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("overlayfs: 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) && ofs->upper_mnt)
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_d_to_fh(struct dentry *dentry, char *buf, int buflen)
215 {
216 struct ovl_fh *fh = NULL;
217 int err, enc_lower;
218
219 /*
220 * Check if we should encode a lower or upper file handle and maybe
221 * copy up an ancestor to make lower file handle connectable.
222 */
223 err = enc_lower = ovl_check_encode_origin(dentry);
224 if (enc_lower < 0)
225 goto fail;
226
227 /* Encode an upper or lower file handle */
228 fh = ovl_encode_real_fh(enc_lower ? ovl_dentry_lower(dentry) :
229 ovl_dentry_upper(dentry), !enc_lower);
230 if (IS_ERR(fh))
231 return PTR_ERR(fh);
232
233 err = -EOVERFLOW;
234 if (fh->len > buflen)
235 goto fail;
236
237 memcpy(buf, (char *)fh, fh->len);
238 err = fh->len;
239
240 out:
241 kfree(fh);
242 return err;
243
244 fail:
245 pr_warn_ratelimited("overlayfs: failed to encode file handle (%pd2, err=%i, buflen=%d, len=%d, type=%d)\n",
246 dentry, err, buflen, fh ? (int)fh->len : 0,
247 fh ? fh->type : 0);
248 goto out;
249 }
250
251 static int ovl_dentry_to_fh(struct dentry *dentry, u32 *fid, int *max_len)
252 {
253 int res, len = *max_len << 2;
254
255 res = ovl_d_to_fh(dentry, (char *)fid, len);
256 if (res <= 0)
257 return FILEID_INVALID;
258
259 len = res;
260
261 /* Round up to dwords */
262 *max_len = (len + 3) >> 2;
263 return OVL_FILEID;
264 }
265
266 static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len,
267 struct inode *parent)
268 {
269 struct dentry *dentry;
270 int type;
271
272 /* TODO: encode connectable file handles */
273 if (parent)
274 return FILEID_INVALID;
275
276 dentry = d_find_any_alias(inode);
277 if (WARN_ON(!dentry))
278 return FILEID_INVALID;
279
280 type = ovl_dentry_to_fh(dentry, fid, max_len);
281
282 dput(dentry);
283 return type;
284 }
285
286 /*
287 * Find or instantiate an overlay dentry from real dentries and index.
288 */
289 static struct dentry *ovl_obtain_alias(struct super_block *sb,
290 struct dentry *upper_alias,
291 struct ovl_path *lowerpath,
292 struct dentry *index)
293 {
294 struct dentry *lower = lowerpath ? lowerpath->dentry : NULL;
295 struct dentry *upper = upper_alias ?: index;
296 struct dentry *dentry;
297 struct inode *inode;
298 struct ovl_entry *oe;
299 struct ovl_inode_params oip = {
300 .lowerpath = lowerpath,
301 .index = index,
302 .numlower = !!lower
303 };
304
305 /* We get overlay directory dentries with ovl_lookup_real() */
306 if (d_is_dir(upper ?: lower))
307 return ERR_PTR(-EIO);
308
309 oip.upperdentry = dget(upper);
310 inode = ovl_get_inode(sb, &oip);
311 if (IS_ERR(inode)) {
312 dput(upper);
313 return ERR_CAST(inode);
314 }
315
316 if (upper)
317 ovl_set_flag(OVL_UPPERDATA, inode);
318
319 dentry = d_find_any_alias(inode);
320 if (!dentry) {
321 dentry = d_alloc_anon(inode->i_sb);
322 if (!dentry)
323 goto nomem;
324 oe = ovl_alloc_entry(lower ? 1 : 0);
325 if (!oe)
326 goto nomem;
327
328 if (lower) {
329 oe->lowerstack->dentry = dget(lower);
330 oe->lowerstack->layer = lowerpath->layer;
331 }
332 dentry->d_fsdata = oe;
333 if (upper_alias)
334 ovl_dentry_set_upper_alias(dentry);
335 }
336
337 return d_instantiate_anon(dentry, inode);
338
339 nomem:
340 iput(inode);
341 dput(dentry);
342 return ERR_PTR(-ENOMEM);
343 }
344
345 /* Get the upper or lower dentry in stach whose on layer @idx */
346 static struct dentry *ovl_dentry_real_at(struct dentry *dentry, int idx)
347 {
348 struct ovl_entry *oe = dentry->d_fsdata;
349 int i;
350
351 if (!idx)
352 return ovl_dentry_upper(dentry);
353
354 for (i = 0; i < oe->numlower; i++) {
355 if (oe->lowerstack[i].layer->idx == idx)
356 return oe->lowerstack[i].dentry;
357 }
358
359 return NULL;
360 }
361
362 /*
363 * Lookup a child overlay dentry to get a connected overlay dentry whose real
364 * dentry is @real. If @real is on upper layer, we lookup a child overlay
365 * dentry with the same name as the real dentry. Otherwise, we need to consult
366 * index for lookup.
