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 <linux/exportfs.h>
  21 #include "overlayfs.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_redirect_always_follow =
  38         IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW);
  39 module_param_named(redirect_always_follow, ovl_redirect_always_follow,
  40                    bool, 0644);
  41 MODULE_PARM_DESC(ovl_redirect_always_follow,
  42                  "Follow redirects even if redirect_dir feature is turned off");
  43
  44 static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
  45 module_param_named(index, ovl_index_def, bool, 0644);
  46 MODULE_PARM_DESC(ovl_index_def,
  47                  "Default to on or off for the inodes index feature");
  48
  49 static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT);
  50 module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644);
  51 MODULE_PARM_DESC(ovl_nfs_export_def,
  52                  "Default to on or off for the NFS export feature");
  53
  54 static bool ovl_xino_auto_def = IS_ENABLED(CONFIG_OVERLAY_FS_XINO_AUTO);
  55 module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
  56 MODULE_PARM_DESC(ovl_xino_auto_def,
  57                  "Auto enable xino feature");
  58
  59 static void ovl_entry_stack_free(struct ovl_entry *oe)
  60 {
  61         unsigned int i;
  62
  63         for (i = 0; i < oe->numlower; i++)
  64                 dput(oe->lowerstack[i].dentry);
  65 }
  66
  67 static bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY);
  68 module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
  69 MODULE_PARM_DESC(ovl_metacopy_def,
  70                  "Default to on or off for the metadata only copy up feature");
  71
  72 static void ovl_dentry_release(struct dentry *dentry)
  73 {
  74         struct ovl_entry *oe = dentry->d_fsdata;
  75
  76         if (oe) {
  77                 ovl_entry_stack_free(oe);
  78                 kfree_rcu(oe, rcu);
  79         }
  80 }
  81
  82 static struct dentry *ovl_d_real(struct dentry *dentry,
  83                                  const struct inode *inode)
  84 {
  85         struct dentry *real;
  86
  87         /* It's an overlay file */
  88         if (inode && d_inode(dentry) == inode)
  89                 return dentry;
  90
  91         if (!d_is_reg(dentry)) {
  92                 if (!inode || inode == d_inode(dentry))
  93                         return dentry;
  94                 goto bug;
  95         }
  96
  97         real = ovl_dentry_upper(dentry);
  98         if (real && (inode == d_inode(real)))
  99                 return real;
 100
 101         if (real && !inode && ovl_has_upperdata(d_inode(dentry)))
 102                 return real;
 103
 104         real = ovl_dentry_lowerdata(dentry);
 105         if (!real)
 106                 goto bug;
 107
 108         /* Handle recursion */
 109         real = d_real(real, inode);
 110
 111         if (!inode || inode == d_inode(real))
 112                 return real;
 113 bug:
 114         WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
 115              inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
 116         return dentry;
 117 }
 118
 119 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
 120 {
 121         struct ovl_entry *oe = dentry->d_fsdata;
 122         unsigned int i;
 123         int ret = 1;
 124
 125         for (i = 0; i < oe->numlower; i++) {
 126                 struct dentry *d = oe->lowerstack[i].dentry;
 127
 128                 if (d->d_flags & DCACHE_OP_REVALIDATE) {
 129                         ret = d->d_op->d_revalidate(d, flags);
 130                         if (ret < 0)
 131                                 return ret;
 132                         if (!ret) {
 133                                 if (!(flags & LOOKUP_RCU))
 134                                         d_invalidate(d);
 135                                 return -ESTALE;
 136                         }
 137                 }
 138         }
 139         return 1;
 140 }
 141
 142 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
 143 {
 144         struct ovl_entry *oe = dentry->d_fsdata;
 145         unsigned int i;
 146         int ret = 1;
 147
 148         for (i = 0; i < oe->numlower; i++) {
 149                 struct dentry *d = oe->lowerstack[i].dentry;
 150
 151                 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
 152                         ret = d->d_op->d_weak_revalidate(d, flags);
 153                         if (ret <= 0)
 154                                 break;
 155                 }
 156         }
 157         return ret;
 158 }
 159
 160 static const struct dentry_operations ovl_dentry_operations = {
 161         .d_release = ovl_dentry_release,
 162         .d_real = ovl_d_real,
 163 };
 164
 165 static const struct dentry_operations ovl_reval_dentry_operations = {
 166         .d_release = ovl_dentry_release,
 167         .d_real = ovl_d_real,
 168         .d_revalidate = ovl_dentry_revalidate,
 169         .d_weak_revalidate = ovl_dentry_weak_revalidate,
 170 };
 171
 172 static struct kmem_cache *ovl_inode_cachep;
 173
 174 static struct inode *ovl_alloc_inode(struct super_block *sb)
 175 {
 176         struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);
 177
 178         if (!oi)
 179                 return NULL;
 180
 181         oi->cache = NULL;
 182         oi->redirect = NULL;
 183         oi->version = 0;
 184         oi->flags = 0;
 185         oi->__upperdentry = NULL;
 186         oi->lower = NULL;
 187         oi->lowerdata = NULL;
 188         mutex_init(&oi->lock);
 189
 190         return &oi->vfs_inode;
 191 }
 192
 193 static void ovl_i_callback(struct rcu_head *head)
 194 {
 195         struct inode *inode = container_of(head, struct inode, i_rcu);
 196
 197         kmem_cache_free(ovl_inode_cachep, OVL_I(inode));
 198 }
 199
 200 static void ovl_destroy_inode(struct inode *inode)
 201 {
 202         struct ovl_inode *oi = OVL_I(inode);
 203
 204         dput(oi->__upperdentry);
 205         iput(oi->lower);
 206         if (S_ISDIR(inode->i_mode))
 207                 ovl_dir_cache_free(inode);
 208         else
 209                 iput(oi->lowerdata);
 210         kfree(oi->redirect);
 211         mutex_destroy(&oi->lock);
 212
 213         call_rcu(&inode->i_rcu, ovl_i_callback);
 214 }
 215
 216 static void ovl_free_fs(struct ovl_fs *ofs)
 217 {
 218         unsigned i;
 219
 220         dput(ofs->indexdir);
 221         dput(ofs->workdir);
 222         if (ofs->workdir_locked)
 223                 ovl_inuse_unlock(ofs->workbasedir);
 224         dput(ofs->workbasedir);
 225         if (ofs->upperdir_locked)
 226                 ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
 227         mntput(ofs->upper_mnt);
 228         for (i = 0; i < ofs->numlower; i++)
 229                 mntput(ofs->lower_layers[i].mnt);
 230         for (i = 0; i < ofs->numlowerfs; i++)
 231                 free_anon_bdev(ofs->lower_fs[i].pseudo_dev);
 232         kfree(ofs->lower_layers);
 233         kfree(ofs->lower_fs);
 234
 235         kfree(ofs->config.lowerdir);
 236         kfree(ofs->config.upperdir);
 237         kfree(ofs->config.workdir);
 238         kfree(ofs->config.redirect_mode);
 239         if (ofs->creator_cred)
 240                 put_cred(ofs->creator_cred);
 241         kfree(ofs);
 242 }
 243
 244 static void ovl_put_super(struct super_block *sb)
 245 {
 246         struct ovl_fs *ofs = sb->s_fs_info;
 247
 248         ovl_free_fs(ofs);
 249 }
 250
 251 /* Sync real dirty inodes in upper filesystem (if it exists) */
 252 static int ovl_sync_fs(struct super_block *sb, int wait)
 253 {
 254         struct ovl_fs *ofs = sb->s_fs_info;
 255         struct super_block *upper_sb;
 256         int ret;
 257
 258         if (!ofs->upper_mnt)
 259                 return 0;
 260
 261         /*
 262          * If this is a sync(2) call or an emergency sync, all the super blocks
 263          * will be iterated, including upper_sb, so no need to do anything.
