1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Overlayfs NFS export support. 4 * 5 * Amir Goldstein <amir73il@gmail.com> 6 * 7 * Copyright (C) 2017-2018 CTERA Networks. All Rights Reserved. 8 */ 9 10 #include <linux/fs.h> 11 #include <linux/cred.h> 12 #include <linux/mount.h> 13 #include <linux/namei.h> 14 #include <linux/xattr.h> 15 #include <linux/exportfs.h> 16 #include <linux/ratelimit.h> 17 #include "overlayfs.h" 18 19 static int ovl_encode_maybe_copy_up(struct dentry *dentry) 20 { 21 int err; 22 23 if (ovl_dentry_upper(dentry)) 24 return 0; 25 26 err = ovl_want_write(dentry); 27 if (!err) { 28 err = ovl_copy_up(dentry); 29 ovl_drop_write(dentry); 30 } 31 32 if (err) { 33 pr_warn_ratelimited("failed to copy up on encode (%pd2, err=%i)\n", 34 dentry, err); 35 } 36 37 return err; 38 } 39 40 /* 41 * Before encoding a non-upper directory file handle from real layer N, we need 42 * to check if it will be possible to reconnect an overlay dentry from the real 43 * lower decoded dentry. This is done by following the overlay ancestry up to a 44 * "layer N connected" ancestor and verifying that all parents along the way are 45 * "layer N connectable". If an ancestor that is NOT "layer N connectable" is 46 * found, we need to copy up an ancestor, which is "layer N connectable", thus 47 * making that ancestor "layer N connected". For example: 48 * 49 * layer 1: /a 50 * layer 2: /a/b/c 51 * 52 * The overlay dentry /a is NOT "layer 2 connectable", because if dir /a is 53 * copied up and renamed, upper dir /a will be indexed by lower dir /a from 54 * layer 1. The dir /a from layer 2 will never be indexed, so the algorithm (*) 55 * in ovl_lookup_real_ancestor() will not be able to lookup a connected overlay 56 * dentry from the connected lower dentry /a/b/c. 57 * 58 * To avoid this problem on decode time, we need to copy up an ancestor of 59 * /a/b/c, which is "layer 2 connectable", on encode time. That ancestor is 60 * /a/b. After copy up (and index) of /a/b, it will become "layer 2 connected" 61 * and when the time comes to decode the file handle from lower dentry /a/b/c, 62 * ovl_lookup_real_ancestor() will find the indexed ancestor /a/b and decoding 63 * a connected overlay dentry will be accomplished. 64 * 65 * (*) the algorithm in ovl_lookup_real_ancestor() can be improved to lookup an 66 * entry /a in the lower layers above layer N and find the indexed dir /a from 67 * layer 1. If that improvement is made, then the check for "layer N connected" 68 * will need to verify there are no redirects in lower layers above N. In the 69 * example above, /a will be "layer 2 connectable". However, if layer 2 dir /a 70 * is a target of a layer 1 redirect, then /a will NOT be "layer 2 connectable": 71 * 72 * layer 1: /A (redirect = /a) 73 * layer 2: /a/b/c 74 */ 75 76 /* Return the lowest layer for encoding a connectable file handle */ 77 static int ovl_connectable_layer(struct dentry *dentry) 78 { 79 struct ovl_entry *oe = OVL_E(dentry); 80 81 /* We can get overlay root from root of any layer */ 82 if (dentry == dentry->d_sb->s_root) 83 return oe->numlower; 84 85 /* 86 * If it's an unindexed merge dir, then it's not connectable with any 87 * lower layer 88 */ 89 if (ovl_dentry_upper(dentry) && 90 !ovl_test_flag(OVL_INDEX, d_inode(dentry))) 91 return 0; 92 93 /* We can get upper/overlay path from indexed/lower dentry */ 94 return oe->lowerstack[0].layer->idx; 95 } 96 97 /* 98 * @dentry is "connected" if all ancestors up to root or a "connected" ancestor 99 * have the same uppermost lower layer as the origin's layer. We may need to 100 * copy up a "connectable" ancestor to make it "connected". A "connected" dentry 101 * cannot become non "connected", so cache positive result in dentry flags. 