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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
19static 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 */
77static 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 */
105static 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 */
183static 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
214static int ovl_dentry_to_fid(struct dentry *dentry, u32 *fid, int buflen)
215{
216 struct ovl_fh *fh = NULL;
217 int err, enc_lower;
218 int len;
219
220 /*
221 * Check if we should encode a lower or upper file handle and maybe
222 * copy up an ancestor to make lower file handle connectable.
223 */
224 err = enc_lower = ovl_check_encode_origin(dentry);
225 if (enc_lower < 0)
226 goto fail;
227
228 /* Encode an upper or lower file handle */
229 fh = ovl_encode_real_fh(enc_lower ? ovl_dentry_lower(dentry) :
230 ovl_dentry_upper(dentry), !enc_lower);
231 if (IS_ERR(fh))
232 return PTR_ERR(fh);
233
234 len = OVL_FH_LEN(fh);
235 if (len <= buflen)
236 memcpy(fid, fh, len);
237 err = len;
238
239out:
240 kfree(fh);
241 return err;
242
243fail:
244 pr_warn_ratelimited("failed to encode file handle (%pd2, err=%i)\n",
245 dentry, err);
246 goto out;
247}
248
249static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len,
250 struct inode *parent)
251{
252 struct dentry *dentry;
253 int bytes, buflen = *max_len << 2;
254
255 /* TODO: encode connectable file handles */
256 if (parent)
257 return FILEID_INVALID;
258
259 dentry = d_find_any_alias(inode);
260 if (WARN_ON(!dentry))
261 return FILEID_INVALID;
262
263 bytes = ovl_dentry_to_fid(dentry, fid, buflen);
264 dput(dentry);
265 if (bytes <= 0)
266 return FILEID_INVALID;
267
268 *max_len = bytes >> 2;
269 if (bytes > buflen)
270 return FILEID_INVALID;
271
272 return OVL_FILEID_V1;
273}
274
275/*
276 * Find or instantiate an overlay dentry from real dentries and index.
277 */
278static struct dentry *ovl_obtain_alias(struct super_block *sb,
279 struct dentry *upper_alias,
280 struct ovl_path *lowerpath,
281 struct dentry *index)
282{
283 struct dentry *lower = lowerpath ? lowerpath->dentry : NULL;
284 struct dentry *upper = upper_alias ?: index;
285 struct dentry *dentry;
286 struct inode *inode;
287 struct ovl_entry *oe;
288 struct ovl_inode_params oip = {
289 .lowerpath = lowerpath,
290 .index = index,
291 .numlower = !!lower
292 };
293
294 /* We get overlay directory dentries with ovl_lookup_real() */
295 if (d_is_dir(upper ?: lower))
296 return ERR_PTR(-EIO);
297
298 oip.upperdentry = dget(upper);
299 inode = ovl_get_inode(sb, &oip);
300 if (IS_ERR(inode)) {
301 dput(upper);
302 return ERR_CAST(inode);
303 }
304
305 if (upper)
306 ovl_set_flag(OVL_UPPERDATA, inode);
307
308 dentry = d_find_any_alias(inode);
309 if (dentry)
310 goto out_iput;
311
312 dentry = d_alloc_anon(inode->i_sb);
313 if (unlikely(!dentry))
314 goto nomem;
315 oe = ovl_alloc_entry(lower ? 1 : 0);
316 if (!oe)
317 goto nomem;
318
319 if (lower) {
320 oe->lowerstack->dentry = dget(lower);
321 oe->lowerstack->layer = lowerpath->layer;
322 }
323 dentry->d_fsdata = oe;
324 if (upper_alias)
325 ovl_dentry_set_upper_alias(dentry);
326
327 ovl_dentry_update_reval(dentry, upper,
328 DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
329
330 return d_instantiate_anon(dentry, inode);
331
332nomem:
333 dput(dentry);
334 dentry = ERR_PTR(-ENOMEM);
335out_iput:
336 iput(inode);
337 return dentry;
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 const 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.name, connected, name.name.len);
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("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 const 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 const struct ovl_layer *layer)
429{
430 struct ovl_fs *ofs = sb->s_fs_info;
431 struct dentry *index = NULL;
432 struct dentry *this = NULL;
433 struct inode *inode;
434
435 /*
436 * Decoding upper dir from index is expensive, so first try to lookup
437 * overlay dentry in inode/dcache.