 264          *
 265          * If this is a syncfs(2) call, then we do need to call
 266          * sync_filesystem() on upper_sb, but enough if we do it when being
 267          * called with wait == 1.
 268          */
 269         if (!wait)
 270                 return 0;
 271
 272         upper_sb = ofs->upper_mnt->mnt_sb;
 273
 274         down_read(&upper_sb->s_umount);
 275         ret = sync_filesystem(upper_sb);
 276         up_read(&upper_sb->s_umount);
 277
 278         return ret;
 279 }
 280
 281 /**
 282  * ovl_statfs
 283  * @sb: The overlayfs super block
 284  * @buf: The struct kstatfs to fill in with stats
 285  *
 286  * Get the filesystem statistics.  As writes always target the upper layer
 287  * filesystem pass the statfs to the upper filesystem (if it exists)
 288  */
 289 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
 290 {
 291         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 292         struct dentry *root_dentry = dentry->d_sb->s_root;
 293         struct path path;
 294         int err;
 295
 296         ovl_path_real(root_dentry, &path);
 297
 298         err = vfs_statfs(&path, buf);
 299         if (!err) {
 300                 buf->f_namelen = ofs->namelen;
 301                 buf->f_type = OVERLAYFS_SUPER_MAGIC;
 302         }
 303
 304         return err;
 305 }
 306
 307 /* Will this overlay be forced to mount/remount ro? */
 308 static bool ovl_force_readonly(struct ovl_fs *ofs)
 309 {
 310         return (!ofs->upper_mnt || !ofs->workdir);
 311 }
 312
 313 static const char *ovl_redirect_mode_def(void)
 314 {
 315         return ovl_redirect_dir_def ? "on" : "off";
 316 }
 317
 318 enum {
 319         OVL_XINO_OFF,
 320         OVL_XINO_AUTO,
 321         OVL_XINO_ON,
 322 };
 323
 324 static const char * const ovl_xino_str[] = {
 325         "off",
 326         "auto",
 327         "on",
 328 };
 329
 330 static inline int ovl_xino_def(void)
 331 {
 332         return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
 333 }
 334
 335 /**
 336  * ovl_show_options
 337  *
 338  * Prints the mount options for a given superblock.
 339  * Returns zero; does not fail.
 340  */
 341 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 342 {
 343         struct super_block *sb = dentry->d_sb;
 344         struct ovl_fs *ofs = sb->s_fs_info;
 345
 346         seq_show_option(m, "lowerdir", ofs->config.lowerdir);
 347         if (ofs->config.upperdir) {
 348                 seq_show_option(m, "upperdir", ofs->config.upperdir);
 349                 seq_show_option(m, "workdir", ofs->config.workdir);
 350         }
 351         if (ofs->config.default_permissions)
 352                 seq_puts(m, ",default_permissions");
 353         if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
 354                 seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
 355         if (ofs->config.index != ovl_index_def)
 356                 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
 357         if (ofs->config.nfs_export != ovl_nfs_export_def)
 358                 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
 359                                                 "on" : "off");
 360         if (ofs->config.xino != ovl_xino_def())
 361                 seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
 362         if (ofs->config.metacopy != ovl_metacopy_def)
 363                 seq_printf(m, ",metacopy=%s",
 364                            ofs->config.metacopy ? "on" : "off");
 365         return 0;
 366 }
 367
 368 static int ovl_remount(struct super_block *sb, int *flags, char *data)
 369 {
 370         struct ovl_fs *ofs = sb->s_fs_info;
 371
 372         if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
 373                 return -EROFS;
 374
 375         return 0;
 376 }
 377
 378 static const struct super_operations ovl_super_operations = {
 379         .alloc_inode    = ovl_alloc_inode,
 380         .destroy_inode  = ovl_destroy_inode,
 381         .drop_inode     = generic_delete_inode,
 382         .put_super      = ovl_put_super,
 383         .sync_fs        = ovl_sync_fs,
 384         .statfs         = ovl_statfs,
 385         .show_options   = ovl_show_options,
 386         .remount_fs     = ovl_remount,
 387 };
 388
 389 enum {
 390         OPT_LOWERDIR,
 391         OPT_UPPERDIR,
 392         OPT_WORKDIR,
 393         OPT_DEFAULT_PERMISSIONS,
 394         OPT_REDIRECT_DIR,
 395         OPT_INDEX_ON,
 396         OPT_INDEX_OFF,
 397         OPT_NFS_EXPORT_ON,
 398         OPT_NFS_EXPORT_OFF,
 399         OPT_XINO_ON,
 400         OPT_XINO_OFF,
 401         OPT_XINO_AUTO,
 402         OPT_METACOPY_ON,
 403         OPT_METACOPY_OFF,
 404         OPT_ERR,
 405 };
 406
 407 static const match_table_t ovl_tokens = {
 408         {OPT_LOWERDIR,                  "lowerdir=%s"},
 409         {OPT_UPPERDIR,                  "upperdir=%s"},
 410         {OPT_WORKDIR,                   "workdir=%s"},
 411         {OPT_DEFAULT_PERMISSIONS,       "default_permissions"},
 412         {OPT_REDIRECT_DIR,              "redirect_dir=%s"},
 413         {OPT_INDEX_ON,                  "index=on"},
 414         {OPT_INDEX_OFF,                 "index=off"},
 415         {OPT_NFS_EXPORT_ON,             "nfs_export=on"},
 416         {OPT_NFS_EXPORT_OFF,            "nfs_export=off"},
 417         {OPT_XINO_ON,                   "xino=on"},
 418         {OPT_XINO_OFF,                  "xino=off"},
 419         {OPT_XINO_AUTO,                 "xino=auto"},
 420         {OPT_METACOPY_ON,               "metacopy=on"},
 421         {OPT_METACOPY_OFF,              "metacopy=off"},
 422         {OPT_ERR,                       NULL}
 423 };
 424
 425 static char *ovl_next_opt(char **s)
 426 {
 427         char *sbegin = *s;
 428         char *p;
 429
 430         if (sbegin == NULL)
 431                 return NULL;
 432
 433         for (p = sbegin; *p; p++) {
 434                 if (*p == '\\') {
 435                         p++;
 436                         if (!*p)
 437                                 break;
 438                 } else if (*p == ',') {
 439                         *p = '\0';
 440                         *s = p + 1;