102 * 103 * Return the connected origin layer or < 0 on error. 104 */ 105 static int ovl_connect_layer(struct dentry *dentry) 106 { 107 struct dentry *next, *parent = NULL; 108 int origin_layer; 109 int err = 0; 110 111 if (WARN_ON(dentry == dentry->d_sb->s_root) || 112 WARN_ON(!ovl_dentry_lower(dentry))) 113 return -EIO; 114 115 origin_layer = OVL_E(dentry)->lowerstack[0].layer->idx; 116 if (ovl_dentry_test_flag(OVL_E_CONNECTED, dentry)) 117 return origin_layer; 118 119 /* Find the topmost origin layer connectable ancestor of @dentry */ 120 next = dget(dentry); 121 for (;;) { 122 parent = dget_parent(next); 123 if (WARN_ON(parent == next)) { 124 err = -EIO; 125 break; 126 } 127 128 /* 129 * If @parent is not origin layer connectable, then copy up 130 * @next which is origin layer connectable and we are done. 131 */ 132 if (ovl_connectable_layer(parent) < origin_layer) { 133 err = ovl_encode_maybe_copy_up(next); 134 break; 135 } 136 137 /* If @parent is connected or indexed we are done */ 138 if (ovl_dentry_test_flag(OVL_E_CONNECTED, parent) || 139 ovl_test_flag(OVL_INDEX, d_inode(parent))) 140 break; 141 142 dput(next); 143 next = parent; 144 } 145 146 dput(parent); 147 dput(next); 148 149 if (!err) 150 ovl_dentry_set_flag(OVL_E_CONNECTED, dentry); 151 152 return err ?: origin_layer; 153 } 154 155 /* 156 * We only need to encode origin if there is a chance that the same object was 157 * encoded pre copy up and then we need to stay consistent with the same 158 * encoding also after copy up. If non-pure upper is not indexed, then it was 159 * copied up before NFS export was enabled. In that case we don't need to worry 160 * about staying consistent with pre copy up encoding and we encode an upper 161 * file handle. Overlay root dentry is a private case of non-indexed upper. 162 * 163 * The following table summarizes the different file handle encodings used for 164 * different overlay object types: 165 * 166 * Object type | Encoding 167 * -------------------------------- 168 * Pure upper | U 169 * Non-indexed upper | U 170 * Indexed upper | L (*) 171 * Non-upper | L (*) 172 * 173 * U = upper file handle 174 * L = lower file handle 175 * 176 * (*) Connecting an overlay dir from real lower dentry is not always 177 * possible when there are redirects in lower layers and non-indexed merge dirs. 178 * To mitigate those case, we may copy up the lower dir ancestor before encode 179 * a lower dir file handle. 180 * 181 * Return 0 for upper file handle, > 0 for lower file handle or < 0 on error. 182 */ 183 static int ovl_check_encode_origin(struct dentry *dentry) 184 { 185 struct ovl_fs *ofs = dentry->d_sb->s_fs_info; 186 187 /* Upper file handle for pure upper */ 188 if (!ovl_dentry_lower(dentry)) 189 return 0; 190 191 /* 192 * Upper file handle for non-indexed upper. 193 * 194 * Root is never indexed, so if there's an upper layer, encode upper for 195 * root. 196 */ 197 if (ovl_dentry_upper(dentry) && 198 !ovl_test_flag(OVL_INDEX, d_inode(dentry))) 199 return 0; 200 201 /* 202 * Decoding a merge dir, whose origin's ancestor is under a redirected 203 * lower dir or under a non-indexed upper is not always possible. 204 * ovl_connect_layer() will try to make origin's layer "connected" by 205 * copying up a "connectable" ancestor. 