fs/overlayfs/super.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *
   4  * Copyright (C) 2011 Novell Inc.
   5  */
   6
   7 #include <uapi/linux/magic.h>
   8 #include <linux/fs.h>
   9 #include <linux/namei.h>
  10 #include <linux/xattr.h>
  11 #include <linux/mount.h>
  12 #include <linux/parser.h>
  13 #include <linux/module.h>
  14 #include <linux/statfs.h>
  15 #include <linux/seq_file.h>
  16 #include <linux/posix_acl_xattr.h>
  17 #include <linux/exportfs.h>
  18 #include "overlayfs.h"
  19
  20 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
  21 MODULE_DESCRIPTION("Overlay filesystem");
  22 MODULE_LICENSE("GPL");
  23
  24
  25 struct ovl_dir_cache;
  26
  27 #define OVL_MAX_STACK 500
  28
  29 static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
  30 module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
  31 MODULE_PARM_DESC(redirect_dir,
  32                  "Default to on or off for the redirect_dir feature");
  33
  34 static bool ovl_redirect_always_follow =
  35         IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW);
  36 module_param_named(redirect_always_follow, ovl_redirect_always_follow,
  37                    bool, 0644);
  38 MODULE_PARM_DESC(redirect_always_follow,
  39                  "Follow redirects even if redirect_dir feature is turned off");
  40
  41 static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
  42 module_param_named(index, ovl_index_def, bool, 0644);
  43 MODULE_PARM_DESC(index,
  44                  "Default to on or off for the inodes index feature");
  45
  46 static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT);
  47 module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644);
  48 MODULE_PARM_DESC(nfs_export,
  49                  "Default to on or off for the NFS export feature");
  50
  51 static bool ovl_xino_auto_def = IS_ENABLED(CONFIG_OVERLAY_FS_XINO_AUTO);
  52 module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
  53 MODULE_PARM_DESC(xino_auto,
  54                  "Auto enable xino feature");
  55
  56 static void ovl_entry_stack_free(struct ovl_entry *oe)
  57 {
  58         unsigned int i;
  59
  60         for (i = 0; i < oe->numlower; i++)
  61                 dput(oe->lowerstack[i].dentry);
  62 }
  63
  64 static bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY);
  65 module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
  66 MODULE_PARM_DESC(metacopy,
  67                  "Default to on or off for the metadata only copy up feature");
  68
  69 static void ovl_dentry_release(struct dentry *dentry)
  70 {
  71         struct ovl_entry *oe = dentry->d_fsdata;
  72
  73         if (oe) {
  74                 ovl_entry_stack_free(oe);
  75                 kfree_rcu(oe, rcu);
  76         }
  77 }
  78
  79 static struct dentry *ovl_d_real(struct dentry *dentry,
  80                                  const struct inode *inode)
  81 {
  82         struct dentry *real = NULL, *lower;
  83
  84         /* It's an overlay file */
  85         if (inode && d_inode(dentry) == inode)
  86                 return dentry;
  87
  88         if (!d_is_reg(dentry)) {
  89                 if (!inode || inode == d_inode(dentry))
  90                         return dentry;
  91                 goto bug;
  92         }
  93
  94         real = ovl_dentry_upper(dentry);
  95         if (real && (inode == d_inode(real)))
  96                 return real;
  97
  98         if (real && !inode && ovl_has_upperdata(d_inode(dentry)))
  99                 return real;
 100
 101         lower = ovl_dentry_lowerdata(dentry);
 102         if (!lower)
 103                 goto bug;
 104         real = lower;
 105
 106         /* Handle recursion */
 107         real = d_real(real, inode);
 108
 109         if (!inode || inode == d_inode(real))
 110                 return real;
 111 bug:
 112         WARN(1, "%s(%pd4, %s:%lu): real dentry (%p/%lu) not found\n",
 113              __func__, dentry, inode ? inode->i_sb->s_id : "NULL",
 114              inode ? inode->i_ino : 0, real,
 115              real && d_inode(real) ? d_inode(real)->i_ino : 0);
 116         return dentry;
 117 }
 118
 119 static int ovl_revalidate_real(struct dentry *d, unsigned int flags, bool weak)
 120 {
 121         int ret = 1;
 122
 123         if (weak) {
 124                 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE)
 125                         ret =  d->d_op->d_weak_revalidate(d, flags);
 126         } else if (d->d_flags & DCACHE_OP_REVALIDATE) {
 127                 ret = d->d_op->d_revalidate(d, flags);
 128                 if (!ret) {
 129                         if (!(flags & LOOKUP_RCU))
 130                                 d_invalidate(d);
 131                         ret = -ESTALE;
 132                 }
 133         }
 134         return ret;
 135 }
 136
 137 static int ovl_dentry_revalidate_common(struct dentry *dentry,
 138                                         unsigned int flags, bool weak)
 139 {
 140         struct ovl_entry *oe = dentry->d_fsdata;
 141         struct inode *inode = d_inode_rcu(dentry);
 142         struct dentry *upper;
 143         unsigned int i;
 144         int ret = 1;
 145
 146         /* Careful in RCU mode */
 147         if (!inode)
 148                 return -ECHILD;
 149
 150         upper = ovl_i_dentry_upper(inode);
 151         if (upper)
 152                 ret = ovl_revalidate_real(upper, flags, weak);
 153
 154         for (i = 0; ret > 0 && i < oe->numlower; i++) {
 155                 ret = ovl_revalidate_real(oe->lowerstack[i].dentry, flags,
 156                                           weak);
 157         }
 158         return ret;
 159 }
 160
 161 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
 162 {
 163         return ovl_dentry_revalidate_common(dentry, flags, false);
 164 }
 165
 166 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
 167 {
 168         return ovl_dentry_revalidate_common(dentry, flags, true);
 169 }
 170
 171 static const struct dentry_operations ovl_dentry_operations = {
 172         .d_release = ovl_dentry_release,
 173         .d_real = ovl_d_real,
 174         .d_revalidate = ovl_dentry_revalidate,
 175         .d_weak_revalidate = ovl_dentry_weak_revalidate,
 176 };
 177
 178 static struct kmem_cache *ovl_inode_cachep;
 179
 180 static struct inode *ovl_alloc_inode(struct super_block *sb)
 181 {
 182         struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);
 183
 184         if (!oi)
 185                 return NULL;
 186
 187         oi->cache = NULL;
 188         oi->redirect = NULL;
 189         oi->version = 0;
 190         oi->flags = 0;
 191         oi->__upperdentry = NULL;
 192         oi->lower = NULL;
 193         oi->lowerdata = NULL;
 194         mutex_init(&oi->lock);
 195
 196         return &oi->vfs_inode;
 197 }
 198
 199 static void ovl_free_inode(struct inode *inode)
 200 {
 201         struct ovl_inode *oi = OVL_I(inode);
 202
 203         kfree(oi->redirect);
 204         mutex_destroy(&oi->lock);
 205         kmem_cache_free(ovl_inode_cachep, oi);
 206 }
 207
 208 static void ovl_destroy_inode(struct inode *inode)
 209 {
 210         struct ovl_inode *oi = OVL_I(inode);
 211
 212         dput(oi->__upperdentry);
 213         iput(oi->lower);
 214         if (S_ISDIR(inode->i_mode))
 215                 ovl_dir_cache_free(inode);
 216         else
 217                 iput(oi->lowerdata);
 218 }
 219
 220 static void ovl_free_fs(struct ovl_fs *ofs)
 221 {
 222         struct vfsmount **mounts;
 223         unsigned i;
 224
 225         iput(ofs->workbasedir_trap);
 226         iput(ofs->indexdir_trap);
 227         iput(ofs->workdir_trap);
 228         dput(ofs->whiteout);
 229         dput(ofs->indexdir);
 230         dput(ofs->workdir);
 231         if (ofs->workdir_locked)
 232                 ovl_inuse_unlock(ofs->workbasedir);
 233         dput(ofs->workbasedir);
 234         if (ofs->upperdir_locked)
 235                 ovl_inuse_unlock(ovl_upper_mnt(ofs)->mnt_root);
 236
 237         /* Hack!  Reuse ofs->layers as a vfsmount array before freeing it */
 238         mounts = (struct vfsmount **) ofs->layers;
 239         for (i = 0; i < ofs->numlayer; i++) {
 240                 iput(ofs->layers[i].trap);
 241                 mounts[i] = ofs->layers[i].mnt;
 242         }
 243         kern_unmount_array(mounts, ofs->numlayer);
 244         kfree(ofs->layers);
 245         for (i = 0; i < ofs->numfs; i++)
 246                 free_anon_bdev(ofs->fs[i].pseudo_dev);
 247         kfree(ofs->fs);
 248
 249         kfree(ofs->config.lowerdir);
 250         kfree(ofs->config.upperdir);
 251         kfree(ofs->config.workdir);
 252         kfree(ofs->config.redirect_mode);
 253         if (ofs->creator_cred)
 254                 put_cred(ofs->creator_cred);
 255         kfree(ofs);
 256 }
 257
 258 static void ovl_put_super(struct super_block *sb)
 259 {
 260         struct ovl_fs *ofs = sb->s_fs_info;
 261
 262         ovl_free_fs(ofs);
 263 }
 264
 265 /* Sync real dirty inodes in upper filesystem (if it exists) */
 266 static int ovl_sync_fs(struct super_block *sb, int wait)
 267 {
 268         struct ovl_fs *ofs = sb->s_fs_info;
 269         struct super_block *upper_sb;
 270         int ret;
 271
 272         ret = ovl_sync_status(ofs);
 273         /*
 274          * We have to always set the err, because the return value isn't
 275          * checked in syncfs, and instead indirectly return an error via
 276          * the sb's writeback errseq, which VFS inspects after this call.