 441                         return sbegin;
 442                 }
 443         }
 444         *s = NULL;
 445         return sbegin;
 446 }
 447
 448 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
 449 {
 450         if (strcmp(mode, "on") == 0) {
 451                 config->redirect_dir = true;
 452                 /*
 453                  * Does not make sense to have redirect creation without
 454                  * redirect following.
 455                  */
 456                 config->redirect_follow = true;
 457         } else if (strcmp(mode, "follow") == 0) {
 458                 config->redirect_follow = true;
 459         } else if (strcmp(mode, "off") == 0) {
 460                 if (ovl_redirect_always_follow)
 461                         config->redirect_follow = true;
 462         } else if (strcmp(mode, "nofollow") != 0) {
 463                 pr_err("overlayfs: bad mount option \"redirect_dir=%s\"\n",
 464                        mode);
 465                 return -EINVAL;
 466         }
 467
 468         return 0;
 469 }
 470
 471 static int ovl_parse_opt(char *opt, struct ovl_config *config)
 472 {
 473         char *p;
 474         int err;
 475
 476         config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
 477         if (!config->redirect_mode)
 478                 return -ENOMEM;
 479
 480         while ((p = ovl_next_opt(&opt)) != NULL) {
 481                 int token;
 482                 substring_t args[MAX_OPT_ARGS];
 483
 484                 if (!*p)
 485                         continue;
 486
 487                 token = match_token(p, ovl_tokens, args);
 488                 switch (token) {
 489                 case OPT_UPPERDIR:
 490                         kfree(config->upperdir);
 491                         config->upperdir = match_strdup(&args[0]);
 492                         if (!config->upperdir)
 493                                 return -ENOMEM;
 494                         break;
 495
 496                 case OPT_LOWERDIR:
 497                         kfree(config->lowerdir);
 498                         config->lowerdir = match_strdup(&args[0]);
 499                         if (!config->lowerdir)
 500                                 return -ENOMEM;
 501                         break;
 502
 503                 case OPT_WORKDIR:
 504                         kfree(config->workdir);
 505                         config->workdir = match_strdup(&args[0]);
 506                         if (!config->workdir)
 507                                 return -ENOMEM;
 508                         break;
 509
 510                 case OPT_DEFAULT_PERMISSIONS:
 511                         config->default_permissions = true;
 512                         break;
 513
 514                 case OPT_REDIRECT_DIR:
 515                         kfree(config->redirect_mode);
 516                         config->redirect_mode = match_strdup(&args[0]);
 517                         if (!config->redirect_mode)
 518                                 return -ENOMEM;
 519                         break;
 520
 521                 case OPT_INDEX_ON:
 522                         config->index = true;
 523                         break;
 524
 525                 case OPT_INDEX_OFF:
 526                         config->index = false;
 527                         break;
 528
 529                 case OPT_NFS_EXPORT_ON:
 530                         config->nfs_export = true;
 531                         break;
 532
 533                 case OPT_NFS_EXPORT_OFF:
 534                         config->nfs_export = false;
 535                         break;
 536
 537                 case OPT_XINO_ON:
 538                         config->xino = OVL_XINO_ON;
 539                         break;
 540
 541                 case OPT_XINO_OFF:
 542                         config->xino = OVL_XINO_OFF;
 543                         break;
 544
 545                 case OPT_XINO_AUTO:
 546                         config->xino = OVL_XINO_AUTO;
 547                         break;
 548
 549                 case OPT_METACOPY_ON:
 550                         config->metacopy = true;
 551                         break;
 552
 553                 case OPT_METACOPY_OFF:
 554                         config->metacopy = false;
 555                         break;
 556
 557                 default:
 558                         pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
 559                         return -EINVAL;
 560                 }
 561         }
 562
 563         /* Workdir is useless in non-upper mount */
 564         if (!config->upperdir && config->workdir) {
 565                 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
 566                         config->workdir);
 567                 kfree(config->workdir);
 568                 config->workdir = NULL;
 569         }
 570
 571         err = ovl_parse_redirect_mode(config, config->redirect_mode);
 572         if (err)
 573                 return err;
 574
 575         /* metacopy feature with upper requires redirect_dir=on */
 576         if (config->upperdir && config->metacopy && !config->redirect_dir) {
 577                 pr_warn("overlayfs: metadata only copy up requires \"redirect_dir=on\", falling back to metacopy=off.\n");
 578                 config->metacopy = false;
 579         } else if (config->metacopy && !config->redirect_follow) {
 580                 pr_warn("overlayfs: metadata only copy up requires \"redirect_dir=follow\" on non-upper mount, falling back to metacopy=off.\n");
 581                 config->metacopy = false;
 582         }
 583
 584         return 0;
 585 }
 586
 587 #define OVL_WORKDIR_NAME "work"
 588 #define OVL_INDEXDIR_NAME "index"
 589
 590 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
 591                                          const char *name, bool persist)
 592 {
 593         struct inode *dir =  ofs->workbasedir->d_inode;
 594         struct vfsmount *mnt = ofs->upper_mnt;
 595         struct dentry *work;
 596         int err;
 597         bool retried = false;
 598         bool locked = false;
 599
 600         inode_lock_nested(dir, I_MUTEX_PARENT);
 601         locked = true;