206 */ 207 if (d_is_dir(dentry) && ovl_upper_mnt(ofs)) 208 return ovl_connect_layer(dentry); 209 210 /* Lower file handle for indexed and non-upper dir/non-dir */ 211 return 1; 212 } 213 214 static int ovl_dentry_to_fid(struct ovl_fs *ofs, struct dentry *dentry, 215 u32 *fid, int buflen) 216 { 217 struct ovl_fh *fh = NULL; 218 int err, enc_lower; 219 int len; 220 221 /* 222 * Check if we should encode a lower or upper file handle and maybe 223 * copy up an ancestor to make lower file handle connectable. 224 */ 225 err = enc_lower = ovl_check_encode_origin(dentry); 226 if (enc_lower < 0) 227 goto fail; 228 229 /* Encode an upper or lower file handle */ 230 fh = ovl_encode_real_fh(ofs, enc_lower ? ovl_dentry_lower(dentry) : 231 ovl_dentry_upper(dentry), !enc_lower); 232 if (IS_ERR(fh)) 233 return PTR_ERR(fh); 234 235 len = OVL_FH_LEN(fh); 236 if (len <= buflen) 237 memcpy(fid, fh, len); 238 err = len; 239 240 out: 241 kfree(fh); 242 return err; 243 244 fail: 245 pr_warn_ratelimited("failed to encode file handle (%pd2, err=%i)\n", 246 dentry, err); 247 goto out; 248 } 249 250 static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len, 251 struct inode *parent) 252 { 253 struct ovl_fs *ofs = OVL_FS(inode->i_sb); 254 struct dentry *dentry; 255 int bytes, buflen = *max_len << 2; 256 257 /* TODO: encode connectable file handles */ 258 if (parent) 259 return FILEID_INVALID; 260 261 dentry = d_find_any_alias(inode); 262 if (!dentry) 263 return FILEID_INVALID; 264 265 bytes = ovl_dentry_to_fid(ofs, dentry, fid, buflen); 266 dput(dentry); 267 if (bytes <= 0) 268 return FILEID_INVALID; 269 270 *max_len = bytes >> 2; 271 if (bytes > buflen) 272 return FILEID_INVALID; 273 274 return OVL_FILEID_V1; 275 } 276 277 /* 278 * Find or instantiate an overlay dentry from real dentries and index. 279 */ 280 static struct dentry *ovl_obtain_alias(struct super_block *sb, 281 struct dentry *upper_alias, 282 struct ovl_path *lowerpath, 283 struct dentry *index) 284 { 285 struct dentry *lower = lowerpath ? lowerpath->dentry : NULL; 286 struct dentry *upper = upper_alias ?: index; 287 struct dentry *dentry; 288 struct inode *inode; 289 struct ovl_entry *oe; 290 struct ovl_inode_params oip = { 291 .lowerpath = lowerpath, 292 .index = index, 293 .numlower = !!lower 294 }; 295 296 /* We get overlay directory dentries with ovl_lookup_real() */ 297 if (d_is_dir(upper ?: lower)) 298 return ERR_PTR(-EIO); 299 300 oip.upperdentry = dget(upper); 301 inode = ovl_get_inode(sb, &oip); 302 if (IS_ERR(inode)) { 303 dput(upper); 304 return ERR_CAST(inode); 305 } 306 307 if (upper) 308 ovl_set_flag(OVL_UPPERDATA, inode); 309 310 dentry = d_find_any_alias(inode); 311 if (dentry) 312 goto out_iput; 313 314 dentry = d_alloc_anon(inode->i_sb); 315 if (unlikely(!dentry)) 316 goto nomem; 317 oe = ovl_alloc_entry(lower ? 1 : 0); 318 if (!oe) 319 goto nomem; 320 321 if (lower) { 322 oe->lowerstack->dentry = dget(lower); 323 oe->lowerstack->layer = lowerpath->layer; 324 } 325 dentry->d_fsdata = oe; 326 if (upper_alias) 327 ovl_dentry_set_upper_alias(dentry); 328 329 ovl_dentry_init_reval(dentry, upper); 330 331 return d_instantiate_anon(dentry, inode); 332 333 nomem: 334 dput(dentry); 335 dentry = ERR_PTR(-ENOMEM); 336 out_iput: 337 iput(inode); 338 return dentry; 339 } 340 341 /* Get the upper or lower dentry in stack whose on layer @idx */ 342 static struct dentry *ovl_dentry_real_at(struct dentry *dentry, int idx) 343 { 344 struct ovl_entry *oe = OVL_E(dentry); 345 int i; 346 347 if (!idx) 348 return ovl_dentry_upper(dentry); 349 350 for (i = 0; i < oe->numlower; i++) { 351 if (oe->lowerstack[i].layer->idx == idx) 352 return oe->lowerstack[i].dentry; 353 } 354 355 return NULL; 356 } 357 358 /* 359 * Lookup a child overlay dentry to get a connected overlay dentry whose real 360 * dentry is @real. If @real is on upper layer, we lookup a child overlay 361 * dentry with the same name as the real dentry. Otherwise, we need to consult 362 * index for lookup. 