESS ||
  57                value == HIDEPID_INVISIBLE ||
  58                value == HIDEPID_NOT_PTRACEABLE);
  59}
  60
  61static int proc_parse_hidepid_param(struct fs_context *fc, struct fs_parameter *param)
  62{
  63        struct proc_fs_context *ctx = fc->fs_private;
  64        struct fs_parameter_spec hidepid_u32_spec = fsparam_u32("hidepid", Opt_hidepid);
  65        struct fs_parse_result result;
  66        int base = (unsigned long)hidepid_u32_spec.data;
  67
  68        if (param->type != fs_value_is_string)
  69                return invalf(fc, "proc: unexpected type of hidepid value\n");
  70
  71        if (!kstrtouint(param->string, base, &result.uint_32)) {
  72                if (!valid_hidepid(result.uint_32))
  73                        return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string);
  74                ctx->hidepid = result.uint_32;
  75                return 0;
  76        }
  77
  78        if (!strcmp(param->string, "off"))
  79                ctx->hidepid = HIDEPID_OFF;
  80        else if (!strcmp(param->string, "noaccess"))
  81                ctx->hidepid = HIDEPID_NO_ACCESS;
  82        else if (!strcmp(param->string, "invisible"))
  83                ctx->hidepid = HIDEPID_INVISIBLE;
  84        else if (!strcmp(param->string, "ptraceable"))
  85                ctx->hidepid = HIDEPID_NOT_PTRACEABLE;
  86        else
  87                return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string);
  88
  89        return 0;
  90}
  91
  92static int proc_parse_subset_param(struct fs_context *fc, char *value)
  93{
  94        struct proc_fs_context *ctx = fc->fs_private;
  95
  96        while (value) {
  97                char *ptr = strchr(value, ',');
  98
  99                if (ptr != NULL)
 100                        *ptr++ = '\0';
 101
 102                if (*value != '\0') {
 103                        if (!strcmp(value, "pid")) {
 104                                ctx->pidonly = PROC_PIDONLY_ON;
 105                        } else {
 106                                return invalf(fc, "proc: unsupported subset option - %s\n", value);
 107                        }
 108                }
 109                value = ptr;
 110        }
 111
 112        return 0;
 113}
 114
 115static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
 116{
 117        struct proc_fs_context *ctx = fc->fs_private;
 118        struct fs_parse_result result;
 119        int opt;
 120
 121        opt = fs_parse(fc, proc_fs_parameters, param, &result);
 122        if (opt < 0)
 123                return opt;
 124
 125        switch (opt) {
 126        case Opt_gid:
 127                ctx->gid = result.uint_32;
 128                break;
 129
 130        case Opt_hidepid:
 131                if (proc_parse_hidepid_param(fc, param))
 132                        return -EINVAL;
 133                break;
 134
 135        case Opt_subset:
 136                if (proc_parse_subset_param(fc, param->string) < 0)
 137                        return -EINVAL;
 138                break;
 139
 140        default:
 141                return -EINVAL;
 142        }
 143
 144        ctx->mask |= 1 << opt;
 145        return 0;
 146}
 147
 148static void proc_apply_options(struct proc_fs_info *fs_info,
 149                               struct fs_context *fc,
 150                               struct user_namespace *user_ns)
 151{
 152        struct proc_fs_context *ctx = fc->fs_private;
 153
 154        if (ctx->mask & (1 << Opt_gid))
 155                fs_info->pid_gid = make_kgid(user_ns, ctx->gid);
 156        if (ctx->mask & (1 << Opt_hidepid))
 157                fs_info->hide_pid = ctx->hidepid;
 158        if (ctx->mask & (1 << Opt_subset))
 159                fs_info->pidonly = ctx->pidonly;
 160}
 161
 162static int proc_fill_super(struct super_block *s, struct fs_context *fc)
 163{
 164        struct proc_fs_context *ctx = fc->fs_private;
 165        struct inode *root_inode;
 166        struct proc_fs_info *fs_info;
 167        int ret;
 168
 169        fs_info = kzalloc(sizeof(*fs_info), GFP_KERNEL);
 170        if (!fs_info)
 171                return -ENOMEM;
 172
 173        fs_info->pid_ns = get_pid_ns(ctx->pid_ns);
 174        proc_apply_options(fs_info, fc, current_user_ns());
 175
 176        /* User space would break if executables or devices appear on proc */
 177        s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
 178        s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
 179        s->s_blocksize = 1024;
 180        s->s_blocksize_bits = 10;
 181        s->s_magic = PROC_SUPER_MAGIC;
 182        s->s_op = &proc_sops;
 183        s->s_time_gran = 1;
 184        s->s_fs_info = fs_info;
 185
 186        /*
 187         * procfs isn't actually a stacking filesystem; however, there is
 188         * too much magic going on inside it to permit stacking things on
 189         * top of it
 190         */
 191        s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
 192
 193        /* procfs dentries and inodes don't require IO to create */
 194        s->s_shrink.seeks = 0;
 195
 196        pde_get(&proc_root);
 197        root_inode = proc_get_inode(s, &proc_root);
 198        if (!root_inode) {
 199                pr_err("proc_fill_super: get root inode failed\n");
 200                return -ENOMEM;
 201        }
 202
 203        s->s_root = d_make_root(root_inode);
 204        if (!s->s_root) {
 205                pr_err("proc_fill_super: allocate dentry failed\n");
