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