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 <linux/file.h> 19#include <linux/fs_context.h> 20#include <linux/fs_parser.h> 21#include "overlayfs.h" 22#include "params.h" 23 24MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>"); 25MODULE_DESCRIPTION("Overlay filesystem"); 26MODULE_LICENSE("GPL"); 27 28 29struct ovl_dir_cache; 30 31static struct dentry *ovl_d_real(struct dentry *dentry, enum d_real_type type) 32{ 33 struct dentry *upper, *lower; 34 int err; 35 36 switch (type) { 37 case D_REAL_DATA: 38 case D_REAL_METADATA: 39 break; 40 default: 41 goto bug; 42 } 43 44 if (!d_is_reg(dentry)) { 45 /* d_real_inode() is only relevant for regular files */ 46 return dentry; 47 } 48 49 upper = ovl_dentry_upper(dentry); 50 if (upper && (type == D_REAL_METADATA || 51 ovl_has_upperdata(d_inode(dentry)))) 52 return upper; 53 54 if (type == D_REAL_METADATA) { 55 lower = ovl_dentry_lower(dentry); 56 goto real_lower; 57 } 58 59 /* 60 * Best effort lazy lookup of lowerdata for D_REAL_DATA case to return 61 * the real lowerdata dentry. The only current caller of d_real() with 62 * D_REAL_DATA is d_real_inode() from trace_uprobe and this caller is 63 * likely going to be followed reading from the file, before placing 64 * uprobes on offset within the file, so lowerdata should be available 65 * when setting the uprobe. 66 */ 67 err = ovl_verify_lowerdata(dentry); 68 if (err) 69 goto bug; 70 lower = ovl_dentry_lowerdata(dentry); 71 if (!lower) 72 goto bug; 73 74real_lower: 75 /* Handle recursion into stacked lower fs */ 76 return d_real(lower, type); 77 78bug: 79 WARN(1, "%s(%pd4, %d): real dentry not found\n", __func__, dentry, type); 80 return dentry; 81} 82 83static int ovl_revalidate_real(struct dentry *d, unsigned int flags, bool weak) 84{ 85 int ret = 1; 86 87 if (!d) 88 return 1; 89 90 if (weak) { 91 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) 92 ret = d->d_op->d_weak_revalidate(d, flags); 93 } else if (d->d_flags & DCACHE_OP_REVALIDATE) { 94 ret = d->d_op->d_revalidate(d, flags); 95 if (!ret) { 96 if (!(flags & LOOKUP_RCU)) 97 d_invalidate(d); 98 ret = -ESTALE; 99 } 100 } 101 return ret; 102} 103 104static int ovl_dentry_revalidate_common(struct dentry *dentry, 105 unsigned int flags, bool weak) 106{ 107 struct ovl_entry *oe; 108 struct ovl_path *lowerstack; 109 struct inode *inode = d_inode_rcu(dentry); 110 struct dentry *upper; 111 unsigned int i; 112 int ret = 1; 113 114 /* Careful in RCU mode */ 115 if (!inode) 116 return -ECHILD; 117 118 oe = OVL_I_E(inode); 119 lowerstack = ovl_lowerstack(oe); 120 upper = ovl_i_dentry_upper(inode); 121 if (upper) 122 ret = ovl_revalidate_real(upper, flags, weak); 123 124 for (i = 0; ret > 0 && i < ovl_numlower(oe); i++) 125 ret = ovl_revalidate_real(lowerstack[i].dentry, flags, weak); 126 127 return ret; 128} 129 130static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags) 131{ 132 return ovl_dentry_revalidate_common(dentry, flags, false); 133} 134 135static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags) 136{ 137 return ovl_dentry_revalidate_common(dentry, flags, true); 138} 139 140static const struct dentry_operations ovl_dentry_operations = { 141 .d_real = ovl_d_real, 142 .d_revalidate = ovl_dentry_revalidate, 143 .d_weak_revalidate = ovl_dentry_weak_revalidate, 144}; 145 146static struct kmem_cache *ovl_inode_cachep; 147 148static struct inode *ovl_alloc_inode(struct super_block *sb) 149{ 150 struct ovl_inode *oi = alloc_inode_sb(sb, ovl_inode_cachep, GFP_KERNEL); 151 152 if (!oi) 153 return NULL; 154 155 oi->cache = NULL; 156 oi->redirect = NULL; 157 oi->version = 0; 158 oi->flags = 0; 159 oi->__upperdentry = NULL; 160 oi->lowerdata_redirect = NULL; 161 oi->oe = NULL; 162 mutex_init(&oi->lock); 163 164 return &oi->vfs_inode; 165} 166 167static void ovl_free_inode(struct inode *inode) 168{ 169 struct ovl_inode *oi = OVL_I(inode); 170 171 kfree(oi->redirect); 172 kfree(oi->oe); 173 mutex_destroy(&oi->lock); 174 kmem_cache_free(ovl_inode_cachep, oi); 175} 176 177static void ovl_destroy_inode(struct inode *inode) 178{ 179 struct ovl_inode *oi = OVL_I(inode); 180 181 dput(oi->__upperdentry); 182 ovl_stack_put(ovl_lowerstack(oi->oe), ovl_numlower(oi->oe)); 183 if (S_ISDIR(inode->i_mode)) 184 ovl_dir_cache_free(inode); 185 else 186 kfree(oi->lowerdata_redirect); 187} 188 189static void ovl_put_super(struct super_block *sb) 190{ 191 struct ovl_fs *ofs = OVL_FS(sb); 192 193 if (ofs) 194 ovl_free_fs(ofs); 195} 196 197/* Sync real dirty inodes in upper filesystem (if it exists) */ 198static int ovl_sync_fs(struct super_block *sb, int wait) 199{ 200 struct ovl_fs *ofs = OVL_FS(sb); 201 struct super_block *upper_sb; 202 int ret; 203 204 ret = ovl_sync_status(ofs); 205 /* 206 * We have to always set the err, because the return value isn't 207 * checked in syncfs, and instead indirectly return an error via 208 * the sb's writeback errseq, which VFS inspects after this call. 209 */ 210 if (ret < 0) { 211 errseq_set(&sb->s_wb_err, -EIO); 212 return -EIO; 213 } 214 215 if (!ret) 216 return ret; 217 218 /* 219 * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC). 220 * All the super blocks will be iterated, including upper_sb. 221 * 222 * If this is a syncfs(2) call, then we do need to call 223 * sync_filesystem() on upper_sb, but enough if we do it when being 224 * called with wait == 1. 