1 /* 2 * 3 * Copyright (C) 2011 Novell Inc. 4 * 5 * This program is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 as published by 7 * the Free Software Foundation. 8 */ 9 10 #include <uapi/linux/magic.h> 11 #include <linux/fs.h> 12 #include <linux/namei.h> 13 #include <linux/xattr.h> 14 #include <linux/mount.h> 15 #include <linux/parser.h> 16 #include <linux/module.h> 17 #include <linux/statfs.h> 18 #include <linux/seq_file.h> 19 #include <linux/posix_acl_xattr.h> 20 #include <linux/exportfs.h> 21 #include "overlayfs.h" 22 23 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>"); 24 MODULE_DESCRIPTION("Overlay filesystem"); 25 MODULE_LICENSE("GPL"); 26 27 28 struct ovl_dir_cache; 29 30 #define OVL_MAX_STACK 500 31 32 static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR); 33 module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644); 34 MODULE_PARM_DESC(ovl_redirect_dir_def, 35 "Default to on or off for the redirect_dir feature"); 36 37 static bool ovl_redirect_always_follow = 38 IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW); 39 module_param_named(redirect_always_follow, ovl_redirect_always_follow, 40 bool, 0644); 41 MODULE_PARM_DESC(ovl_redirect_always_follow, 42 "Follow redirects even if redirect_dir feature is turned off"); 43 44 static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX); 45 module_param_named(index, ovl_index_def, bool, 0644); 46 MODULE_PARM_DESC(ovl_index_def, 47 "Default to on or off for the inodes index feature"); 48 49 static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT); 50 module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644); 51 MODULE_PARM_DESC(ovl_nfs_export_def, 52 "Default to on or off for the NFS export feature"); 53 54 static bool ovl_xino_auto_def = IS_ENABLED(CONFIG_OVERLAY_FS_XINO_AUTO); 55 module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644); 56 MODULE_PARM_DESC(ovl_xino_auto_def, 57 "Auto enable xino feature"); 58 59 static void ovl_entry_stack_free(struct ovl_entry *oe) 60 { 61 unsigned int i; 62 63 for (i = 0; i < oe->numlower; i++) 64 dput(oe->lowerstack[i].dentry); 65 } 66 67 static void ovl_dentry_release(struct dentry *dentry) 68 { 69 struct ovl_entry *oe = dentry->d_fsdata; 70 71 if (oe) { 72 ovl_entry_stack_free(oe); 73 kfree_rcu(oe, rcu); 74 } 75 } 76 77 static int ovl_check_append_only(struct inode *inode, int flag) 78 { 79 /* 80 * This test was moot in vfs may_open() because overlay inode does 81 * not have the S_APPEND flag, so re-check on real upper inode 82 */ 83 if (IS_APPEND(inode)) { 84 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) 85 return -EPERM; 86 if (flag & O_TRUNC) 87 return -EPERM; 88 } 89 90 return 0; 91 } 92 93 static struct dentry *ovl_d_real(struct dentry *dentry, 94 const struct inode *inode, 95 unsigned int open_flags, unsigned int flags) 96 { 97 struct dentry *real; 98 int err; 99 100 if (flags & D_REAL_UPPER) 101 return ovl_dentry_upper(dentry); 102 103 if (!d_is_reg(dentry)) { 104 if (!inode || inode == d_inode(dentry)) 105 return dentry; 106 goto bug; 107 } 108 109 if (open_flags) { 110 err = ovl_open_maybe_copy_up(dentry, open_flags); 111 if (err) 112 return ERR_PTR(err); 113 } 114 115 real = ovl_dentry_upper(dentry); 116 if (real && (!inode || inode == d_inode(real))) { 117 if (!inode) { 118 err = ovl_check_append_only(d_inode(real), open_flags); 119 if (err) 120 return ERR_PTR(err); 121 } 122 return real; 123 } 124 125 real = ovl_dentry_lower(dentry); 126 if (!real) 127 goto bug; 128 129 /* Handle recursion */ 130 real = d_real(real, inode, open_flags, 0); 131 132 if (!inode || inode == d_inode(real)) 133 return real; 134 bug: 135 WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry, 136 inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0); 137 return dentry; 138 } 139 140 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags) 141 { 142 struct ovl_entry *oe = dentry->d_fsdata; 143 unsigned int i; 144 int ret = 1; 145 146 for (i = 0; i < oe->numlower; i++) { 147 struct dentry *d = oe->lowerstack[i].dentry; 148 149 if (d->d_flags & DCACHE_OP_REVALIDATE) { 150 ret = d->d_op->d_revalidate(d, flags); 151 if (ret < 0) 152 return ret; 153 if (!ret) { 154 if (!(flags & LOOKUP_RCU)) 155 d_invalidate(d); 156 return -ESTALE; 157 } 158 } 159 } 160 return 1; 161 } 162 163 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags) 164 { 165 struct ovl_entry *oe = dentry->d_fsdata; 166 unsigned int i; 167 int ret = 1; 168 169 for (i = 0; i < oe->numlower; i++) { 170 struct dentry *d = oe->lowerstack[i].dentry; 171 172 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) { 173 ret = d->d_op->d_weak_revalidate(d, flags); 174 if (ret <= 0) 175 break; 176 } 177 } 178 return ret; 179 } 180 181 static const struct dentry_operations ovl_dentry_operations = { 182 .d_release = ovl_dentry_release, 183 .d_real = ovl_d_real, 184 }; 185 186 static const struct dentry_operations ovl_reval_dentry_operations = { 187 .d_release = ovl_dentry_release, 188 .d_real = ovl_d_real, 189 .d_revalidate = ovl_dentry_revalidate, 190 .d_weak_revalidate = ovl_dentry_weak_revalidate, 191 }; 