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