 277          */
 278         if (ret < 0) {
 279                 errseq_set(&sb->s_wb_err, -EIO);
 280                 return -EIO;
 281         }
 282
 283         if (!ret)
 284                 return ret;
 285
 286         /*
 287          * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC).
 288          * All the super blocks will be iterated, including upper_sb.
 289          *
 290          * If this is a syncfs(2) call, then we do need to call
 291          * sync_filesystem() on upper_sb, but enough if we do it when being
 292          * called with wait == 1.
 293          */
 294         if (!wait)
 295                 return 0;
 296
 297         upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
 298
 299         down_read(&upper_sb->s_umount);
 300         ret = sync_filesystem(upper_sb);
 301         up_read(&upper_sb->s_umount);
 302
 303         return ret;
 304 }
 305
 306 /**
 307  * ovl_statfs
 308  * @sb: The overlayfs super block
 309  * @buf: The struct kstatfs to fill in with stats
 310  *
 311  * Get the filesystem statistics.  As writes always target the upper layer
 312  * filesystem pass the statfs to the upper filesystem (if it exists)
 313  */
 314 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
 315 {
 316         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 317         struct dentry *root_dentry = dentry->d_sb->s_root;
 318         struct path path;
 319         int err;
 320
 321         ovl_path_real(root_dentry, &path);
 322
 323         err = vfs_statfs(&path, buf);
 324         if (!err) {
 325                 buf->f_namelen = ofs->namelen;
 326                 buf->f_type = OVERLAYFS_SUPER_MAGIC;
 327         }
 328
 329         return err;
 330 }
 331
 332 /* Will this overlay be forced to mount/remount ro? */
 333 static bool ovl_force_readonly(struct ovl_fs *ofs)
 334 {
 335         return (!ovl_upper_mnt(ofs) || !ofs->workdir);
 336 }
 337
 338 static const char *ovl_redirect_mode_def(void)
 339 {
 340         return ovl_redirect_dir_def ? "on" : "off";
 341 }
 342
 343 static const char * const ovl_xino_str[] = {
 344         "off",
 345         "auto",
 346         "on",
 347 };
 348
 349 static inline int ovl_xino_def(void)
 350 {
 351         return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
 352 }
 353
 354 /**
 355  * ovl_show_options
 356  *
 357  * Prints the mount options for a given superblock.
 358  * Returns zero; does not fail.
 359  */
 360 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 361 {
 362         struct super_block *sb = dentry->d_sb;
 363         struct ovl_fs *ofs = sb->s_fs_info;
 364
 365         seq_show_option(m, "lowerdir", ofs->config.lowerdir);
 366         if (ofs->config.upperdir) {
 367                 seq_show_option(m, "upperdir", ofs->config.upperdir);
 368                 seq_show_option(m, "workdir", ofs->config.workdir);
 369         }
 370         if (ofs->config.default_permissions)
 371                 seq_puts(m, ",default_permissions");
 372         if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
 373                 seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
 374         if (ofs->config.index != ovl_index_def)
 375                 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
 376         if (ofs->config.nfs_export != ovl_nfs_export_def)
 377                 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
 378                                                 "on" : "off");
 379         if (ofs->config.xino != ovl_xino_def() && !ovl_same_fs(sb))
 380                 seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]);
 381         if (ofs->config.metacopy != ovl_metacopy_def)
 382                 seq_printf(m, ",metacopy=%s",
 383                            ofs->config.metacopy ? "on" : "off");
 384         if (ofs->config.ovl_volatile)
 385                 seq_puts(m, ",volatile");
 386         return 0;
 387 }
 388
 389 static int ovl_remount(struct super_block *sb, int *flags, char *data)
 390 {
 391         struct ovl_fs *ofs = sb->s_fs_info;
 392         struct super_block *upper_sb;
 393         int ret = 0;
 394
 395         if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
 396                 return -EROFS;
 397
 398         if (*flags & SB_RDONLY && !sb_rdonly(sb)) {
 399                 upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
 400                 if (ovl_should_sync(ofs)) {
 401                         down_read(&upper_sb->s_umount);
 402                         ret = sync_filesystem(upper_sb);
 403                         up_read(&upper_sb->s_umount);
 404                 }
 405         }
 406
 407         return ret;
 408 }
 409
 410 static const struct super_operations ovl_super_operations = {
 411         .alloc_inode    = ovl_alloc_inode,
 412         .free_inode     = ovl_free_inode,
 413         .destroy_inode  = ovl_destroy_inode,
 414         .drop_inode     = generic_delete_inode,
 415         .put_super      = ovl_put_super,
 416         .sync_fs        = ovl_sync_fs,
 417         .statfs         = ovl_statfs,
 418         .show_options   = ovl_show_options,
 419         .remount_fs     = ovl_remount,
 420 };
 421
 422 enum {
 423         OPT_LOWERDIR,
 424         OPT_UPPERDIR,
 425         OPT_WORKDIR,
 426         OPT_DEFAULT_PERMISSIONS,
 427         OPT_REDIRECT_DIR,
 428         OPT_INDEX_ON,
 429         OPT_INDEX_OFF,
 430         OPT_NFS_EXPORT_ON,
 431         OPT_NFS_EXPORT_OFF,
 432         OPT_XINO_ON,
 433         OPT_XINO_OFF,
 434         OPT_XINO_AUTO,
 435         OPT_METACOPY_ON,
 436         OPT_METACOPY_OFF,
 437         OPT_VOLATILE,
 438         OPT_ERR,
 439 };
 440
 441 static const match_table_t ovl_tokens = {
 442         {OPT_LOWERDIR,                  "lowerdir=%s"},
 443         {OPT_UPPERDIR,                  "upperdir=%s"},
 444         {OPT_WORKDIR,                   "workdir=%s"},
 445         {OPT_DEFAULT_PERMISSIONS,       "default_permissions"},
 446         {OPT_REDIRECT_DIR,              "redirect_dir=%s"},
 447         {OPT_INDEX_ON,                  "index=on"},
 448         {OPT_INDEX_OFF,                 "index=off"},
 449         {OPT_NFS_EXPORT_ON,             "nfs_export=on"},
 450         {OPT_NFS_EXPORT_OFF,            "nfs_export=off"},
 451         {OPT_XINO_ON,                   "xino=on"},
 452         {OPT_XINO_OFF,                  "xino=off"},
 453         {OPT_XINO_AUTO,                 "xino=auto"},
 454         {OPT_METACOPY_ON,               "metacopy=on"},
 455         {OPT_METACOPY_OFF,              "metacopy=off"},
 456         {OPT_VOLATILE,                  "volatile"},
 457         {OPT_ERR,                       NULL}
 458 };
 459
 460 static char *ovl_next_opt(char **s)
 461 {
 462         char *sbegin = *s;
 463         char *p;
 464
 465         if (sbegin == NULL)
 466                 return NULL;
 467
 468         for (p = sbegin; *p; p++) {
 469                 if (*p == '\\') {
 470                         p++;
 471                         if (!*p)
 472                                 break;
 473                 } else if (*p == ',') {
 474                         *p = '\0';
 475                         *s = p + 1;
 476                         return sbegin;
 477                 }
 478         }
 479         *s = NULL;
 480         return sbegin;
 481 }
 482
 483 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
 484 {
 485         if (strcmp(mode, "on") == 0) {
 486                 config->redirect_dir = true;
 487                 /*
 488                  * Does not make sense to have redirect creation without
 489                  * redirect following.