192 193 static struct kmem_cache *ovl_inode_cachep; 194 195 static struct inode *ovl_alloc_inode(struct super_block *sb) 196 { 197 struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL); 198 199 if (!oi) 200 return NULL; 201 202 oi->cache = NULL; 203 oi->redirect = NULL; 204 oi->version = 0; 205 oi->flags = 0; 206 oi->__upperdentry = NULL; 207 oi->lower = NULL; 208 mutex_init(&oi->lock); 209 210 return &oi->vfs_inode; 211 } 212 213 static void ovl_i_callback(struct rcu_head *head) 214 { 215 struct inode *inode = container_of(head, struct inode, i_rcu); 216 217 kmem_cache_free(ovl_inode_cachep, OVL_I(inode)); 218 } 219 220 static void ovl_destroy_inode(struct inode *inode) 221 { 222 struct ovl_inode *oi = OVL_I(inode); 223 224 dput(oi->__upperdentry); 225 iput(oi->lower); 226 kfree(oi->redirect); 227 ovl_dir_cache_free(inode); 228 mutex_destroy(&oi->lock); 229 230 call_rcu(&inode->i_rcu, ovl_i_callback); 231 } 232 233 static void ovl_free_fs(struct ovl_fs *ofs) 234 { 235 unsigned i; 236 237 dput(ofs->indexdir); 238 dput(ofs->workdir); 239 if (ofs->workdir_locked) 240 ovl_inuse_unlock(ofs->workbasedir); 241 dput(ofs->workbasedir); 242 if (ofs->upperdir_locked) 243 ovl_inuse_unlock(ofs->upper_mnt->mnt_root); 244 mntput(ofs->upper_mnt); 245 for (i = 0; i < ofs->numlower; i++) 246 mntput(ofs->lower_layers[i].mnt); 247 for (i = 0; i < ofs->numlowerfs; i++) 248 free_anon_bdev(ofs->lower_fs[i].pseudo_dev); 249 kfree(ofs->lower_layers); 250 kfree(ofs->lower_fs); 251 252 kfree(ofs->config.lowerdir); 253 kfree(ofs->config.upperdir); 254 kfree(ofs->config.workdir); 255 kfree(ofs->config.redirect_mode); 256 if (ofs->creator_cred) 257 put_cred(ofs->creator_cred); 258 kfree(ofs); 259 } 260 261 static void ovl_put_super(struct super_block *sb) 262 { 263 struct ovl_fs *ofs = sb->s_fs_info; 264 265 ovl_free_fs(ofs); 266 } 267 268 /* Sync real dirty inodes in upper filesystem (if it exists) */ 269 static int ovl_sync_fs(struct super_block *sb, int wait) 270 { 271 struct ovl_fs *ofs = sb->s_fs_info; 272 struct super_block *upper_sb; 273 int ret; 274 275 if (!ofs->upper_mnt) 276 return 0; 277 278 /* 279 * If this is a sync(2) call or an emergency sync, all the super blocks 280 * will be iterated, including upper_sb, so no need to do anything. 281 * 282 * If this is a syncfs(2) call, then we do need to call 283 * sync_filesystem() on upper_sb, but enough if we do it when being 284 * called with wait == 1. 285 */ 286 if (!wait) 287 return 0; 288 289 upper_sb = ofs->upper_mnt->mnt_sb; 290 291 down_read(&upper_sb->s_umount); 292 ret = sync_filesystem(upper_sb); 293 up_read(&upper_sb->s_umount); 294 295 return ret; 296 } 297 298 /** 299 * ovl_statfs 300 * @sb: The overlayfs super block 301 * @buf: The struct kstatfs to fill in with stats 302 * 303 * Get the filesystem statistics. As writes always target the upper layer 304 * filesystem pass the statfs to the upper filesystem (if it exists) 305 */ 306 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf) 307 { 308 struct ovl_fs *ofs = dentry->d_sb->s_fs_info; 309 struct dentry *root_dentry = dentry->d_sb->s_root; 310 struct path path; 311 int err; 312 313 ovl_path_real(root_dentry, &path); 314 315 err = vfs_statfs(&path, buf); 316 if (!err) { 317 buf->f_namelen = ofs->namelen; 318 buf->f_type = OVERLAYFS_SUPER_MAGIC; 319 } 320 321 return err; 322 } 323 324 /* Will this overlay be forced to mount/remount ro? */ 325 static bool ovl_force_readonly(struct ovl_fs *ofs) 326 { 327 return (!ofs->upper_mnt || !ofs->workdir); 328 } 329 330 static const char *ovl_redirect_mode_def(void) 331 { 332 return ovl_redirect_dir_def ? "on" : "off"; 333 } 334 335 enum { 336 OVL_XINO_OFF, 337 OVL_XINO_AUTO, 338 OVL_XINO_ON, 339 }; 340 341 static const char * const ovl_xino_str[] = { 342 "off", 343 "auto", 344 "on", 345 }; 346 347 static inline int ovl_xino_def(void) 348 { 349 return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF; 350 } 351 352 /** 353 * ovl_show_options 354 * 355 * Prints the mount options for a given superblock. 356 * Returns zero; does not fail. 357 */ 358 static int ovl_show_options(struct seq_file *m, struct dentry *dentry) 359 { 360 struct super_block *sb = dentry->d_sb; 361 struct ovl_fs *ofs = sb->s_fs_info; 362 363 seq_show_option(m, "lowerdir", ofs->config.lowerdir); 364 if (ofs->config.upperdir) { 365 seq_show_option(m, "upperdir", ofs->config.upperdir); 366 seq_show_option(m, "workdir", ofs->config.workdir); 367 } 368 if (ofs->config.default_permissions) 369 seq_puts(m, ",default_permissions"); 370 if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0) 371 seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode); 372 if (ofs->config.index != ovl_index_def) 373 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off"); 374 if (ofs->config.nfs_export != ovl_nfs_export_def) 375 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ? 