225 */ 226 if (!wait) 227 return 0; 228 229 upper_sb = ovl_upper_mnt(ofs)->mnt_sb; 230 231 down_read(&upper_sb->s_umount); 232 ret = sync_filesystem(upper_sb); 233 up_read(&upper_sb->s_umount); 234 235 return ret; 236} 237 238/** 239 * ovl_statfs 240 * @dentry: The dentry to query 241 * @buf: The struct kstatfs to fill in with stats 242 * 243 * Get the filesystem statistics. As writes always target the upper layer 244 * filesystem pass the statfs to the upper filesystem (if it exists) 245 */ 246static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf) 247{ 248 struct super_block *sb = dentry->d_sb; 249 struct ovl_fs *ofs = OVL_FS(sb); 250 struct dentry *root_dentry = sb->s_root; 251 struct path path; 252 int err; 253 254 ovl_path_real(root_dentry, &path); 255 256 err = vfs_statfs(&path, buf); 257 if (!err) { 258 buf->f_namelen = ofs->namelen; 259 buf->f_type = OVERLAYFS_SUPER_MAGIC; 260 if (ovl_has_fsid(ofs)) 261 buf->f_fsid = uuid_to_fsid(sb->s_uuid.b); 262 } 263 264 return err; 265} 266 267static const struct super_operations ovl_super_operations = { 268 .alloc_inode = ovl_alloc_inode, 269 .free_inode = ovl_free_inode, 270 .destroy_inode = ovl_destroy_inode, 271 .drop_inode = generic_delete_inode, 272 .put_super = ovl_put_super, 273 .sync_fs = ovl_sync_fs, 274 .statfs = ovl_statfs, 275 .show_options = ovl_show_options, 276}; 277 278#define OVL_WORKDIR_NAME "work" 279#define OVL_INDEXDIR_NAME "index" 280 281static struct dentry *ovl_workdir_create(struct ovl_fs *ofs, 282 const char *name, bool persist) 283{ 284 struct inode *dir = ofs->workbasedir->d_inode; 285 struct vfsmount *mnt = ovl_upper_mnt(ofs); 286 struct dentry *work; 287 int err; 288 bool retried = false; 289 290 inode_lock_nested(dir, I_MUTEX_PARENT); 291retry: 292 work = ovl_lookup_upper(ofs, name, ofs->workbasedir, strlen(name)); 293 294 if (!IS_ERR(work)) { 295 struct iattr attr = { 296 .ia_valid = ATTR_MODE, 297 .ia_mode = S_IFDIR | 0, 298 }; 299 300 if (work->d_inode) { 301 err = -EEXIST; 302 if (retried) 303 goto out_dput; 304 305 if (persist) 306 goto out_unlock; 307 308 retried = true; 309 err = ovl_workdir_cleanup(ofs, dir, mnt, work, 0); 310 dput(work); 311 if (err == -EINVAL) { 312 work = ERR_PTR(err); 313 goto out_unlock; 314 } 315 goto retry; 316 } 317 318 err = ovl_mkdir_real(ofs, dir, &work, attr.ia_mode); 319 if (err) 320 goto out_dput; 321 322 /* Weird filesystem returning with hashed negative (kernfs)? */ 323 err = -EINVAL; 324 if (d_really_is_negative(work)) 325 goto out_dput; 326 327 /* 328 * Try to remove POSIX ACL xattrs from workdir. We are good if: 329 * 330 * a) success (there was a POSIX ACL xattr and was removed) 331 * b) -ENODATA (there was no POSIX ACL xattr) 332 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported) 333 * 334 * There are various other error values that could effectively 335 * mean that the xattr doesn't exist (e.g. -ERANGE is returned 336 * if the xattr name is too long), but the set of filesystems 337 * allowed as upper are limited to "normal" ones, where checking 338 * for the above two errors is sufficient. 339 */ 340 err = ovl_do_remove_acl(ofs, work, XATTR_NAME_POSIX_ACL_DEFAULT); 341 if (err && err != -ENODATA && err != -EOPNOTSUPP) 342 goto out_dput; 343 344 err = ovl_do_remove_acl(ofs, work, XATTR_NAME_POSIX_ACL_ACCESS); 345 if (err && err != -ENODATA && err != -EOPNOTSUPP) 346 goto out_dput; 347 348 /* Clear any inherited mode bits */ 349 inode_lock(work->d_inode); 350 err = ovl_do_notify_change(ofs, work, &attr); 351 inode_unlock(work->d_inode); 352 if (err) 353 goto out_dput; 354 } else { 355 err = PTR_ERR(work); 356 goto out_err; 357 } 358out_unlock: 359 inode_unlock(dir); 360 return work; 361 362out_dput: 363 dput(work); 364out_err: 365 pr_warn("failed to create directory %s/%s (errno: %i); mounting read-only\n", 366 ofs->config.workdir, name, -err); 367 work = NULL; 368 goto out_unlock; 369} 370 371static int ovl_check_namelen(const struct path *path, struct ovl_fs *ofs, 372 const char *name) 373{ 374 struct kstatfs statfs; 375 int err = vfs_statfs(path, &statfs); 376 377 if (err) 378 pr_err("statfs failed on '%s'\n", name); 379 else 380 ofs->namelen = max(ofs->namelen, statfs.f_namelen); 381 382 return err; 383} 384 385static int ovl_lower_dir(const char *name, struct path *path, 386 struct ovl_fs *ofs, int *stack_depth) 387{ 388 int fh_type; 389 int err; 390 391 err = ovl_check_namelen(path, ofs, name); 392 if (err) 393 return err; 394 395 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth); 396 397 /* 398 * The inodes index feature and NFS export need to encode and decode 399 * file handles, so they require that all layers support them. 400 */ 401 fh_type = ovl_can_decode_fh(path->dentry->d_sb); 402 if ((ofs->config.nfs_export || 403 (ofs->config.index && ofs->config.upperdir)) && !fh_type) { 404 ofs->config.index = false; 405 ofs->config.nfs_export = false; 406 pr_warn("fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n", 407 name); 408 } 409 ofs->nofh |= !fh_type; 410 /* 411 * Decoding origin file handle is required for persistent st_ino. 412 * Without persistent st_ino, xino=auto falls back to xino=off. 413 */ 414 if (ofs->config.xino == OVL_XINO_AUTO && 415 ofs->config.upperdir && !fh_type) { 416 ofs->config.xino = OVL_XINO_OFF; 417 pr_warn("fs on '%s' does not support file handles, falling back to xino=off.