 490                  */
 491                 config->redirect_follow = true;
 492         } else if (strcmp(mode, "follow") == 0) {
 493                 config->redirect_follow = true;
 494         } else if (strcmp(mode, "off") == 0) {
 495                 if (ovl_redirect_always_follow)
 496                         config->redirect_follow = true;
 497         } else if (strcmp(mode, "nofollow") != 0) {
 498                 pr_err("bad mount option \"redirect_dir=%s\"\n",
 499                        mode);
 500                 return -EINVAL;
 501         }
 502
 503         return 0;
 504 }
 505
 506 static int ovl_parse_opt(char *opt, struct ovl_config *config)
 507 {
 508         char *p;
 509         int err;
 510         bool metacopy_opt = false, redirect_opt = false;
 511         bool nfs_export_opt = false, index_opt = false;
 512
 513         config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
 514         if (!config->redirect_mode)
 515                 return -ENOMEM;
 516
 517         while ((p = ovl_next_opt(&opt)) != NULL) {
 518                 int token;
 519                 substring_t args[MAX_OPT_ARGS];
 520
 521                 if (!*p)
 522                         continue;
 523
 524                 token = match_token(p, ovl_tokens, args);
 525                 switch (token) {
 526                 case OPT_UPPERDIR:
 527                         kfree(config->upperdir);
 528                         config->upperdir = match_strdup(&args[0]);
 529                         if (!config->upperdir)
 530                                 return -ENOMEM;
 531                         break;
 532
 533                 case OPT_LOWERDIR:
 534                         kfree(config->lowerdir);
 535                         config->lowerdir = match_strdup(&args[0]);
 536                         if (!config->lowerdir)
 537                                 return -ENOMEM;
 538                         break;
 539
 540                 case OPT_WORKDIR:
 541                         kfree(config->workdir);
 542                         config->workdir = match_strdup(&args[0]);
 543                         if (!config->workdir)
 544                                 return -ENOMEM;
 545                         break;
 546
 547                 case OPT_DEFAULT_PERMISSIONS:
 548                         config->default_permissions = true;
 549                         break;
 550
 551                 case OPT_REDIRECT_DIR:
 552                         kfree(config->redirect_mode);
 553                         config->redirect_mode = match_strdup(&args[0]);
 554                         if (!config->redirect_mode)
 555                                 return -ENOMEM;
 556                         redirect_opt = true;
 557                         break;
 558
 559                 case OPT_INDEX_ON:
 560                         config->index = true;
 561                         index_opt = true;
 562                         break;
 563
 564                 case OPT_INDEX_OFF:
 565                         config->index = false;
 566                         index_opt = true;
 567                         break;
 568
 569                 case OPT_NFS_EXPORT_ON:
 570                         config->nfs_export = true;
 571                         nfs_export_opt = true;
 572                         break;
 573
 574                 case OPT_NFS_EXPORT_OFF:
 575                         config->nfs_export = false;
 576                         nfs_export_opt = true;
 577                         break;
 578
 579                 case OPT_XINO_ON:
 580                         config->xino = OVL_XINO_ON;
 581                         break;
 582
 583                 case OPT_XINO_OFF:
 584                         config->xino = OVL_XINO_OFF;
 585                         break;
 586
 587                 case OPT_XINO_AUTO:
 588                         config->xino = OVL_XINO_AUTO;
 589                         break;
 590
 591                 case OPT_METACOPY_ON:
 592                         config->metacopy = true;
 593                         metacopy_opt = true;
 594                         break;
 595
 596                 case OPT_METACOPY_OFF:
 597                         config->metacopy = false;
 598                         metacopy_opt = true;
 599                         break;
 600
 601                 case OPT_VOLATILE:
 602                         config->ovl_volatile = true;
 603                         break;
 604
 605                 default:
 606                         pr_err("unrecognized mount option \"%s\" or missing value\n",
 607                                         p);
 608                         return -EINVAL;
 609                 }
 610         }
 611
 612         /* Workdir/index are useless in non-upper mount */
 613         if (!config->upperdir) {
 614                 if (config->workdir) {
 615                         pr_info("option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
 616                                 config->workdir);
 617                         kfree(config->workdir);
 618                         config->workdir = NULL;
 619                 }
 620                 if (config->index && index_opt) {
 621                         pr_info("option \"index=on\" is useless in a non-upper mount, ignore\n");
 622                         index_opt = false;
 623                 }
 624                 config->index = false;
 625         }
 626
 627         if (!config->upperdir && config->ovl_volatile) {
 628                 pr_info("option \"volatile\" is meaningless in a non-upper mount, ignoring it.\n");
 629                 config->ovl_volatile = false;
 630         }
 631
 632         err = ovl_parse_redirect_mode(config, config->redirect_mode);
 633         if (err)
 634                 return err;
 635
 636         /*
 637          * This is to make the logic below simpler.  It doesn't make any other
 638          * difference, since config->redirect_dir is only used for upper.
 639          */
 640         if (!config->upperdir && config->redirect_follow)
 641                 config->redirect_dir = true;
 642
 643         /* Resolve metacopy -> redirect_dir dependency */
 644         if (config->metacopy && !config->redirect_dir) {
 645                 if (metacopy_opt && redirect_opt) {
 646                         pr_err("conflicting options: metacopy=on,redirect_dir=%s\n",
 647                                config->redirect_mode);
 648                         return -EINVAL;
 649                 }
 650                 if (redirect_opt) {
 651                         /*
 652                          * There was an explicit redirect_dir=... that resulted
 653                          * in this conflict.
 654                          */
 655                         pr_info("disabling metacopy due to redirect_dir=%s\n",
 656                                 config->redirect_mode);
 657                         config->metacopy = false;
 658                 } else {
 659                         /* Automatically enable redirect otherwise. */
 660                         config->redirect_follow = config->redirect_dir = true;
 661                 }
 662         }
 663
 664         /* Resolve nfs_export -> index dependency */
 665         if (config->nfs_export && !config->index) {
 666                 if (!config->upperdir && config->redirect_follow) {
 667                         pr_info("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
 668                         config->nfs_export = false;
 669                 } else if (nfs_export_opt && index_opt) {
 670                         pr_err("conflicting options: nfs_export=on,index=off\n");
 671                         return -EINVAL;
 672                 } else if (index_opt) {
 673                         /*
 674                          * There was an explicit index=off that resulted
 675                          * in this conflict.
 676                          */
 677                         pr_info("disabling nfs_export due to index=off\n");
 678                         config->nfs_export = false;
 679                 } else {
 680                         /* Automatically enable index otherwise. */
 681                         config->index = true;
 682                 }
 683         }
 684
 685         /* Resolve nfs_export -> !metacopy dependency */
 686         if (config->nfs_export && config->metacopy) {
 687                 if (nfs_export_opt && metacopy_opt) {
 688                         pr_err("conflicting options: nfs_export=on,metacopy=on\n");
 689                         return -EINVAL;
 690                 }
 691                 if (metacopy_opt) {
 692                         /*
 693                          * There was an explicit metacopy=on that resulted
 694                          * in this conflict.
 695                          */
 696                         pr_info("disabling nfs_export due to metacopy=on\n");
 697                         config->nfs_export = false;
 698                 } else {
 699                         /*
 700                          * There was an explicit nfs_export=on that resulted
 701                          * in this conflict.
 702                          */
 703                         pr_info("disabling metacopy due to nfs_export=on\n");
 704                         config->metacopy = false;
 705                 }
 706         }
 707
 708         return 0;
 709 }
 710
 711 #define OVL_WORKDIR_NAME "work"
 712 #define OVL_INDEXDIR_NAME "index"
 713
 714 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
 715                                          const char *name, bool persist)
 716 {
 717         struct inode *dir =  ofs->workbasedir->d_inode;
 718         struct vfsmount *mnt = ovl_upper_mnt(ofs);
 719         struct dentry *work;
 720         int err;
 721         bool retried = false;
 722
 723         inode_lock_nested(dir, I_MUTEX_PARENT);
 724 retry:
 725         work = lookup_one_len(name, ofs->workbasedir, strlen(name));
 726
 727         if (!IS_ERR(work)) {
 728                 struct iattr attr = {
 729                         .ia_valid = ATTR_MODE,
 730                         .ia_mode = S_IFDIR | 0,
 731                 };
 732
 733                 if (work->d_inode) {
 734                         err = -EEXIST;
 735                         if (retried)
 736                                 goto out_dput;
 737
 738                         if (persist)
 739                                 goto out_unlock;
 740
 741                         retried = true;
 742                         err = ovl_workdir_cleanup(dir, mnt, work, 0);
 743                         dput(work);
 744                         if (err == -EINVAL) {
 745                                 work = ERR_PTR(err);
 746                                 goto out_unlock;
 747                         }
 748                         goto retry;
 749                 }
 750
 751                 err = ovl_mkdir_real(dir, &work, attr.ia_mode);
 752                 if (err)
 753                         goto out_dput;
 754
 755                 /* Weird filesystem returning with hashed negative (kernfs)? */
 756                 err = -EINVAL;
 757                 if (d_really_is_negative(work))
 758                         goto out_dput;
 759
 760                 /*
 761                  * Try to remove POSIX ACL xattrs from workdir.  We are good if:
 762                  *
 763                  * a) success (there was a POSIX ACL xattr and was removed)
 764                  * b) -ENODATA (there was no POSIX ACL xattr)
 765                  * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
 766                  *
 767                  * There are various other error values that could effectively
 768                  * mean that the xattr doesn't exist (e.g. -ERANGE is returned
 769                  * if the xattr name is too long), but the set of filesystems
 770                  * allowed as upper are limited to "normal" ones, where checking
 771                  * for the above two errors is sufficient.