376 "on" : "off"); 377 if (ofs->config.xino != ovl_xino_def()) 378 seq_printf(m, ",xino=%s", ovl_xino_str[ofs->config.xino]); 379 return 0; 380 } 381 382 static int ovl_remount(struct super_block *sb, int *flags, char *data) 383 { 384 struct ovl_fs *ofs = sb->s_fs_info; 385 386 if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs)) 387 return -EROFS; 388 389 return 0; 390 } 391 392 static const struct super_operations ovl_super_operations = { 393 .alloc_inode = ovl_alloc_inode, 394 .destroy_inode = ovl_destroy_inode, 395 .drop_inode = generic_delete_inode, 396 .put_super = ovl_put_super, 397 .sync_fs = ovl_sync_fs, 398 .statfs = ovl_statfs, 399 .show_options = ovl_show_options, 400 .remount_fs = ovl_remount, 401 }; 402 403 enum { 404 OPT_LOWERDIR, 405 OPT_UPPERDIR, 406 OPT_WORKDIR, 407 OPT_DEFAULT_PERMISSIONS, 408 OPT_REDIRECT_DIR, 409 OPT_INDEX_ON, 410 OPT_INDEX_OFF, 411 OPT_NFS_EXPORT_ON, 412 OPT_NFS_EXPORT_OFF, 413 OPT_XINO_ON, 414 OPT_XINO_OFF, 415 OPT_XINO_AUTO, 416 OPT_ERR, 417 }; 418 419 static const match_table_t ovl_tokens = { 420 {OPT_LOWERDIR, "lowerdir=%s"}, 421 {OPT_UPPERDIR, "upperdir=%s"}, 422 {OPT_WORKDIR, "workdir=%s"}, 423 {OPT_DEFAULT_PERMISSIONS, "default_permissions"}, 424 {OPT_REDIRECT_DIR, "redirect_dir=%s"}, 425 {OPT_INDEX_ON, "index=on"}, 426 {OPT_INDEX_OFF, "index=off"}, 427 {OPT_NFS_EXPORT_ON, "nfs_export=on"}, 428 {OPT_NFS_EXPORT_OFF, "nfs_export=off"}, 429 {OPT_XINO_ON, "xino=on"}, 430 {OPT_XINO_OFF, "xino=off"}, 431 {OPT_XINO_AUTO, "xino=auto"}, 432 {OPT_ERR, NULL} 433 }; 434 435 static char *ovl_next_opt(char **s) 436 { 437 char *sbegin = *s; 438 char *p; 439 440 if (sbegin == NULL) 441 return NULL; 442 443 for (p = sbegin; *p; p++) { 444 if (*p == '\\') { 445 p++; 446 if (!*p) 447 break; 448 } else if (*p == ',') { 449 *p = '\0'; 450 *s = p + 1; 451 return sbegin; 452 } 453 } 454 *s = NULL; 455 return sbegin; 456 } 457 458 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode) 459 { 460 if (strcmp(mode, "on") == 0) { 461 config->redirect_dir = true; 462 /* 463 * Does not make sense to have redirect creation without 464 * redirect following. 465 */ 466 config->redirect_follow = true; 467 } else if (strcmp(mode, "follow") == 0) { 468 config->redirect_follow = true; 469 } else if (strcmp(mode, "off") == 0) { 470 if (ovl_redirect_always_follow) 471 config->redirect_follow = true; 472 } else if (strcmp(mode, "nofollow") != 0) { 473 pr_err("overlayfs: bad mount option \"redirect_dir=%s\"\n", 474 mode); 475 return -EINVAL; 476 } 477 478 return 0; 479 } 480 481 static int ovl_parse_opt(char *opt, struct ovl_config *config) 482 { 483 char *p; 484 485 config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL); 486 if (!config->redirect_mode) 487 return -ENOMEM; 488 489 while ((p = ovl_next_opt(&opt)) != NULL) { 490 int token; 491 substring_t args[MAX_OPT_ARGS]; 492 493 if (!*p) 494 continue; 495 496 token = match_token(p, ovl_tokens, args); 497 switch (token) { 498 case OPT_UPPERDIR: 499 kfree(config->upperdir); 500 config->upperdir = match_strdup(&args[0]); 501 if (!config->upperdir) 502 return -ENOMEM; 503 break; 504 505 case OPT_LOWERDIR: 506 kfree(config->lowerdir); 507 config->lowerdir = match_strdup(&args[0]); 508 if (!config->lowerdir) 509 return -ENOMEM; 510 break; 511 512 case OPT_WORKDIR: 513 kfree(config->workdir); 514 config->workdir = match_strdup(&args[0]); 515 if (!config->workdir) 516 return -ENOMEM; 517 break; 518 519 case OPT_DEFAULT_PERMISSIONS: 520 config->default_permissions = true; 521 break; 522 523 case OPT_REDIRECT_DIR: 524 kfree(config->redirect_mode); 525 config->redirect_mode = match_strdup(&args[0]); 526 if (!config->redirect_mode) 527 return -ENOMEM; 528 break; 529 530 case OPT_INDEX_ON: 531 config->index = true; 532 break; 533 534 case OPT_INDEX_OFF: 535 config->index = false; 536 break; 537 538 case OPT_NFS_EXPORT_ON: 539 config->nfs_export = true; 540 break; 541 542 case OPT_NFS_EXPORT_OFF: 543 config->nfs_export = false; 544 break; 545 546 case OPT_XINO_ON: 547 config->xino = OVL_XINO_ON; 548 break; 549 550 case OPT_XINO_OFF: 551 config->xino = OVL_XINO_OFF; 552 break; 553 554 case OPT_XINO_AUTO: 555 config->xino = OVL_XINO_AUTO; 556 break; 557 558 default: 559 pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p); 560 return -EINVAL; 561 } 562 } 563 564 /* Workdir is useless in non-upper mount */ 565 if (!config->upperdir && config->workdir) { 566 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n", 567 config->workdir); 568 kfree(config->workdir); 569 config->workdir = NULL; 570 } 571 572 return ovl_parse_redirect_mode(config, config->redirect_mode); 573 } 574 575 #define OVL_WORKDIR_NAME "work" 576 #define OVL_INDEXDIR_NAME "index" 577 578 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs, 579 const char *name, bool persist) 580 { 581 struct inode *dir = ofs->workbasedir->d_inode; 582 struct vfsmount *mnt = ofs->upper_mnt; 583 struct dentry *work; 584 int err; 585 bool retried = false; 586 bool locked = false; 587 588 inode_lock_nested(dir, I_MUTEX_PARENT); 589 locked = true; 590 591 retry: 592 work = lookup_one_len(name, ofs->workbasedir, strlen(name)); 593 594 if (!IS_ERR(work)) { 595 struct iattr attr = { 596 .ia_valid = ATTR_MODE, 597 .ia_mode = S_IFDIR | 0, 598 }; 599 600 if (work->d_inode) { 601 err = -EEXIST; 602 if (retried) 603 goto out_dput; 604 