fs/overlayfs/super.c

   1 /*
   2  *
   3  * Copyright (C) 2011 Novell Inc.
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 as published by
   7  * the Free Software Foundation.
   8  */
   9
  10 #include <uapi/linux/magic.h>
  11 #include <linux/fs.h>
  12 #include <linux/namei.h>
  13 #include <linux/xattr.h>
  14 #include <linux/mount.h>
  15 #include <linux/parser.h>
  16 #include <linux/module.h>
  17 #include <linux/statfs.h>
  18 #include <linux/seq_file.h>
  19 #include <linux/posix_acl_xattr.h>
  20 #include "overlayfs.h"
  21
  22 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
  23 MODULE_DESCRIPTION("Overlay filesystem");
  24 MODULE_LICENSE("GPL");
  25
  26
  27 struct ovl_dir_cache;
  28
  29 #define OVL_MAX_STACK 500
  30
  31 static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
  32 module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
  33 MODULE_PARM_DESC(ovl_redirect_dir_def,
  34                  "Default to on or off for the redirect_dir feature");
  35
  36 static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
  37 module_param_named(index, ovl_index_def, bool, 0644);
  38 MODULE_PARM_DESC(ovl_index_def,
  39                  "Default to on or off for the inodes index feature");
  40
  41 static void ovl_entry_stack_free(struct ovl_entry *oe)
  42 {
  43         unsigned int i;
  44
  45         for (i = 0; i < oe->numlower; i++)
  46                 dput(oe->lowerstack[i].dentry);
  47 }
  48
  49 static void ovl_dentry_release(struct dentry *dentry)
  50 {
  51         struct ovl_entry *oe = dentry->d_fsdata;
  52
  53         if (oe) {
  54                 ovl_entry_stack_free(oe);
  55                 kfree_rcu(oe, rcu);
  56         }
  57 }
  58
  59 static int ovl_check_append_only(struct inode *inode, int flag)
  60 {
  61         /*
  62          * This test was moot in vfs may_open() because overlay inode does
  63          * not have the S_APPEND flag, so re-check on real upper inode
  64          */
  65         if (IS_APPEND(inode)) {
  66                 if  ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
  67                         return -EPERM;
  68                 if (flag & O_TRUNC)
  69                         return -EPERM;
  70         }
  71
  72         return 0;
  73 }
  74
  75 static struct dentry *ovl_d_real(struct dentry *dentry,
  76                                  const struct inode *inode,
  77                                  unsigned int open_flags, unsigned int flags)
  78 {
  79         struct dentry *real;
  80         int err;
  81
  82         if (flags & D_REAL_UPPER)
  83                 return ovl_dentry_upper(dentry);
  84
  85         if (!d_is_reg(dentry)) {
  86                 if (!inode || inode == d_inode(dentry))
  87                         return dentry;
  88                 goto bug;
  89         }
  90
  91         if (open_flags) {
  92                 err = ovl_open_maybe_copy_up(dentry, open_flags);
  93                 if (err)
  94                         return ERR_PTR(err);
  95         }
  96
  97         real = ovl_dentry_upper(dentry);
  98         if (real && (!inode || inode == d_inode(real))) {
  99                 if (!inode) {
 100                         err = ovl_check_append_only(d_inode(real), open_flags);
 101                         if (err)
 102                                 return ERR_PTR(err);
 103                 }
 104                 return real;
 105         }
 106
 107         real = ovl_dentry_lower(dentry);
 108         if (!real)
 109                 goto bug;
 110
 111         /* Handle recursion */
 112         real = d_real(real, inode, open_flags, 0);
 113
 114         if (!inode || inode == d_inode(real))
 115                 return real;
 116 bug:
 117         WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
 118              inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
 119         return dentry;
 120 }
 121
 122 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
 123 {
 124         struct ovl_entry *oe = dentry->d_fsdata;
 125         unsigned int i;
 126         int ret = 1;
 127
 128         for (i = 0; i < oe->numlower; i++) {
 129                 struct dentry *d = oe->lowerstack[i].dentry;
 130
 131                 if (d->d_flags & DCACHE_OP_REVALIDATE) {
 132                         ret = d->d_op->d_revalidate(d, flags);
 133                         if (ret < 0)
 134                                 return ret;
 135                         if (!ret) {
 136                                 if (!(flags & LOOKUP_RCU))
 137                                         d_invalidate(d);
 138                                 return -ESTALE;
 139                         }
 140                 }
 141         }
 142         return 1;
 143 }
 144
 145 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
 146 {
 147         struct ovl_entry *oe = dentry->d_fsdata;
