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 work = ovl_create_real(dir, work, OVL_CATTR(attr.ia_mode)); 615 err = PTR_ERR(work); 616 if (IS_ERR(work)) 617 goto out_err; 618 619 /* 620 * Try to remove POSIX ACL xattrs from workdir. We are good if: 621 * 622 * a) success (there was a POSIX ACL xattr and was removed) 623 * b) -ENODATA (there was no POSIX ACL xattr) 624 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported) 625 * 626 * There are various other error values that could effectively 627 * mean that the xattr doesn't exist (e.g. -ERANGE is returned 628 * if the xattr name is too long), but the set of filesystems 629 * allowed as upper are limited to "normal" ones, where checking 630 * for the above two errors is sufficient. 631 */ 632 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT); 633 if (err && err != -ENODATA && err != -EOPNOTSUPP) 634 goto out_dput; 635 636 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS); 637 if (err && err != -ENODATA && err != -EOPNOTSUPP) 638 goto out_dput; 639 640 /* Clear any inherited mode bits */ 641 inode_lock(work->d_inode); 642 err = notify_change(work, &attr, NULL); 643 inode_unlock(work->d_inode); 644 if (err) 645 goto out_dput; 646 } else { 647 err = PTR_ERR(work); 648 goto out_err; 649 } 650 out_unlock: 651 if (locked) 652 inode_unlock(dir); 653 654 return work; 655 656 out_dput: 657 dput(work); 658 out_err: 659 pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n", 660 ofs->config.workdir, name, -err); 661 work = NULL; 662 goto out_unlock; 663 } 664 665 static void ovl_unescape(char *s) 666 { 667 char *d = s; 668 669 for (;; s++, d++) { 670 if (*s == '\\') 671 s++; 672 *d = *s; 673 if (!*s) 674 break; 675 } 676 } 677 678 static int ovl_mount_dir_noesc(const char *name, struct path *path) 679 { 680 int err = -EINVAL; 681 682 if (!*name) { 683 pr_err("overlayfs: empty lowerdir\n"); 684 goto out; 685 } 686 err = kern_path(name, LOOKUP_FOLLOW, path); 687 if (err) { 688 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err); 689 goto out; 690 } 691 err = -EINVAL; 692 if (ovl_dentry_weird(path->dentry)) { 693 pr_err("overlayfs: filesystem on '%s' not supported\n", name); 694 goto out_put; 695 } 696 if (!d_is_dir(path->dentry)) { 697 pr_err("overlayfs: '%s' not a directory\n", name); 698 goto out_put; 699 } 700 return 0; 701 702 out_put: 703 path_put_init(path); 704 out: 705 return err; 706 } 707 708 static int ovl_mount_dir(const char *name, struct path *path) 709 { 710 int err = -ENOMEM; 711 char *tmp = kstrdup(name, GFP_KERNEL); 712 713 if (tmp) { 714 ovl_unescape(tmp); 715 err = ovl_mount_dir_noesc(tmp, path); 716 717 if (!err) 718 if (ovl_dentry_remote(path->dentry)) { 719 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n", 720 tmp); 721 path_put_init(path); 722 err = -EINVAL; 723 } 724 kfree(tmp); 725 } 726 return err; 727 } 728 729 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs, 730 const char *name) 731 { 732 struct kstatfs statfs; 733 int err = vfs_statfs(path, &statfs); 734 735 if (err) 736 pr_err("overlayfs: statfs failed on '%s'\n", name); 737 else 738 ofs->namelen = max(ofs->namelen, statfs.f_namelen); 739 740 return err; 741 } 742 743 static int ovl_lower_dir(const char *name, struct path *path, 744 struct ovl_fs *ofs, int *stack_depth, bool *remote) 745 { 746 int fh_type; 747 int err; 748 749 err = ovl_mount_dir_noesc(name, path); 750 if (err) 751 goto out; 752 753 err = ovl_check_namelen(path, ofs, name); 754 if (err) 755 goto out_put; 756 757 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth); 758 759 if (ovl_dentry_remote(path->dentry)) 760 *remote = true; 761 762 /* 763 * The inodes index feature and NFS export need to encode and decode 764 * file handles, so they require that all layers support them. 765 */ 766 fh_type = ovl_can_decode_fh(path->dentry->d_sb); 767 if ((ofs->config.nfs_export || 768 (ofs->config.index && ofs->config.upperdir)) && !fh_type) { 769 ofs->config.index = false; 770 ofs->config.nfs_export = false; 771 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n", 772 name); 773 } 774 775 /* Check if lower fs has 32bit inode numbers */ 776 if (fh_type != FILEID_INO32_GEN) 777 ofs->xino_bits = 0; 778 779 return 0; 780 781 out_put: 782 path_put_init(path); 783 out: 784 return err; 785 } 786 787 /* Workdir should not be subdir of upperdir and vice versa */ 788 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir) 789 { 790 bool ok = false; 791 792 if (workdir != upperdir) { 793 ok = (lock_rename(workdir, upperdir) == NULL); 794 unlock_rename(workdir, upperdir); 795 } 796 return ok; 797 } 798 799 static unsigned int ovl_split_lowerdirs(char *str) 800 { 801 unsigned int ctr = 1; 802 char *s, *d; 803 804 for (s = d = str;; s++, d++) { 805 if (*s == '\\') { 806 s++; 807 } else if (*s == ':') { 808 *d = '\0'; 809 ctr++; 810 continue; 811 } 812 *d = *s; 813 if (!*s) 814 break; 815 } 816 return ctr; 817 } 818 819 static int __maybe_unused 820 ovl_posix_acl_xattr_get(const struct xattr_handler *handler, 821 struct dentry *dentry, struct inode *inode, 822 const char *name, void *buffer, size_t size) 823 { 824 return ovl_xattr_get(dentry, inode, handler->name, buffer, size); 825 } 826 827 static int __maybe_unused 828 ovl_posix_acl_xattr_set(const struct xattr_handler *handler, 829 struct dentry *dentry, struct inode *inode, 830 const char *name, const void *value, 831 size_t size, int flags) 832 { 833 struct dentry *workdir = ovl_workdir(dentry); 834 struct inode *realinode = ovl_inode_real(inode); 835 struct posix_acl *acl = NULL; 836 int err; 837 838 /* Check that everything is OK before copy-up */ 839 if (value) { 840 acl = posix_acl_from_xattr(&init_user_ns, value, size); 841 if (IS_ERR(acl)) 842 return PTR_ERR(acl); 843 } 844 err = -EOPNOTSUPP; 845 if (!IS_POSIXACL(d_inode(workdir))) 846 goto out_acl_release; 847 if (!realinode->i_op->set_acl) 848 goto out_acl_release; 849 if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) { 850 err = acl ? -EACCES : 0; 851 goto out_acl_release; 852 } 853 err = -EPERM; 854 if (!inode_owner_or_capable(inode)) 855 goto out_acl_release; 856 857 posix_acl_release(acl); 858 859 /* 860 * Check if sgid bit needs to be cleared (actual setacl operation will 861 * be done with mounter's capabilities and so that won't do it for us). 862 */ 863 if (unlikely(inode->i_mode & S_ISGID) && 864 handler->flags == ACL_TYPE_ACCESS && 865 !in_group_p(inode->i_gid) && 866 !capable_wrt_inode_uidgid(inode, CAP_FSETID)) { 867 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID }; 868 869 err = ovl_setattr(dentry, &iattr); 870 if (err) 871 return err; 872 } 873 874 err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags); 875 if (!err) 876 ovl_copyattr(ovl_inode_real(inode), inode); 877 878 return err; 879 880 out_acl_release: 881 posix_acl_release(acl); 882 return err; 883 } 884 885 static int ovl_own_xattr_get(const struct xattr_handler *handler, 886 struct dentry *dentry, struct inode *inode, 887 const char *name, void *buffer, size_t size) 888 { 889 return -EOPNOTSUPP; 890 } 891 892 static int ovl_own_xattr_set(const struct xattr_handler *handler, 893 struct dentry *dentry, struct inode *inode, 894 const char *name, const void *value, 895 size_t