 772                  */
 773                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
 774                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
 775                         goto out_dput;
 776
 777                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
 778                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
 779                         goto out_dput;
 780
 781                 /* Clear any inherited mode bits */
 782                 inode_lock(work->d_inode);
 783                 err = notify_change(work, &attr, NULL);
 784                 inode_unlock(work->d_inode);
 785                 if (err)
 786                         goto out_dput;
 787         } else {
 788                 err = PTR_ERR(work);
 789                 goto out_err;
 790         }
 791 out_unlock:
 792         inode_unlock(dir);
 793         return work;
 794
 795 out_dput:
 796         dput(work);
 797 out_err:
 798         pr_warn("failed to create directory %s/%s (errno: %i); mounting read-only\n",
 799                 ofs->config.workdir, name, -err);
 800         work = NULL;
 801         goto out_unlock;
 802 }
 803
 804 static void ovl_unescape(char *s)
 805 {
 806         char *d = s;
 807
 808         for (;; s++, d++) {
 809                 if (*s == '\\')
 810                         s++;
 811                 *d = *s;
 812                 if (!*s)
 813                         break;
 814         }
 815 }
 816
 817 static int ovl_mount_dir_noesc(const char *name, struct path *path)
 818 {
 819         int err = -EINVAL;
 820
 821         if (!*name) {
 822                 pr_err("empty lowerdir\n");
 823                 goto out;
 824         }
 825         err = kern_path(name, LOOKUP_FOLLOW, path);
 826         if (err) {
 827                 pr_err("failed to resolve '%s': %i\n", name, err);
 828                 goto out;
 829         }
 830         err = -EINVAL;
 831         if (ovl_dentry_weird(path->dentry)) {
 832                 pr_err("filesystem on '%s' not supported\n", name);
 833                 goto out_put;
 834         }
 835         if (!d_is_dir(path->dentry)) {
 836                 pr_err("'%s' not a directory\n", name);
 837                 goto out_put;
 838         }
 839         return 0;
 840
 841 out_put:
 842         path_put_init(path);
 843 out:
 844         return err;
 845 }
 846
 847 static int ovl_mount_dir(const char *name, struct path *path)
 848 {
 849         int err = -ENOMEM;
 850         char *tmp = kstrdup(name, GFP_KERNEL);
 851
 852         if (tmp) {
 853                 ovl_unescape(tmp);
 854                 err = ovl_mount_dir_noesc(tmp, path);
 855
 856                 if (!err && path->dentry->d_flags & DCACHE_OP_REAL) {
 857                         pr_err("filesystem on '%s' not supported as upperdir\n",
 858                                tmp);
 859                         path_put_init(path);
 860                         err = -EINVAL;
 861                 }
 862                 kfree(tmp);
 863         }
 864         return err;
 865 }
 866
 867 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
 868                              const char *name)
 869 {
 870         struct kstatfs statfs;
 871         int err = vfs_statfs(path, &statfs);
 872
 873         if (err)
 874                 pr_err("statfs failed on '%s'\n", name);
 875         else
 876                 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
 877
 878         return err;
 879 }
 880
 881 static int ovl_lower_dir(const char *name, struct path *path,
 882                          struct ovl_fs *ofs, int *stack_depth)
 883 {
 884         int fh_type;
 885         int err;
 886
 887         err = ovl_mount_dir_noesc(name, path);
 888         if (err)
 889                 return err;
 890
 891         err = ovl_check_namelen(path, ofs, name);
 892         if (err)
 893                 return err;
 894
 895         *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
 896
 897         /*
 898          * The inodes index feature and NFS export need to encode and decode
 899          * file handles, so they require that all layers support them.
 900          */
 901         fh_type = ovl_can_decode_fh(path->dentry->d_sb);
 902         if ((ofs->config.nfs_export ||
 903              (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
 904                 ofs->config.index = false;
 905                 ofs->config.nfs_export = false;
 906                 pr_warn("fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
 907                         name);
 908         }
 909
 910         /* Check if lower fs has 32bit inode numbers */
 911         if (fh_type != FILEID_INO32_GEN)
 912                 ofs->xino_mode = -1;
 913
 914         return 0;
 915 }
 916
 917 /* Workdir should not be subdir of upperdir and vice versa */
 918 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
 919 {
 920         bool ok = false;
 921
 922         if (workdir != upperdir) {
 923                 ok = (lock_rename(workdir, upperdir) == NULL);
 924                 unlock_rename(workdir, upperdir);
 925         }
 926         return ok;
 927 }
 928
 929 static unsigned int ovl_split_lowerdirs(char *str)
 930 {
 931         unsigned int ctr = 1;
 932         char *s, *d;
 933
 934         for (s = d = str;; s++, d++) {
 935                 if (*s == '\\') {
 936                         s++;
 937                 } else if (*s == ':') {
 938                         *d = '\0';
 939                         ctr++;
 940                         continue;
 941                 }
 942                 *d = *s;
 943                 if (!*s)
 944                         break;
 945         }
 946         return ctr;
 947 }
 948
 949 static int __maybe_unused
 950 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
 951                         struct dentry *dentry, struct inode *inode,
 952                         const char *name, void *buffer, size_t size)
 953 {
 954         return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
 955 }
 956
 957 static int __maybe_unused
 958 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
 959                         struct dentry *dentry, struct inode *inode,
 960                         const char *name, const void *value,
 961                         size_t size, int flags)
 962 {
 963         struct dentry *workdir = ovl_workdir(dentry);
 964         struct inode *realinode = ovl_inode_real(inode);
 965         struct posix_acl *acl = NULL;
 966         int err;
 967
 968         /* Check that everything is OK before copy-up */
 969         if (value) {
 970                 acl = posix_acl_from_xattr(&init_user_ns, value, size);
 971                 if (IS_ERR(acl))
 972                         return PTR_ERR(acl);
 973         }
 974         err = -EOPNOTSUPP;
 975         if (!IS_POSIXACL(d_inode(workdir)))
 976                 goto out_acl_release;
 977         if (!realinode->i_op->set_acl)
 978                 goto out_acl_release;
 979         if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
 980                 err = acl ? -EACCES : 0;
 981                 goto out_acl_release;
 982         }
 983         err = -EPERM;
 984         if (!inode_owner_or_capable(inode))
 985                 goto out_acl_release;
 986
 987         posix_acl_release(acl);
 988
 989         /*
 990          * Check if sgid bit needs to be cleared (actual setacl operation will
 991          * be done with mounter's capabilities and so that won't do it for us).
 992          */
 993         if (unlikely(inode->i_mode & S_ISGID) &&
 994             handler->flags == ACL_TYPE_ACCESS &&
 995             !in_group_p(inode->i_gid) &&
 996             !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
 997                 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
 998
 999                 err = ovl_setattr(dentry, &iattr);
1000                 if (err)
1001                         return err;
1002         }
1003
1004         err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
1005         if (!err)
1006                 ovl_copyattr(ovl_inode_real(inode), inode);
1007
1008         return err;
1009
1010 out_acl_release:
1011         posix_acl_release(acl);
1012         return err;
1013 }
1014
1015 static int ovl_own_xattr_get(const struct xattr_handler *handler,
1016                              struct dentry *dentry, struct inode *inode,
1017                              const char *name, void *buffer, size_t size)
1018 {
1019         return -EOPNOTSUPP;
1020 }
1021
1022 static int ovl_own_xattr_set(const struct xattr_handler *handler,
1023                              struct dentry *dentry, struct inode *inode,
1024                              const char *name, const void *value,
1025                              size_t size, int flags)
1026 {
1027         return -EOPNOTSUPP;
1028 }
1029
1030 static int ovl_other_xattr_get(const struct xattr_handler *handler,
1031                                struct dentry *dentry, struct inode *inode,
1032                                const char *name, void *buffer, size_t size)
1033 {
1034         return ovl_xattr_get(dentry, inode, name, buffer, size);
1035 }
1036
1037 static int ovl_other_xattr_set(const struct xattr_handler *handler,
1038                                struct dentry *dentry, struct inode *inode,
1039                                const char *name, const void *value,
1040                                size_t size, int flags)
1041 {
1042         return ovl_xattr_set(dentry, inode, name, value, size, flags);
1043 }
1044
1045 static const struct xattr_handler __maybe_unused
1046 ovl_posix_acl_access_xattr_handler = {
1047         .name = XATTR_NAME_POSIX_ACL_ACCESS,
1048         .flags = ACL_TYPE_ACCESS,
1049         .get = ovl_posix_acl_xattr_get,
1050         .set = ovl_posix_acl_xattr_set,
1051 };
1052
1053 static const struct xattr_handler __maybe_unused
1054 ovl_posix_acl_default_xattr_handler = {
1055         .name = XATTR_NAME_POSIX_ACL_DEFAULT,
1056         .flags = ACL_TYPE_DEFAULT,
1057         .get = ovl_posix_acl_xattr_get,
1058         .set = ovl_posix_acl_xattr_set,
1059 };
1060
1061 static const struct xattr_handler ovl_own_xattr_handler = {
1062         .prefix = OVL_XATTR_PREFIX,
1063         .get = ovl_own_xattr_get,
1064         .set = ovl_own_xattr_set,
1065 };
1066
1067 static const struct xattr_handler ovl_other_xattr_handler = {
1068         .prefix = "", /* catch all */
1069         .get = ovl_other_xattr_get,
1070         .set = ovl_other_xattr_set,
1071 };
1072
1073 static const struct xattr_handler *ovl_xattr_handlers[] = {
1074 #ifdef CONFIG_FS_POSIX_ACL
1075         &ovl_posix_acl_access_xattr_handler,
1076         &ovl_posix_acl_default_xattr_handler,
1077 #endif
1078         &ovl_own_xattr_handler,
1079         &ovl_other_xattr_handler,
1080         NULL
1081 };
1082
1083 static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
1084                           struct inode **ptrap, const char *name)
1085 {
1086         struct inode *trap;
1087         int err;
1088
1089         trap = ovl_get_trap_inode(sb, dir);
1090         err = PTR_ERR_OR_ZERO(trap);
1091         if (err) {
1092                 if (err == -ELOOP)
1093                         pr_err("conflicting %s path\n", name);
1094                 return err;
1095         }
1096
1097         *ptrap = trap;
1098         return 0;
1099 }
1100
1101 /*
1102  * Determine how we treat concurrent use of upperdir/workdir based on the
1103  * index feature. This is papering over mount leaks of container runtimes,
1104  * for example, an old overlay mount is leaked and now its upperdir is
1105  * attempted to be used as a lower layer in a new overlay mount.