605 if (persist) 606 goto out_unlock; 607 608 retried = true; 609 ovl_workdir_cleanup(dir, mnt, work, 0); 610 dput(work); 611 goto retry; 612 } 613 614 err = ovl_create_real(dir, work, 615 &(struct cattr){.mode = S_IFDIR | 0}, 616 NULL, true); 617 if (err) 618 goto out_dput; 619 620 /* 621 * Try to remove POSIX ACL xattrs from workdir. We are good if: 622 * 623 * a) success (there was a POSIX ACL xattr and was removed) 624 * b) -ENODATA (there was no POSIX ACL xattr) 625 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported) 626 * 627 * There are various other error values that could effectively 628 * mean that the xattr doesn't exist (e.g. -ERANGE is returned 629 * if the xattr name is too long), but the set of filesystems 630 * allowed as upper are limited to "normal" ones, where checking 631 * for the above two errors is sufficient. 632 */ 633 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT); 634 if (err && err != -ENODATA && err != -EOPNOTSUPP) 635 goto out_dput; 636 637 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS); 638 if (err && err != -ENODATA && err != -EOPNOTSUPP) 639 goto out_dput; 640 641 /* Clear any inherited mode bits */ 642 inode_lock(work->d_inode); 643 err = notify_change(work, &attr, NULL); 644 inode_unlock(work->d_inode); 645 if (err) 646 goto out_dput; 647 } else { 648 err = PTR_ERR(work); 649 goto out_err; 650 } 651 out_unlock: 652 if (locked) 653 inode_unlock(dir); 654 655 return work; 656 657 out_dput: 658 dput(work); 659 out_err: 660 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n", 661 ofs->config.workdir, name, -err); 662 work = NULL; 663 goto out_unlock; 664 } 665 666 static void ovl_unescape(char *s) 667 { 668 char *d = s; 669 670 for (;; s++, d++) { 671 if (*s == '\\') 672 s++; 673 *d = *s; 674 if (!*s) 675 break; 676 } 677 } 678 679 static int ovl_mount_dir_noesc(const char *name, struct path *path) 680 { 681 int err = -EINVAL; 682 683 if (!*name) { 684 pr_err("overlayfs: empty lowerdir\n"); 685 goto out; 686 } 687 err = kern_path(name, LOOKUP_FOLLOW, path); 688 if (err) { 689 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err); 690 goto out; 691 } 692 err = -EINVAL; 693 if (ovl_dentry_weird(path->dentry)) { 694 pr_err("overlayfs: filesystem on '%s' not supported\n", name); 695 goto out_put; 696 } 697 if (!d_is_dir(path->dentry)) { 698 pr_err("overlayfs: '%s' not a directory\n", name); 699 goto out_put; 700 } 701 return 0; 702 703 out_put: 704 path_put_init(path); 705 out: 706 return err; 707 } 708 709 static int ovl_mount_dir(const char *name, struct path *path) 710 { 711 int err = -ENOMEM; 712 char *tmp = kstrdup(name, GFP_KERNEL); 713 714 if (tmp) { 715 ovl_unescape(tmp); 716 err = ovl_mount_dir_noesc(tmp, path); 717 718 if (!err) 719 if (ovl_dentry_remote(path->dentry)) { 720 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n", 721 tmp); 722 path_put_init(path); 723 err = -EINVAL; 724 } 725 kfree(tmp); 726 } 727 return err; 728 } 729 730 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs, 731 const char *name) 732 { 733 struct kstatfs statfs; 734 int err = vfs_statfs(path, &statfs); 735 736 if (err) 737 pr_err("overlayfs: statfs failed on '%s'\n", name); 738 else 739 ofs->namelen = max(ofs->namelen, statfs.f_namelen); 740 741 return err; 742 } 743 744 static int ovl_lower_dir(const char *name, struct path *path, 745 struct ovl_fs *ofs, int *stack_depth, bool *remote) 746 { 747 int fh_type; 748 int err; 749 750 err = ovl_mount_dir_noesc(name, path); 751 if (err) 752 goto out; 753 754 err = ovl_check_namelen(path, ofs, name); 755 if (err) 756 goto out_put; 757 758 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth); 759 760 if (ovl_dentry_remote(path->dentry)) 761 *remote = true; 762 763 /* 764 * The inodes index feature and NFS export need to encode and decode 765 * file handles, so they require that all layers support them. 766 */ 767 fh_type = ovl_can_decode_fh(path->dentry->d_sb); 768 if ((ofs->config.nfs_export || 769 (ofs->config.index && ofs->config.upperdir)) && !fh_type) { 770 ofs->config.index = false; 771 ofs->config.nfs_export = false; 772 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n", 773 name); 774 } 775 776 /* Check if lower fs has 32bit inode numbers */ 777 if (fh_type != FILEID_INO32_GEN) 778 ofs->xino_bits = 0; 779 780 return 0; 781 782 out_put: 783 path_put_init(path); 784 out: 785 return err; 786 } 787 788 /* Workdir should not be subdir of upperdir and vice versa */ 789 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir) 790 { 791 bool ok = false; 792 793 if (workdir != upperdir) { 794 ok = (lock_rename(workdir, upperdir) == NULL); 795 unlock_rename(workdir, upperdir); 796 } 797 return ok; 798 } 799 800 static unsigned int ovl_split_lowerdirs(char *str) 801 { 802 unsigned int ctr = 1; 803 char *s, *d; 804 805 for (s = d = str;; s++, d++) { 806 if (*s == '\\') { 807 s++; 808 } else if (*s == ':') { 809 *d = '\0'; 810 ctr++; 811 continue; 812 } 813 *d = *s; 814 if (!