\n", 418 name); 419 } 420 421 /* Check if lower fs has 32bit inode numbers */ 422 if (fh_type != FILEID_INO32_GEN) 423 ofs->xino_mode = -1; 424 425 return 0; 426} 427 428/* Workdir should not be subdir of upperdir and vice versa */ 429static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir) 430{ 431 bool ok = false; 432 433 if (workdir != upperdir) { 434 struct dentry *trap = lock_rename(workdir, upperdir); 435 if (!IS_ERR(trap)) 436 unlock_rename(workdir, upperdir); 437 ok = (trap == NULL); 438 } 439 return ok; 440} 441 442static int ovl_setup_trap(struct super_block *sb, struct dentry *dir, 443 struct inode **ptrap, const char *name) 444{ 445 struct inode *trap; 446 int err; 447 448 trap = ovl_get_trap_inode(sb, dir); 449 err = PTR_ERR_OR_ZERO(trap); 450 if (err) { 451 if (err == -ELOOP) 452 pr_err("conflicting %s path\n", name); 453 return err; 454 } 455 456 *ptrap = trap; 457 return 0; 458} 459 460/* 461 * Determine how we treat concurrent use of upperdir/workdir based on the 462 * index feature. This is papering over mount leaks of container runtimes, 463 * for example, an old overlay mount is leaked and now its upperdir is 464 * attempted to be used as a lower layer in a new overlay mount. 465 */ 466static int ovl_report_in_use(struct ovl_fs *ofs, const char *name) 467{ 468 if (ofs->config.index) { 469 pr_err("%s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n", 470 name); 471 return -EBUSY; 472 } else { 473 pr_warn("%s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n", 474 name); 475 return 0; 476 } 477} 478 479static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs, 480 struct ovl_layer *upper_layer, 481 const struct path *upperpath) 482{ 483 struct vfsmount *upper_mnt; 484 int err; 485 486 /* Upperdir path should not be r/o */ 487 if (__mnt_is_readonly(upperpath->mnt)) { 488 pr_err("upper fs is r/o, try multi-lower layers mount\n"); 489 err = -EINVAL; 490 goto out; 491 } 492 493 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir); 494 if (err) 495 goto out; 496 497 err = ovl_setup_trap(sb, upperpath->dentry, &upper_layer->trap, 498 "upperdir"); 499 if (err) 500 goto out; 501 502 upper_mnt = clone_private_mount(upperpath); 503 err = PTR_ERR(upper_mnt); 504 if (IS_ERR(upper_mnt)) { 505 pr_err("failed to clone upperpath\n"); 506 goto out; 507 } 508 509 /* Don't inherit atime flags */ 510 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME); 511 upper_layer->mnt = upper_mnt; 512 upper_layer->idx = 0; 513 upper_layer->fsid = 0; 514 515 /* 516 * Inherit SB_NOSEC flag from upperdir. 517 * 518 * This optimization changes behavior when a security related attribute 519 * (suid/sgid/security.*) is changed on an underlying layer. This is 520 * okay because we don't yet have guarantees in that case, but it will 521 * need careful treatment once we want to honour changes to underlying 522 * filesystems. 523 */ 524 if (upper_mnt->mnt_sb->s_flags & SB_NOSEC) 525 sb->s_flags |= SB_NOSEC; 526 527 if (ovl_inuse_trylock(ovl_upper_mnt(ofs)->mnt_root)) { 528 ofs->upperdir_locked = true; 529 } else { 530 err = ovl_report_in_use(ofs, "upperdir"); 531 if (err) 532 goto out; 533 } 534 535 err = 0; 536out: 537 return err; 538} 539 540/* 541 * Returns 1 if RENAME_WHITEOUT is supported, 0 if not supported and 542 * negative values if error is encountered. 543 */ 544static int ovl_check_rename_whiteout(struct ovl_fs *ofs) 545{ 546 struct dentry *workdir = ofs->workdir; 547 struct inode *dir = d_inode(workdir); 548 struct dentry *temp; 549 struct dentry *dest; 550 struct dentry *whiteout; 551 struct name_snapshot name; 552 int err; 553 554 inode_lock_nested(dir, I_MUTEX_PARENT); 555 556 temp = ovl_create_temp(ofs, workdir, OVL_CATTR(S_IFREG | 0)); 557 err = PTR_ERR(temp); 558 if (IS_ERR(temp)) 559 goto out_unlock; 560 561 dest = ovl_lookup_temp(ofs, workdir); 562 err = PTR_ERR(dest); 563 if (IS_ERR(dest)) { 564 dput(temp); 565 goto out_unlock; 566 } 567 568 /* Name is inline and stable - using snapshot as a copy helper */ 569 take_dentry_name_snapshot(&name, temp); 570 err = ovl_do_rename(ofs, dir, temp, dir, dest, RENAME_WHITEOUT); 571 if (err) { 572 if (err == -EINVAL) 573 err = 0; 574 goto cleanup_temp; 575 } 576 577 whiteout = ovl_lookup_upper(ofs, name.name.name, workdir, name.name.len); 578 err = PTR_ERR(whiteout); 579 if (IS_ERR(whiteout)) 580 goto cleanup_temp; 581 582 err = ovl_upper_is_whiteout(ofs, whiteout); 583 584 /* Best effort cleanup of whiteout and temp file */ 585 if (err) 586 ovl_cleanup(ofs, dir, whiteout); 587 dput(whiteout); 588 589cleanup_temp: 590 ovl_cleanup(ofs, dir, temp); 591 release_dentry_name_snapshot(&name); 592 dput(temp); 593 dput(dest); 594 595out_unlock: 596 inode_unlock(dir); 597 598 return err; 599} 600 601static struct dentry *ovl_lookup_or_create(struct ovl_fs *ofs, 602 struct dentry *parent, 603 const char *name, umode_t mode) 604{ 605 size_t len = strlen(name); 606 struct dentry *child; 607 608 inode_lock_nested(parent->d_inode, I_MUTEX_PARENT); 609 child = ovl_lookup_upper(ofs, name, parent, len); 610 if (!IS_ERR(child) && !child->d_inode) 611 child = ovl_create_real(ofs, parent->d_inode, child, 612 OVL_CATTR(mode)); 613 inode_unlock(parent->d_inode); 614 dput(parent); 615 616 return child; 617} 618 619/* 620 * Creates $workdir/work/incompat/volatile/dirty file if it is not already 621 * present. 