363 */ 364 static struct dentry *ovl_lookup_real_one(struct dentry *connected, 365 struct dentry *real, 366 const struct ovl_layer *layer) 367 { 368 struct inode *dir = d_inode(connected); 369 struct dentry *this, *parent = NULL; 370 struct name_snapshot name; 371 int err; 372 373 /* 374 * Lookup child overlay dentry by real name. The dir mutex protects us 375 * from racing with overlay rename. If the overlay dentry that is above 376 * real has already been moved to a parent that is not under the 377 * connected overlay dir, we return -ECHILD and restart the lookup of 378 * connected real path from the top. 379 */ 380 inode_lock_nested(dir, I_MUTEX_PARENT); 381 err = -ECHILD; 382 parent = dget_parent(real); 383 if (ovl_dentry_real_at(connected, layer->idx) != parent) 384 goto fail; 385 386 /* 387 * We also need to take a snapshot of real dentry name to protect us 388 * from racing with underlying layer rename. In this case, we don't 389 * care about returning ESTALE, only from dereferencing a free name 390 * pointer because we hold no lock on the real dentry. 391 */ 392 take_dentry_name_snapshot(&name, real); 393 /* 394 * No idmap handling here: it's an internal lookup. Could skip 395 * permission checking altogether, but for now just use non-idmap 396 * transformed ids. 397 */ 398 this = lookup_one_len(name.name.name, connected, name.name.len); 399 release_dentry_name_snapshot(&name); 400 err = PTR_ERR(this); 401 if (IS_ERR(this)) { 402 goto fail; 403 } else if (!this || !this->d_inode) { 404 dput(this); 405 err = -ENOENT; 406 goto fail; 407 } else if (ovl_dentry_real_at(this, layer->idx) != real) { 408 dput(this); 409 err = -ESTALE; 410 goto fail; 411 } 412 413 out: 414 dput(parent); 415 inode_unlock(dir); 416 return this; 417 418 fail: 419 pr_warn_ratelimited("failed to lookup one by real (%pd2, layer=%d, connected=%pd2, err=%i)\n", 420 real, layer->idx, connected, err); 421 this = ERR_PTR(err); 422 goto out; 423 } 424 425 static struct dentry *ovl_lookup_real(struct super_block *sb, 426 struct dentry *real, 427 const struct ovl_layer *layer); 428 429 /* 430 * Lookup an indexed or hashed overlay dentry by real inode. 431 */ 432 static struct dentry *ovl_lookup_real_inode(struct super_block *sb, 433 struct dentry *real, 434 const struct ovl_layer *layer) 435 { 436 struct ovl_fs *ofs = sb->s_fs_info; 437 struct dentry *index = NULL; 438 struct dentry *this = NULL; 439 struct inode *inode; 440 441 /* 442 * Decoding upper dir from index is expensive, so first try to lookup 443 * overlay dentry in inode/dcache. 444 */ 445 inode = ovl_lookup_inode(sb, real, !layer->idx); 446 if (IS_ERR(inode)) 447 return ERR_CAST(inode); 448 if (inode) { 449 this = d_find_any_alias(inode); 450 iput(inode); 451 } 452 453 /* 454 * For decoded lower dir file handle, lookup index by origin to check 455 * if lower dir was copied up and and/or removed. 456 */ 457 if (!this && layer->idx && ofs->indexdir && !WARN_ON(!d_is_dir(real))) { 458 index = ovl_lookup_index(ofs, NULL, real, false); 459 if (IS_ERR(index)) 460 return index; 461 } 462 463 /* Get connected upper overlay dir from index */ 464 if (index) { 465 struct dentry *upper = ovl_index_upper(ofs, index, true); 466 467 dput(index); 468 if (IS_ERR_OR_NULL(upper)) 469 return upper; 470 471 /* 472 * ovl_lookup_real() in lower layer may call recursively once to 473 * ovl_lookup_real() in upper layer. The first level call walks 474 * back lower parents to the topmost indexed parent. The second 475 * recursive call walks back from indexed upper to the topmost 476 * connected/hashed upper parent (or up to root). 