367 */
368 static struct dentry *ovl_lookup_real_one(struct dentry *connected,
369 struct dentry *real,
370 struct ovl_layer *layer)
371 {
372 struct inode *dir = d_inode(connected);
373 struct dentry *this, *parent = NULL;
374 struct name_snapshot name;
375 int err;
376
377 /*
378 * Lookup child overlay dentry by real name. The dir mutex protects us
379 * from racing with overlay rename. If the overlay dentry that is above
380 * real has already been moved to a parent that is not under the
381 * connected overlay dir, we return -ECHILD and restart the lookup of
382 * connected real path from the top.
383 */
384 inode_lock_nested(dir, I_MUTEX_PARENT);
385 err = -ECHILD;
386 parent = dget_parent(real);
387 if (ovl_dentry_real_at(connected, layer->idx) != parent)
388 goto fail;
389
390 /*
391 * We also need to take a snapshot of real dentry name to protect us
392 * from racing with underlying layer rename. In this case, we don't
393 * care about returning ESTALE, only from dereferencing a free name
394 * pointer because we hold no lock on the real dentry.
395 */
396 take_dentry_name_snapshot(&name, real);
397 this = lookup_one_len(name.name.name, connected, name.name.len);
398 err = PTR_ERR(this);
399 if (IS_ERR(this)) {
400 goto fail;
401 } else if (!this || !this->d_inode) {
402 dput(this);
403 err = -ENOENT;
404 goto fail;
405 } else if (ovl_dentry_real_at(this, layer->idx) != real) {
406 dput(this);
407 err = -ESTALE;
408 goto fail;
409 }
410
411 out:
412 release_dentry_name_snapshot(&name);
413 dput(parent);
414 inode_unlock(dir);
415 return this;
416
417 fail:
418 pr_warn_ratelimited("overlayfs: failed to lookup one by real (%pd2, layer=%d, connected=%pd2, err=%i)\n",
419 real, layer->idx, connected, err);
420 this = ERR_PTR(err);
421 goto out;
422 }
423
424 static struct dentry *ovl_lookup_real(struct super_block *sb,
425 struct dentry *real,
426 struct ovl_layer *layer);
427
428 /*
429 * Lookup an indexed or hashed overlay dentry by real inode.
430 */
431 static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
432 struct dentry *real,
433 struct ovl_layer *layer)
434 {
435 struct ovl_fs *ofs = sb->s_fs_info;
436 struct ovl_layer upper_layer = { .mnt = ofs->upper_mnt };
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);
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, &upper_layer);
479 dput(upper);
480 }
481
482 if (IS_ERR_OR_NULL(this))
483 return this;
484
485 if (WARN_ON(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 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 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("overlayfs: 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 struct ovl_layer upper_layer = { .mnt = ofs->upper_mnt };
659 struct ovl_layer *layer = upper ? &upper_layer : lowerpath->layer;
660 struct dentry *real = upper ?: (index ?: lowerpath->dentry);
661
662 /*
663 * Obtain a disconnected overlay dentry from a non-dir real dentry
664 * and index.
665 */
666 if (!d_is_dir(real))
667 return ovl_obtain_alias(sb, upper, lowerpath, index);
668
669 /* Removed empty directory? */
670 if ((real->d_flags & DCACHE_DISCONNECTED) || d_unhashed(real))
671 return ERR_PTR(-ENOENT);
672
673 /*
674 * If real dentry is connected and hashed, get a connected overlay
675 * dentry whose real dentry is @real.