1106  */
1107 static int ovl_report_in_use(struct ovl_fs *ofs, const char *name)
1108 {
1109         if (ofs->config.index) {
1110                 pr_err("%s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n",
1111                        name);
1112                 return -EBUSY;
1113         } else {
1114                 pr_warn("%s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n",
1115                         name);
1116                 return 0;
1117         }
1118 }
1119
1120 static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
1121                          struct ovl_layer *upper_layer, struct path *upperpath)
1122 {
1123         struct vfsmount *upper_mnt;
1124         int err;
1125
1126         err = ovl_mount_dir(ofs->config.upperdir, upperpath);
1127         if (err)
1128                 goto out;
1129
1130         /* Upper fs should not be r/o */
1131         if (sb_rdonly(upperpath->mnt->mnt_sb)) {
1132                 pr_err("upper fs is r/o, try multi-lower layers mount\n");
1133                 err = -EINVAL;
1134                 goto out;
1135         }
1136
1137         err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
1138         if (err)
1139                 goto out;
1140
1141         err = ovl_setup_trap(sb, upperpath->dentry, &upper_layer->trap,
1142                              "upperdir");
1143         if (err)
1144                 goto out;
1145
1146         upper_mnt = clone_private_mount(upperpath);
1147         err = PTR_ERR(upper_mnt);
1148         if (IS_ERR(upper_mnt)) {
1149                 pr_err("failed to clone upperpath\n");
1150                 goto out;
1151         }
1152
1153         /* Don't inherit atime flags */
1154         upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
1155         upper_layer->mnt = upper_mnt;
1156         upper_layer->idx = 0;
1157         upper_layer->fsid = 0;
1158
1159         /*
1160          * Inherit SB_NOSEC flag from upperdir.
1161          *
1162          * This optimization changes behavior when a security related attribute
1163          * (suid/sgid/security.*) is changed on an underlying layer.  This is
1164          * okay because we don't yet have guarantees in that case, but it will
1165          * need careful treatment once we want to honour changes to underlying
1166          * filesystems.
1167          */
1168         if (upper_mnt->mnt_sb->s_flags & SB_NOSEC)
1169                 sb->s_flags |= SB_NOSEC;
1170
1171         if (ovl_inuse_trylock(ovl_upper_mnt(ofs)->mnt_root)) {
1172                 ofs->upperdir_locked = true;
1173         } else {
1174                 err = ovl_report_in_use(ofs, "upperdir");
1175                 if (err)
1176                         goto out;
1177         }
1178
1179         err = 0;
1180 out:
1181         return err;
1182 }
1183
1184 /*
1185  * Returns 1 if RENAME_WHITEOUT is supported, 0 if not supported and
1186  * negative values if error is encountered.
1187  */
1188 static int ovl_check_rename_whiteout(struct dentry *workdir)
1189 {
1190         struct inode *dir = d_inode(workdir);
1191         struct dentry *temp;
1192         struct dentry *dest;
1193         struct dentry *whiteout;
1194         struct name_snapshot name;
1195         int err;
1196
1197         inode_lock_nested(dir, I_MUTEX_PARENT);
1198
1199         temp = ovl_create_temp(workdir, OVL_CATTR(S_IFREG | 0));
1200         err = PTR_ERR(temp);
1201         if (IS_ERR(temp))
1202                 goto out_unlock;
1203
1204         dest = ovl_lookup_temp(workdir);
1205         err = PTR_ERR(dest);
1206         if (IS_ERR(dest)) {
1207                 dput(temp);
1208                 goto out_unlock;
1209         }
1210
1211         /* Name is inline and stable - using snapshot as a copy helper */
1212         take_dentry_name_snapshot(&name, temp);
1213         err = ovl_do_rename(dir, temp, dir, dest, RENAME_WHITEOUT);
1214         if (err) {
1215                 if (err == -EINVAL)
1216                         err = 0;
1217                 goto cleanup_temp;
1218         }
1219
1220         whiteout = lookup_one_len(name.name.name, workdir, name.name.len);
1221         err = PTR_ERR(whiteout);
1222         if (IS_ERR(whiteout))
1223                 goto cleanup_temp;
1224
1225         err = ovl_is_whiteout(whiteout);
1226
1227         /* Best effort cleanup of whiteout and temp file */
1228         if (err)
1229                 ovl_cleanup(dir, whiteout);
1230         dput(whiteout);
1231
1232 cleanup_temp:
1233         ovl_cleanup(dir, temp);
1234         release_dentry_name_snapshot(&name);
1235         dput(temp);
1236         dput(dest);
1237
1238 out_unlock:
1239         inode_unlock(dir);
1240
1241         return err;
1242 }
1243
1244 static struct dentry *ovl_lookup_or_create(struct dentry *parent,
1245                                            const char *name, umode_t mode)
1246 {
1247         size_t len = strlen(name);
1248         struct dentry *child;
1249
1250         inode_lock_nested(parent->d_inode, I_MUTEX_PARENT);
1251         child = lookup_one_len(name, parent, len);
1252         if (!IS_ERR(child) && !child->d_inode)
1253                 child = ovl_create_real(parent->d_inode, child,
1254                                         OVL_CATTR(mode));
1255         inode_unlock(parent->d_inode);
1256         dput(parent);
1257
1258         return child;
1259 }
1260
1261 /*
1262  * Creates $workdir/work/incompat/volatile/dirty file if it is not already
1263  * present.
1264  */
1265 static int ovl_create_volatile_dirty(struct ovl_fs *ofs)
1266 {
1267         unsigned int ctr;
1268         struct dentry *d = dget(ofs->workbasedir);
1269         static const char *const volatile_path[] = {
1270                 OVL_WORKDIR_NAME, "incompat", "volatile", "dirty"
1271         };
1272         const char *const *name = volatile_path;
1273
1274         for (ctr = ARRAY_SIZE(volatile_path); ctr; ctr--, name++) {
1275                 d = ovl_lookup_or_create(d, *name, ctr > 1 ? S_IFDIR : S_IFREG);
1276                 if (IS_ERR(d))
1277                         return PTR_ERR(d);
1278         }
1279         dput(d);
1280         return 0;
1281 }
1282
1283 static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
1284                             struct path *workpath)
1285 {
1286         struct vfsmount *mnt = ovl_upper_mnt(ofs);
1287         struct dentry *temp, *workdir;
1288         bool rename_whiteout;
1289         bool d_type;
1290         int fh_type;
1291         int err;
1292
1293         err = mnt_want_write(mnt);
1294         if (err)
1295                 return err;
1296
1297         workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
1298         err = PTR_ERR(workdir);
1299         if (IS_ERR_OR_NULL(workdir))
1300                 goto out;
1301
1302         ofs->workdir = workdir;
1303
1304         err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir");
1305         if (err)
1306                 goto out;
1307
1308         /*
1309          * Upper should support d_type, else whiteouts are visible.  Given
1310          * workdir and upper are on same fs, we can do iterate_dir() on
1311          * workdir. This check requires successful creation of workdir in
1312          * previous step.
1313          */
1314         err = ovl_check_d_type_supported(workpath);
1315         if (err < 0)
1316                 goto out;
1317
1318         d_type = err;
1319         if (!d_type)
1320                 pr_warn("upper fs needs to support d_type.\n");
1321
1322         /* Check if upper/work fs supports O_TMPFILE */
1323         temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
1324         ofs->tmpfile = !IS_ERR(temp);
1325         if (ofs->tmpfile)
1326                 dput(temp);
1327         else
1328                 pr_warn("upper fs does not support tmpfile.\n");
1329
1330
1331         /* Check if upper/work fs supports RENAME_WHITEOUT */
1332         err = ovl_check_rename_whiteout(ofs->workdir);
1333         if (err < 0)
1334                 goto out;
1335
1336         rename_whiteout = err;
1337         if (!rename_whiteout)
1338                 pr_warn("upper fs does not support RENAME_WHITEOUT.\n");
1339
1340         /*
1341          * Check if upper/work fs supports trusted.overlay.* xattr
1342          */
1343         err = ovl_do_setxattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE, "0", 1);
1344         if (err) {
1345                 ofs->noxattr = true;
1346                 ofs->config.index = false;
1347                 ofs->config.metacopy = false;
1348                 pr_warn("upper fs does not support xattr, falling back to index=off and metacopy=off.\n");
1349                 err = 0;
1350         } else {
1351                 ovl_do_removexattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE);
1352         }
1353
1354         /*
1355          * We allowed sub-optimal upper fs configuration and don't want to break
1356          * users over kernel upgrade, but we never allowed remote upper fs, so
1357          * we can enforce strict requirements for remote upper fs.