*s) 815 break; 816 } 817 return ctr; 818 } 819 820 static int __maybe_unused 821 ovl_posix_acl_xattr_get(const struct xattr_handler *handler, 822 struct dentry *dentry, struct inode *inode, 823 const char *name, void *buffer, size_t size) 824 { 825 return ovl_xattr_get(dentry, inode, handler->name, buffer, size); 826 } 827 828 static int __maybe_unused 829 ovl_posix_acl_xattr_set(const struct xattr_handler *handler, 830 struct dentry *dentry, struct inode *inode, 831 const char *name, const void *value, 832 size_t size, int flags) 833 { 834 struct dentry *workdir = ovl_workdir(dentry); 835 struct inode *realinode = ovl_inode_real(inode); 836 struct posix_acl *acl = NULL; 837 int err; 838 839 /* Check that everything is OK before copy-up */ 840 if (value) { 841 acl = posix_acl_from_xattr(&init_user_ns, value, size); 842 if (IS_ERR(acl)) 843 return PTR_ERR(acl); 844 } 845 err = -EOPNOTSUPP; 846 if (!IS_POSIXACL(d_inode(workdir))) 847 goto out_acl_release; 848 if (!realinode->i_op->set_acl) 849 goto out_acl_release; 850 if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) { 851 err = acl ? -EACCES : 0; 852 goto out_acl_release; 853 } 854 err = -EPERM; 855 if (!inode_owner_or_capable(inode)) 856 goto out_acl_release; 857 858 posix_acl_release(acl); 859 860 /* 861 * Check if sgid bit needs to be cleared (actual setacl operation will 862 * be done with mounter's capabilities and so that won't do it for us). 863 */ 864 if (unlikely(inode->i_mode & S_ISGID) && 865 handler->flags == ACL_TYPE_ACCESS && 866 !in_group_p(inode->i_gid) && 867 !capable_wrt_inode_uidgid(inode, CAP_FSETID)) { 868 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID }; 869 870 err = ovl_setattr(dentry, &iattr); 871 if (err) 872 return err; 873 } 874 875 err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags); 876 if (!err) 877 ovl_copyattr(ovl_inode_real(inode), inode); 878 879 return err; 880 881 out_acl_release: 882 posix_acl_release(acl); 883 return err; 884 } 885 886 static int ovl_own_xattr_get(const struct xattr_handler *handler, 887 struct dentry *dentry, struct inode *inode, 888 const char *name, void *buffer, size_t size) 889 { 890 return -EOPNOTSUPP; 891 } 892 893 static int ovl_own_xattr_set(const struct xattr_handler *handler, 894 struct dentry *dentry, struct inode *inode, 895 const char *name, const void *value, 896 size_t size, int flags) 897 { 898 return -EOPNOTSUPP; 899 } 900 901 static int ovl_other_xattr_get(const struct xattr_handler *handler, 902 struct dentry *dentry, struct inode *inode, 903 const char *name, void *buffer, size_t size) 904 { 905 return ovl_xattr_get(dentry, inode, name, buffer, size); 906 } 907 908 static int ovl_other_xattr_set(const struct xattr_handler *handler, 909 struct dentry *dentry, struct inode *inode, 910 const char *name, const void *value, 911 size_t size, int flags) 912 { 913 return ovl_xattr_set(dentry, inode, name, value, size, flags); 914 } 915 916 static const struct xattr_handler __maybe_unused 917 ovl_posix_acl_access_xattr_handler = { 918 .name = XATTR_NAME_POSIX_ACL_ACCESS, 919 .flags = ACL_TYPE_ACCESS, 920 .get = ovl_posix_acl_xattr_get, 921 .set = ovl_posix_acl_xattr_set, 922 }; 923 924 static const struct xattr_handler __maybe_unused 925 ovl_posix_acl_default_xattr_handler = { 926 .name = XATTR_NAME_POSIX_ACL_DEFAULT, 927 .flags = ACL_TYPE_DEFAULT, 928 .get = ovl_posix_acl_xattr_get, 929 .set = ovl_posix_acl_xattr_set, 930 }; 931 932 static const struct xattr_handler ovl_own_xattr_handler = { 933 .prefix = OVL_XATTR_PREFIX, 934 .get = ovl_own_xattr_get, 935 .set = ovl_own_xattr_set, 936 }; 937 938 static const struct xattr_handler ovl_other_xattr_handler = { 939 .prefix = "", /* catch all */ 940 .get = ovl_other_xattr_get, 941 .set = ovl_other_xattr_set, 942 }; 943 944 static const struct xattr_handler *ovl_xattr_handlers[] = { 945 #ifdef CONFIG_FS_POSIX_ACL 946 &ovl_posix_acl_access_xattr_handler, 947 &ovl_posix_acl_default_xattr_handler, 948 #endif 949 &ovl_own_xattr_handler, 950 &ovl_other_xattr_handler, 951 NULL 952 }; 953 954 static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath) 955 { 956 struct vfsmount *upper_mnt; 957 int err; 958 959 err = ovl_mount_dir(ofs->config.upperdir, upperpath); 960 if (err) 961 goto out; 962 963 /* Upper fs should not be r/o */ 964 if (sb_rdonly(upperpath->mnt->mnt_sb)) { 965 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n"); 966 err = -EINVAL; 967 goto out; 968 } 969 970 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir); 971 if (err) 972 goto out; 973 974 err = -EBUSY; 975 if (ovl_inuse_trylock(upperpath->dentry)) { 976 ofs->upperdir_locked = true; 977 } else if (ofs->config.index) { 978 pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n"); 979 goto out; 980 } else { 981 pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n"); 982 } 983 984 upper_mnt = clone_private_mount(upperpath); 985 err = PTR_ERR(upper_mnt); 986 if (IS_ERR(upper_mnt)) { 987 pr_err("overlayfs: failed to clone upperpath\n"); 988 goto out; 989 } 990 991 /* Don't inherit atime flags */ 992 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME); 993 ofs->upper_mnt = upper_mnt; 994 err = 0; 995 out: 996 return err; 997 } 998 999 