477 */ 478 this = ovl_lookup_real(sb, upper, &ofs->layers[0]); 479 dput(upper); 480 } 481 482 if (IS_ERR_OR_NULL(this)) 483 return this; 484 485 if (ovl_dentry_real_at(this, layer->idx) != real) { 486 dput(this); 487 this = ERR_PTR(-EIO); 488 } 489 490 return this; 491 } 492 493 /* 494 * Lookup an indexed or hashed overlay dentry, whose real dentry is an 495 * ancestor of @real. 496 */ 497 static struct dentry *ovl_lookup_real_ancestor(struct super_block *sb, 498 struct dentry *real, 499 const struct ovl_layer *layer) 500 { 501 struct dentry *next, *parent = NULL; 502 struct dentry *ancestor = ERR_PTR(-EIO); 503 504 if (real == layer->mnt->mnt_root) 505 return dget(sb->s_root); 506 507 /* Find the topmost indexed or hashed ancestor */ 508 next = dget(real); 509 for (;;) { 510 parent = dget_parent(next); 511 512 /* 513 * Lookup a matching overlay dentry in inode/dentry 514 * cache or in index by real inode. 515 */ 516 ancestor = ovl_lookup_real_inode(sb, next, layer); 517 if (ancestor) 518 break; 519 520 if (parent == layer->mnt->mnt_root) { 521 ancestor = dget(sb->s_root); 522 break; 523 } 524 525 /* 526 * If @real has been moved out of the layer root directory, 527 * we will eventully hit the real fs root. This cannot happen 528 * by legit overlay rename, so we return error in that case. 529 */ 530 if (parent == next) { 531 ancestor = ERR_PTR(-EXDEV); 532 break; 533 } 534 535 dput(next); 536 next = parent; 537 } 538 539 dput(parent); 540 dput(next); 541 542 return ancestor; 543 } 544 545 /* 546 * Lookup a connected overlay dentry whose real dentry is @real. 547 * If @real is on upper layer, we lookup a child overlay dentry with the same 548 * path the real dentry. Otherwise, we need to consult index for lookup. 549 */ 550 static struct dentry *ovl_lookup_real(struct super_block *sb, 551 struct dentry *real, 552 const struct ovl_layer *layer) 553 { 554 struct dentry *connected; 555 int err = 0; 556 557 connected = ovl_lookup_real_ancestor(sb, real, layer); 558 if (IS_ERR(connected)) 559 return connected; 560 561 while (!err) { 562 struct dentry *next, *this; 563 struct dentry *parent = NULL; 564 struct dentry *real_connected = ovl_dentry_real_at(connected, 565 layer->idx); 566 567 if (real_connected == real) 568 break; 569 570 /* Find the topmost dentry not yet connected */ 571 next = dget(real); 572 for (;;) { 573 parent = dget_parent(next); 574 575 if (parent == real_connected) 576 break; 577 578 /* 579 * If real has been moved out of 'real_connected', 580 * we will not find 'real_connected' and hit the layer 581 * root. In that case, we need to restart connecting. 582 * This game can go on forever in the worst case. We 583 * may want to consider taking s_vfs_rename_mutex if 584 * this happens more than once. 585 */ 586 if (parent == layer->mnt->mnt_root) { 587 dput(connected); 588 connected = dget(sb->s_root); 589 break; 590 } 591 592 /* 593 * If real file has been moved out of the layer root 594 * directory, we will eventully hit the real fs root. 595 * This cannot happen by legit overlay rename, so we 596 * return error in that case. 597 */ 598 if (parent == next) { 599 err = -EXDEV; 600 break; 601 } 602 603 dput(next); 604 next = parent; 605 } 606 607 if (!err) { 608 this = ovl_lookup_real_one(connected, next, layer); 609 if (IS_ERR(this)) 610 err = PTR_ERR(this); 611 612 /* 613 * Lookup of child in overlay can fail when racing with 614 * overlay rename of child away from 'connected' parent. 