size, int flags) 896 { 897 return -EOPNOTSUPP; 898 } 899 900 static int ovl_other_xattr_get(const struct xattr_handler *handler, 901 struct dentry *dentry, struct inode *inode, 902 const char *name, void *buffer, size_t size) 903 { 904 return ovl_xattr_get(dentry, inode, name, buffer, size); 905 } 906 907 static int ovl_other_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 return ovl_xattr_set(dentry, inode, name, value, size, flags); 913 } 914 915 static const struct xattr_handler __maybe_unused 916 ovl_posix_acl_access_xattr_handler = { 917 .name = XATTR_NAME_POSIX_ACL_ACCESS, 918 .flags = ACL_TYPE_ACCESS, 919 .get = ovl_posix_acl_xattr_get, 920 .set = ovl_posix_acl_xattr_set, 921 }; 922 923 static const struct xattr_handler __maybe_unused 924 ovl_posix_acl_default_xattr_handler = { 925 .name = XATTR_NAME_POSIX_ACL_DEFAULT, 926 .flags = ACL_TYPE_DEFAULT, 927 .get = ovl_posix_acl_xattr_get, 928 .set = ovl_posix_acl_xattr_set, 929 }; 930 931 static const struct xattr_handler ovl_own_xattr_handler = { 932 .prefix = OVL_XATTR_PREFIX, 933 .get = ovl_own_xattr_get, 934 .set = ovl_own_xattr_set, 935 }; 936 937 static const struct xattr_handler ovl_other_xattr_handler = { 938 .prefix = "", /* catch all */ 939 .get = ovl_other_xattr_get, 940 .set = ovl_other_xattr_set, 941 }; 942 943 static const struct xattr_handler *ovl_xattr_handlers[] = { 944 #ifdef CONFIG_FS_POSIX_ACL 945 &ovl_posix_acl_access_xattr_handler, 946 &ovl_posix_acl_default_xattr_handler, 947 #endif 948 &ovl_own_xattr_handler, 949 &ovl_other_xattr_handler, 950 NULL 951 }; 952 953 static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath) 954 { 955 struct vfsmount *upper_mnt; 956 int err; 957 958 err = ovl_mount_dir(ofs->config.upperdir, upperpath); 959 if (err) 960 goto out; 961 962 /* Upper fs should not be r/o */ 963 if (sb_rdonly(upperpath->mnt->mnt_sb)) { 964 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n"); 965 err = -EINVAL; 966 goto out; 967 } 968 969 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir); 970 if (err) 971 goto out; 972 973 err = -EBUSY; 974 if (ovl_inuse_trylock(upperpath->dentry)) { 975 ofs->upperdir_locked = true; 976 } else if (ofs->config.index) { 977 pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n"); 978 goto out; 979 } else { 980 pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n"); 981 } 982 983 upper_mnt = clone_private_mount(upperpath); 984 err = PTR_ERR(upper_mnt); 985 if (IS_ERR(upper_mnt)) { 986 pr_err("overlayfs: failed to clone upperpath\n"); 987 goto out; 988 } 989 990 /* Don't inherit atime flags */ 991 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME); 992 ofs->upper_mnt = upper_mnt; 993 err = 0; 994 out: 995 return err; 996 } 997 998 static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath) 999 { 1000 struct vfsmount *mnt = ofs->upper_mnt; 1001 struct dentry *temp; 1002 int fh_type; 1003 int err; 1004 1005 err = mnt_want_write(mnt); 1006 if (err) 1007 return err; 1008 1009 ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false); 1010 if (!ofs->workdir) 1011 goto out; 1012 1013 /* 1014 * Upper should support d_type, else whiteouts are visible. Given 1015 * workdir and upper are on same fs, we can do iterate_dir() on 1016 * workdir. This check requires successful creation of workdir in 1017 * previous step. 1018 */ 1019 err = ovl_check_d_type_supported(workpath); 1020 if (err < 0) 1021 goto out; 1022 1023 /* 1024 * We allowed this configuration and don't want to break users over 1025 * kernel upgrade. So warn instead of erroring out. 1026 */ 1027 if (!err) 1028 pr_warn("overlayfs: upper fs needs to support d_type.