 602
 603 retry:
 604         work = lookup_one_len(name, ofs->workbasedir, strlen(name));
 605
 606         if (!IS_ERR(work)) {
 607                 struct iattr attr = {
 608                         .ia_valid = ATTR_MODE,
 609                         .ia_mode = S_IFDIR | 0,
 610                 };
 611
 612                 if (work->d_inode) {
 613                         err = -EEXIST;
 614                         if (retried)
 615                                 goto out_dput;
 616
 617                         if (persist)
 618                                 goto out_unlock;
 619
 620                         retried = true;
 621                         ovl_workdir_cleanup(dir, mnt, work, 0);
 622                         dput(work);
 623                         goto retry;
 624                 }
 625
 626                 work = ovl_create_real(dir, work, OVL_CATTR(attr.ia_mode));
 627                 err = PTR_ERR(work);
 628                 if (IS_ERR(work))
 629                         goto out_err;
 630
 631                 /*
 632                  * Try to remove POSIX ACL xattrs from workdir.  We are good if:
 633                  *
 634                  * a) success (there was a POSIX ACL xattr and was removed)
 635                  * b) -ENODATA (there was no POSIX ACL xattr)
 636                  * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
 637                  *
 638                  * There are various other error values that could effectively
 639                  * mean that the xattr doesn't exist (e.g. -ERANGE is returned
 640                  * if the xattr name is too long), but the set of filesystems
 641                  * allowed as upper are limited to "normal" ones, where checking
 642                  * for the above two errors is sufficient.
 643                  */
 644                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
 645                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
 646                         goto out_dput;
 647
 648                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
 649                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
 650                         goto out_dput;
 651
 652                 /* Clear any inherited mode bits */
 653                 inode_lock(work->d_inode);
 654                 err = notify_change(work, &attr, NULL);
 655                 inode_unlock(work->d_inode);
 656                 if (err)
 657                         goto out_dput;
 658         } else {
 659                 err = PTR_ERR(work);
 660                 goto out_err;
 661         }
 662 out_unlock:
 663         if (locked)
 664                 inode_unlock(dir);
 665
 666         return work;
 667
 668 out_dput:
 669         dput(work);
 670 out_err:
 671         pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
 672                 ofs->config.workdir, name, -err);
 673         work = NULL;
 674         goto out_unlock;
 675 }
 676
 677 static void ovl_unescape(char *s)
 678 {
 679         char *d = s;
 680
 681         for (;; s++, d++) {
 682                 if (*s == '\\')
 683                         s++;
 684                 *d = *s;
 685                 if (!*s)
 686                         break;
 687         }
 688 }
 689
 690 static int ovl_mount_dir_noesc(const char *name, struct path *path)
 691 {
 692         int err = -EINVAL;
 693
 694         if (!*name) {
 695                 pr_err("overlayfs: empty lowerdir\n");
 696                 goto out;
 697         }
 698         err = kern_path(name, LOOKUP_FOLLOW, path);
 699         if (err) {
 700                 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
 701                 goto out;
 702         }
 703         err = -EINVAL;
 704         if (ovl_dentry_weird(path->dentry)) {
 705                 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
 706                 goto out_put;
 707         }
 708         if (!d_is_dir(path->dentry)) {
 709                 pr_err("overlayfs: '%s' not a directory\n", name);
 710                 goto out_put;
 711         }
 712         return 0;
 713
 714 out_put:
 715         path_put_init(path);
 716 out:
 717         return err;
 718 }
 719
 720 static int ovl_mount_dir(const char *name, struct path *path)
 721 {
 722         int err = -ENOMEM;
 723         char *tmp = kstrdup(name, GFP_KERNEL);
 724
 725         if (tmp) {
 726                 ovl_unescape(tmp);
 727                 err = ovl_mount_dir_noesc(tmp, path);
 728
 729                 if (!err)
 730                         if (ovl_dentry_remote(path->dentry)) {
 731                                 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
 732                                        tmp);
 733                                 path_put_init(path);
 734                                 err = -EINVAL;
 735                         }
 736                 kfree(tmp);
 737         }
 738         return err;
 739 }
 740
 741 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
 742                              const char *name)
 743 {
 744         struct kstatfs statfs;
 745         int err = vfs_statfs(path, &statfs);
 746
 747         if (err)
 748                 pr_err("overlayfs: statfs failed on '%s'\n", name);
 749         else
 750                 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
 751
 752         return err;
 753 }
 754
 755 static int ovl_lower_dir(const char *name, struct path *path,
 756                          struct ovl_fs *ofs, int *stack_depth, bool *remote)
 757 {
 758         int fh_type;
 759         int err;
 760
 761         err = ovl_mount_dir_noesc(name, path);
 762         if (err)
 763                 goto out;
 764
 765         err = ovl_check_namelen(path, ofs, name);
 766         if (err)
 767                 goto out_put;
 768
 769         *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
 770
 771         if (ovl_dentry_remote(path->dentry))
 772                 *remote = true;
 773
 774         /*
 775          * The inodes index feature and NFS export need to encode and decode
 776          * file handles, so they require that all layers support them.