 148         unsigned int i;
 149         int ret = 1;
 150
 151         for (i = 0; i < oe->numlower; i++) {
 152                 struct dentry *d = oe->lowerstack[i].dentry;
 153
 154                 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
 155                         ret = d->d_op->d_weak_revalidate(d, flags);
 156                         if (ret <= 0)
 157                                 break;
 158                 }
 159         }
 160         return ret;
 161 }
 162
 163 static const struct dentry_operations ovl_dentry_operations = {
 164         .d_release = ovl_dentry_release,
 165         .d_real = ovl_d_real,
 166 };
 167
 168 static const struct dentry_operations ovl_reval_dentry_operations = {
 169         .d_release = ovl_dentry_release,
 170         .d_real = ovl_d_real,
 171         .d_revalidate = ovl_dentry_revalidate,
 172         .d_weak_revalidate = ovl_dentry_weak_revalidate,
 173 };
 174
 175 static struct kmem_cache *ovl_inode_cachep;
 176
 177 static struct inode *ovl_alloc_inode(struct super_block *sb)
 178 {
 179         struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);
 180
 181         if (!oi)
 182                 return NULL;
 183
 184         oi->cache = NULL;
 185         oi->redirect = NULL;
 186         oi->version = 0;
 187         oi->flags = 0;
 188         oi->__upperdentry = NULL;
 189         oi->lower = NULL;
 190         mutex_init(&oi->lock);
 191
 192         return &oi->vfs_inode;
 193 }
 194
 195 static void ovl_i_callback(struct rcu_head *head)
 196 {
 197         struct inode *inode = container_of(head, struct inode, i_rcu);
 198
 199         kmem_cache_free(ovl_inode_cachep, OVL_I(inode));
 200 }
 201
 202 static void ovl_destroy_inode(struct inode *inode)
 203 {
 204         struct ovl_inode *oi = OVL_I(inode);
 205
 206         dput(oi->__upperdentry);
 207         kfree(oi->redirect);
 208         ovl_dir_cache_free(inode);
 209         mutex_destroy(&oi->lock);
 210
 211         call_rcu(&inode->i_rcu, ovl_i_callback);
 212 }
 213
 214 static void ovl_free_fs(struct ovl_fs *ofs)
 215 {
 216         unsigned i;
 217
 218         dput(ofs->indexdir);
 219         dput(ofs->workdir);
 220         if (ofs->workdir_locked)
 221                 ovl_inuse_unlock(ofs->workbasedir);
 222         dput(ofs->workbasedir);
 223         if (ofs->upperdir_locked)
 224                 ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
 225         mntput(ofs->upper_mnt);
 226         for (i = 0; i < ofs->numlower; i++) {
 227                 mntput(ofs->lower_layers[i].mnt);
 228                 free_anon_bdev(ofs->lower_layers[i].pseudo_dev);
 229         }
 230         kfree(ofs->lower_layers);
 231
 232         kfree(ofs->config.lowerdir);
 233         kfree(ofs->config.upperdir);
 234         kfree(ofs->config.workdir);
 235         if (ofs->creator_cred)
 236                 put_cred(ofs->creator_cred);
 237         kfree(ofs);
 238 }
 239
 240 static void ovl_put_super(struct super_block *sb)
 241 {
 242         struct ovl_fs *ofs = sb->s_fs_info;
 243
 244         ovl_free_fs(ofs);
 245 }
 246
 247 static int ovl_sync_fs(struct super_block *sb, int wait)
 248 {
 249         struct ovl_fs *ofs = sb->s_fs_info;
 250         struct super_block *upper_sb;
 251         int ret;
 252
 253         if (!ofs->upper_mnt)
 254                 return 0;
 255         upper_sb = ofs->upper_mnt->mnt_sb;
 256         if (!upper_sb->s_op->sync_fs)
 257                 return 0;
 258
 259         /* real inodes have already been synced by sync_filesystem(ovl_sb) */
 260         down_read(&upper_sb->s_umount);
 261         ret = upper_sb->s_op->sync_fs(upper_sb, wait);
 262         up_read(&upper_sb->s_umount);
 263         return ret;
 264 }
 265
 266 /**
 267  * ovl_statfs
 268  * @sb: The overlayfs super block
 269  * @buf: The struct kstatfs to fill in with stats
 270  *
 271  * Get the filesystem statistics.  As writes always target the upper layer
 272  * filesystem pass the statfs to the upper filesystem (if it exists)
 273  */
 274 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
 275 {
 276         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 277         struct dentry *root_dentry = dentry->d_sb->s_root;
 278         struct path path;
 279         int err;
 280
 281         ovl_path_real(root_dentry, &path);
 282
 283         err = vfs_statfs(&path, buf);
 284         if (!err) {
 285                 buf->f_namelen = ofs->namelen;
 286                 buf->f_type = OVERLAYFS_SUPER_MAGIC;
 287         }
 288
 289         return err;
 290 }
 291
 292 /* Will this overlay be forced to mount/remount ro? */
 293 static bool ovl_force_readonly(struct ovl_fs *ofs)
 294 {
 295         return (!ofs->upper_mnt || !ofs->workdir);
 296 }
 297
 298 /**
 299  * ovl_show_options
 300  *
 301  * Prints the mount options for a given superblock.
 302  * Returns zero; does not fail.