\n"); 1029 1030 /* Check if upper/work fs supports O_TMPFILE */ 1031 temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0); 1032 ofs->tmpfile = !IS_ERR(temp); 1033 if (ofs->tmpfile) 1034 dput(temp); 1035 else 1036 pr_warn("overlayfs: upper fs does not support tmpfile.\n"); 1037 1038 /* 1039 * Check if upper/work fs supports trusted.overlay.* xattr 1040 */ 1041 err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0); 1042 if (err) { 1043 ofs->noxattr = true; 1044 ofs->config.index = false; 1045 pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off.\n"); 1046 err = 0; 1047 } else { 1048 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE); 1049 } 1050 1051 /* Check if upper/work fs supports file handles */ 1052 fh_type = ovl_can_decode_fh(ofs->workdir->d_sb); 1053 if (ofs->config.index && !fh_type) { 1054 ofs->config.index = false; 1055 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n"); 1056 } 1057 1058 /* Check if upper fs has 32bit inode numbers */ 1059 if (fh_type != FILEID_INO32_GEN) 1060 ofs->xino_bits = 0; 1061 1062 /* NFS export of r/w mount depends on index */ 1063 if (ofs->config.nfs_export && !ofs->config.index) { 1064 pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n"); 1065 ofs->config.nfs_export = false; 1066 } 1067 1068 out: 1069 mnt_drop_write(mnt); 1070 return err; 1071 } 1072 1073 static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath) 1074 { 1075 int err; 1076 struct path workpath = { }; 1077 1078 err = ovl_mount_dir(ofs->config.workdir, &workpath); 1079 if (err) 1080 goto out; 1081 1082 err = -EINVAL; 1083 if (upperpath->mnt != workpath.mnt) { 1084 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n"); 1085 goto out; 1086 } 1087 if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) { 1088 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n"); 1089 goto out; 1090 } 1091 1092 err = -EBUSY; 1093 if (ovl_inuse_trylock(workpath.dentry)) { 1094 ofs->workdir_locked = true; 1095 } else if (ofs->config.index) { 1096 pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n"); 1097 goto out; 1098 } else { 1099 pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n"); 1100 } 1101 1102 ofs->workbasedir = dget(workpath.dentry); 1103 err = ovl_make_workdir(ofs, &workpath); 1104 if (err) 1105 goto out; 1106 1107 err = 0; 1108 out: 1109 path_put(&workpath); 1110 1111 return err; 1112 } 1113 1114 static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe, 1115 struct path *upperpath) 1116 { 1117 struct vfsmount *mnt = ofs->upper_mnt; 1118 int err; 1119 1120 err = mnt_want_write(mnt); 1121 if (err) 1122 return err; 1123 1124 /* Verify lower root is upper root origin */ 1125 err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry, 1126 true); 1127 if (err) { 1128 pr_err("overlayfs: failed to verify upper root origin\n"); 1129 goto out; 1130 } 1131 1132 ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true); 1133 if (ofs->indexdir) { 1134 /* 1135 * Verify upper root is exclusively associated with index dir. 1136 * Older kernels stored upper fh in "trusted.overlay.origin" 1137 * xattr. If that xattr exists, verify that it is a match to 1138 * upper dir file handle. In any case, verify or set xattr 1139 * "trusted.overlay.upper" to indicate that index may have 1140 * directory entries. 