 777          */
 778         fh_type = ovl_can_decode_fh(path->dentry->d_sb);
 779         if ((ofs->config.nfs_export ||
 780              (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
 781                 ofs->config.index = false;
 782                 ofs->config.nfs_export = false;
 783                 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
 784                         name);
 785         }
 786
 787         /* Check if lower fs has 32bit inode numbers */
 788         if (fh_type != FILEID_INO32_GEN)
 789                 ofs->xino_bits = 0;
 790
 791         return 0;
 792
 793 out_put:
 794         path_put_init(path);
 795 out:
 796         return err;
 797 }
 798
 799 /* Workdir should not be subdir of upperdir and vice versa */
 800 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
 801 {
 802         bool ok = false;
 803
 804         if (workdir != upperdir) {
 805                 ok = (lock_rename(workdir, upperdir) == NULL);
 806                 unlock_rename(workdir, upperdir);
 807         }
 808         return ok;
 809 }
 810
 811 static unsigned int ovl_split_lowerdirs(char *str)
 812 {
 813         unsigned int ctr = 1;
 814         char *s, *d;
 815
 816         for (s = d = str;; s++, d++) {
 817                 if (*s == '\\') {
 818                         s++;
 819                 } else if (*s == ':') {
 820                         *d = '\0';
 821                         ctr++;
 822                         continue;
 823                 }
 824                 *d = *s;
 825                 if (!*s)
 826                         break;
 827         }
 828         return ctr;
 829 }
 830
 831 static int __maybe_unused
 832 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
 833                         struct dentry *dentry, struct inode *inode,
 834                         const char *name, void *buffer, size_t size)
 835 {
 836         return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
 837 }
 838
 839 static int __maybe_unused
 840 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
 841                         struct dentry *dentry, struct inode *inode,
 842                         const char *name, const void *value,
 843                         size_t size, int flags)
 844 {
 845         struct dentry *workdir = ovl_workdir(dentry);
 846         struct inode *realinode = ovl_inode_real(inode);
 847         struct posix_acl *acl = NULL;
 848         int err;
 849
 850         /* Check that everything is OK before copy-up */
 851         if (value) {
 852                 acl = posix_acl_from_xattr(&init_user_ns, value, size);
 853                 if (IS_ERR(acl))
 854                         return PTR_ERR(acl);
 855         }
 856         err = -EOPNOTSUPP;
 857         if (!IS_POSIXACL(d_inode(workdir)))
 858                 goto out_acl_release;
 859         if (!realinode->i_op->set_acl)
 860                 goto out_acl_release;
 861         if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
 862                 err = acl ? -EACCES : 0;
 863                 goto out_acl_release;
 864         }
 865         err = -EPERM;
 866         if (!inode_owner_or_capable(inode))
 867                 goto out_acl_release;
 868
 869         posix_acl_release(acl);
 870
 871         /*
 872          * Check if sgid bit needs to be cleared (actual setacl operation will
 873          * be done with mounter's capabilities and so that won't do it for us).
 874          */
 875         if (unlikely(inode->i_mode & S_ISGID) &&
 876             handler->flags == ACL_TYPE_ACCESS &&
 877             !in_group_p(inode->i_gid) &&
 878             !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
 879                 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
 880
 881                 err = ovl_setattr(dentry, &iattr);
 882                 if (err)
 883                         return err;
 884         }
 885
 886         err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
 887         if (!err)
 888                 ovl_copyattr(ovl_inode_real(inode), inode);
 889
 890         return err;
 891
 892 out_acl_release:
 893         posix_acl_release(acl);
 894         return err;
 895 }
 896
 897 static int ovl_own_xattr_get(const struct xattr_handler *handler,
 898                              struct dentry *dentry, struct inode *inode,
 899                              const char *name, void *buffer, size_t size)
 900 {
 901         return -EOPNOTSUPP;
 902 }
 903
 904 static int ovl_own_xattr_set(const struct xattr_handler *handler,
 905                              struct dentry *dentry, struct inode *inode,
 906                              const char *name, const void *value,
 907                              size_t size, int flags)
 908 {
 909         return -EOPNOTSUPP;
 910 }
 911
 912 static int ovl_other_xattr_get(const struct xattr_handler *handler,
 913                                struct dentry *dentry, struct inode *inode,
 914                                const char *name, void *buffer, size_t size)
 915 {
 916         return ovl_xattr_get(dentry, inode, name, buffer, size);
 917 }
 918
 919 static int ovl_other_xattr_set(const struct xattr_handler *handler,
 920                                struct dentry *dentry, struct inode *inode,
 921                                const char *name, const void *value,
 922                                size_t size, int flags)
 923 {
 924         return ovl_xattr_set(dentry, inode, name, value, size, flags);
 925 }
 926
 927 static const struct xattr_handler __maybe_unused
 928 ovl_posix_acl_access_xattr_handler = {
 929         .name = XATTR_NAME_POSIX_ACL_ACCESS,
 930         .flags = ACL_TYPE_ACCESS,
 931         .get = ovl_posix_acl_xattr_get,
 932         .set = ovl_posix_acl_xattr_set,
 933 };
 934
 935 static const struct xattr_handler __maybe_unused
 936 ovl_posix_acl_default_xattr_handler = {
 937         .name = XATTR_NAME_POSIX_ACL_DEFAULT,
 938         .flags = ACL_TYPE_DEFAULT,
 939         .get = ovl_posix_acl_xattr_get,
 940         .set = ovl_posix_acl_xattr_set,
 941 };
 942
 943 static const struct xattr_handler ovl_own_xattr_handler = {
 944         .prefix = OVL_XATTR_PREFIX,
 945         .get = ovl_own_xattr_get,
 946         .set = ovl_own_xattr_set,
 947 };
 948
 949 static const struct xattr_handler ovl_other_xattr_handler = {
 950         .prefix = "", /* catch all */
 951         .get = ovl_other_xattr_get,
 952         .set = ovl_other_xattr_set,
 953 };
 954
 955 static const struct xattr_handler *ovl_xattr_handlers[] = {
 956 #ifdef CONFIG_FS_POSIX_ACL
 957         &ovl_posix_acl_access_xattr_handler,
 958         &ovl_posix_acl_default_xattr_handler,
 959 #endif
 960         &ovl_own_xattr_handler,
 961         &ovl_other_xattr_handler,
 962         NULL
 963 };
 964
 965 static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
 966 {
 967         struct vfsmount *upper_mnt;
 968         int err;
 969
 970         err = ovl_mount_dir(ofs->config.upperdir, upperpath);
 971         if (err)
 972                 goto out;
 973
 974         /* Upper fs should not be r/o */
 975         if (sb_rdonly(upperpath->mnt->mnt_sb)) {
 976                 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
 977                 err = -EINVAL;
 978                 goto out;
 979         }
 980
 981         err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
 982         if (err)
 983                 goto out;
 984
 985         err = -EBUSY;
 986         if (ovl_inuse_trylock(upperpath->dentry)) {
 987                 ofs->upperdir_locked = true;
 988         } else if (ofs->config.index) {
 989                 pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
 990                 goto out;
 991         } else {
 992                 pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
 993         }
 994
 995         upper_mnt = clone_private_mount(upperpath);
 996         err = PTR_ERR(upper_mnt);
 997         if (IS_ERR(upper_mnt)) {
 998                 pr_err("overlayfs: failed to clone upperpath\n");
 999                 goto out;
1000         }
1001
1002         /* Don't inherit atime flags */
1003         upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
1004         ofs->upper_mnt = upper_mnt;
1005         err = 0;
1006 out:
1007         return err;
1008 }
1009
1010 static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
1011 {
1012         struct vfsmount *mnt = ofs->upper_mnt;
1013         struct dentry *temp;
1014         int fh_type;
1015         int err;
1016
1017         err = mnt_want_write(mnt);
1018         if (err)
1019                 return err;
1020
1021         ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
1022         if (!ofs->workdir)
1023                 goto out;
1024
1025         /*
1026          * Upper should support d_type, else whiteouts are visible.  Given
1027          * workdir and upper are on same fs, we can do iterate_dir() on
1028          * workdir. This check requires successful creation of workdir in
1029          * previous step.