438 */
439 inode = ovl_lookup_inode(sb, real, !layer->idx);
440 if (IS_ERR(inode))
441 return ERR_CAST(inode);
442 if (inode) {
443 this = d_find_any_alias(inode);
444 iput(inode);
445 }
446
447 /*
448 * For decoded lower dir file handle, lookup index by origin to check
449 * if lower dir was copied up and and/or removed.
450 */
451 if (!this && layer->idx && ofs->indexdir && !WARN_ON(!d_is_dir(real))) {
452 index = ovl_lookup_index(ofs, NULL, real, false);
453 if (IS_ERR(index))
454 return index;
455 }
456
457 /* Get connected upper overlay dir from index */
458 if (index) {
459 struct dentry *upper = ovl_index_upper(ofs, index);
460
461 dput(index);
462 if (IS_ERR_OR_NULL(upper))
463 return upper;
464
465 /*
466 * ovl_lookup_real() in lower layer may call recursively once to
467 * ovl_lookup_real() in upper layer. The first level call walks
468 * back lower parents to the topmost indexed parent. The second
469 * recursive call walks back from indexed upper to the topmost
470 * connected/hashed upper parent (or up to root).
471 */
472 this = ovl_lookup_real(sb, upper, &ofs->layers[0]);
473 dput(upper);
474 }
475
476 if (IS_ERR_OR_NULL(this))
477 return this;
478
479 if (ovl_dentry_real_at(this, layer->idx) != real) {
480 dput(this);
481 this = ERR_PTR(-EIO);
482 }
483
484 return this;
485}
486
487/*
488 * Lookup an indexed or hashed overlay dentry, whose real dentry is an
489 * ancestor of @real.
490 */
491static struct dentry *ovl_lookup_real_ancestor(struct super_block *sb,
492 struct dentry *real,
493 const struct ovl_layer *layer)
494{
495 struct dentry *next, *parent = NULL;
496 struct dentry *ancestor = ERR_PTR(-EIO);
497
498 if (real == layer->mnt->mnt_root)
499 return dget(sb->s_root);
500
501 /* Find the topmost indexed or hashed ancestor */
502 next = dget(real);
503 for (;;) {
504 parent = dget_parent(next);
505
506 /*
507 * Lookup a matching overlay dentry in inode/dentry
508 * cache or in index by real inode.
509 */
510 ancestor = ovl_lookup_real_inode(sb, next, layer);
511 if (ancestor)
512 break;
513
514 if (parent == layer->mnt->mnt_root) {
515 ancestor = dget(sb->s_root);
516 break;
517 }
518
519 /*
520 * If @real has been moved out of the layer root directory,
521 * we will eventully hit the real fs root. This cannot happen
522 * by legit overlay rename, so we return error in that case.
523 */
524 if (parent == next) {
525 ancestor = ERR_PTR(-EXDEV);
526 break;
527 }
528
529 dput(next);
530 next = parent;
531 }
532
533 dput(parent);
534 dput(next);
535
536 return ancestor;
537}
538
539/*
540 * Lookup a connected overlay dentry whose real dentry is @real.
541 * If @real is on upper layer, we lookup a child overlay dentry with the same
542 * path the real dentry. Otherwise, we need to consult index for lookup.
543 */
544static struct dentry *ovl_lookup_real(struct super_block *sb,
545 struct dentry *real,
546 const struct ovl_layer *layer)
547{
548 struct dentry *connected;
549 int err = 0;
550
551 connected = ovl_lookup_real_ancestor(sb, real, layer);
552 if (IS_ERR(connected))
553 return connected;
554
555 while (!err) {
556 struct dentry *next, *this;
557 struct dentry *parent = NULL;
558 struct dentry *real_connected = ovl_dentry_real_at(connected,
559 layer->idx);
560
561 if (real_connected == real)
562 break;
563
564 /* Find the topmost dentry not yet connected */
565 next = dget(real);
566 for (;;) {
567 parent = dget_parent(next);
568
569 if (parent == real_connected)
570 break;
571
572 /*
573 * If real has been moved out of 'real_connected',
574 * we will not find 'real_connected' and hit the layer
575 * root. In that case, we need to restart connecting.
576 * This game can go on forever in the worst case. We
577 * may want to consider taking s_vfs_rename_mutex if
578 * this happens more than once.
579 */
580 if (parent == layer->mnt->mnt_root) {
581 dput(connected);
582 connected = dget(sb->s_root);
583 break;
584 }
585
586 /*
587 * If real file has been moved out of the layer root
588 * directory, we will eventully hit the real fs root.
589 * This cannot happen by legit overlay rename, so we
590 * return error in that case.
