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