1030          */
1031         err = ovl_check_d_type_supported(workpath);
1032         if (err < 0)
1033                 goto out;
1034
1035         /*
1036          * We allowed this configuration and don't want to break users over
1037          * kernel upgrade. So warn instead of erroring out.
1038          */
1039         if (!err)
1040                 pr_warn("overlayfs: upper fs needs to support d_type.\n");
1041
1042         /* Check if upper/work fs supports O_TMPFILE */
1043         temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
1044         ofs->tmpfile = !IS_ERR(temp);
1045         if (ofs->tmpfile)
1046                 dput(temp);
1047         else
1048                 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
1049
1050         /*
1051          * Check if upper/work fs supports trusted.overlay.* xattr
1052          */
1053         err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
1054         if (err) {
1055                 ofs->noxattr = true;
1056                 ofs->config.index = false;
1057                 ofs->config.metacopy = false;
1058                 pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off and metacopy=off.\n");
1059                 err = 0;
1060         } else {
1061                 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
1062         }
1063
1064         /* Check if upper/work fs supports file handles */
1065         fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
1066         if (ofs->config.index && !fh_type) {
1067                 ofs->config.index = false;
1068                 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
1069         }
1070
1071         /* Check if upper fs has 32bit inode numbers */
1072         if (fh_type != FILEID_INO32_GEN)
1073                 ofs->xino_bits = 0;
1074
1075         /* NFS export of r/w mount depends on index */
1076         if (ofs->config.nfs_export && !ofs->config.index) {
1077                 pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n");
1078                 ofs->config.nfs_export = false;
1079         }
1080 out:
1081         mnt_drop_write(mnt);
1082         return err;
1083 }
1084
1085 static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
1086 {
1087         int err;
1088         struct path workpath = { };
1089
1090         err = ovl_mount_dir(ofs->config.workdir, &workpath);
1091         if (err)
1092                 goto out;
1093
1094         err = -EINVAL;
1095         if (upperpath->mnt != workpath.mnt) {
1096                 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
1097                 goto out;
1098         }
1099         if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
1100                 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
1101                 goto out;
1102         }
1103
1104         err = -EBUSY;
1105         if (ovl_inuse_trylock(workpath.dentry)) {
1106                 ofs->workdir_locked = true;
1107         } else if (ofs->config.index) {
1108                 pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
1109                 goto out;
1110         } else {
1111                 pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
1112         }
1113
1114         ofs->workbasedir = dget(workpath.dentry);
1115         err = ovl_make_workdir(ofs, &workpath);
1116         if (err)
1117                 goto out;
1118
1119         err = 0;
1120 out:
1121         path_put(&workpath);
1122
1123         return err;
1124 }
1125
1126 static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe,
1127                             struct path *upperpath)
1128 {
1129         struct vfsmount *mnt = ofs->upper_mnt;
1130         int err;
1131
1132         err = mnt_want_write(mnt);
1133         if (err)
1134                 return err;
1135
1136         /* Verify lower root is upper root origin */
1137         err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
1138                                 true);
1139         if (err) {
1140                 pr_err("overlayfs: failed to verify upper root origin\n");
1141                 goto out;
1142         }
1143
1144         ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
1145         if (ofs->indexdir) {
1146                 /*
1147                  * Verify upper root is exclusively associated with index dir.
1148                  * Older kernels stored upper fh in "trusted.overlay.origin"
1149                  * xattr. If that xattr exists, verify that it is a match to
1150                  * upper dir file handle. In any case, verify or set xattr
1151                  * "trusted.overlay.upper" to indicate that index may have
1152                  * directory entries.