 303  */
 304 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 305 {
 306         struct super_block *sb = dentry->d_sb;
 307         struct ovl_fs *ofs = sb->s_fs_info;
 308
 309         seq_show_option(m, "lowerdir", ofs->config.lowerdir);
 310         if (ofs->config.upperdir) {
 311                 seq_show_option(m, "upperdir", ofs->config.upperdir);
 312                 seq_show_option(m, "workdir", ofs->config.workdir);
 313         }
 314         if (ofs->config.default_permissions)
 315                 seq_puts(m, ",default_permissions");
 316         if (ofs->config.redirect_dir != ovl_redirect_dir_def)
 317                 seq_printf(m, ",redirect_dir=%s",
 318                            ofs->config.redirect_dir ? "on" : "off");
 319         if (ofs->config.index != ovl_index_def)
 320                 seq_printf(m, ",index=%s",
 321                            ofs->config.index ? "on" : "off");
 322         return 0;
 323 }
 324
 325 static int ovl_remount(struct super_block *sb, int *flags, char *data)
 326 {
 327         struct ovl_fs *ofs = sb->s_fs_info;
 328
 329         if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
 330                 return -EROFS;
 331
 332         return 0;
 333 }
 334
 335 static const struct super_operations ovl_super_operations = {
 336         .alloc_inode    = ovl_alloc_inode,
 337         .destroy_inode  = ovl_destroy_inode,
 338         .drop_inode     = generic_delete_inode,
 339         .put_super      = ovl_put_super,
 340         .sync_fs        = ovl_sync_fs,
 341         .statfs         = ovl_statfs,
 342         .show_options   = ovl_show_options,
 343         .remount_fs     = ovl_remount,
 344 };
 345
 346 enum {
 347         OPT_LOWERDIR,
 348         OPT_UPPERDIR,
 349         OPT_WORKDIR,
 350         OPT_DEFAULT_PERMISSIONS,
 351         OPT_REDIRECT_DIR_ON,
 352         OPT_REDIRECT_DIR_OFF,
 353         OPT_INDEX_ON,
 354         OPT_INDEX_OFF,
 355         OPT_ERR,
 356 };
 357
 358 static const match_table_t ovl_tokens = {
 359         {OPT_LOWERDIR,                  "lowerdir=%s"},
 360         {OPT_UPPERDIR,                  "upperdir=%s"},
 361         {OPT_WORKDIR,                   "workdir=%s"},
 362         {OPT_DEFAULT_PERMISSIONS,       "default_permissions"},
 363         {OPT_REDIRECT_DIR_ON,           "redirect_dir=on"},
 364         {OPT_REDIRECT_DIR_OFF,          "redirect_dir=off"},
 365         {OPT_INDEX_ON,                  "index=on"},
 366         {OPT_INDEX_OFF,                 "index=off"},
 367         {OPT_ERR,                       NULL}
 368 };
 369
 370 static char *ovl_next_opt(char **s)
 371 {
 372         char *sbegin = *s;
 373         char *p;
 374
 375         if (sbegin == NULL)
 376                 return NULL;
 377
 378         for (p = sbegin; *p; p++) {
 379                 if (*p == '\\') {
 380                         p++;
 381                         if (!*p)
 382                                 break;
 383                 } else if (*p == ',') {
 384                         *p = '\0';
 385                         *s = p + 1;
 386                         return sbegin;
 387                 }
 388         }
 389         *s = NULL;
 390         return sbegin;
 391 }
 392
 393 static int ovl_parse_opt(char *opt, struct ovl_config *config)
 394 {
 395         char *p;
 396
 397         while ((p = ovl_next_opt(&opt)) != NULL) {
 398                 int token;
 399                 substring_t args[MAX_OPT_ARGS];
 400
 401                 if (!*p)
 402                         continue;
 403
 404                 token = match_token(p, ovl_tokens, args);
 405                 switch (token) {
 406                 case OPT_UPPERDIR:
 407                         kfree(config->upperdir);
 408                         config->upperdir = match_strdup(&args[0]);
 409                         if (!config->upperdir)
 410                                 return -ENOMEM;
 411                         break;
 412
 413                 case OPT_LOWERDIR:
 414                         kfree(config->lowerdir);
 415                         config->lowerdir = match_strdup(&args[0]);
 416                         if (!config->lowerdir)
 417                                 return -ENOMEM;
 418                         break;
 419
 420                 case OPT_WORKDIR:
 421                         kfree(config->workdir);
 422                         config->workdir = match_strdup(&args[0]);
 423                         if (!config->workdir)
 424                                 return -ENOMEM;
 425                         break;
 426
 427                 case OPT_DEFAULT_PERMISSIONS:
 428                         config->default_permissions = true;
 429                         break;
 430
 431                 case OPT_REDIRECT_DIR_ON:
 432                         config->redirect_dir = true;
 433                         break;
 434
 435                 case OPT_REDIRECT_DIR_OFF:
 436                         config->redirect_dir = false;
 437                         break;
 438
 439                 case OPT_INDEX_ON:
 440                         config->index = true;
 441                         break;
 442
 443                 case OPT_INDEX_OFF:
 444                         config->index = false;
 445                         break;
 446
 447                 default:
 448                         pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
 449                         return -EINVAL;
 450                 }
 451         }
 452
 453         /* Workdir is useless in non-upper mount */
 454         if (!config->upperdir && config->workdir) {
 455                 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
 456                         config->workdir);
 457                 kfree(config->workdir);
 458                 config->workdir = NULL;
 459         }
 460
 461         return 0;
 462 }
 463
 464 #define OVL_WORKDIR_NAME "work"
 465 #define OVL_INDEXDIR_NAME "index"
 466
 467 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
 468                                          const char *name, bool persist)
 469 {
 470         struct inode *dir =  ofs->workbasedir->d_inode;
 471         struct vfsmount *mnt = ofs->upper_mnt;
 472         struct dentry *work;
 473         int err;
 474         bool retried = false;
 475         bool locked = false;
 476
 477         err = mnt_want_write(mnt);