1141 */ 1142 if (ovl_check_origin_xattr(ofs->indexdir)) { 1143 err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN, 1144 upperpath->dentry, true, false); 1145 if (err) 1146 pr_err("overlayfs: failed to verify index dir 'origin' xattr\n"); 1147 } 1148 err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true); 1149 if (err) 1150 pr_err("overlayfs: failed to verify index dir 'upper' xattr\n"); 1151 1152 /* Cleanup bad/stale/orphan index entries */ 1153 if (!err) 1154 err = ovl_indexdir_cleanup(ofs); 1155 } 1156 if (err || !ofs->indexdir) 1157 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n"); 1158 1159 out: 1160 mnt_drop_write(mnt); 1161 return err; 1162 } 1163 1164 /* Get a unique fsid for the layer */ 1165 static int ovl_get_fsid(struct ovl_fs *ofs, struct super_block *sb) 1166 { 1167 unsigned int i; 1168 dev_t dev; 1169 int err; 1170 1171 /* fsid 0 is reserved for upper fs even with non upper overlay */ 1172 if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb) 1173 return 0; 1174 1175 for (i = 0; i < ofs->numlowerfs; i++) { 1176 if (ofs->lower_fs[i].sb == sb) 1177 return i + 1; 1178 } 1179 1180 err = get_anon_bdev(&dev); 1181 if (err) { 1182 pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n"); 1183 return err; 1184 } 1185 1186 ofs->lower_fs[ofs->numlowerfs].sb = sb; 1187 ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev; 1188 ofs->numlowerfs++; 1189 1190 return ofs->numlowerfs; 1191 } 1192 1193 static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack, 1194 unsigned int numlower) 1195 { 1196 int err; 1197 unsigned int i; 1198 1199 err = -ENOMEM; 1200 ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer), 1201 GFP_KERNEL); 1202 if (ofs->lower_layers == NULL) 1203 goto out; 1204 1205 ofs->lower_fs = kcalloc(numlower, sizeof(struct ovl_sb), 1206 GFP_KERNEL); 1207 if (ofs->lower_fs == NULL) 1208 goto out; 1209 1210 for (i = 0; i < numlower; i++) { 1211 struct vfsmount *mnt; 1212 int fsid; 1213 1214 err = fsid = ovl_get_fsid(ofs, stack[i].mnt->mnt_sb); 1215 if (err < 0) 1216 goto out; 1217 1218 mnt = clone_private_mount(&stack[i]); 1219 err = PTR_ERR(mnt); 1220 if (IS_ERR(mnt)) { 1221 pr_err("overlayfs: failed to clone lowerpath\n"); 1222 goto out; 1223 } 1224 1225 /* 1226 * Make lower layers R/O. That way fchmod/fchown on lower file 1227 * will fail instead of modifying lower fs. 1228 */ 1229 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME; 1230 1231 ofs->lower_layers[ofs->numlower].mnt = mnt; 1232 ofs->lower_layers[ofs->numlower].idx = i + 1; 1233 ofs->lower_layers[ofs->numlower].fsid = fsid; 1234 if (fsid) { 1235 ofs->lower_layers[ofs->numlower].fs = 1236 &ofs->lower_fs[fsid - 1]; 1237 } 1238 ofs->numlower++; 1239 } 1240 1241 /* 1242 * When all layers on same fs, overlay can use real inode numbers. 1243 * With mount option "xino=on", mounter declares that there are enough 1244 * free high bits in underlying fs to hold the unique fsid. 1245 * If overlayfs does encounter underlying inodes using the high xino 1246 * bits reserved for fsid, it emits a warning and uses the original 1247 * inode number. 1248 */ 1249 if (!ofs->numlowerfs || (ofs->numlowerfs == 1 && !ofs->upper_mnt)) { 1250 ofs->xino_bits = 0; 1251 ofs->config.xino = OVL_XINO_OFF; 1252 } else if (ofs->config.xino == OVL_XINO_ON && !ofs->xino_bits) { 1253 /* 1254 * This is a roundup of number of bits needed for numlowerfs+1 1255 * (i.e. ilog2(numlowerfs+1 - 1) + 1). fsid 0 is reserved for 1256 * upper fs even with non upper overlay. 1257 */ 1258 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31); 1259 ofs->xino_bits = ilog2(ofs->numlowerfs) + 1; 1260 } 1261 1262 if (ofs->xino_bits) { 1263 pr_info("overlayfs: \"xino\" feature enabled using %d upper inode bits.