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