1358          */
1359         if (ovl_dentry_remote(ofs->workdir) &&
1360             (!d_type || !rename_whiteout || ofs->noxattr)) {
1361                 pr_err("upper fs missing required features.\n");
1362                 err = -EINVAL;
1363                 goto out;
1364         }
1365
1366         /*
1367          * For volatile mount, create a incompat/volatile/dirty file to keep
1368          * track of it.
1369          */
1370         if (ofs->config.ovl_volatile) {
1371                 err = ovl_create_volatile_dirty(ofs);
1372                 if (err < 0) {
1373                         pr_err("Failed to create volatile/dirty file.\n");
1374                         goto out;
1375                 }
1376         }
1377
1378         /* Check if upper/work fs supports file handles */
1379         fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
1380         if (ofs->config.index && !fh_type) {
1381                 ofs->config.index = false;
1382                 pr_warn("upper fs does not support file handles, falling back to index=off.\n");
1383         }
1384
1385         /* Check if upper fs has 32bit inode numbers */
1386         if (fh_type != FILEID_INO32_GEN)
1387                 ofs->xino_mode = -1;
1388
1389         /* NFS export of r/w mount depends on index */
1390         if (ofs->config.nfs_export && !ofs->config.index) {
1391                 pr_warn("NFS export requires \"index=on\", falling back to nfs_export=off.\n");
1392                 ofs->config.nfs_export = false;
1393         }
1394 out:
1395         mnt_drop_write(mnt);
1396         return err;
1397 }
1398
1399 static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
1400                            struct path *upperpath)
1401 {
1402         int err;
1403         struct path workpath = { };
1404
1405         err = ovl_mount_dir(ofs->config.workdir, &workpath);
1406         if (err)
1407                 goto out;
1408
1409         err = -EINVAL;
1410         if (upperpath->mnt != workpath.mnt) {
1411                 pr_err("workdir and upperdir must reside under the same mount\n");
1412                 goto out;
1413         }
1414         if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
1415                 pr_err("workdir and upperdir must be separate subtrees\n");
1416                 goto out;
1417         }
1418
1419         ofs->workbasedir = dget(workpath.dentry);
1420
1421         if (ovl_inuse_trylock(ofs->workbasedir)) {
1422                 ofs->workdir_locked = true;
1423         } else {
1424                 err = ovl_report_in_use(ofs, "workdir");
1425                 if (err)
1426                         goto out;
1427         }
1428
1429         err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap,
1430                              "workdir");
1431         if (err)
1432                 goto out;
1433
1434         err = ovl_make_workdir(sb, ofs, &workpath);
1435
1436 out:
1437         path_put(&workpath);
1438
1439         return err;
1440 }
1441
1442 static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
1443                             struct ovl_entry *oe, struct path *upperpath)
1444 {
1445         struct vfsmount *mnt = ovl_upper_mnt(ofs);
1446         struct dentry *indexdir;
1447         int err;
1448
1449         err = mnt_want_write(mnt);
1450         if (err)
1451                 return err;
1452
1453         /* Verify lower root is upper root origin */
1454         err = ovl_verify_origin(ofs, upperpath->dentry,
1455                                 oe->lowerstack[0].dentry, true);
1456         if (err) {
1457                 pr_err("failed to verify upper root origin\n");
1458                 goto out;
1459         }
1460
1461         /* index dir will act also as workdir */
1462         iput(ofs->workdir_trap);
1463         ofs->workdir_trap = NULL;
1464         dput(ofs->workdir);
1465         ofs->workdir = NULL;
1466         indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
1467         if (IS_ERR(indexdir)) {
1468                 err = PTR_ERR(indexdir);
1469         } else if (indexdir) {
1470                 ofs->indexdir = indexdir;
1471                 ofs->workdir = dget(indexdir);
1472
1473                 err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
1474                                      "indexdir");
1475                 if (err)
1476                         goto out;
1477
1478                 /*
1479                  * Verify upper root is exclusively associated with index dir.
1480                  * Older kernels stored upper fh in "trusted.overlay.origin"
1481                  * xattr. If that xattr exists, verify that it is a match to
1482                  * upper dir file handle. In any case, verify or set xattr
1483                  * "trusted.overlay.upper" to indicate that index may have
1484                  * directory entries.
1485                  */
1486                 if (ovl_check_origin_xattr(ofs, ofs->indexdir)) {
1487                         err = ovl_verify_set_fh(ofs, ofs->indexdir,
1488                                                 OVL_XATTR_ORIGIN,
1489                                                 upperpath->dentry, true, false);
1490                         if (err)
1491                                 pr_err("failed to verify index dir 'origin' xattr\n");
1492                 }
1493                 err = ovl_verify_upper(ofs, ofs->indexdir, upperpath->dentry,
1494                                        true);
1495                 if (err)
1496                         pr_err("failed to verify index dir 'upper' xattr\n");
1497
1498                 /* Cleanup bad/stale/orphan index entries */
1499                 if (!err)
1500                         err = ovl_indexdir_cleanup(ofs);
1501         }
1502         if (err || !ofs->indexdir)
1503                 pr_warn("try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1504
1505 out:
1506         mnt_drop_write(mnt);
1507         return err;
1508 }
1509
1510 static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
1511 {
1512         unsigned int i;
1513
1514         if (!ofs->config.nfs_export && !ovl_upper_mnt(ofs))
1515                 return true;
1516
1517         /*
1518          * We allow using single lower with null uuid for index and nfs_export
1519          * for example to support those features with single lower squashfs.
1520          * To avoid regressions in setups of overlay with re-formatted lower
1521          * squashfs, do not allow decoding origin with lower null uuid unless
1522          * user opted-in to one of the new features that require following the
1523          * lower inode of non-dir upper.
1524          */
1525         if (!ofs->config.index && !ofs->config.metacopy && !ofs->config.xino &&
1526             uuid_is_null(uuid))
1527                 return false;
1528
1529         for (i = 0; i < ofs->numfs; i++) {
1530                 /*
1531                  * We use uuid to associate an overlay lower file handle with a
1532                  * lower layer, so we can accept lower fs with null uuid as long
1533                  * as all lower layers with null uuid are on the same fs.
1534                  * if we detect multiple lower fs with the same uuid, we
1535                  * disable lower file handle decoding on all of them.
1536                  */
1537                 if (ofs->fs[i].is_lower &&
1538                     uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) {
1539                         ofs->fs[i].bad_uuid = true;
1540                         return false;
1541                 }
1542         }
1543         return true;
1544 }
1545
1546 /* Get a unique fsid for the layer */
1547 static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
1548 {
1549         struct super_block *sb = path->mnt->mnt_sb;
1550         unsigned int i;
1551         dev_t dev;
1552         int err;
1553         bool bad_uuid = false;
1554
1555         for (i = 0; i < ofs->numfs; i++) {
1556                 if (ofs->fs[i].sb == sb)
1557                         return i;
1558         }
1559
1560         if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
1561                 bad_uuid = true;
1562                 if (ofs->config.index || ofs->config.nfs_export) {
1563                         ofs->config.index = false;
1564                         ofs->config.nfs_export = false;
1565                         pr_warn("%s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n",
1566                                 uuid_is_null(&sb->s_uuid) ? "null" :
1567                                                             "conflicting",
1568                                 path->dentry);
1569                 }
1570         }
1571
1572         err = get_anon_bdev(&dev);
1573         if (err) {
1574                 pr_err("failed to get anonymous bdev for lowerpath\n");
1575                 return err;
1576         }
1577
1578         ofs->fs[ofs->numfs].sb = sb;
1579         ofs->fs[ofs->numfs].pseudo_dev = dev;
1580         ofs->fs[ofs->numfs].bad_uuid = bad_uuid;
1581
1582         return ofs->numfs++;
1583 }
1584
1585 static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
1586                           struct path *stack, unsigned int numlower,
1587                           struct ovl_layer *layers)
1588 {
1589         int err;
1590         unsigned int i;
1591
1592         err = -ENOMEM;
1593         ofs->fs = kcalloc(numlower + 1, sizeof(struct ovl_sb), GFP_KERNEL);
1594         if (ofs->fs == NULL)
1595                 goto out;
1596
1597         /* idx/fsid 0 are reserved for upper fs even with lower only overlay */
1598         ofs->numfs++;
1599
1600         /*
1601          * All lower layers that share the same fs as upper layer, use the same
1602          * pseudo_dev as upper layer.  Allocate fs[0].pseudo_dev even for lower
1603          * only overlay to simplify ovl_fs_free().
1604          * is_lower will be set if upper fs is shared with a lower layer.