622 */ 623static int ovl_create_volatile_dirty(struct ovl_fs *ofs) 624{ 625 unsigned int ctr; 626 struct dentry *d = dget(ofs->workbasedir); 627 static const char *const volatile_path[] = { 628 OVL_WORKDIR_NAME, "incompat", "volatile", "dirty" 629 }; 630 const char *const *name = volatile_path; 631 632 for (ctr = ARRAY_SIZE(volatile_path); ctr; ctr--, name++) { 633 d = ovl_lookup_or_create(ofs, d, *name, ctr > 1 ? S_IFDIR : S_IFREG); 634 if (IS_ERR(d)) 635 return PTR_ERR(d); 636 } 637 dput(d); 638 return 0; 639} 640 641static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs, 642 const struct path *workpath) 643{ 644 struct vfsmount *mnt = ovl_upper_mnt(ofs); 645 struct dentry *workdir; 646 struct file *tmpfile; 647 bool rename_whiteout; 648 bool d_type; 649 int fh_type; 650 int err; 651 652 err = mnt_want_write(mnt); 653 if (err) 654 return err; 655 656 workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false); 657 err = PTR_ERR(workdir); 658 if (IS_ERR_OR_NULL(workdir)) 659 goto out; 660 661 ofs->workdir = workdir; 662 663 err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir"); 664 if (err) 665 goto out; 666 667 /* 668 * Upper should support d_type, else whiteouts are visible. Given 669 * workdir and upper are on same fs, we can do iterate_dir() on 670 * workdir. This check requires successful creation of workdir in 671 * previous step. 672 */ 673 err = ovl_check_d_type_supported(workpath); 674 if (err < 0) 675 goto out; 676 677 d_type = err; 678 if (!d_type) 679 pr_warn("upper fs needs to support d_type.\n"); 680 681 /* Check if upper/work fs supports O_TMPFILE */ 682 tmpfile = ovl_do_tmpfile(ofs, ofs->workdir, S_IFREG | 0); 683 ofs->tmpfile = !IS_ERR(tmpfile); 684 if (ofs->tmpfile) 685 fput(tmpfile); 686 else 687 pr_warn("upper fs does not support tmpfile.\n"); 688 689 690 /* Check if upper/work fs supports RENAME_WHITEOUT */ 691 err = ovl_check_rename_whiteout(ofs); 692 if (err < 0) 693 goto out; 694 695 rename_whiteout = err; 696 if (!rename_whiteout) 697 pr_warn("upper fs does not support RENAME_WHITEOUT.\n"); 698 699 /* 700 * Check if upper/work fs supports (trusted|user).overlay.* xattr 701 */ 702 err = ovl_setxattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE, "0", 1); 703 if (err) { 704 pr_warn("failed to set xattr on upper\n"); 705 ofs->noxattr = true; 706 if (ovl_redirect_follow(ofs)) { 707 ofs->config.redirect_mode = OVL_REDIRECT_NOFOLLOW; 708 pr_warn("...falling back to redirect_dir=nofollow.\n"); 709 } 710 if (ofs->config.metacopy) { 711 ofs->config.metacopy = false; 712 pr_warn("...falling back to metacopy=off.\n"); 713 } 714 if (ofs->config.index) { 715 ofs->config.index = false; 716 pr_warn("...falling back to index=off.\n"); 717 } 718 if (ovl_has_fsid(ofs)) { 719 ofs->config.uuid = OVL_UUID_NULL; 720 pr_warn("...falling back to uuid=null.\n"); 721 } 722 /* 723 * xattr support is required for persistent st_ino. 724 * Without persistent st_ino, xino=auto falls back to xino=off. 725 */ 726 if (ofs->config.xino == OVL_XINO_AUTO) { 727 ofs->config.xino = OVL_XINO_OFF; 728 pr_warn("...falling back to xino=off.\n"); 729 } 730 if (err == -EPERM && !ofs->config.userxattr) 731 pr_info("try mounting with 'userxattr' option\n"); 732 err = 0; 733 } else { 734 ovl_removexattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE); 735 } 736 737 /* 738 * We allowed sub-optimal upper fs configuration and don't want to break 739 * users over kernel upgrade, but we never allowed remote upper fs, so 740 * we can enforce strict requirements for remote upper fs. 741 */ 742 if (ovl_dentry_remote(ofs->workdir) && 743 (!d_type || !rename_whiteout || ofs->noxattr)) { 744 pr_err("upper fs missing required features.\n"); 745 err = -EINVAL; 746 goto out; 747 } 748 749 /* 750 * For volatile mount, create a incompat/volatile/dirty file to keep 751 * track of it. 752 */ 753 if (ofs->config.ovl_volatile) { 754 err = ovl_create_volatile_dirty(ofs); 755 if (err < 0) { 756 pr_err("Failed to create volatile/dirty file.\n"); 757 goto out; 758 } 759 } 760 761 /* Check if upper/work fs supports file handles */ 762 fh_type = ovl_can_decode_fh(ofs->workdir->d_sb); 763 if (ofs->config.index && !fh_type) { 764 ofs->config.index = false; 765 pr_warn("upper fs does not support file handles, falling back to index=off.\n"); 766 } 767 ofs->nofh |= !fh_type; 768 769 /* Check if upper fs has 32bit inode numbers */ 770 if (fh_type != FILEID_INO32_GEN) 771 ofs->xino_mode = -1; 772 773 /* NFS export of r/w mount depends on index */ 774 if (ofs->config.nfs_export && !ofs->config.index) { 775 pr_warn("NFS export requires \"index=on\", falling back to nfs_export=off.