676 */
677 return ovl_lookup_real(sb, real, layer);
678 }
679
680 static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
681 struct ovl_fh *fh)
682 {
683 struct ovl_fs *ofs = sb->s_fs_info;
684 struct dentry *dentry;
685 struct dentry *upper;
686
687 if (!ofs->upper_mnt)
688 return ERR_PTR(-EACCES);
689
690 upper = ovl_decode_real_fh(fh, ofs->upper_mnt, true);
691 if (IS_ERR_OR_NULL(upper))
692 return upper;
693
694 dentry = ovl_get_dentry(sb, upper, NULL, NULL);
695 dput(upper);
696
697 return dentry;
698 }
699
700 static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
701 struct ovl_fh *fh)
702 {
703 struct ovl_fs *ofs = sb->s_fs_info;
704 struct ovl_path origin = { };
705 struct ovl_path *stack = &origin;
706 struct dentry *dentry = NULL;
707 struct dentry *index = NULL;
708 struct inode *inode;
709 int err;
710
711 /* First lookup overlay inode in inode cache by origin fh */
712 err = ovl_check_origin_fh(ofs, fh, false, NULL, &stack);
713 if (err)
714 return ERR_PTR(err);
715
716 if (!d_is_dir(origin.dentry) ||
717 !(origin.dentry->d_flags & DCACHE_DISCONNECTED)) {
718 inode = ovl_lookup_inode(sb, origin.dentry, false);
719 err = PTR_ERR(inode);
720 if (IS_ERR(inode))
721 goto out_err;
722 if (inode) {
723 dentry = d_find_any_alias(inode);
724 iput(inode);
725 if (dentry)
726 goto out;
727 }
728 }
729
730 /* Then lookup indexed upper/whiteout by origin fh */
731 if (ofs->indexdir) {
732 index = ovl_get_index_fh(ofs, fh);
733 err = PTR_ERR(index);
734 if (IS_ERR(index)) {
735 index = NULL;
736 goto out_err;
737 }
738 }
739
740 /* Then try to get a connected upper dir by index */
741 if (index && d_is_dir(index)) {
742 struct dentry *upper = ovl_index_upper(ofs, index);
743
744 err = PTR_ERR(upper);
745 if (IS_ERR_OR_NULL(upper))
746 goto out_err;
747
748 dentry = ovl_get_dentry(sb, upper, NULL, NULL);
749 dput(upper);
750 goto out;
751 }
752
753 /* Find origin.dentry again with ovl_acceptable() layer check */
754 if (d_is_dir(origin.dentry)) {
755 dput(origin.dentry);
756 origin.dentry = NULL;
757 err = ovl_check_origin_fh(ofs, fh, true, NULL, &stack);
758 if (err)
759 goto out_err;
760 }
761 if (index) {
762 err = ovl_verify_origin(index, origin.dentry, false);
763 if (err)
764 goto out_err;
765 }
766
767 /* Get a connected non-upper dir or disconnected non-dir */
768 dentry = ovl_get_dentry(sb, NULL, &origin, index);
769
770 out:
771 dput(origin.dentry);
772 dput(index);
773 return dentry;
774
775 out_err:
776 dentry = ERR_PTR(err);
777 goto out;
778 }
779
780 static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid,
781 int fh_len, int fh_type)
782 {
783 struct dentry *dentry = NULL;
784 struct ovl_fh *fh = (struct ovl_fh *) fid;
785 int len = fh_len << 2;
786 unsigned int flags = 0;
787 int err;
788
789 err = -EINVAL;
790 if (fh_type != OVL_FILEID)
791 goto out_err;
792
793 err = ovl_check_fh_len(fh, len);
794 if (err)
795 goto out_err;
796
797 flags = fh->flags;
798 dentry = (flags & OVL_FH_FLAG_PATH_UPPER) ?
799 ovl_upper_fh_to_d(sb, fh) :
800 ovl_lower_fh_to_d(sb, fh);
801 err = PTR_ERR(dentry);
802 if (IS_ERR(dentry) && err != -ESTALE)
803 goto out_err;
804
805 return dentry;
806
807 out_err:
808 pr_warn_ratelimited("overlayfs: failed to decode file handle (len=%d, type=%d, flags=%x, err=%i)\n",
809 len, fh_type, flags, err);
810 return ERR_PTR(err);
811 }
812
813 static struct dentry *ovl_fh_to_parent(struct super_block *sb, struct fid *fid,
814 int fh_len, int fh_type)
815 {
816 pr_warn_ratelimited("overlayfs: connectable file handles not supported; use 'no_subtree_check' exportfs option.\n");
817 return ERR_PTR(-EACCES);
818 }
819
820 static int ovl_get_name(struct dentry *parent, char *name,
821 struct dentry *child)
822 {
823 /*
824 * ovl_fh_to_dentry() returns connected dir overlay dentries and
825 * ovl_fh_to_parent() is not implemented, so we should not get here.
826 */
827 WARN_ON_ONCE(1);
828 return -EIO;
829 }
830
831 static struct dentry *ovl_get_parent(struct dentry *dentry)
832 {
833 /*
834 * ovl_fh_to_dentry() returns connected dir overlay dentries, so we
835 * should not get here.
836 */
837 WARN_ON_ONCE(1);
838 return ERR_PTR(-EIO);
839 }
840
841 const struct export_operations ovl_export_operations = {
842 .encode_fh = ovl_encode_fh,
843 .fh_to_dentry = ovl_fh_to_dentry,
844 .fh_to_parent = ovl_fh_to_parent,
845 .get_name = ovl_get_name,
846 .get_parent = ovl_get_parent,
847 };