1605          */
1606         err = get_anon_bdev(&ofs->fs[0].pseudo_dev);
1607         if (err) {
1608                 pr_err("failed to get anonymous bdev for upper fs\n");
1609                 goto out;
1610         }
1611
1612         if (ovl_upper_mnt(ofs)) {
1613                 ofs->fs[0].sb = ovl_upper_mnt(ofs)->mnt_sb;
1614                 ofs->fs[0].is_lower = false;
1615         }
1616
1617         for (i = 0; i < numlower; i++) {
1618                 struct vfsmount *mnt;
1619                 struct inode *trap;
1620                 int fsid;
1621
1622                 err = fsid = ovl_get_fsid(ofs, &stack[i]);
1623                 if (err < 0)
1624                         goto out;
1625
1626                 /*
1627                  * Check if lower root conflicts with this overlay layers before
1628                  * checking if it is in-use as upperdir/workdir of "another"
1629                  * mount, because we do not bother to check in ovl_is_inuse() if
1630                  * the upperdir/workdir is in fact in-use by our
1631                  * upperdir/workdir.
1632                  */
1633                 err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
1634                 if (err)
1635                         goto out;
1636
1637                 if (ovl_is_inuse(stack[i].dentry)) {
1638                         err = ovl_report_in_use(ofs, "lowerdir");
1639                         if (err) {
1640                                 iput(trap);
1641                                 goto out;
1642                         }
1643                 }
1644
1645                 mnt = clone_private_mount(&stack[i]);
1646                 err = PTR_ERR(mnt);
1647                 if (IS_ERR(mnt)) {
1648                         pr_err("failed to clone lowerpath\n");
1649                         iput(trap);
1650                         goto out;
1651                 }
1652
1653                 /*
1654                  * Make lower layers R/O.  That way fchmod/fchown on lower file
1655                  * will fail instead of modifying lower fs.
1656                  */
1657                 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1658
1659                 layers[ofs->numlayer].trap = trap;
1660                 layers[ofs->numlayer].mnt = mnt;
1661                 layers[ofs->numlayer].idx = ofs->numlayer;
1662                 layers[ofs->numlayer].fsid = fsid;
1663                 layers[ofs->numlayer].fs = &ofs->fs[fsid];
1664                 ofs->numlayer++;
1665                 ofs->fs[fsid].is_lower = true;
1666         }
1667
1668         /*
1669          * When all layers on same fs, overlay can use real inode numbers.
1670          * With mount option "xino=<on|auto>", mounter declares that there are
1671          * enough free high bits in underlying fs to hold the unique fsid.
1672          * If overlayfs does encounter underlying inodes using the high xino
1673          * bits reserved for fsid, it emits a warning and uses the original
1674          * inode number or a non persistent inode number allocated from a
1675          * dedicated range.
1676          */
1677         if (ofs->numfs - !ovl_upper_mnt(ofs) == 1) {
1678                 if (ofs->config.xino == OVL_XINO_ON)
1679                         pr_info("\"xino=on\" is useless with all layers on same fs, ignore.\n");
1680                 ofs->xino_mode = 0;
1681         } else if (ofs->config.xino == OVL_XINO_OFF) {
1682                 ofs->xino_mode = -1;
1683         } else if (ofs->xino_mode < 0) {
1684                 /*
1685                  * This is a roundup of number of bits needed for encoding
1686                  * fsid, where fsid 0 is reserved for upper fs (even with
1687                  * lower only overlay) +1 extra bit is reserved for the non
1688                  * persistent inode number range that is used for resolving
1689                  * xino lower bits overflow.
1690                  */
1691                 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 30);
1692                 ofs->xino_mode = ilog2(ofs->numfs - 1) + 2;
1693         }
1694
1695         if (ofs->xino_mode > 0) {
1696                 pr_info("\"xino\" feature enabled using %d upper inode bits.\n",
1697                         ofs->xino_mode);
1698         }
1699
1700         err = 0;
1701 out:
1702         return err;
1703 }
1704
1705 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1706                                 const char *lower, unsigned int numlower,
1707                                 struct ovl_fs *ofs, struct ovl_layer *layers)
1708 {
1709         int err;
1710         struct path *stack = NULL;
1711         unsigned int i;
1712         struct ovl_entry *oe;
1713
1714         if (!ofs->config.upperdir && numlower == 1) {
1715                 pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n");
1716                 return ERR_PTR(-EINVAL);
1717         }
1718
1719         stack = kcalloc(numlower, sizeof(struct path), GFP_KERNEL);
1720         if (!stack)
1721                 return ERR_PTR(-ENOMEM);
1722
1723         err = -EINVAL;
1724         for (i = 0; i < numlower; i++) {
1725                 err = ovl_lower_dir(lower, &stack[i], ofs, &sb->s_stack_depth);
1726                 if (err)
1727                         goto out_err;
1728
1729                 lower = strchr(lower, '\0') + 1;
1730         }
1731
1732         err = -EINVAL;
1733         sb->s_stack_depth++;
1734         if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1735                 pr_err("maximum fs stacking depth exceeded\n");
1736                 goto out_err;
1737         }
1738
1739         err = ovl_get_layers(sb, ofs, stack, numlower, layers);
1740         if (err)
1741                 goto out_err;
1742
1743         err = -ENOMEM;
1744         oe = ovl_alloc_entry(numlower);
1745         if (!oe)
1746                 goto out_err;
1747
1748         for (i = 0; i < numlower; i++) {
1749                 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1750                 oe->lowerstack[i].layer = &ofs->layers[i+1];
1751         }
1752
1753 out:
1754         for (i = 0; i < numlower; i++)
1755                 path_put(&stack[i]);
1756         kfree(stack);
1757
1758         return oe;
1759
1760 out_err:
1761         oe = ERR_PTR(err);
1762         goto out;
1763 }
1764
1765 /*
1766  * Check if this layer root is a descendant of:
1767  * - another layer of this overlayfs instance
1768  * - upper/work dir of any overlayfs instance
1769  */
1770 static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs,
1771                            struct dentry *dentry, const char *name,
1772                            bool is_lower)
1773 {
1774         struct dentry *next = dentry, *parent;
1775         int err = 0;
1776
1777         if (!dentry)
1778                 return 0;
1779
1780         parent = dget_parent(next);
1781
1782         /* Walk back ancestors to root (inclusive) looking for traps */
1783         while (!err && parent != next) {
1784                 if (is_lower && ovl_lookup_trap_inode(sb, parent)) {
1785                         err = -ELOOP;
1786                         pr_err("overlapping %s path\n", name);
1787                 } else if (ovl_is_inuse(parent)) {
1788                         err = ovl_report_in_use(ofs, name);
1789                 }
1790                 next = parent;
1791                 parent = dget_parent(next);
1792                 dput(next);
1793         }
1794
1795         dput(parent);
1796
1797         return err;
1798 }
1799
1800 /*
1801  * Check if any of the layers or work dirs overlap.
1802  */
1803 static int ovl_check_overlapping_layers(struct super_block *sb,
1804                                         struct ovl_fs *ofs)
1805 {
1806         int i, err;
1807
1808         if (ovl_upper_mnt(ofs)) {
1809                 err = ovl_check_layer(sb, ofs, ovl_upper_mnt(ofs)->mnt_root,
1810                                       "upperdir", false);
1811                 if (err)
1812                         return err;
1813
1814                 /*
1815                  * Checking workbasedir avoids hitting ovl_is_inuse(parent) of
1816                  * this instance and covers overlapping work and index dirs,
1817                  * unless work or index dir have been moved since created inside
1818                  * workbasedir.  In that case, we already have their traps in
1819                  * inode cache and we will catch that case on lookup.