 478         if (err)
 479                 goto out_err;
 480
 481         inode_lock_nested(dir, I_MUTEX_PARENT);
 482         locked = true;
 483
 484 retry:
 485         work = lookup_one_len(name, ofs->workbasedir, strlen(name));
 486
 487         if (!IS_ERR(work)) {
 488                 struct iattr attr = {
 489                         .ia_valid = ATTR_MODE,
 490                         .ia_mode = S_IFDIR | 0,
 491                 };
 492
 493                 if (work->d_inode) {
 494                         err = -EEXIST;
 495                         if (retried)
 496                                 goto out_dput;
 497
 498                         if (persist)
 499                                 goto out_unlock;
 500
 501                         retried = true;
 502                         ovl_workdir_cleanup(dir, mnt, work, 0);
 503                         dput(work);
 504                         goto retry;
 505                 }
 506
 507                 err = ovl_create_real(dir, work,
 508                                       &(struct cattr){.mode = S_IFDIR | 0},
 509                                       NULL, true);
 510                 if (err)
 511                         goto out_dput;
 512
 513                 /*
 514                  * Try to remove POSIX ACL xattrs from workdir.  We are good if:
 515                  *
 516                  * a) success (there was a POSIX ACL xattr and was removed)
 517                  * b) -ENODATA (there was no POSIX ACL xattr)
 518                  * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
 519                  *
 520                  * There are various other error values that could effectively
 521                  * mean that the xattr doesn't exist (e.g. -ERANGE is returned
 522                  * if the xattr name is too long), but the set of filesystems
 523                  * allowed as upper are limited to "normal" ones, where checking
 524                  * for the above two errors is sufficient.
 525                  */
 526                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
 527                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
 528                         goto out_dput;
 529
 530                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
 531                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
 532                         goto out_dput;
 533
 534                 /* Clear any inherited mode bits */
 535                 inode_lock(work->d_inode);
 536                 err = notify_change(work, &attr, NULL);
 537                 inode_unlock(work->d_inode);
 538                 if (err)
 539                         goto out_dput;
 540         } else {
 541                 err = PTR_ERR(work);
 542                 goto out_err;
 543         }
 544 out_unlock:
 545         mnt_drop_write(mnt);
 546         if (locked)
 547                 inode_unlock(dir);
 548
 549         return work;
 550
 551 out_dput:
 552         dput(work);
 553 out_err:
 554         pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
 555                 ofs->config.workdir, name, -err);
 556         work = NULL;
 557         goto out_unlock;
 558 }
 559
 560 static void ovl_unescape(char *s)
 561 {
 562         char *d = s;
 563
 564         for (;; s++, d++) {
 565                 if (*s == '\\')
 566                         s++;
 567                 *d = *s;
 568                 if (!*s)
 569                         break;
 570         }
 571 }
 572
 573 static int ovl_mount_dir_noesc(const char *name, struct path *path)
 574 {
 575         int err = -EINVAL;
 576
 577         if (!*name) {
 578                 pr_err("overlayfs: empty lowerdir\n");
 579                 goto out;
 580         }
 581         err = kern_path(name, LOOKUP_FOLLOW, path);
 582         if (err) {
 583                 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
 584                 goto out;
 585         }
 586         err = -EINVAL;
 587         if (ovl_dentry_weird(path->dentry)) {
 588                 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
 589                 goto out_put;
 590         }
 591         if (!d_is_dir(path->dentry)) {
 592                 pr_err("overlayfs: '%s' not a directory\n", name);
 593                 goto out_put;
 594         }
 595         return 0;
 596
 597 out_put:
 598         path_put_init(path);
 599 out:
 600         return err;
 601 }
 602
 603 static int ovl_mount_dir(const char *name, struct path *path)
 604 {
 605         int err = -ENOMEM;
 606         char *tmp = kstrdup(name, GFP_KERNEL);
 607
 608         if (tmp) {
 609                 ovl_unescape(tmp);
 610                 err = ovl_mount_dir_noesc(tmp, path);
 611
 612                 if (!err)
 613                         if (ovl_dentry_remote(path->dentry)) {
 614                                 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
 615                                        tmp);
 616                                 path_put_init(path);
 617                                 err = -EINVAL;
 618                         }
 619                 kfree(tmp);
 620         }
 621         return err;
 622 }
 623
 624 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
 625                              const char *name)
 626 {
 627         struct kstatfs statfs;
 628         int err = vfs_statfs(path, &statfs);
 629
 630         if (err)
 631                 pr_err("overlayfs: statfs failed on '%s'\n", name);
 632         else
 633                 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
 634
 635         return err;
 636 }
 637
 638 static int ovl_lower_dir(const char *name, struct path *path,
 639                          struct ovl_fs *ofs, int *stack_depth, bool *remote)
 640 {
 641         int err;
 642
 643         err = ovl_mount_dir_noesc(name, path);
 644         if (err)
 645                 goto out;
 646
 647         err = ovl_check_namelen(path, ofs, name);
 648         if (err)
 649                 goto out_put;
 650
 651         *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
 652
 653         if (ovl_dentry_remote(path->dentry))
 654                 *remote = true;
 655
 656         /*
 657          * The inodes index feature needs to encode and decode file
 658          * handles, so it requires that all layers support them.