\n", 1264 ofs->xino_bits); 1265 } 1266 1267 err = 0; 1268 out: 1269 return err; 1270 } 1271 1272 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb, 1273 struct ovl_fs *ofs) 1274 { 1275 int err; 1276 char *lowertmp, *lower; 1277 struct path *stack = NULL; 1278 unsigned int stacklen, numlower = 0, i; 1279 bool remote = false; 1280 struct ovl_entry *oe; 1281 1282 err = -ENOMEM; 1283 lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL); 1284 if (!lowertmp) 1285 goto out_err; 1286 1287 err = -EINVAL; 1288 stacklen = ovl_split_lowerdirs(lowertmp); 1289 if (stacklen > OVL_MAX_STACK) { 1290 pr_err("overlayfs: too many lower directories, limit is %d\n", 1291 OVL_MAX_STACK); 1292 goto out_err; 1293 } else if (!ofs->config.upperdir && stacklen == 1) { 1294 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n"); 1295 goto out_err; 1296 } else if (!ofs->config.upperdir && ofs->config.nfs_export && 1297 ofs->config.redirect_follow) { 1298 pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n"); 1299 ofs->config.nfs_export = false; 1300 } 1301 1302 err = -ENOMEM; 1303 stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL); 1304 if (!stack) 1305 goto out_err; 1306 1307 err = -EINVAL; 1308 lower = lowertmp; 1309 for (numlower = 0; numlower < stacklen; numlower++) { 1310 err = ovl_lower_dir(lower, &stack[numlower], ofs, 1311 &sb->s_stack_depth, &remote); 1312 if (err) 1313 goto out_err; 1314 1315 lower = strchr(lower, '\0') + 1; 1316 } 1317 1318 err = -EINVAL; 1319 sb->s_stack_depth++; 1320 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) { 1321 pr_err("overlayfs: maximum fs stacking depth exceeded\n"); 1322 goto out_err; 1323 } 1324 1325 err = ovl_get_lower_layers(ofs, stack, numlower); 1326 if (err) 1327 goto out_err; 1328 1329 err = -ENOMEM; 1330 oe = ovl_alloc_entry(numlower); 1331 if (!oe) 1332 goto out_err; 1333 1334 for (i = 0; i < numlower; i++) { 1335 oe->lowerstack[i].dentry = dget(stack[i].dentry); 1336 oe->lowerstack[i].layer = &ofs->lower_layers[i]; 1337 } 1338 1339 if (remote) 1340 sb->s_d_op = &ovl_reval_dentry_operations; 1341 else 1342 sb->s_d_op = &ovl_dentry_operations; 1343 1344 out: 1345 for (i = 0; i < numlower; i++) 1346 path_put(&stack[i]); 1347 kfree(stack); 1348 kfree(lowertmp); 1349 1350 return oe; 1351 1352 out_err: 1353 oe = ERR_PTR(err); 1354 goto out; 1355 } 1356 1357 static int ovl_fill_super(struct super_block *sb, void *data, int silent) 1358 { 1359 struct path upperpath = { }; 1360 struct dentry *root_dentry; 1361 struct ovl_entry *oe; 1362 struct ovl_fs *ofs; 1363 struct cred *cred; 1364 int err; 1365 1366 err = -ENOMEM; 1367 ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL); 1368 if (!ofs) 1369 goto out; 1370 1371 ofs->creator_cred = cred = prepare_creds(); 1372 if (!cred) 1373 goto out_err; 1374 1375 ofs->config.index = ovl_index_def; 1376 ofs->config.nfs_export = ovl_nfs_export_def; 1377 ofs->config.xino = ovl_xino_def(); 1378 err = ovl_parse_opt((char *) data, &ofs->config); 1379 if (err) 1380 goto out_err; 1381 1382 err = -EINVAL; 1383 if (!ofs->config.lowerdir) { 1384 if (!silent) 1385 pr_err("overlayfs: missing 'lowerdir'\n"); 1386 goto out_err; 1387 } 1388 1389 sb->s_stack_depth = 0; 1390 sb->s_maxbytes = MAX_LFS_FILESIZE; 1391 /* Assume underlaying fs uses 32bit inodes unless proven otherwise */ 1392 if (ofs->config.xino != OVL_XINO_OFF) 1393 ofs->xino_bits = BITS_PER_LONG - 32; 1394 1395 if (ofs->config.upperdir) { 1396 if (!ofs->config.workdir) { 1397 pr_err("overlayfs: missing 'workdir'\n"); 1398 goto out_err; 1399 } 1400 1401 err = ovl_get_upper(ofs, &upperpath); 1402 if (err) 1403 goto out_err; 1404 1405 err = ovl_get_workdir(ofs, &upperpath); 1406 if (err) 1407 goto out_err; 1408 1409 if (!ofs->workdir) 1410 sb->s_flags |= SB_RDONLY; 1411 1412 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth; 1413 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran; 1414 1415 } 1416 oe = ovl_get_lowerstack(sb, ofs); 1417 err = PTR_ERR(oe); 1418 if (IS_ERR(oe)) 1419 goto out_err; 1420 1421 /* If the upper fs is nonexistent, we mark overlayfs r/o too */ 1422 if (!ofs->upper_mnt) 1423 sb->s_flags |= SB_RDONLY; 1424 1425 if (!