\n"); 776 ofs->config.nfs_export = false; 777 } 778out: 779 mnt_drop_write(mnt); 780 return err; 781} 782 783static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs, 784 const struct path *upperpath, 785 const struct path *workpath) 786{ 787 int err; 788 789 err = -EINVAL; 790 if (upperpath->mnt != workpath->mnt) { 791 pr_err("workdir and upperdir must reside under the same mount\n"); 792 return err; 793 } 794 if (!ovl_workdir_ok(workpath->dentry, upperpath->dentry)) { 795 pr_err("workdir and upperdir must be separate subtrees\n"); 796 return err; 797 } 798 799 ofs->workbasedir = dget(workpath->dentry); 800 801 if (ovl_inuse_trylock(ofs->workbasedir)) { 802 ofs->workdir_locked = true; 803 } else { 804 err = ovl_report_in_use(ofs, "workdir"); 805 if (err) 806 return err; 807 } 808 809 err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap, 810 "workdir"); 811 if (err) 812 return err; 813 814 return ovl_make_workdir(sb, ofs, workpath); 815} 816 817static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs, 818 struct ovl_entry *oe, const struct path *upperpath) 819{ 820 struct vfsmount *mnt = ovl_upper_mnt(ofs); 821 struct dentry *indexdir; 822 struct dentry *origin = ovl_lowerstack(oe)->dentry; 823 const struct ovl_fh *fh; 824 int err; 825 826 fh = ovl_get_origin_fh(ofs, origin); 827 if (IS_ERR(fh)) 828 return PTR_ERR(fh); 829 830 err = mnt_want_write(mnt); 831 if (err) 832 goto out_free_fh; 833 834 /* Verify lower root is upper root origin */ 835 err = ovl_verify_origin_fh(ofs, upperpath->dentry, fh, true); 836 if (err) { 837 pr_err("failed to verify upper root origin\n"); 838 goto out; 839 } 840 841 /* index dir will act also as workdir */ 842 iput(ofs->workdir_trap); 843 ofs->workdir_trap = NULL; 844 dput(ofs->workdir); 845 ofs->workdir = NULL; 846 indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true); 847 if (IS_ERR(indexdir)) { 848 err = PTR_ERR(indexdir); 849 } else if (indexdir) { 850 ofs->workdir = indexdir; 851 err = ovl_setup_trap(sb, indexdir, &ofs->workdir_trap, 852 "indexdir"); 853 if (err) 854 goto out; 855 856 /* 857 * Verify upper root is exclusively associated with index dir. 858 * Older kernels stored upper fh in ".overlay.origin" 859 * xattr. If that xattr exists, verify that it is a match to 860 * upper dir file handle. In any case, verify or set xattr 861 * ".overlay.upper" to indicate that index may have 862 * directory entries. 863 */ 864 if (ovl_check_origin_xattr(ofs, indexdir)) { 865 err = ovl_verify_origin_xattr(ofs, indexdir, 866 OVL_XATTR_ORIGIN, 867 upperpath->dentry, true, 868 false); 869 if (err) 870 pr_err("failed to verify index dir 'origin' xattr\n"); 871 } 872 err = ovl_verify_upper(ofs, indexdir, upperpath->dentry, true); 873 if (err) 874 pr_err("failed to verify index dir 'upper' xattr\n"); 875 876 /* Cleanup bad/stale/orphan index entries */ 877 if (!err) 878 err = ovl_indexdir_cleanup(ofs); 879 } 880 if (err || !indexdir) 881 pr_warn("try deleting index dir or mounting with '-o index=off' to disable inodes index.\n"); 882 883out: 884 mnt_drop_write(mnt); 885out_free_fh: 886 kfree(fh); 887 return err; 888} 889 890static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) 891{ 892 unsigned int i; 893 894 if (!ofs->config.nfs_export && !ovl_upper_mnt(ofs)) 895 return true; 896 897 /* 898 * We allow using single lower with null uuid for index and nfs_export 899 * for example to support those features with single lower squashfs. 900 * To avoid regressions in setups of overlay with re-formatted lower 901 * squashfs, do not allow decoding origin with lower null uuid unless 902 * user opted-in to one of the new features that require following the 903 * lower inode of non-dir upper. 904 */ 905 if (ovl_allow_offline_changes(ofs) && uuid_is_null(uuid)) 906 return false; 907 908 for (i = 0; i < ofs->numfs; i++) { 909 /* 910 * We use uuid to associate an overlay lower file handle with a 911 * lower layer, so we can accept lower fs with null uuid as long 912 * as all lower layers with null uuid are on the same fs. 913 * if we detect multiple lower fs with the same uuid, we 914 * disable lower file handle decoding on all of them. 915 */ 916 if (ofs->fs[i].is_lower && 917 uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) { 918 ofs->fs[i].bad_uuid = true; 919 return false; 920 } 921 } 922 return true; 923} 924 925/* Get a unique fsid for the layer */ 926static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) 927{ 928 struct super_block *sb = path->mnt->mnt_sb; 929 unsigned int i; 930 dev_t dev; 931 int err; 932 bool bad_uuid = false; 933 bool warn = false; 934 935 for (i = 0; i < ofs->numfs; i++) { 936 if (ofs->fs[i].sb == sb) 937 return i; 938 } 939 940 if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) { 941 bad_uuid = true; 942 if (ofs->config.xino == OVL_XINO_AUTO) { 943 ofs->config.xino = OVL_XINO_OFF; 944 warn = true; 945 } 946 if (ofs->config.index || ofs->config.nfs_export) { 947 ofs->config.index = false; 948 ofs->config.nfs_export = false; 949 warn = true; 950 } 951 if (warn) { 952 pr_warn("%s uuid detected in lower fs '%pd2', falling back to xino=%s,index=off,nfs_export=off.\n", 953 uuid_is_null(&sb->s_uuid) ? "null" : 954 "conflicting", 955 path->dentry, ovl_xino_mode(&ofs->config)); 956 } 957 } 958 959 err = get_anon_bdev(&dev); 960 if (err) { 961 pr_err("failed to get anonymous bdev for lowerpath\n"); 962 return err; 963 } 964 965 ofs->fs[ofs->numfs].sb = sb; 966 ofs->fs[ofs->numfs].pseudo_dev = dev; 967 ofs->fs[ofs->numfs].bad_uuid = bad_uuid; 968 969 return ofs->numfs++; 970} 971 972/* 973 * The fsid after the last lower fsid is used for the data layers. 