 206                return -ENOMEM;
 207        }
 208
 209        ret = proc_setup_self(s);
 210        if (ret) {
 211                return ret;
 212        }
 213        return proc_setup_thread_self(s);
 214}
 215
 216static int proc_reconfigure(struct fs_context *fc)
 217{
 218        struct super_block *sb = fc->root->d_sb;
 219        struct proc_fs_info *fs_info = proc_sb_info(sb);
 220
 221        sync_filesystem(sb);
 222
 223        proc_apply_options(fs_info, fc, current_user_ns());
 224        return 0;
 225}
 226
 227static int proc_get_tree(struct fs_context *fc)
 228{
 229        return get_tree_nodev(fc, proc_fill_super);
 230}
 231
 232static void proc_fs_context_free(struct fs_context *fc)
 233{
 234        struct proc_fs_context *ctx = fc->fs_private;
 235
 236        put_pid_ns(ctx->pid_ns);
 237        kfree(ctx);
 238}
 239
 240static const struct fs_context_operations proc_fs_context_ops = {
 241        .free           = proc_fs_context_free,
 242        .parse_param    = proc_parse_param,
 243        .get_tree       = proc_get_tree,
 244        .reconfigure    = proc_reconfigure,
 245};
 246
 247static int proc_init_fs_context(struct fs_context *fc)
 248{
 249        struct proc_fs_context *ctx;
 250
 251        ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL);
 252        if (!ctx)
 253                return -ENOMEM;
 254
 255        ctx->pid_ns = get_pid_ns(task_active_pid_ns(current));
 256        put_user_ns(fc->user_ns);
 257        fc->user_ns = get_user_ns(ctx->pid_ns->user_ns);
 258        fc->fs_private = ctx;
 259        fc->ops = &proc_fs_context_ops;
 260        return 0;
 261}
 262
 263static void proc_kill_sb(struct super_block *sb)
 264{
 265        struct proc_fs_info *fs_info = proc_sb_info(sb);
 266
 267        if (!fs_info) {
 268                kill_anon_super(sb);
 269                return;
 270        }
 271
 272        dput(fs_info->proc_self);
 273        dput(fs_info->proc_thread_self);
 274
 275        kill_anon_super(sb);
 276        put_pid_ns(fs_info->pid_ns);
 277        kfree(fs_info);
 278}
 279
 280static struct file_system_type proc_fs_type = {
 281        .name                   = "proc",
 282        .init_fs_context        = proc_init_fs_context,
 283        .parameters             = proc_fs_parameters,
 284        .kill_sb                = proc_kill_sb,
 285        .fs_flags               = FS_USERNS_MOUNT | FS_DISALLOW_NOTIFY_PERM,
 286};
 287
 288void __init proc_root_init(void)
 289{
 290        proc_init_kmemcache();
 291        set_proc_pid_nlink();
 292        proc_self_init();
 293        proc_thread_self_init();
 294        proc_symlink("mounts", NULL, "self/mounts");
 295
 296        proc_net_init();
 297        proc_mkdir("fs", NULL);
 298        proc_mkdir("driver", NULL);
 299        proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
 300#if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
 301        /* just give it a mountpoint */
 302        proc_create_mount_point("openprom");
 303#endif
 304        proc_tty_init();
 305        proc_mkdir("bus", NULL);
 306        proc_sys_init();
 307
 308        register_filesystem(&proc_fs_type);
 309}
 310
 311static int proc_root_getattr(struct user_namespace *mnt_userns,
 312                             const struct path *path, struct kstat *stat,
 313                             u32 request_mask, unsigned int query_flags)
 314{
 315        generic_fillattr(&init_user_ns, d_inode(path->dentry), stat);
 316        stat->nlink = proc_root.nlink + nr_processes();
 317        return 0;
 318}
 319
 320static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
 321{
 322        if (!proc_pid_lookup(dentry, flags))
 323                return NULL;
 324
 325        return proc_lookup(dir, dentry, flags);
 326}
 327
 328static int proc_root_readdir(struct file *file, struct dir_context *ctx)
 329{
 330        if (ctx->pos < FIRST_PROCESS_ENTRY) {
 331                int error = proc_readdir(file, ctx);
 332                if (unlikely(error <= 0))
 333                        return error;
 334                ctx->pos = FIRST_PROCESS_ENTRY;
 335        }
 336
 337        return proc_pid_readdir(file, ctx);
 338}
 339
 340/*
 341 * The root /proc directory is special, as it has the
 342 * <pid> directories. Thus we don't use the generic
 343 * directory handling functions for that..
 344 */
 345static const struct file_operations proc_root_operations = {
 346        .read            = generic_read_dir,
 347        .iterate_shared  = proc_root_readdir,
 348        .llseek         = generic_file_llseek,
 349};
 350
 351/*
 352 * proc root can do almost nothing..
 353 */
 354static const struct inode_operations proc_root_inode_operations = {
 355        .lookup         = proc_root_lookup,
 356        .getattr        = proc_root_getattr,
 357};
 358
 359/*
 360 * This is the root "inode" in the /proc tree..
 361 */
 362struct proc_dir_entry proc_root = {
 363        .low_ino        = PROC_ROOT_INO, 
 364        .namelen        = 5, 
 365        .mode           = S_IFDIR | S_IRUGO | S_IXUGO, 
 366        .nlink          = 2, 
 367        .refcnt         = REFCOUNT_INIT(1),
 368        .proc_iops      = &proc_root_inode_operations, 
 369        .proc_dir_ops   = &proc_root_operations,
 370        .parent         = &proc_root,
 371        .subdir         = RB_ROOT,
 372        .name           = "/proc",
 373};
 374
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