static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath) 1000 { 1001 struct vfsmount *mnt = ofs->upper_mnt; 1002 struct dentry *temp; 1003 int fh_type; 1004 int err; 1005 1006 err = mnt_want_write(mnt); 1007 if (err) 1008 return err; 1009 1010 ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false); 1011 if (!ofs->workdir) 1012 goto out; 1013 1014 /* 1015 * Upper should support d_type, else whiteouts are visible. Given 1016 * workdir and upper are on same fs, we can do iterate_dir() on 1017 * workdir. This check requires successful creation of workdir in 1018 * previous step. 1019 */ 1020 err = ovl_check_d_type_supported(workpath); 1021 if (err < 0) 1022 goto out; 1023 1024 /* 1025 * We allowed this configuration and don't want to break users over 1026 * kernel upgrade. So warn instead of erroring out. 1027 */ 1028 if (!err) 1029 pr_warn("overlayfs: upper fs needs to support d_type.\n"); 1030 1031 /* Check if upper/work fs supports O_TMPFILE */ 1032 temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0); 1033 ofs->tmpfile = !IS_ERR(temp); 1034 if (ofs->tmpfile) 1035 dput(temp); 1036 else 1037 pr_warn("overlayfs: upper fs does not support tmpfile.\n"); 1038 1039 /* 1040 * Check if upper/work fs supports trusted.overlay.* xattr 1041 */ 1042 err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0); 1043 if (err) { 1044 ofs->noxattr = true; 1045 ofs->config.index = false; 1046 pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off.\n"); 1047 err = 0; 1048 } else { 1049 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE); 1050 } 1051 1052 /* Check if upper/work fs supports file handles */ 1053 fh_type = ovl_can_decode_fh(ofs->workdir->d_sb); 1054 if (ofs->config.index && !fh_type) { 1055 ofs->config.index = false; 1056 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n"); 1057 } 1058 1059 /* Check if upper fs has 32bit inode numbers */ 1060 if (fh_type != FILEID_INO32_GEN) 1061 ofs->xino_bits = 0; 1062 1063 /* NFS export of r/w mount depends on index */ 1064 if (ofs->config.nfs_export && !ofs->config.index) { 1065 pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n"); 1066 ofs->config.nfs_export = false; 1067 } 1068 1069 out: 1070 mnt_drop_write(mnt); 1071 return err; 1072 } 1073 1074 static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath) 1075 { 1076 int err; 1077 struct path workpath = { }; 1078 1079 err = ovl_mount_dir(ofs->config.workdir, &workpath); 1080 if (err) 1081 goto out; 1082 1083 err = -EINVAL; 1084 if (upperpath->mnt != workpath.mnt) { 1085 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n"); 1086 goto out; 1087 } 1088 if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) { 1089 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n"); 1090 goto out; 1091 } 1092 1093 err = -EBUSY; 1094 if (ovl_inuse_trylock(workpath.dentry)) { 1095 ofs->workdir_locked = true; 1096 } else if (ofs->config.index) { 1097 pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n"); 1098 goto out; 1099 } else { 1100 pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n"); 1101 } 1102 1103 ofs->workbasedir = dget(workpath.dentry); 1104 err = ovl_make_workdir(ofs, &workpath); 1105 if (err) 1106 goto out; 1107 1108 err = 0; 1109 out: 1110 path_put(&workpath); 1111 1112 return err; 1113 } 1114 1115 static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe, 1116 struct path *upperpath) 1117 { 1118 struct vfsmount *mnt = ofs->upper_mnt; 1119 int err; 1120 1121 err = mnt_want_write(mnt); 1122 if (err) 1123 return err; 1124 1125 /* Verify lower root is upper root origin */ 1126 err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry, 1127 true); 1128 if (err) { 1129 pr_err("overlayfs: failed to verify upper root origin\n"); 1130 goto out; 1131 } 1132 1133 ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true); 1134 if (ofs->indexdir) { 1135 /* 1136 * Verify upper root is exclusively associated with index dir. 1137 * Older kernels stored upper fh in "trusted.overlay.origin" 1138 * xattr. If that xattr exists, verify that it is a match to 1139 * upper dir file handle. In any case, verify or set xattr 1140 * "trusted.overlay.upper" to indicate that index may have 1141 * directory entries. 1142 */ 1143 if (ovl_check_origin_xattr(ofs->indexdir)) { 1144 err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN, 1145 upperpath->dentry, true, false); 1146 if (err) 1147 pr_err("overlayfs: failed to verify index dir 'origin' xattr\n"); 1148 } 1149 err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true); 1150 if (err) 1151 pr_err("overlayfs: failed to verify index dir 'upper' xattr\n"); 1152 1153 /* Cleanup bad/stale/orphan index entries */ 1154 if (!err) 1155 err = ovl_indexdir_cleanup(ofs); 1156 } 1157 if (err || !ofs->indexdir) 1158 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n"); 1159 1160 out: 1161 mnt_drop_write(mnt); 1162 return err; 1163 } 1164 1165 /* Get a unique fsid for the layer */ 1166 static int ovl_get_fsid(struct ovl_fs *ofs, struct super_block *sb) 1167 { 1168 unsigned int i; 1169 dev_t dev; 1170 int err; 1171 1172 /* fsid 0 is reserved for upper fs even with non upper overlay */ 