615 * In this case, we need to restart the lookup from the 616 * top, because we cannot trust that 'real_connected' is 617 * still an ancestor of 'real'. There is a good chance 618 * that the renamed overlay ancestor is now in cache, so 619 * ovl_lookup_real_ancestor() will find it and we can 620 * continue to connect exactly from where lookup failed. 621 */ 622 if (err == -ECHILD) { 623 this = ovl_lookup_real_ancestor(sb, real, 624 layer); 625 err = PTR_ERR_OR_ZERO(this); 626 } 627 if (!err) { 628 dput(connected); 629 connected = this; 630 } 631 } 632 633 dput(parent); 634 dput(next); 635 } 636 637 if (err) 638 goto fail; 639 640 return connected; 641 642 fail: 643 pr_warn_ratelimited("failed to lookup by real (%pd2, layer=%d, connected=%pd2, err=%i)\n", 644 real, layer->idx, connected, err); 645 dput(connected); 646 return ERR_PTR(err); 647 } 648 649 /* 650 * Get an overlay dentry from upper/lower real dentries and index. 651 */ 652 static struct dentry *ovl_get_dentry(struct super_block *sb, 653 struct dentry *upper, 654 struct ovl_path *lowerpath, 655 struct dentry *index) 656 { 657 struct ovl_fs *ofs = sb->s_fs_info; 658 const struct ovl_layer *layer = upper ? &ofs->layers[0] : lowerpath->layer; 659 struct dentry *real = upper ?: (index ?: lowerpath->dentry); 660 661 /* 662 * Obtain a disconnected overlay dentry from a non-dir real dentry 663 * and index. 664 */ 665 if (!d_is_dir(real)) 666 return ovl_obtain_alias(sb, upper, lowerpath, index); 667 668 /* Removed empty directory? */ 669 if ((real->d_flags & DCACHE_DISCONNECTED) || d_unhashed(real)) 670 return ERR_PTR(-ENOENT); 671 672 /* 673 * If real dentry is connected and hashed, get a connected overlay 674 * dentry whose real dentry is @real. 675 */ 676 return ovl_lookup_real(sb, real, layer); 677 } 678 679 static struct dentry *ovl_upper_fh_to_d(struct super_block *sb, 680 struct ovl_fh *fh) 681 { 682 struct ovl_fs *ofs = sb->s_fs_info; 683 struct dentry *dentry; 684 struct dentry *upper; 685 686 if (!ovl_upper_mnt(ofs)) 687 return ERR_PTR(-EACCES); 688 689 upper = ovl_decode_real_fh(ofs, fh, ovl_upper_mnt(ofs), true); 690 if (IS_ERR_OR_NULL(upper)) 691 return upper; 692 693 dentry = ovl_get_dentry(sb, upper, NULL, NULL); 694 dput(upper); 695 696 return dentry; 697 } 698 699 static struct dentry *ovl_lower_fh_to_d(struct super_block *sb, 700 struct ovl_fh *fh) 701 { 702 struct ovl_fs *ofs = sb->s_fs_info; 703 struct ovl_path origin = { }; 704 struct ovl_path *stack = &origin; 705 struct dentry *dentry = NULL; 706 struct dentry *index = NULL; 707 struct inode *inode; 708 int err; 709 710 /* First lookup overlay inode in inode cache by origin fh */ 711 err = ovl_check_origin_fh(ofs, fh, false, NULL, &stack); 712 if (err) 713 return ERR_PTR(err); 714 715 if (!d_is_dir(origin.dentry) || 716 !(origin.dentry->d_flags & DCACHE_DISCONNECTED)) { 717 inode = ovl_lookup_inode(sb, origin.dentry, false); 718 err = PTR_ERR(inode); 719 if (IS_ERR(inode)) 720 goto out_err; 721 if (inode) { 722 dentry = d_find_any_alias(inode); 723 iput(inode); 724 if (dentry) 725 goto out; 726 } 727 } 728 729 /* Then lookup indexed upper/whiteout by origin fh */ 730 if (ofs->indexdir) { 731 index = ovl_get_index_fh(ofs, fh); 732 err = PTR_ERR(index); 733 if (IS_ERR(index)) { 734 index = NULL; 735 goto out_err; 736 } 737 } 738 739 /* Then try to get a connected