591 */
592 if (parent == next) {
593 err = -EXDEV;
594 break;
595 }
596
597 dput(next);
598 next = parent;
599 }
600
601 if (!err) {
602 this = ovl_lookup_real_one(connected, next, layer);
603 if (IS_ERR(this))
604 err = PTR_ERR(this);
605
606 /*
607 * Lookup of child in overlay can fail when racing with
608 * overlay rename of child away from 'connected' parent.
609 * In this case, we need to restart the lookup from the
610 * top, because we cannot trust that 'real_connected' is
611 * still an ancestor of 'real'. There is a good chance
612 * that the renamed overlay ancestor is now in cache, so
613 * ovl_lookup_real_ancestor() will find it and we can
614 * continue to connect exactly from where lookup failed.
615 */
616 if (err == -ECHILD) {
617 this = ovl_lookup_real_ancestor(sb, real,
618 layer);
619 err = PTR_ERR_OR_ZERO(this);
620 }
621 if (!err) {
622 dput(connected);
623 connected = this;
624 }
625 }
626
627 dput(parent);
628 dput(next);
629 }
630
631 if (err)
632 goto fail;
633
634 return connected;
635
636fail:
637 pr_warn_ratelimited("failed to lookup by real (%pd2, layer=%d, connected=%pd2, err=%i)\n",
638 real, layer->idx, connected, err);
639 dput(connected);
640 return ERR_PTR(err);
641}
642
643/*
644 * Get an overlay dentry from upper/lower real dentries and index.
645 */
646static struct dentry *ovl_get_dentry(struct super_block *sb,
647 struct dentry *upper,
648 struct ovl_path *lowerpath,
649 struct dentry *index)
650{
651 struct ovl_fs *ofs = sb->s_fs_info;
652 const struct ovl_layer *layer = upper ? &ofs->layers[0] : lowerpath->layer;
653 struct dentry *real = upper ?: (index ?: lowerpath->dentry);
654
655 /*
656 * Obtain a disconnected overlay dentry from a non-dir real dentry
657 * and index.
658 */
659 if (!d_is_dir(real))
660 return ovl_obtain_alias(sb, upper, lowerpath, index);
661
662 /* Removed empty directory? */
663 if ((real->d_flags & DCACHE_DISCONNECTED) || d_unhashed(real))
664 return ERR_PTR(-ENOENT);
665
666 /*
667 * If real dentry is connected and hashed, get a connected overlay
668 * dentry whose real dentry is @real.
669 */
670 return ovl_lookup_real(sb, real, layer);
671}
672
673static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
674 struct ovl_fh *fh)
675{
676 struct ovl_fs *ofs = sb->s_fs_info;
677 struct dentry *dentry;
678 struct dentry *upper;
679
680 if (!ovl_upper_mnt(ofs))
681 return ERR_PTR(-EACCES);
682
683 upper = ovl_decode_real_fh(fh, ovl_upper_mnt(ofs), true);
684 if (IS_ERR_OR_NULL(upper))
685 return upper;
686
687 dentry = ovl_get_dentry(sb, upper, NULL, NULL);
688 dput(upper);
689
690 return dentry;
691}
692
693static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
694 struct ovl_fh *fh)
695{
696 struct ovl_fs *ofs = sb->s_fs_info;
697 struct ovl_path origin = { };
698 struct ovl_path *stack = &origin;
699 struct dentry *dentry = NULL;
700 struct dentry *index = NULL;
701 struct inode *inode;
702 int err;
703
704 /* First lookup overlay inode in inode cache by origin fh */
705 err = ovl_check_origin_fh(ofs, fh, false, NULL, &stack);
706 if (err)
707 return ERR_PTR(err);
708
709 if (!d_is_dir(origin.dentry) ||
710 !(origin.dentry->d_flags & DCACHE_DISCONNECTED)) {
711 inode = ovl_lookup_inode(sb, origin.dentry, false);
712 err = PTR_ERR(inode);
713 if (IS_ERR(inode))
714 goto out_err;
715 if (inode) {
716 dentry = d_find_any_alias(inode);
717 iput(inode);
718 if (dentry)
719 goto out;
720 }
721 }
722
723 /* Then lookup indexed upper/whiteout by origin fh */
724 if (ofs->indexdir) {
725 index = ovl_get_index_fh(ofs, fh);
726 err = PTR_ERR(index);
727 if (IS_ERR(index)) {