 659          */
 660         if (ofs->config.index && !ovl_can_decode_fh(path->dentry->d_sb)) {
 661                 ofs->config.index = false;
 662                 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off.\n", name);
 663         }
 664
 665         return 0;
 666
 667 out_put:
 668         path_put_init(path);
 669 out:
 670         return err;
 671 }
 672
 673 /* Workdir should not be subdir of upperdir and vice versa */
 674 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
 675 {
 676         bool ok = false;
 677
 678         if (workdir != upperdir) {
 679                 ok = (lock_rename(workdir, upperdir) == NULL);
 680                 unlock_rename(workdir, upperdir);
 681         }
 682         return ok;
 683 }
 684
 685 static unsigned int ovl_split_lowerdirs(char *str)
 686 {
 687         unsigned int ctr = 1;
 688         char *s, *d;
 689
 690         for (s = d = str;; s++, d++) {
 691                 if (*s == '\\') {
 692                         s++;
 693                 } else if (*s == ':') {
 694                         *d = '\0';
 695                         ctr++;
 696                         continue;
 697                 }
 698                 *d = *s;
 699                 if (!*s)
 700                         break;
 701         }
 702         return ctr;
 703 }
 704
 705 static int __maybe_unused
 706 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
 707                         struct dentry *dentry, struct inode *inode,
 708                         const char *name, void *buffer, size_t size)
 709 {
 710         return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
 711 }
 712
 713 static int __maybe_unused
 714 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
 715                         struct dentry *dentry, struct inode *inode,
 716                         const char *name, const void *value,
 717                         size_t size, int flags)
 718 {
 719         struct dentry *workdir = ovl_workdir(dentry);
 720         struct inode *realinode = ovl_inode_real(inode);
 721         struct posix_acl *acl = NULL;
 722         int err;
 723
 724         /* Check that everything is OK before copy-up */
 725         if (value) {
 726                 acl = posix_acl_from_xattr(&init_user_ns, value, size);
 727                 if (IS_ERR(acl))
 728                         return PTR_ERR(acl);
 729         }
 730         err = -EOPNOTSUPP;
 731         if (!IS_POSIXACL(d_inode(workdir)))
 732                 goto out_acl_release;
 733         if (!realinode->i_op->set_acl)
 734                 goto out_acl_release;
 735         if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
 736                 err = acl ? -EACCES : 0;
 737                 goto out_acl_release;
 738         }
 739         err = -EPERM;
 740         if (!inode_owner_or_capable(inode))
 741                 goto out_acl_release;
 742
 743         posix_acl_release(acl);
 744
 745         /*
 746          * Check if sgid bit needs to be cleared (actual setacl operation will
 747          * be done with mounter's capabilities and so that won't do it for us).
 748          */
 749         if (unlikely(inode->i_mode & S_ISGID) &&
 750             handler->flags == ACL_TYPE_ACCESS &&
 751             !in_group_p(inode->i_gid) &&
 752             !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
 753                 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
 754
 755                 err = ovl_setattr(dentry, &iattr);
 756                 if (err)
 757                         return err;
 758         }
 759
 760         err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
 761         if (!err)
 762                 ovl_copyattr(ovl_inode_real(inode), inode);
 763
 764         return err;
 765
 766 out_acl_release:
 767         posix_acl_release(acl);
 768         return err;
 769 }
 770
 771 static int ovl_own_xattr_get(const struct xattr_handler *handler,
 772                              struct dentry *dentry, struct inode *inode,
 773                              const char *name, void *buffer, size_t size)
 774 {
 775         return -EOPNOTSUPP;
 776 }
 777
 778 static int ovl_own_xattr_set(const struct xattr_handler *handler,
 779                              struct dentry *dentry, struct inode *inode,
 780                              const char *name, const void *value,
 781                              size_t size, int flags)
 782 {
 783         return -EOPNOTSUPP;
 784 }
 785
 786 static int ovl_other_xattr_get(const struct xattr_handler *handler,
 787                                struct dentry *dentry, struct inode *inode,
 788                                const char *name, void *buffer, size_t size)
 789 {
 790         return ovl_xattr_get(dentry, inode, name, buffer, size);
 791 }
 792
 793 static int ovl_other_xattr_set(const struct xattr_handler *handler,
 794                                struct dentry *dentry, struct inode *inode,
 795                                const char *name, const void *value,
 796                                size_t size, int flags)
 797 {
 798         return ovl_xattr_set(dentry, inode, name, value, size, flags);
 799 }
 800
 801 static const struct xattr_handler __maybe_unused
 802 ovl_posix_acl_access_xattr_handler = {
 803         .name = XATTR_NAME_POSIX_ACL_ACCESS,
 804         .flags = ACL_TYPE_ACCESS,
 805         .get = ovl_posix_acl_xattr_get,
 806         .set = ovl_posix_acl_xattr_set,
 807 };
 808
 809 static const struct xattr_handler __maybe_unused
 810 ovl_posix_acl_default_xattr_handler = {
 811         .name = XATTR_NAME_POSIX_ACL_DEFAULT,
 812         .flags = ACL_TYPE_DEFAULT,
 813         .get = ovl_posix_acl_xattr_get,
 814         .set = ovl_posix_acl_xattr_set,
 815 };
 816
 817 static const struct xattr_handler ovl_own_xattr_handler = {
 818         .prefix = OVL_XATTR_PREFIX,