upper dir by index */ 740 if (index && d_is_dir(index)) { 741 struct dentry *upper = ovl_index_upper(ofs, index, true); 742 743 err = PTR_ERR(upper); 744 if (IS_ERR_OR_NULL(upper)) 745 goto out_err; 746 747 dentry = ovl_get_dentry(sb, upper, NULL, NULL); 748 dput(upper); 749 goto out; 750 } 751 752 /* Find origin.dentry again with ovl_acceptable() layer check */ 753 if (d_is_dir(origin.dentry)) { 754 dput(origin.dentry); 755 origin.dentry = NULL; 756 err = ovl_check_origin_fh(ofs, fh, true, NULL, &stack); 757 if (err) 758 goto out_err; 759 } 760 if (index) { 761 err = ovl_verify_origin(ofs, index, origin.dentry, false); 762 if (err) 763 goto out_err; 764 } 765 766 /* Get a connected non-upper dir or disconnected non-dir */ 767 dentry = ovl_get_dentry(sb, NULL, &origin, index); 768 769 out: 770 dput(origin.dentry); 771 dput(index); 772 return dentry; 773 774 out_err: 775 dentry = ERR_PTR(err); 776 goto out; 777 } 778 779 static struct ovl_fh *ovl_fid_to_fh(struct fid *fid, int buflen, int fh_type) 780 { 781 struct ovl_fh *fh; 782 783 /* If on-wire inner fid is aligned - nothing to do */ 784 if (fh_type == OVL_FILEID_V1) 785 return (struct ovl_fh *)fid; 786 787 if (fh_type != OVL_FILEID_V0) 788 return ERR_PTR(-EINVAL); 789 790 if (buflen <= OVL_FH_WIRE_OFFSET) 791 return ERR_PTR(-EINVAL); 792 793 fh = kzalloc(buflen, GFP_KERNEL); 794 if (!fh) 795 return ERR_PTR(-ENOMEM); 796 797 /* Copy unaligned inner fh into aligned buffer */ 798 memcpy(fh->buf, fid, buflen - OVL_FH_WIRE_OFFSET); 799 return fh; 800 } 801 802 static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid, 803 int fh_len, int fh_type) 804 { 805 struct dentry *dentry = NULL; 806 struct ovl_fh *fh = NULL; 807 int len = fh_len << 2; 808 unsigned int flags = 0; 809 int err; 810 811 fh = ovl_fid_to_fh(fid, len, fh_type); 812 err = PTR_ERR(fh); 813 if (IS_ERR(fh)) 814 goto out_err; 815 816 err = ovl_check_fh_len(fh, len); 817 if (err) 818 goto out_err; 819 820 flags = fh->fb.flags; 821 dentry = (flags & OVL_FH_FLAG_PATH_UPPER) ? 822 ovl_upper_fh_to_d(sb, fh) : 823 ovl_lower_fh_to_d(sb, fh); 824 err = PTR_ERR(dentry); 825 if (IS_ERR(dentry) && err != -ESTALE) 826 goto out_err; 827 828 out: 829 /* We may have needed to re-align OVL_FILEID_V0 */ 830 if (!IS_ERR_OR_NULL(fh) && fh != (void *)fid) 831 kfree(fh); 832 833 return dentry; 834 835 out_err: 836 pr_warn_ratelimited("failed to decode file handle (len=%d, type=%d, flags=%x, err=%i)\n", 837 fh_len, fh_type, flags, err); 838 dentry = ERR_PTR(err); 839 goto out; 840 } 841 842 static struct dentry *ovl_fh_to_parent(struct super_block *sb, struct fid *fid, 843 int fh_len, int fh_type) 844 { 845 pr_warn_ratelimited("connectable file handles not supported; use 'no_subtree_check' exportfs option.\n"); 846 return ERR_PTR(-EACCES); 847 } 848 849 static int ovl_get_name(struct dentry *parent, char *name, 850 struct dentry *child) 851 { 852 /* 853 * ovl_fh_to_dentry() returns connected dir overlay dentries and 854 * ovl_fh_to_parent() is not implemented, so we should not get here. 855 */ 856 WARN_ON_ONCE(1); 857 return -EIO; 858 } 859 860 static struct dentry *ovl_get_parent(struct dentry *dentry) 861 { 862 /* 863 * ovl_fh_to_dentry() returns connected dir overlay dentries, so we 864 * should not get here. 865 */ 866 WARN_ON_ONCE(1); 867 return ERR_PTR(-EIO); 868 } 869 870 const struct export_operations ovl_export_operations = { 871 .encode_fh = ovl_encode_fh, 872 .fh_to_dentry = ovl_fh_to_dentry, 873 .fh_to_parent = ovl_fh_to_parent, 874 .get_name = ovl_get_name, 875 .get_parent = ovl_get_parent, 876 }; 877