(ovl_force_readonly(ofs)) && ofs->config.index) { 1426 err = ovl_get_indexdir(ofs, oe, &upperpath); 1427 if (err) 1428 goto out_free_oe; 1429 1430 /* Force r/o mount with no index dir */ 1431 if (!ofs->indexdir) { 1432 dput(ofs->workdir); 1433 ofs->workdir = NULL; 1434 sb->s_flags |= SB_RDONLY; 1435 } 1436 1437 } 1438 1439 /* Show index=off in /proc/mounts for forced r/o mount */ 1440 if (!ofs->indexdir) { 1441 ofs->config.index = false; 1442 if (ofs->upper_mnt && ofs->config.nfs_export) { 1443 pr_warn("overlayfs: NFS export requires an index dir, falling back to nfs_export=off.\n"); 1444 ofs->config.nfs_export = false; 1445 } 1446 } 1447 1448 if (ofs->config.nfs_export) 1449 sb->s_export_op = &ovl_export_operations; 1450 1451 /* Never override disk quota limits or use reserved space */ 1452 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE); 1453 1454 sb->s_magic = OVERLAYFS_SUPER_MAGIC; 1455 sb->s_op = &ovl_super_operations; 1456 sb->s_xattr = ovl_xattr_handlers; 1457 sb->s_fs_info = ofs; 1458 sb->s_flags |= SB_POSIXACL | SB_NOREMOTELOCK; 1459 1460 err = -ENOMEM; 1461 root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0)); 1462 if (!root_dentry) 1463 goto out_free_oe; 1464 1465 root_dentry->d_fsdata = oe; 1466 1467 mntput(upperpath.mnt); 1468 if (upperpath.dentry) { 1469 ovl_dentry_set_upper_alias(root_dentry); 1470 if (ovl_is_impuredir(upperpath.dentry)) 1471 ovl_set_flag(OVL_IMPURE, d_inode(root_dentry)); 1472 } 1473 1474 /* Root is always merge -> can have whiteouts */ 1475 ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry)); 1476 ovl_dentry_set_flag(OVL_E_CONNECTED, root_dentry); 1477 ovl_inode_init(d_inode(root_dentry), upperpath.dentry, 1478 ovl_dentry_lower(root_dentry)); 1479 1480 sb->s_root = root_dentry; 1481 1482 return 0; 1483 1484 out_free_oe: 1485 ovl_entry_stack_free(oe); 1486 kfree(oe); 1487 out_err: 1488 path_put(&upperpath); 1489 ovl_free_fs(ofs); 1490 out: 1491 return err; 1492 } 1493 1494 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags, 1495 const char *dev_name, void *raw_data) 1496 { 1497 return mount_nodev(fs_type, flags, raw_data, ovl_fill_super); 1498 } 1499 1500 static struct file_system_type ovl_fs_type = { 1501 .owner = THIS_MODULE, 1502 .name = "overlay", 1503 .mount = ovl_mount, 1504 .kill_sb = kill_anon_super, 1505 }; 1506 MODULE_ALIAS_FS("overlay"); 1507 1508 static void ovl_inode_init_once(void *foo) 1509 { 1510 struct ovl_inode *oi = foo; 1511 1512 inode_init_once(&oi->vfs_inode); 1513 } 1514 1515 static int __init ovl_init(void) 1516 { 1517 int err; 1518 1519 ovl_inode_cachep = kmem_cache_create("ovl_inode", 1520 sizeof(struct ovl_inode), 0, 1521 (SLAB_RECLAIM_ACCOUNT| 1522 SLAB_MEM_SPREAD|SLAB_ACCOUNT), 1523 ovl_inode_init_once); 1524 if (ovl_inode_cachep == NULL) 1525 return -ENOMEM; 1526 1527 err = register_filesystem(&ovl_fs_type); 1528 if (err) 1529 kmem_cache_destroy(ovl_inode_cachep); 1530 1531 return err; 1532 } 1533 1534 static void __exit ovl_exit(void) 1535 { 1536 unregister_filesystem(&ovl_fs_type); 1537 1538 /* 1539 * Make sure all delayed rcu free inodes are flushed before we 1540 * destroy cache. 1541 */ 1542 rcu_barrier(); 1543 kmem_cache_destroy(ovl_inode_cachep); 1544 1545 } 1546 1547 module_init(ovl_init); 1548 module_exit(ovl_exit); 1549