 819         .get = ovl_own_xattr_get,
 820         .set = ovl_own_xattr_set,
 821 };
 822
 823 static const struct xattr_handler ovl_other_xattr_handler = {
 824         .prefix = "", /* catch all */
 825         .get = ovl_other_xattr_get,
 826         .set = ovl_other_xattr_set,
 827 };
 828
 829 static const struct xattr_handler *ovl_xattr_handlers[] = {
 830 #ifdef CONFIG_FS_POSIX_ACL
 831         &ovl_posix_acl_access_xattr_handler,
 832         &ovl_posix_acl_default_xattr_handler,
 833 #endif
 834         &ovl_own_xattr_handler,
 835         &ovl_other_xattr_handler,
 836         NULL
 837 };
 838
 839 static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
 840 {
 841         struct vfsmount *upper_mnt;
 842         int err;
 843
 844         err = ovl_mount_dir(ofs->config.upperdir, upperpath);
 845         if (err)
 846                 goto out;
 847
 848         /* Upper fs should not be r/o */
 849         if (sb_rdonly(upperpath->mnt->mnt_sb)) {
 850                 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
 851                 err = -EINVAL;
 852                 goto out;
 853         }
 854
 855         err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
 856         if (err)
 857                 goto out;
 858
 859         err = -EBUSY;
 860         if (ovl_inuse_trylock(upperpath->dentry)) {
 861                 ofs->upperdir_locked = true;
 862         } else if (ofs->config.index) {
 863                 pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
 864                 goto out;
 865         } else {
 866                 pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
 867         }
 868
 869         upper_mnt = clone_private_mount(upperpath);
 870         err = PTR_ERR(upper_mnt);
 871         if (IS_ERR(upper_mnt)) {
 872                 pr_err("overlayfs: failed to clone upperpath\n");
 873                 goto out;
 874         }
 875
 876         /* Don't inherit atime flags */
 877         upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
 878         ofs->upper_mnt = upper_mnt;
 879         err = 0;
 880 out:
 881         return err;
 882 }
 883
 884 static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
 885 {
 886         struct dentry *temp;
 887         int err;
 888
 889         ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
 890         if (!ofs->workdir)
 891                 return 0;
 892
 893         /*
 894          * Upper should support d_type, else whiteouts are visible.  Given
 895          * workdir and upper are on same fs, we can do iterate_dir() on
 896          * workdir. This check requires successful creation of workdir in
 897          * previous step.
 898          */
 899         err = ovl_check_d_type_supported(workpath);
 900         if (err < 0)
 901                 return err;
 902
 903         /*
 904          * We allowed this configuration and don't want to break users over
 905          * kernel upgrade. So warn instead of erroring out.
 906          */
 907         if (!err)
 908                 pr_warn("overlayfs: upper fs needs to support d_type.\n");
 909
 910         /* Check if upper/work fs supports O_TMPFILE */
 911         temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
 912         ofs->tmpfile = !IS_ERR(temp);
 913         if (ofs->tmpfile)
 914                 dput(temp);
 915         else
 916                 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
 917
 918         /*
 919          * Check if upper/work fs supports trusted.overlay.* xattr
 920          */
 921         err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
 922         if (err) {
 923                 ofs->noxattr = true;
 924                 pr_warn("overlayfs: upper fs does not support xattr.\n");
 925         } else {
 926                 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
 927         }
 928
 929         /* Check if upper/work fs supports file handles */
 930         if (ofs->config.index &&
 931             !ovl_can_decode_fh(ofs->workdir->d_sb)) {
 932                 ofs->config.index = false;
 933                 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
 934         }
 935
 936         return 0;
 937 }
 938
 939 static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
 940 {
 941         int err;
 942         struct path workpath = { };
 943
 944         err = ovl_mount_dir(ofs->config.workdir, &workpath);
 945         if (err)
 946                 goto out;
 947
 948         err = -EINVAL;
 949         if (upperpath->mnt != workpath.mnt) {
 950                 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
 951                 goto out;
 952         }
 953         if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
 954                 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
 955                 goto out;
 956         }
 957
 958         err = -EBUSY;
 959         if (ovl_inuse_trylock(workpath.dentry)) {
 960                 ofs->workdir_locked = true;
 961         } else if (ofs->config.index) {
 962                 pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
 963                 goto out;
 964         } else {
 965                 pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
 966         }
 967
 968         ofs->workbasedir = dget(workpath.dentry);
 969         err = ovl_make_workdir(ofs, &workpath);
 970         if (err)
 971                 goto out;
 972
 973         err = 0;
 974 out:
 975         path_put(&workpath);
 976
 977         return err;
 978 }
 979
 980 static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe,
 981                             struct path *upperpath)
 982 {
 983         int err;
 984
 985         /* Verify lower root is upper root origin */
 986         err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
 987                                 false, true);