1153                  */
1154                 if (ovl_check_origin_xattr(ofs->indexdir)) {
1155                         err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN,
1156                                                 upperpath->dentry, true, false);
1157                         if (err)
1158                                 pr_err("overlayfs: failed to verify index dir 'origin' xattr\n");
1159                 }
1160                 err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true);
1161                 if (err)
1162                         pr_err("overlayfs: failed to verify index dir 'upper' xattr\n");
1163
1164                 /* Cleanup bad/stale/orphan index entries */
1165                 if (!err)
1166                         err = ovl_indexdir_cleanup(ofs);
1167         }
1168         if (err || !ofs->indexdir)
1169                 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1170
1171 out:
1172         mnt_drop_write(mnt);
1173         return err;
1174 }
1175
1176 /* Get a unique fsid for the layer */
1177 static int ovl_get_fsid(struct ovl_fs *ofs, struct super_block *sb)
1178 {
1179         unsigned int i;
1180         dev_t dev;
1181         int err;
1182
1183         /* fsid 0 is reserved for upper fs even with non upper overlay */
1184         if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb)
1185                 return 0;
1186
1187         for (i = 0; i < ofs->numlowerfs; i++) {
1188                 if (ofs->lower_fs[i].sb == sb)
1189                         return i + 1;
1190         }
1191
1192         err = get_anon_bdev(&dev);
1193         if (err) {
1194                 pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
1195                 return err;
1196         }
1197
1198         ofs->lower_fs[ofs->numlowerfs].sb = sb;
1199         ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev;
1200         ofs->numlowerfs++;
1201
1202         return ofs->numlowerfs;
1203 }
1204
1205 static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
1206                                 unsigned int numlower)
1207 {
1208         int err;
1209         unsigned int i;
1210
1211         err = -ENOMEM;
1212         ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
1213                                     GFP_KERNEL);
1214         if (ofs->lower_layers == NULL)
1215                 goto out;
1216
1217         ofs->lower_fs = kcalloc(numlower, sizeof(struct ovl_sb),
1218                                 GFP_KERNEL);
1219         if (ofs->lower_fs == NULL)
1220                 goto out;
1221
1222         for (i = 0; i < numlower; i++) {
1223                 struct vfsmount *mnt;
1224                 int fsid;
1225
1226                 err = fsid = ovl_get_fsid(ofs, stack[i].mnt->mnt_sb);
1227                 if (err < 0)
1228                         goto out;
1229
1230                 mnt = clone_private_mount(&stack[i]);
1231                 err = PTR_ERR(mnt);
1232                 if (IS_ERR(mnt)) {
1233                         pr_err("overlayfs: failed to clone lowerpath\n");
1234                         goto out;
1235                 }
1236
1237                 /*
1238                  * Make lower layers R/O.  That way fchmod/fchown on lower file
1239                  * will fail instead of modifying lower fs.
1240                  */
1241                 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1242
1243                 ofs->lower_layers[ofs->numlower].mnt = mnt;
1244                 ofs->lower_layers[ofs->numlower].idx = i + 1;
1245                 ofs->lower_layers[ofs->numlower].fsid = fsid;
1246                 if (fsid) {
1247                         ofs->lower_layers[ofs->numlower].fs =
1248                                 &ofs->lower_fs[fsid - 1];
1249                 }
1250                 ofs->numlower++;
1251         }
1252
1253         /*
1254          * When all layers on same fs, overlay can use real inode numbers.
1255          * With mount option "xino=on", mounter declares that there are enough
1256          * free high bits in underlying fs to hold the unique fsid.
1257          * If overlayfs does encounter underlying inodes using the high xino
1258          * bits reserved for fsid, it emits a warning and uses the original
1259          * inode number.
1260          */
1261         if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt)) {
1262                 ofs->xino_bits = 0;
1263                 ofs->config.xino = OVL_XINO_OFF;
1264         } else if (ofs->config.xino == OVL_XINO_ON && !ofs->xino_bits) {
1265                 /*
1266                  * This is a roundup of number of bits needed for numlowerfs+1
1267                  * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for
1268                  * upper fs even with non upper overlay.
1269                  */
1270                 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31);
1271                 ofs->xino_bits = ilog2(ofs->numlowerfs) + 1;
1272         }
1273
1274         if (ofs->xino_bits) {
1275                 pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n",
1276                         ofs->xino_bits);
1277         }
1278
1279         err = 0;
1280 out:
1281         return err;
1282 }
1283
1284 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1285                                             struct ovl_fs *ofs)
1286 {
1287         int err;
1288         char *lowertmp, *lower;
1289         struct path *stack = NULL;
1290         unsigned int stacklen, numlower = 0, i;
1291         bool remote = false;
1292         struct ovl_entry *oe;
1293
1294         err = -ENOMEM;
1295         lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1296         if (!lowertmp)
1297                 goto out_err;
1298
1299         err = -EINVAL;
1300         stacklen = ovl_split_lowerdirs(lowertmp);
1301         if (stacklen > OVL_MAX_STACK) {
1302                 pr_err("overlayfs: too many lower directories, limit is %d\n",
1303                        OVL_MAX_STACK);
1304                 goto out_err;
1305         } else if (!ofs->config.upperdir && stacklen == 1) {
1306                 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1307                 goto out_err;
1308         } else if (!ofs->config.upperdir && ofs->config.nfs_export &&
1309                    ofs->config.redirect_follow) {
1310                 pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
1311                 ofs->config.nfs_export = false;
1312         }
1313
1314         err = -ENOMEM;
1315         stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1316         if (!stack)
1317                 goto out_err;
1318
1319         err = -EINVAL;
1320         lower = lowertmp;
1321         for (numlower = 0; numlower < stacklen; numlower++) {
1322                 err = ovl_lower_dir(lower, &stack[numlower], ofs,
1323                                     &sb->s_stack_depth, &remote);
1324                 if (err)
1325                         goto out_err;
1326
1327                 lower = strchr(lower, '\0') + 1;
1328         }
1329
1330         err = -EINVAL;
1331         sb->s_stack_depth++;
1332         if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1333                 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1334                 goto out_err;
1335         }
1336
1337         err = ovl_get_lower_layers(ofs, stack, numlower);
1338         if (err)
1339                 goto out_err;
1340
1341         err = -ENOMEM;
1342         oe = ovl_alloc_entry(numlower);
1343         if (!oe)
1344                 goto out_err;
1345
1346         for (i = 0; i < numlower; i++) {