974 * It is a "null fs" with a null sb, null uuid, and no pseudo dev. 975 */ 976static int ovl_get_data_fsid(struct ovl_fs *ofs) 977{ 978 return ofs->numfs; 979} 980 981 982static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs, 983 struct ovl_fs_context *ctx, struct ovl_layer *layers) 984{ 985 int err; 986 unsigned int i; 987 size_t nr_merged_lower; 988 989 ofs->fs = kcalloc(ctx->nr + 2, sizeof(struct ovl_sb), GFP_KERNEL); 990 if (ofs->fs == NULL) 991 return -ENOMEM; 992 993 /* 994 * idx/fsid 0 are reserved for upper fs even with lower only overlay 995 * and the last fsid is reserved for "null fs" of the data layers. 996 */ 997 ofs->numfs++; 998 999 /* 1000 * All lower layers that share the same fs as upper layer, use the same 1001 * pseudo_dev as upper layer. Allocate fs[0].pseudo_dev even for lower 1002 * only overlay to simplify ovl_fs_free(). 1003 * is_lower will be set if upper fs is shared with a lower layer. 1004 */ 1005 err = get_anon_bdev(&ofs->fs[0].pseudo_dev); 1006 if (err) { 1007 pr_err("failed to get anonymous bdev for upper fs\n"); 1008 return err; 1009 } 1010 1011 if (ovl_upper_mnt(ofs)) { 1012 ofs->fs[0].sb = ovl_upper_mnt(ofs)->mnt_sb; 1013 ofs->fs[0].is_lower = false; 1014 } 1015 1016 nr_merged_lower = ctx->nr - ctx->nr_data; 1017 for (i = 0; i < ctx->nr; i++) { 1018 struct ovl_fs_context_layer *l = &ctx->lower[i]; 1019 struct vfsmount *mnt; 1020 struct inode *trap; 1021 int fsid; 1022 1023 if (i < nr_merged_lower) 1024 fsid = ovl_get_fsid(ofs, &l->path); 1025 else 1026 fsid = ovl_get_data_fsid(ofs); 1027 if (fsid < 0) 1028 return fsid; 1029 1030 /* 1031 * Check if lower root conflicts with this overlay layers before 1032 * checking if it is in-use as upperdir/workdir of "another" 1033 * mount, because we do not bother to check in ovl_is_inuse() if 1034 * the upperdir/workdir is in fact in-use by our 1035 * upperdir/workdir. 1036 */ 1037 err = ovl_setup_trap(sb, l->path.dentry, &trap, "lowerdir"); 1038 if (err) 1039 return err; 1040 1041 if (ovl_is_inuse(l->path.dentry)) { 1042 err = ovl_report_in_use(ofs, "lowerdir"); 1043 if (err) { 1044 iput(trap); 1045 return err; 1046 } 1047 } 1048 1049 mnt = clone_private_mount(&l->path); 1050 err = PTR_ERR(mnt); 1051 if (IS_ERR(mnt)) { 1052 pr_err("failed to clone lowerpath\n"); 1053 iput(trap); 1054 return err; 1055 } 1056 1057 /* 1058 * Make lower layers R/O. That way fchmod/fchown on lower file 1059 * will fail instead of modifying lower fs. 1060 */ 1061 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME; 1062 1063 layers[ofs->numlayer].trap = trap; 1064 layers[ofs->numlayer].mnt = mnt; 1065 layers[ofs->numlayer].idx = ofs->numlayer; 1066 layers[ofs->numlayer].fsid = fsid; 1067 layers[ofs->numlayer].fs = &ofs->fs[fsid]; 1068 /* Store for printing lowerdir=... in ovl_show_options() */ 1069 ofs->config.lowerdirs[ofs->numlayer] = l->name; 1070 l->name = NULL; 1071 ofs->numlayer++; 1072 ofs->fs[fsid].is_lower = true; 1073 } 1074 1075 /* 1076 * When all layers on same fs, overlay can use real inode numbers. 1077 * With mount option "xino=<on|auto>", mounter declares that there are 1078 * enough free high bits in underlying fs to hold the unique fsid. 1079 * If overlayfs does encounter underlying inodes using the high xino 1080 * bits reserved for fsid, it emits a warning and uses the original 1081 * inode number or a non persistent inode number allocated from a 1082 * dedicated range. 1083 */ 1084 if (ofs->numfs - !ovl_upper_mnt(ofs) == 1) { 1085 if (ofs->config.xino == OVL_XINO_ON) 1086 pr_info("\"xino=on\" is useless with all layers on same fs, ignore.\n"); 1087 ofs->xino_mode = 0; 1088 } else if (ofs->config.xino == OVL_XINO_OFF) { 1089 ofs->xino_mode = -1; 1090 } else if (ofs->xino_mode < 0) { 1091 /* 1092 * This is a roundup of number of bits needed for encoding 1093 * fsid, where fsid 0 is reserved for upper fs (even with 1094 * lower only overlay) +1 extra bit is reserved for the non 1095 * persistent inode number range that is used for resolving 1096 * xino lower bits overflow. 1097 */ 1098 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 30); 1099 ofs->xino_mode = ilog2(ofs->numfs - 1) + 2; 1100 } 1101 1102 if (ofs->xino_mode > 0) { 1103 pr_info("\"xino\" feature enabled using %d upper inode bits.\n", 1104 ofs->xino_mode); 1105 } 1106 1107 return 0; 1108} 1109 1110static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb, 1111 struct ovl_fs_context *ctx, 1112 struct ovl_fs *ofs, 1113 struct ovl_layer *layers) 1114{ 1115 int err; 1116 unsigned int i; 1117 size_t nr_merged_lower; 1118 struct ovl_entry *oe; 1119 struct ovl_path *lowerstack; 1120 1121 struct ovl_fs_context_layer *l; 1122 1123 if (!ofs->config.upperdir && ctx->nr == 1) { 1124 pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n"); 1125 return ERR_PTR(-EINVAL); 1126 } 1127 1128 err = -EINVAL; 1129 for (i = 0; i < ctx->nr; i++) { 1130 l = &ctx->lower[i]; 1131 1132 err = ovl_lower_dir(l->name, &l->path, ofs, &sb->s_stack_depth); 1133 if (err) 1134 return ERR_PTR(err); 1135 } 1136 1137 err = -EINVAL; 1138 sb->s_stack_depth++; 1139 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) { 1140 pr_err("maximum fs stacking depth exceeded\n"); 1141 return ERR_PTR(err); 1142 } 1143 1144 err = ovl_get_layers(sb, ofs, ctx, layers); 1145 if (err) 1146 return ERR_PTR(err); 1147 1148 err = -ENOMEM; 1149 /* Data-only layers are not merged in root directory */ 1150 nr_merged_lower = ctx->nr - ctx->nr_data; 1151 oe = ovl_alloc_entry(nr_merged_lower); 1152 if (!oe) 1153 return ERR_PTR(err); 1154 1155 lowerstack = ovl_lowerstack(oe); 1156 for (i = 0; i < nr_merged_lower; i++) { 