 988         if (err) {
 989                 pr_err("overlayfs: failed to verify upper root origin\n");
 990                 goto out;
 991         }
 992
 993         ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
 994         if (ofs->indexdir) {
 995                 /* Verify upper root is index dir origin */
 996                 err = ovl_verify_origin(ofs->indexdir, upperpath->dentry,
 997                                         true, true);
 998                 if (err)
 999                         pr_err("overlayfs: failed to verify index dir origin\n");
1000
1001                 /* Cleanup bad/stale/orphan index entries */
1002                 if (!err)
1003                         err = ovl_indexdir_cleanup(ofs->indexdir,
1004                                                    ofs->upper_mnt,
1005                                                    oe->lowerstack,
1006                                                    oe->numlower);
1007         }
1008         if (err || !ofs->indexdir)
1009                 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1010
1011 out:
1012         return err;
1013 }
1014
1015 static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
1016                                 unsigned int numlower)
1017 {
1018         int err;
1019         unsigned int i;
1020
1021         err = -ENOMEM;
1022         ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
1023                                     GFP_KERNEL);
1024         if (ofs->lower_layers == NULL)
1025                 goto out;
1026         for (i = 0; i < numlower; i++) {
1027                 struct vfsmount *mnt;
1028                 dev_t dev;
1029
1030                 err = get_anon_bdev(&dev);
1031                 if (err) {
1032                         pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
1033                         goto out;
1034                 }
1035
1036                 mnt = clone_private_mount(&stack[i]);
1037                 err = PTR_ERR(mnt);
1038                 if (IS_ERR(mnt)) {
1039                         pr_err("overlayfs: failed to clone lowerpath\n");
1040                         free_anon_bdev(dev);
1041                         goto out;
1042                 }
1043                 /*
1044                  * Make lower layers R/O.  That way fchmod/fchown on lower file
1045                  * will fail instead of modifying lower fs.
1046                  */
1047                 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1048
1049                 ofs->lower_layers[ofs->numlower].mnt = mnt;
1050                 ofs->lower_layers[ofs->numlower].pseudo_dev = dev;
1051                 ofs->numlower++;
1052
1053                 /* Check if all lower layers are on same sb */
1054                 if (i == 0)
1055                         ofs->same_sb = mnt->mnt_sb;
1056                 else if (ofs->same_sb != mnt->mnt_sb)
1057                         ofs->same_sb = NULL;
1058         }
1059         err = 0;
1060 out:
1061         return err;
1062 }
1063
1064 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1065                                             struct ovl_fs *ofs)
1066 {
1067         int err;
1068         char *lowertmp, *lower;
1069         struct path *stack = NULL;
1070         unsigned int stacklen, numlower = 0, i;
1071         bool remote = false;
1072         struct ovl_entry *oe;
1073
1074         err = -ENOMEM;
1075         lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1076         if (!lowertmp)
1077                 goto out_err;
1078
1079         err = -EINVAL;
1080         stacklen = ovl_split_lowerdirs(lowertmp);
1081         if (stacklen > OVL_MAX_STACK) {
1082                 pr_err("overlayfs: too many lower directories, limit is %d\n",
1083                        OVL_MAX_STACK);
1084                 goto out_err;
1085         } else if (!ofs->config.upperdir && stacklen == 1) {
1086                 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1087                 goto out_err;
1088         }
1089
1090         err = -ENOMEM;
1091         stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1092         if (!stack)
1093                 goto out_err;
1094
1095         err = -EINVAL;
1096         lower = lowertmp;
1097         for (numlower = 0; numlower < stacklen; numlower++) {
1098                 err = ovl_lower_dir(lower, &stack[numlower], ofs,
1099                                     &sb->s_stack_depth, &remote);
1100                 if (err)
1101                         goto out_err;
1102
1103                 lower = strchr(lower, '\0') + 1;
1104         }
1105
1106         err = -EINVAL;
1107         sb->s_stack_depth++;
1108         if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1109                 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1110                 goto out_err;
1111         }
1112
1113         err = ovl_get_lower_layers(ofs, stack, numlower);
1114         if (err)
1115                 goto out_err;
1116
1117         err = -ENOMEM;
1118         oe = ovl_alloc_entry(numlower);
1119         if (!oe)
1120                 goto out_err;
1121
1122         for (i = 0; i < numlower; i++) {
1123                 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1124                 oe->lowerstack[i].layer = &ofs->lower_layers[i];
1125         }
1126
1127         if (remote)
1128                 sb->s_d_op = &ovl_reval_dentry_operations;
1129         else
1130                 sb->s_d_op = &ovl_dentry_operations;
1131
1132 out:
1133         for (i = 0; i < numlower; i++)
1134                 path_put(&stack[i]);
1135         kfree(stack);
1136         kfree(lowertmp);
1137
1138         return oe;
1139
1140 out_err:
1141         oe = ERR_PTR(err);
1142         goto out;
1143 }
1144
1145 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1146 {
1147         struct path upperpath = { };