1173 if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb) 1174 return 0; 1175 1176 for (i = 0; i < ofs->numlowerfs; i++) { 1177 if (ofs->lower_fs[i].sb == sb) 1178 return i + 1; 1179 } 1180 1181 err = get_anon_bdev(&dev); 1182 if (err) { 1183 pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n"); 1184 return err; 1185 } 1186 1187 ofs->lower_fs[ofs->numlowerfs].sb = sb; 1188 ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev; 1189 ofs->numlowerfs++; 1190 1191 return ofs->numlowerfs; 1192 } 1193 1194 static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack, 1195 unsigned int numlower) 1196 { 1197 int err; 1198 unsigned int i; 1199 1200 err = -ENOMEM; 1201 ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer), 1202 GFP_KERNEL); 1203 if (ofs->lower_layers == NULL) 1204 goto out; 1205 1206 ofs->lower_fs = kcalloc(numlower, sizeof(struct ovl_sb), 1207 GFP_KERNEL); 1208 if (ofs->lower_fs == NULL) 1209 goto out; 1210 1211 for (i = 0; i < numlower; i++) { 1212 struct vfsmount *mnt; 1213 int fsid; 1214 1215 err = fsid = ovl_get_fsid(ofs, stack[i].mnt->mnt_sb); 1216 if (err < 0) 1217 goto out; 1218 1219 mnt = clone_private_mount(&stack[i]); 1220 err = PTR_ERR(mnt); 1221 if (IS_ERR(mnt)) { 1222 pr_err("overlayfs: failed to clone lowerpath\n"); 1223 goto out; 1224 } 1225 1226 /* 1227 * Make lower layers R/O. That way fchmod/fchown on lower file 1228 * will fail instead of modifying lower fs. 1229 */ 1230 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME; 1231 1232 ofs->lower_layers[ofs->numlower].mnt = mnt; 1233 ofs->lower_layers[ofs->numlower].idx = i + 1; 1234 ofs->lower_layers[ofs->numlower].fsid = fsid; 1235 if (fsid) { 1236 ofs->lower_layers[ofs->numlower].fs = 1237 &ofs->lower_fs[fsid - 1]; 1238 } 1239 ofs->numlower++; 1240 } 1241 1242 /* 1243 * When all layers on same fs, overlay can use real inode numbers. 1244 * With mount option "xino=on", mounter declares that there are enough 1245 * free high bits in underlying fs to hold the unique fsid. 1246 * If overlayfs does encounter underlying inodes using the high xino 1247 * bits reserved for fsid, it emits a warning and uses the original 1248 * inode number. 1249 */ 1250 if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt)) { 1251 ofs->xino_bits = 0; 1252 ofs->config.xino = OVL_XINO_OFF; 1253 } else if (ofs->config.xino == OVL_XINO_ON && !ofs->xino_bits) { 1254 /* 1255 * This is a roundup of number of bits needed for numlowerfs+1 1256 * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for 1257 * upper fs even with non upper overlay. 1258 */ 1259 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31); 1260 ofs->xino_bits = ilog2(ofs->numlowerfs) + 1; 1261 } 1262 1263 if (ofs->xino_bits) { 1264 pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n", 1265 ofs->xino_bits); 1266 } 1267 1268 err = 0; 1269 out: 1270 return err; 1271 } 1272 1273 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb, 1274 struct ovl_fs *ofs) 1275 { 1276 int err; 1277 char *lowertmp, *lower; 1278 struct path *stack = NULL; 1279 unsigned int stacklen, numlower = 0, i; 1280 bool remote = false; 1281 struct ovl_entry *oe; 1282 1283 err = -ENOMEM; 1284 lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL); 1285 if (!lowertmp) 1286 goto out_err; 1287 1288 err = -EINVAL; 1289 stacklen = ovl_split_lowerdirs(lowertmp); 1290 if (stacklen > OVL_MAX_STACK) { 1291 pr_err("overlayfs: too many lower directories, limit is %d\n", 1292 OVL_MAX_STACK); 1293 goto out_err; 1294 } else if (!ofs->config.upperdir && stacklen == 1) { 1295 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n"); 1296 goto out_err; 1297 } else if (!ofs->config.upperdir && ofs->config.nfs_export && 1298 ofs->config.redirect_follow) { 1299 pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n"); 1300 ofs->config.nfs_export = false; 1301 } 1302 1303 err = -ENOMEM; 1304 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL); 1305 if (!stack) 1306 goto out_err; 1307 1308 err = -EINVAL; 1309 lower = lowertmp; 1310 for (numlower = 0; numlower < stacklen; numlower++) { 1311 err = ovl_lower_dir(lower, &stack[numlower], ofs, 1312 &sb->s_stack_depth, &remote); 1313 if (err) 1314 goto out_err; 1315 1316 lower = strchr(lower, '\0') + 1; 1317 } 1318 1319 err = -EINVAL; 1320 sb->s_stack_depth++; 1321 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) { 1322 pr_err("overlayfs: maximum fs stacking depth exceeded\n"); 1323 goto out_err; 1324 } 1325 1326 err = ovl_get_lower_layers(ofs, stack, numlower); 1327 if (err) 1328 goto out_err; 1329 1330 err = -ENOMEM; 1331 oe = ovl_alloc_entry(numlower); 1332 if (!oe) 1333 goto out_err; 1334 1335 for (i = 0; i < numlower; i++) { 1336 oe->lowerstack[i].dentry = dget(stack[i].dentry); 1337 oe->lowerstack[i].layer = &ofs->lower_layers[i]; 1338 } 1339 1340 if (remote) 1341 sb->s_d_op = &ovl_reval_dentry_operations; 1342 else 1343 sb->s_d_op = &ovl_dentry_operations; 1344 1345 out: 1346 for (i = 0; i < numlower; i++) 1347 path_put(&stack[i]); 1348 kfree(stack); 1349 kfree(lowertmp); 1350 1351 return oe; 1352 1353 out_err: 1354 oe = ERR_PTR(err); 1355 goto out; 