1157 l = &ctx->lower[i]; 1158 lowerstack[i].dentry = dget(l->path.dentry); 1159 lowerstack[i].layer = &ofs->layers[i + 1]; 1160 } 1161 ofs->numdatalayer = ctx->nr_data; 1162 1163 return oe; 1164} 1165 1166/* 1167 * Check if this layer root is a descendant of: 1168 * - another layer of this overlayfs instance 1169 * - upper/work dir of any overlayfs instance 1170 */ 1171static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs, 1172 struct dentry *dentry, const char *name, 1173 bool is_lower) 1174{ 1175 struct dentry *next = dentry, *parent; 1176 int err = 0; 1177 1178 if (!dentry) 1179 return 0; 1180 1181 parent = dget_parent(next); 1182 1183 /* Walk back ancestors to root (inclusive) looking for traps */ 1184 while (!err && parent != next) { 1185 if (is_lower && ovl_lookup_trap_inode(sb, parent)) { 1186 err = -ELOOP; 1187 pr_err("overlapping %s path\n", name); 1188 } else if (ovl_is_inuse(parent)) { 1189 err = ovl_report_in_use(ofs, name); 1190 } 1191 next = parent; 1192 parent = dget_parent(next); 1193 dput(next); 1194 } 1195 1196 dput(parent); 1197 1198 return err; 1199} 1200 1201/* 1202 * Check if any of the layers or work dirs overlap. 1203 */ 1204static int ovl_check_overlapping_layers(struct super_block *sb, 1205 struct ovl_fs *ofs) 1206{ 1207 int i, err; 1208 1209 if (ovl_upper_mnt(ofs)) { 1210 err = ovl_check_layer(sb, ofs, ovl_upper_mnt(ofs)->mnt_root, 1211 "upperdir", false); 1212 if (err) 1213 return err; 1214 1215 /* 1216 * Checking workbasedir avoids hitting ovl_is_inuse(parent) of 1217 * this instance and covers overlapping work and index dirs, 1218 * unless work or index dir have been moved since created inside 1219 * workbasedir. In that case, we already have their traps in 1220 * inode cache and we will catch that case on lookup. 1221 */ 1222 err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir", 1223 false); 1224 if (err) 1225 return err; 1226 } 1227 1228 for (i = 1; i < ofs->numlayer; i++) { 1229 err = ovl_check_layer(sb, ofs, 1230 ofs->layers[i].mnt->mnt_root, 1231 "lowerdir", true); 1232 if (err) 1233 return err; 1234 } 1235 1236 return 0; 1237} 1238 1239static struct dentry *ovl_get_root(struct super_block *sb, 1240 struct dentry *upperdentry, 1241 struct ovl_entry *oe) 1242{ 1243 struct dentry *root; 1244 struct ovl_fs *ofs = OVL_FS(sb); 1245 struct ovl_path *lowerpath = ovl_lowerstack(oe); 1246 unsigned long ino = d_inode(lowerpath->dentry)->i_ino; 1247 int fsid = lowerpath->layer->fsid; 1248 struct ovl_inode_params oip = { 1249 .upperdentry = upperdentry, 1250 .oe = oe, 1251 }; 1252 1253 root = d_make_root(ovl_new_inode(sb, S_IFDIR, 0)); 1254 if (!root) 1255 return NULL; 1256 1257 if (upperdentry) { 1258 /* Root inode uses upper st_ino/i_ino */ 1259 ino = d_inode(upperdentry)->i_ino; 1260 fsid = 0; 1261 ovl_dentry_set_upper_alias(root); 1262 if (ovl_is_impuredir(sb, upperdentry)) 1263 ovl_set_flag(OVL_IMPURE, d_inode(root)); 1264 } 1265 1266 /* Look for xwhiteouts marker except in the lowermost layer */ 1267 for (int i = 0; i < ovl_numlower(oe) - 1; i++, lowerpath++) { 1268 struct path path = { 1269 .mnt = lowerpath->layer->mnt, 1270 .dentry = lowerpath->dentry, 1271 }; 1272 1273 /* overlay.opaque=x means xwhiteouts directory */ 1274 if (ovl_get_opaquedir_val(ofs, &path) == 'x') { 1275 ovl_layer_set_xwhiteouts(ofs, lowerpath->layer); 1276 ovl_dentry_set_xwhiteouts(root); 1277 } 1278 } 1279 1280 /* Root is always merge -> can have whiteouts */ 1281 ovl_set_flag(OVL_WHITEOUTS, d_inode(root)); 1282 ovl_dentry_set_flag(OVL_E_CONNECTED, root); 1283 ovl_set_upperdata(d_inode(root)); 1284 ovl_inode_init(d_inode(root), &oip, ino, fsid); 1285 ovl_dentry_init_flags(root, upperdentry, oe, DCACHE_OP_WEAK_REVALIDATE); 1286 /* root keeps a reference of upperdentry */ 1287 dget(upperdentry); 1288 1289 return root; 1290} 1291 1292int ovl_fill_super(struct super_block *sb, struct fs_context *fc) 1293{ 1294 struct ovl_fs *ofs = sb->s_fs_info; 1295 struct ovl_fs_context *ctx = fc->fs_private; 1296 struct dentry *root_dentry; 1297 struct ovl_entry *oe; 1298 struct ovl_layer *layers; 1299 struct cred *cred; 1300 int err; 1301 1302 err = -EIO; 1303 if (WARN_ON(fc->user_ns != current_user_ns())) 1304 goto out_err; 1305 1306 sb->s_d_op = &ovl_dentry_operations; 1307 1308 err = -ENOMEM; 1309 ofs->creator_cred = cred = prepare_creds(); 1310 if (!cred) 1311 goto out_err; 1312 1313 err = ovl_fs_params_verify(ctx, &ofs->config); 1314 if (err) 1315 goto out_err; 1316 1317 err = -EINVAL; 1318 if (ctx->nr == 0) { 1319 if (!(fc->sb_flags & SB_SILENT)) 1320 pr_err("missing 'lowerdir'\n"); 1321 goto out_err; 1322 } 1323 1324 err = -ENOMEM; 1325 layers = kcalloc(ctx->nr + 1, sizeof(struct ovl_layer), GFP_KERNEL); 1326 if (!layers) 1327 goto out_err; 1328 1329 ofs->config.lowerdirs = kcalloc(ctx->nr + 1, sizeof(char *), GFP_KERNEL); 1330 if (!ofs->config.lowerdirs) { 1331 kfree(layers); 1332 goto out_err; 1333 } 1334 ofs->layers = layers; 1335 /* 1336 * Layer 0 is reserved for upper even if there's no upper. 1337 * config.lowerdirs[0] is used for storing the user provided colon 1338 * separated lowerdir string. 