1347                 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1348                 oe->lowerstack[i].layer = &ofs->lower_layers[i];
1349         }
1350
1351         if (remote)
1352                 sb->s_d_op = &ovl_reval_dentry_operations;
1353         else
1354                 sb->s_d_op = &ovl_dentry_operations;
1355
1356 out:
1357         for (i = 0; i < numlower; i++)
1358                 path_put(&stack[i]);
1359         kfree(stack);
1360         kfree(lowertmp);
1361
1362         return oe;
1363
1364 out_err:
1365         oe = ERR_PTR(err);
1366         goto out;
1367 }
1368
1369 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1370 {
1371         struct path upperpath = { };
1372         struct dentry *root_dentry;
1373         struct ovl_entry *oe;
1374         struct ovl_fs *ofs;
1375         struct cred *cred;
1376         int err;
1377
1378         err = -ENOMEM;
1379         ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1380         if (!ofs)
1381                 goto out;
1382
1383         ofs->creator_cred = cred = prepare_creds();
1384         if (!cred)
1385                 goto out_err;
1386
1387         ofs->config.index = ovl_index_def;
1388         ofs->config.nfs_export = ovl_nfs_export_def;
1389         ofs->config.xino = ovl_xino_def();
1390         ofs->config.metacopy = ovl_metacopy_def;
1391         err = ovl_parse_opt((char *) data, &ofs->config);
1392         if (err)
1393                 goto out_err;
1394
1395         err = -EINVAL;
1396         if (!ofs->config.lowerdir) {
1397                 if (!silent)
1398                         pr_err("overlayfs: missing 'lowerdir'\n");
1399                 goto out_err;
1400         }
1401
1402         sb->s_stack_depth = 0;
1403         sb->s_maxbytes = MAX_LFS_FILESIZE;
1404         /* Assume underlaying fs uses 32bit inodes unless proven otherwise */
1405         if (ofs->config.xino != OVL_XINO_OFF)
1406                 ofs->xino_bits = BITS_PER_LONG - 32;
1407
1408         if (ofs->config.upperdir) {
1409                 if (!ofs->config.workdir) {
1410                         pr_err("overlayfs: missing 'workdir'\n");
1411                         goto out_err;
1412                 }
1413
1414                 err = ovl_get_upper(ofs, &upperpath);
1415                 if (err)
1416                         goto out_err;
1417
1418                 err = ovl_get_workdir(ofs, &upperpath);
1419                 if (err)
1420                         goto out_err;
1421
1422                 if (!ofs->workdir)
1423                         sb->s_flags |= SB_RDONLY;
1424
1425                 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
1426                 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
1427
1428         }
1429         oe = ovl_get_lowerstack(sb, ofs);
1430         err = PTR_ERR(oe);
1431         if (IS_ERR(oe))
1432                 goto out_err;
1433
1434         /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1435         if (!ofs->upper_mnt)
1436                 sb->s_flags |= SB_RDONLY;
1437
1438         if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
1439                 err = ovl_get_indexdir(ofs, oe, &upperpath);
1440                 if (err)
1441                         goto out_free_oe;
1442
1443                 /* Force r/o mount with no index dir */
1444                 if (!ofs->indexdir) {
1445                         dput(ofs->workdir);
1446                         ofs->workdir = NULL;
1447                         sb->s_flags |= SB_RDONLY;
1448                 }
1449
1450         }
1451
1452         /* Show index=off in /proc/mounts for forced r/o mount */
1453         if (!ofs->indexdir) {
1454                 ofs->config.index = false;
1455                 if (ofs->upper_mnt && ofs->config.nfs_export) {
1456                         pr_warn("overlayfs: NFS export requires an index dir, falling back to nfs_export=off.\n");
1457                         ofs->config.nfs_export = false;
1458                 }
1459         }
1460
1461         if (ofs->config.metacopy && ofs->config.nfs_export) {
1462                 pr_warn("overlayfs: NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
1463                 ofs->config.nfs_export = false;
1464         }
1465
1466         if (ofs->config.nfs_export)
1467                 sb->s_export_op = &ovl_export_operations;
1468
1469         /* Never override disk quota limits or use reserved space */
1470         cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1471
1472         sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1473         sb->s_op = &ovl_super_operations;
1474         sb->s_xattr = ovl_xattr_handlers;
1475         sb->s_fs_info = ofs;
1476         sb->s_flags |= SB_POSIXACL;
1477
1478         err = -ENOMEM;
1479         root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1480         if (!root_dentry)
1481                 goto out_free_oe;
1482
1483         root_dentry->d_fsdata = oe;
1484
1485         mntput(upperpath.mnt);
1486         if (upperpath.dentry) {
1487                 ovl_dentry_set_upper_alias(root_dentry);
1488                 if (ovl_is_impuredir(upperpath.dentry))
1489                         ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1490         }
1491
1492         /* Root is always merge -> can have whiteouts */
1493         ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1494         ovl_dentry_set_flag(OVL_E_CONNECTED, root_dentry);
1495         ovl_set_upperdata(d_inode(root_dentry));
1496         ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
1497                        ovl_dentry_lower(root_dentry), NULL);
1498
1499         sb->s_root = root_dentry;
1500
1501         return 0;
1502
1503 out_free_oe:
1504         ovl_entry_stack_free(oe);
1505         kfree(oe);
1506 out_err:
1507         path_put(&upperpath);
1508         ovl_free_fs(ofs);
1509 out:
1510         return err;
1511 }
1512
1513 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1514                                 const char *dev_name, void *raw_data)
1515 {
1516         return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1517 }
1518
1519 static struct file_system_type ovl_fs_type = {
1520         .owner          = THIS_MODULE,
1521         .name           = "overlay",
1522         .mount          = ovl_mount,
1523         .kill_sb        = kill_anon_super,
1524 };
1525 MODULE_ALIAS_FS("overlay");
1526
1527 static void ovl_inode_init_once(void *foo)
1528 {
1529         struct ovl_inode *oi = foo;
1530
1531         inode_init_once(&oi->vfs_inode);
1532 }
1533
1534 static int __init ovl_init(void)
1535 {
1536         int err;
1537
1538         ovl_inode_cachep = kmem_cache_create("ovl_inode",
1539                                              sizeof(struct ovl_inode), 0,
1540                                              (SLAB_RECLAIM_ACCOUNT|
1541                                               SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1542                                              ovl_inode_init_once);
1543         if (ovl_inode_cachep == NULL)
1544                 return -ENOMEM;
1545
1546         err = register_filesystem(&ovl_fs_type);
1547         if (err)
1548                 kmem_cache_destroy(ovl_inode_cachep);
1549
1550         return err;
1551 }
1552
1553 static void __exit ovl_exit(void)
1554 {
1555         unregister_filesystem(&ovl_fs_type);
1556
1557         /*
1558          * Make sure all delayed rcu free inodes are flushed before we
1559          * destroy cache.
1560          */
1561         rcu_barrier();
1562         kmem_cache_destroy(ovl_inode_cachep);
1563
1564 }
1565
1566 module_init(ovl_init);
1567 module_exit(ovl_exit);