1820                  */
1821                 err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir",
1822                                       false);
1823                 if (err)
1824                         return err;
1825         }
1826
1827         for (i = 1; i < ofs->numlayer; i++) {
1828                 err = ovl_check_layer(sb, ofs,
1829                                       ofs->layers[i].mnt->mnt_root,
1830                                       "lowerdir", true);
1831                 if (err)
1832                         return err;
1833         }
1834
1835         return 0;
1836 }
1837
1838 static struct dentry *ovl_get_root(struct super_block *sb,
1839                                    struct dentry *upperdentry,
1840                                    struct ovl_entry *oe)
1841 {
1842         struct dentry *root;
1843         struct ovl_path *lowerpath = &oe->lowerstack[0];
1844         unsigned long ino = d_inode(lowerpath->dentry)->i_ino;
1845         int fsid = lowerpath->layer->fsid;
1846         struct ovl_inode_params oip = {
1847                 .upperdentry = upperdentry,
1848                 .lowerpath = lowerpath,
1849         };
1850
1851         root = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1852         if (!root)
1853                 return NULL;
1854
1855         root->d_fsdata = oe;
1856
1857         if (upperdentry) {
1858                 /* Root inode uses upper st_ino/i_ino */
1859                 ino = d_inode(upperdentry)->i_ino;
1860                 fsid = 0;
1861                 ovl_dentry_set_upper_alias(root);
1862                 if (ovl_is_impuredir(sb, upperdentry))
1863                         ovl_set_flag(OVL_IMPURE, d_inode(root));
1864         }
1865
1866         /* Root is always merge -> can have whiteouts */
1867         ovl_set_flag(OVL_WHITEOUTS, d_inode(root));
1868         ovl_dentry_set_flag(OVL_E_CONNECTED, root);
1869         ovl_set_upperdata(d_inode(root));
1870         ovl_inode_init(d_inode(root), &oip, ino, fsid);
1871         ovl_dentry_init_flags(root, upperdentry, DCACHE_OP_WEAK_REVALIDATE);
1872
1873         return root;
1874 }
1875
1876 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1877 {
1878         struct path upperpath = { };
1879         struct dentry *root_dentry;
1880         struct ovl_entry *oe;
1881         struct ovl_fs *ofs;
1882         struct ovl_layer *layers;
1883         struct cred *cred;
1884         char *splitlower = NULL;
1885         unsigned int numlower;
1886         int err;
1887
1888         sb->s_d_op = &ovl_dentry_operations;
1889
1890         err = -ENOMEM;
1891         ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1892         if (!ofs)
1893                 goto out;
1894
1895         ofs->creator_cred = cred = prepare_creds();
1896         if (!cred)
1897                 goto out_err;
1898
1899         /* Is there a reason anyone would want not to share whiteouts? */
1900         ofs->share_whiteout = true;
1901
1902         ofs->config.index = ovl_index_def;
1903         ofs->config.nfs_export = ovl_nfs_export_def;
1904         ofs->config.xino = ovl_xino_def();
1905         ofs->config.metacopy = ovl_metacopy_def;
1906         err = ovl_parse_opt((char *) data, &ofs->config);
1907         if (err)
1908                 goto out_err;
1909
1910         err = -EINVAL;
1911         if (!ofs->config.lowerdir) {
1912                 if (!silent)
1913                         pr_err("missing 'lowerdir'\n");
1914                 goto out_err;
1915         }
1916
1917         err = -ENOMEM;
1918         splitlower = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1919         if (!splitlower)
1920                 goto out_err;
1921
1922         numlower = ovl_split_lowerdirs(splitlower);
1923         if (numlower > OVL_MAX_STACK) {
1924                 pr_err("too many lower directories, limit is %d\n",
1925                        OVL_MAX_STACK);
1926                 goto out_err;
1927         }
1928
1929         layers = kcalloc(numlower + 1, sizeof(struct ovl_layer), GFP_KERNEL);
1930         if (!layers)
1931                 goto out_err;
1932
1933         ofs->layers = layers;
1934         /* Layer 0 is reserved for upper even if there's no upper */
1935         ofs->numlayer = 1;
1936
1937         sb->s_stack_depth = 0;
1938         sb->s_maxbytes = MAX_LFS_FILESIZE;
1939         atomic_long_set(&ofs->last_ino, 1);
1940         /* Assume underlaying fs uses 32bit inodes unless proven otherwise */
1941         if (ofs->config.xino != OVL_XINO_OFF) {
1942                 ofs->xino_mode = BITS_PER_LONG - 32;
1943                 if (!ofs->xino_mode) {
1944                         pr_warn("xino not supported on 32bit kernel, falling back to xino=off.\n");
1945                         ofs->config.xino = OVL_XINO_OFF;
1946                 }
1947         }
1948
1949         /* alloc/destroy_inode needed for setting up traps in inode cache */
1950         sb->s_op = &ovl_super_operations;
1951
1952         if (ofs->config.upperdir) {
1953                 struct super_block *upper_sb;
1954
1955                 if (!ofs->config.workdir) {
1956                         pr_err("missing 'workdir'\n");
1957                         goto out_err;
1958                 }
1959
1960                 err = ovl_get_upper(sb, ofs, &layers[0], &upperpath);
1961                 if (err)
1962                         goto out_err;
1963
1964                 upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
1965                 if (!ovl_should_sync(ofs)) {
1966                         ofs->errseq = errseq_sample(&upper_sb->s_wb_err);
1967                         if (errseq_check(&upper_sb->s_wb_err, ofs->errseq)) {
1968                                 err = -EIO;
1969                                 pr_err("Cannot mount volatile when upperdir has an unseen error. Sync upperdir fs to clear state.\n");
1970                                 goto out_err;
1971                         }
1972                 }
1973
1974                 err = ovl_get_workdir(sb, ofs, &upperpath);
1975                 if (err)
1976                         goto out_err;
1977
1978                 if (!ofs->workdir)
1979                         sb->s_flags |= SB_RDONLY;
1980
1981                 sb->s_stack_depth = upper_sb->s_stack_depth;
1982                 sb->s_time_gran = upper_sb->s_time_gran;
1983         }
1984         oe = ovl_get_lowerstack(sb, splitlower, numlower, ofs, layers);
1985         err = PTR_ERR(oe);
1986         if (IS_ERR(oe))
1987                 goto out_err;
1988
1989         /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1990         if (!ovl_upper_mnt(ofs))
1991                 sb->s_flags |= SB_RDONLY;
1992
1993         if (!ovl_force_readonly(ofs) && ofs->config.index) {
1994                 err = ovl_get_indexdir(sb, ofs, oe, &upperpath);
1995                 if (err)
1996                         goto out_free_oe;
1997
1998                 /* Force r/o mount with no index dir */
1999                 if (!ofs->indexdir)
2000                         sb->s_flags |= SB_RDONLY;
2001         }
2002
2003         err = ovl_check_overlapping_layers(sb, ofs);
2004         if (err)
2005                 goto out_free_oe;
2006
2007         /* Show index=off in /proc/mounts for forced r/o mount */
2008         if (!ofs->indexdir) {
2009                 ofs->config.index = false;
2010                 if (ovl_upper_mnt(ofs) && ofs->config.nfs_export) {
2011                         pr_warn("NFS export requires an index dir, falling back to nfs_export=off.\n");
2012                         ofs->config.nfs_export = false;
2013                 }
2014         }
2015
2016         if (ofs->config.metacopy && ofs->config.nfs_export) {
2017                 pr_warn("NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
2018                 ofs->config.nfs_export = false;
2019         }
2020
2021         if (ofs->config.nfs_export)
2022                 sb->s_export_op = &ovl_export_operations;
2023
2024         /* Never override disk quota limits or use reserved space */
2025         cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
2026
2027         sb->s_magic = OVERLAYFS_SUPER_MAGIC;
2028         sb->s_xattr = ovl_xattr_handlers;
2029         sb->s_fs_info = ofs;
2030         sb->s_flags |= SB_POSIXACL;
2031         sb->s_iflags |= SB_I_SKIP_SYNC;
2032
2033         err = -ENOMEM;
2034         root_dentry = ovl_get_root(sb, upperpath.dentry, oe);
2035         if (!root_dentry)
2036                 goto out_free_oe;
2037
2038         mntput(upperpath.mnt);
2039         kfree(splitlower);
2040
2041         sb->s_root = root_dentry;
2042
2043         return 0;
2044
2045 out_free_oe:
2046         ovl_entry_stack_free(oe);
2047         kfree(oe);
2048 out_err:
2049         kfree(splitlower);
2050         path_put(&upperpath);
2051         ovl_free_fs(ofs);
2052 out:
2053         return err;
2054 }
2055
2056 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
2057                                 const char *dev_name, void *raw_data)
2058 {
2059         return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
2060 }
2061
2062 static struct file_system_type ovl_fs_type = {
2063         .owner          = THIS_MODULE,
2064         .name           = "overlay",
2065         .mount          = ovl_mount,
2066         .kill_sb        = kill_anon_super,
2067 };
2068 MODULE_ALIAS_FS("overlay");
2069
2070 static void ovl_inode_init_once(void *foo)
2071 {
2072         struct ovl_inode *oi = foo;
2073
2074         inode_init_once(&oi->vfs_inode);
2075 }
2076
2077 static int __init ovl_init(void)
2078 {
2079         int err;
2080
2081         ovl_inode_cachep = kmem_cache_create("ovl_inode",
2082                                              sizeof(struct ovl_inode), 0,
2083                                              (SLAB_RECLAIM_ACCOUNT|
2084                                               SLAB_MEM_SPREAD|SLAB_ACCOUNT),
2085                                              ovl_inode_init_once);
2086         if (ovl_inode_cachep == NULL)
2087                 return -ENOMEM;
2088
2089         err = ovl_aio_request_cache_init();
2090         if (!err) {
2091                 err = register_filesystem(&ovl_fs_type);
2092                 if (!err)
2093                         return 0;
2094
2095                 ovl_aio_request_cache_destroy();
2096         }
2097         kmem_cache_destroy(ovl_inode_cachep);
2098
2099         return err;
2100 }
2101
2102 static void __exit ovl_exit(void)
2103 {
2104         unregister_filesystem(&ovl_fs_type);
2105
2106         /*
2107          * Make sure all delayed rcu free inodes are flushed before we
2108          * destroy cache.
2109          */
2110         rcu_barrier();
2111         kmem_cache_destroy(ovl_inode_cachep);
2112         ovl_aio_request_cache_destroy();
2113 }
2114
2115 module_init(ovl_init);
2116 module_exit(ovl_exit);