1339 */ 1340 ofs->config.lowerdirs[0] = ctx->lowerdir_all; 1341 ctx->lowerdir_all = NULL; 1342 ofs->numlayer = 1; 1343 1344 sb->s_stack_depth = 0; 1345 sb->s_maxbytes = MAX_LFS_FILESIZE; 1346 atomic_long_set(&ofs->last_ino, 1); 1347 /* Assume underlying fs uses 32bit inodes unless proven otherwise */ 1348 if (ofs->config.xino != OVL_XINO_OFF) { 1349 ofs->xino_mode = BITS_PER_LONG - 32; 1350 if (!ofs->xino_mode) { 1351 pr_warn("xino not supported on 32bit kernel, falling back to xino=off.\n"); 1352 ofs->config.xino = OVL_XINO_OFF; 1353 } 1354 } 1355 1356 /* alloc/destroy_inode needed for setting up traps in inode cache */ 1357 sb->s_op = &ovl_super_operations; 1358 1359 if (ofs->config.upperdir) { 1360 struct super_block *upper_sb; 1361 1362 err = -EINVAL; 1363 if (!ofs->config.workdir) { 1364 pr_err("missing 'workdir'\n"); 1365 goto out_err; 1366 } 1367 1368 err = ovl_get_upper(sb, ofs, &layers[0], &ctx->upper); 1369 if (err) 1370 goto out_err; 1371 1372 upper_sb = ovl_upper_mnt(ofs)->mnt_sb; 1373 if (!ovl_should_sync(ofs)) { 1374 ofs->errseq = errseq_sample(&upper_sb->s_wb_err); 1375 if (errseq_check(&upper_sb->s_wb_err, ofs->errseq)) { 1376 err = -EIO; 1377 pr_err("Cannot mount volatile when upperdir has an unseen error. Sync upperdir fs to clear state.\n"); 1378 goto out_err; 1379 } 1380 } 1381 1382 err = ovl_get_workdir(sb, ofs, &ctx->upper, &ctx->work); 1383 if (err) 1384 goto out_err; 1385 1386 if (!ofs->workdir) 1387 sb->s_flags |= SB_RDONLY; 1388 1389 sb->s_stack_depth = upper_sb->s_stack_depth; 1390 sb->s_time_gran = upper_sb->s_time_gran; 1391 } 1392 oe = ovl_get_lowerstack(sb, ctx, ofs, layers); 1393 err = PTR_ERR(oe); 1394 if (IS_ERR(oe)) 1395 goto out_err; 1396 1397 /* If the upper fs is nonexistent, we mark overlayfs r/o too */ 1398 if (!ovl_upper_mnt(ofs)) 1399 sb->s_flags |= SB_RDONLY; 1400 1401 if (!ovl_origin_uuid(ofs) && ofs->numfs > 1) { 1402 pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=null.\n"); 1403 ofs->config.uuid = OVL_UUID_NULL; 1404 } else if (ovl_has_fsid(ofs) && ovl_upper_mnt(ofs)) { 1405 /* Use per instance persistent uuid/fsid */ 1406 ovl_init_uuid_xattr(sb, ofs, &ctx->upper); 1407 } 1408 1409 if (!ovl_force_readonly(ofs) && ofs->config.index) { 1410 err = ovl_get_indexdir(sb, ofs, oe, &ctx->upper); 1411 if (err) 1412 goto out_free_oe; 1413 1414 /* Force r/o mount with no index dir */ 1415 if (!ofs->workdir) 1416 sb->s_flags |= SB_RDONLY; 1417 } 1418 1419 err = ovl_check_overlapping_layers(sb, ofs); 1420 if (err) 1421 goto out_free_oe; 1422 1423 /* Show index=off in /proc/mounts for forced r/o mount */ 1424 if (!ofs->workdir) { 1425 ofs->config.index = false; 1426 if (ovl_upper_mnt(ofs) && ofs->config.nfs_export) { 1427 pr_warn("NFS export requires an index dir, falling back to nfs_export=off.\n"); 1428 ofs->config.nfs_export = false; 1429 } 1430 } 1431 1432 if (ofs->config.metacopy && ofs->config.nfs_export) { 1433 pr_warn("NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n"); 1434 ofs->config.nfs_export = false; 1435 } 1436 1437 /* 1438 * Support encoding decodable file handles with nfs_export=on 1439 * and encoding non-decodable file handles with nfs_export=off 1440 * if all layers support file handles. 1441 */ 1442 if (ofs->config.nfs_export) 1443 sb->s_export_op = &ovl_export_operations; 1444 else if (!ofs->nofh) 1445 sb->s_export_op = &ovl_export_fid_operations; 1446 1447 /* Never override disk quota limits or use reserved space */ 1448 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE); 1449 1450 sb->s_magic = OVERLAYFS_SUPER_MAGIC; 1451 sb->s_xattr = ovl_xattr_handlers(ofs); 1452 sb->s_fs_info = ofs; 1453#ifdef CONFIG_FS_POSIX_ACL 1454 sb->s_flags |= SB_POSIXACL; 1455#endif 1456 sb->s_iflags |= SB_I_SKIP_SYNC; 1457 /* 1458 * Ensure that umask handling is done by the filesystems used 1459 * for the the upper layer instead of overlayfs as that would 1460 * lead to unexpected results. 1461 */ 1462 sb->s_iflags |= SB_I_NOUMASK; 1463 sb->s_iflags |= SB_I_EVM_UNSUPPORTED; 1464 1465 err = -ENOMEM; 1466 root_dentry = ovl_get_root(sb, ctx->upper.dentry, oe); 1467 if (!root_dentry) 1468 goto out_free_oe; 1469 1470 sb->s_root = root_dentry; 1471 1472 return 0; 1473 1474out_free_oe: 1475 ovl_free_entry(oe); 1476out_err: 1477 ovl_free_fs(ofs); 1478 sb->s_fs_info = NULL; 1479 return err; 1480} 1481 1482struct file_system_type ovl_fs_type = { 1483 .owner = THIS_MODULE, 1484 .name = "overlay", 1485 .init_fs_context = ovl_init_fs_context, 1486 .parameters = ovl_parameter_spec, 1487 .fs_flags = FS_USERNS_MOUNT, 1488 .kill_sb = kill_anon_super, 1489}; 1490MODULE_ALIAS_FS("overlay"); 1491 1492static void ovl_inode_init_once(void *foo) 1493{ 1494 struct ovl_inode *oi = foo; 1495 1496 inode_init_once(&oi->vfs_inode); 1497} 1498 1499static int __init ovl_init(void) 1500{ 1501 int err; 1502 1503 ovl_inode_cachep = kmem_cache_create("ovl_inode", 1504 sizeof(struct ovl_inode), 0, 1505 (SLAB_RECLAIM_ACCOUNT| 1506 SLAB_ACCOUNT), 1507 ovl_inode_init_once); 1508 if (ovl_inode_cachep == NULL) 1509 return -ENOMEM; 1510 1511 err = register_filesystem(&ovl_fs_type); 1512 if (!err) 1513 return 0; 1514 1515 kmem_cache_destroy(ovl_inode_cachep); 1516 1517 return err; 1518} 1519 1520static void __exit ovl_exit(void) 1521{ 1522 unregister_filesystem(&ovl_fs_type); 1523 1524 /* 1525 * Make sure all delayed rcu free inodes are flushed before we 1526 * destroy cache. 1527 */ 1528 rcu_barrier(); 1529 kmem_cache_destroy(ovl_inode_cachep); 1530} 1531 1532module_init(ovl_init); 1533module_exit(ovl_exit); 1534