728 index = NULL;
729 goto out_err;
730 }
731 }
732
733 /* Then try to get a connected upper dir by index */
734 if (index && d_is_dir(index)) {
735 struct dentry *upper = ovl_index_upper(ofs, index);
736
737 err = PTR_ERR(upper);
738 if (IS_ERR_OR_NULL(upper))
739 goto out_err;
740
741 dentry = ovl_get_dentry(sb, upper, NULL, NULL);
742 dput(upper);
743 goto out;
744 }
745
746 /* Find origin.dentry again with ovl_acceptable() layer check */
747 if (d_is_dir(origin.dentry)) {
748 dput(origin.dentry);
749 origin.dentry = NULL;
750 err = ovl_check_origin_fh(ofs, fh, true, NULL, &stack);
751 if (err)
752 goto out_err;
753 }
754 if (index) {
755 err = ovl_verify_origin(index, origin.dentry, false);
756 if (err)
757 goto out_err;
758 }
759
760 /* Get a connected non-upper dir or disconnected non-dir */
761 dentry = ovl_get_dentry(sb, NULL, &origin, index);
762
763out:
764 dput(origin.dentry);
765 dput(index);
766 return dentry;
767
768out_err:
769 dentry = ERR_PTR(err);
770 goto out;
771}
772
773static struct ovl_fh *ovl_fid_to_fh(struct fid *fid, int buflen, int fh_type)
774{
775 struct ovl_fh *fh;
776
777 /* If on-wire inner fid is aligned - nothing to do */
778 if (fh_type == OVL_FILEID_V1)
779 return (struct ovl_fh *)fid;
780
781 if (fh_type != OVL_FILEID_V0)
782 return ERR_PTR(-EINVAL);
783
784 if (buflen <= OVL_FH_WIRE_OFFSET)
785 return ERR_PTR(-EINVAL);
786
787 fh = kzalloc(buflen, GFP_KERNEL);
788 if (!fh)
789 return ERR_PTR(-ENOMEM);
790
791 /* Copy unaligned inner fh into aligned buffer */
792 memcpy(&fh->fb, fid, buflen - OVL_FH_WIRE_OFFSET);
793 return fh;
794}
795
796static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid,
797 int fh_len, int fh_type)
798{
799 struct dentry *dentry = NULL;
800 struct ovl_fh *fh = NULL;
801 int len = fh_len << 2;
802 unsigned int flags = 0;
803 int err;
804
805 fh = ovl_fid_to_fh(fid, len, fh_type);
806 err = PTR_ERR(fh);
807 if (IS_ERR(fh))
808 goto out_err;
809
810 err = ovl_check_fh_len(fh, len);
811 if (err)
812 goto out_err;
813
814 flags = fh->fb.flags;
815 dentry = (flags & OVL_FH_FLAG_PATH_UPPER) ?
816 ovl_upper_fh_to_d(sb, fh) :
817 ovl_lower_fh_to_d(sb, fh);
818 err = PTR_ERR(dentry);
819 if (IS_ERR(dentry) && err != -ESTALE)
820 goto out_err;
821
822out:
823 /* We may have needed to re-align OVL_FILEID_V0 */
824 if (!IS_ERR_OR_NULL(fh) && fh != (void *)fid)
825 kfree(fh);
826
827 return dentry;
828
829out_err:
830 pr_warn_ratelimited("failed to decode file handle (len=%d, type=%d, flags=%x, err=%i)\n",
831 fh_len, fh_type, flags, err);
832 dentry = ERR_PTR(err);
833 goto out;
834}
835
836static struct dentry *ovl_fh_to_parent(struct super_block *sb, struct fid *fid,
837 int fh_len, int fh_type)
838{
839 pr_warn_ratelimited("connectable file handles not supported; use 'no_subtree_check' exportfs option.\n");
840 return ERR_PTR(-EACCES);
841}
842
843static int ovl_get_name(struct dentry *parent, char *name,
844 struct dentry *child)
845{
846 /*
847 * ovl_fh_to_dentry() returns connected dir overlay dentries and
848 * ovl_fh_to_parent() is not implemented, so we should not get here.
849 */
850 WARN_ON_ONCE(1);
851 return -EIO;
852}
853
854static struct dentry *ovl_get_parent(struct dentry *dentry)
855{
856 /*
857 * ovl_fh_to_dentry() returns connected dir overlay dentries, so we
858 * should not get here.
859 */
860 WARN_ON_ONCE(1);
861 return ERR_PTR(-EIO);
862}
863
864const struct export_operations ovl_export_operations = {
865 .encode_fh = ovl_encode_fh,
866 .fh_to_dentry = ovl_fh_to_dentry,
867 .fh_to_parent = ovl_fh_to_parent,
868 .get_name = ovl_get_name,
869 .get_parent = ovl_get_parent,
870};