1356 } 1357 1358 static int ovl_fill_super(struct super_block *sb, void *data, int silent) 1359 { 1360 struct path upperpath = { }; 1361 struct dentry *root_dentry; 1362 struct ovl_entry *oe; 1363 struct ovl_fs *ofs; 1364 struct cred *cred; 1365 int err; 1366 1367 err = -ENOMEM; 1368 ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL); 1369 if (!ofs) 1370 goto out; 1371 1372 ofs->creator_cred = cred = prepare_creds(); 1373 if (!cred) 1374 goto out_err; 1375 1376 ofs->config.index = ovl_index_def; 1377 ofs->config.nfs_export = ovl_nfs_export_def; 1378 ofs->config.xino = ovl_xino_def(); 1379 err = ovl_parse_opt((char *) data, &ofs->config); 1380 if (err) 1381 goto out_err; 1382 1383 err = -EINVAL; 1384 if (!ofs->config.lowerdir) { 1385 if (!silent) 1386 pr_err("overlayfs: missing 'lowerdir'\n"); 1387 goto out_err; 1388 } 1389 1390 sb->s_stack_depth = 0; 1391 sb->s_maxbytes = MAX_LFS_FILESIZE; 1392 /* Assume underlaying fs uses 32bit inodes unless proven otherwise */ 1393 if (ofs->config.xino != OVL_XINO_OFF) 1394 ofs->xino_bits = BITS_PER_LONG - 32; 1395 1396 if (ofs->config.upperdir) { 1397 if (!ofs->config.workdir) { 1398 pr_err("overlayfs: missing 'workdir'\n"); 1399 goto out_err; 1400 } 1401 1402 err = ovl_get_upper(ofs, &upperpath); 1403 if (err) 1404 goto out_err; 1405 1406 err = ovl_get_workdir(ofs, &upperpath); 1407 if (err) 1408 goto out_err; 1409 1410 if (!ofs->workdir) 1411 sb->s_flags |= SB_RDONLY; 1412 1413 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth; 1414 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran; 1415 1416 } 1417 oe = ovl_get_lowerstack(sb, ofs); 1418 err = PTR_ERR(oe); 1419 if (IS_ERR(oe)) 1420 goto out_err; 1421 1422 /* If the upper fs is nonexistent, we mark overlayfs r/o too */ 1423 if (!ofs->upper_mnt) 1424 sb->s_flags |= SB_RDONLY; 1425 1426 if (!(ovl_force_readonly(ofs)) && ofs->config.index) { 1427 err = ovl_get_indexdir(ofs, oe, &upperpath); 1428 if (err) 1429 goto out_free_oe; 1430 1431 /* Force r/o mount with no index dir */ 1432 if (!ofs->indexdir) { 1433 dput(ofs->workdir); 1434 ofs->workdir = NULL; 1435 sb->s_flags |= SB_RDONLY; 1436 } 1437 1438 } 1439 1440 /* Show index=off in /proc/mounts for forced r/o mount */ 1441 if (!ofs->indexdir) { 1442 ofs->config.index = false; 1443 if (ofs->upper_mnt && ofs->config.nfs_export) { 1444 pr_warn("overlayfs: NFS export requires an index dir, falling back to nfs_export=off.\n"); 1445 ofs->config.nfs_export = false; 1446 } 1447 } 1448 1449 if (ofs->config.nfs_export) 1450 sb->s_export_op = &ovl_export_operations; 1451 1452 /* Never override disk quota limits or use reserved space */ 1453 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE); 1454 1455 sb->s_magic = OVERLAYFS_SUPER_MAGIC; 1456 sb->s_op = &ovl_super_operations; 1457 sb->s_xattr = ovl_xattr_handlers; 1458 sb->s_fs_info = ofs; 1459 sb->s_flags |= SB_POSIXACL | SB_NOREMOTELOCK; 1460 1461 err = -ENOMEM; 1462 root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0)); 1463 if (!root_dentry) 1464 goto out_free_oe; 1465 1466 root_dentry->d_fsdata = oe; 1467 1468 mntput(upperpath.mnt); 1469 if (upperpath.dentry) { 1470 ovl_dentry_set_upper_alias(root_dentry); 1471 if (ovl_is_impuredir(upperpath.dentry)) 1472 ovl_set_flag(OVL_IMPURE, d_inode(root_dentry)); 1473 } 1474 1475 /* Root is always merge -> can have whiteouts */ 1476 ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry)); 1477 ovl_dentry_set_flag(OVL_E_CONNECTED, root_dentry); 1478 ovl_inode_init(d_inode(root_dentry), upperpath.dentry, 1479 ovl_dentry_lower(root_dentry)); 1480 1481 sb->s_root = root_dentry; 1482 1483 return 0; 1484 1485 out_free_oe: 1486 ovl_entry_stack_free(oe); 1487 kfree(oe); 1488 out_err: 1489 path_put(&upperpath); 1490 ovl_free_fs(ofs); 1491 out: 1492 return err; 1493 } 1494 1495 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags, 1496 const char *dev_name, void *raw_data) 1497 { 1498 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super); 1499 } 1500 1501 static struct file_system_type ovl_fs_type = { 1502 .owner = THIS_MODULE, 1503 .name = "overlay", 1504 .mount = ovl_mount, 1505 .kill_sb = kill_anon_super, 1506 }; 1507 MODULE_ALIAS_FS("overlay"); 1508 1509 static void ovl_inode_init_once(void *foo) 1510 { 1511 struct ovl_inode *oi = foo; 1512 1513 inode_init_once(&oi->vfs_inode); 1514 } 1515 1516 static int __init ovl_init(void) 1517 { 1518 int err; 1519 1520 ovl_inode_cachep = kmem_cache_create("ovl_inode", 1521 sizeof(struct ovl_inode), 0, 1522 (SLAB_RECLAIM_ACCOUNT| 1523 SLAB_MEM_SPREAD|SLAB_ACCOUNT), 1524 ovl_inode_init_once); 1525 if (ovl_inode_cachep == NULL) 1526 return -ENOMEM; 1527 1528 err = register_filesystem(&ovl_fs_type); 1529 if (err) 1530 kmem_cache_destroy(ovl_inode_cachep); 1531 1532 return err; 1533 } 1534 1535 static void __exit ovl_exit(void) 1536 { 1537 unregister_filesystem(&ovl_fs_type); 1538 1539 /* 1540 * Make sure all delayed rcu free inodes are flushed before we 1541 * destroy cache. 1542 */ 1543 rcu_barrier(); 1544 kmem_cache_destroy(ovl_inode_cachep); 1545 1546 } 1547 1548 module_init(ovl_init); 1549 module_exit(ovl_exit); 1550