1148         struct dentry *root_dentry;
1149         struct ovl_entry *oe;
1150         struct ovl_fs *ofs;
1151         struct cred *cred;
1152         int err;
1153
1154         err = -ENOMEM;
1155         ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1156         if (!ofs)
1157                 goto out;
1158
1159         ofs->creator_cred = cred = prepare_creds();
1160         if (!cred)
1161                 goto out_err;
1162
1163         ofs->config.redirect_dir = ovl_redirect_dir_def;
1164         ofs->config.index = ovl_index_def;
1165         err = ovl_parse_opt((char *) data, &ofs->config);
1166         if (err)
1167                 goto out_err;
1168
1169         err = -EINVAL;
1170         if (!ofs->config.lowerdir) {
1171                 if (!silent)
1172                         pr_err("overlayfs: missing 'lowerdir'\n");
1173                 goto out_err;
1174         }
1175
1176         sb->s_stack_depth = 0;
1177         sb->s_maxbytes = MAX_LFS_FILESIZE;
1178         if (ofs->config.upperdir) {
1179                 if (!ofs->config.workdir) {
1180                         pr_err("overlayfs: missing 'workdir'\n");
1181                         goto out_err;
1182                 }
1183
1184                 err = ovl_get_upper(ofs, &upperpath);
1185                 if (err)
1186                         goto out_err;
1187
1188                 err = ovl_get_workdir(ofs, &upperpath);
1189                 if (err)
1190                         goto out_err;
1191
1192                 if (!ofs->workdir)
1193                         sb->s_flags |= SB_RDONLY;
1194
1195                 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
1196                 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
1197
1198         }
1199         oe = ovl_get_lowerstack(sb, ofs);
1200         err = PTR_ERR(oe);
1201         if (IS_ERR(oe))
1202                 goto out_err;
1203
1204         /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1205         if (!ofs->upper_mnt)
1206                 sb->s_flags |= SB_RDONLY;
1207         else if (ofs->upper_mnt->mnt_sb != ofs->same_sb)
1208                 ofs->same_sb = NULL;
1209
1210         if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
1211                 err = ovl_get_indexdir(ofs, oe, &upperpath);
1212                 if (err)
1213                         goto out_free_oe;
1214
1215                 if (!ofs->indexdir)
1216                         sb->s_flags |= SB_RDONLY;
1217         }
1218
1219         /* Show index=off/on in /proc/mounts for any of the reasons above */
1220         if (!ofs->indexdir)
1221                 ofs->config.index = false;
1222
1223         /* Never override disk quota limits or use reserved space */
1224         cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1225
1226         sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1227         sb->s_op = &ovl_super_operations;
1228         sb->s_xattr = ovl_xattr_handlers;
1229         sb->s_fs_info = ofs;
1230         sb->s_flags |= SB_POSIXACL | SB_NOREMOTELOCK;
1231
1232         err = -ENOMEM;
1233         root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1234         if (!root_dentry)
1235                 goto out_free_oe;
1236
1237         mntput(upperpath.mnt);
1238         if (upperpath.dentry) {
1239                 oe->has_upper = true;
1240                 if (ovl_is_impuredir(upperpath.dentry))
1241                         ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1242         }
1243
1244         root_dentry->d_fsdata = oe;
1245
1246         /* Root is always merge -> can have whiteouts */
1247         ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1248         ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
1249                        ovl_dentry_lower(root_dentry));
1250
1251         sb->s_root = root_dentry;
1252
1253         return 0;
1254
1255 out_free_oe:
1256         ovl_entry_stack_free(oe);
1257         kfree(oe);
1258 out_err:
1259         path_put(&upperpath);
1260         ovl_free_fs(ofs);
1261 out:
1262         return err;
1263 }
1264
1265 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1266                                 const char *dev_name, void *raw_data)
1267 {
1268         return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1269 }
1270
1271 static struct file_system_type ovl_fs_type = {
1272         .owner          = THIS_MODULE,
1273         .name           = "overlay",
1274         .mount          = ovl_mount,
1275         .kill_sb        = kill_anon_super,
1276 };
1277 MODULE_ALIAS_FS("overlay");
1278
1279 static void ovl_inode_init_once(void *foo)
1280 {
1281         struct ovl_inode *oi = foo;
1282
1283         inode_init_once(&oi->vfs_inode);
1284 }
1285
1286 static int __init ovl_init(void)
1287 {
1288         int err;
1289
1290         ovl_inode_cachep = kmem_cache_create("ovl_inode",
1291                                              sizeof(struct ovl_inode), 0,
1292                                              (SLAB_RECLAIM_ACCOUNT|
1293                                               SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1294                                              ovl_inode_init_once);
1295         if (ovl_inode_cachep == NULL)
1296                 return -ENOMEM;
1297
1298         err = register_filesystem(&ovl_fs_type);
1299         if (err)
1300                 kmem_cache_destroy(ovl_inode_cachep);
1301
1302         return err;
1303 }
1304
1305 static void __exit ovl_exit(void)
1306 {
1307         unregister_filesystem(&ovl_fs_type);
1308
1309         /*
1310          * Make sure all delayed rcu free inodes are flushed before we
1311          * destroy cache.
1312          */
1313         rcu_barrier();
1314         kmem_cache_destroy(ovl_inode_cachep);
1315
1316 }
1317
1318 module_init(ovl_init);
1319 module_exit(ovl_exit);