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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Overlayfs NFS export support.
4 *
5 * Amir Goldstein <[email protected]>
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_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 */
72static 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 */
100static 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 */
179static int ovl_check_encode_origin(struct inode *inode)
180{
181 struct ovl_fs *ofs = OVL_FS(inode->i_sb);
182 bool decodable = ofs->config.nfs_export;
183 struct dentry *dentry;
184 int err;
185
186 /* No upper layer? */
187 if (!ovl_upper_mnt(ofs))
188 return 1;
189
190 /* Lower file handle for non-upper non-decodable */
191 if (!ovl_inode_upper(inode) && !decodable)
192 return 1;
193
194 /* Upper file handle for pure upper */
195 if (!ovl_inode_lower(inode))
196 return 0;
197
198 /*
199 * Root is never indexed, so if there's an upper layer, encode upper for
200 * root.
201 */
202 if (inode == d_inode(inode->i_sb->s_root))
203 return 0;
204
205 /*
206 * Upper decodable file handle for non-indexed upper.
207 */
208 if (ovl_inode_upper(inode) && decodable &&
209 !ovl_test_flag(OVL_INDEX, inode))
210 return 0;
211
212 /*
213 * Decoding a merge dir, whose origin's ancestor is under a redirected
214 * lower dir or under a non-indexed upper is not always possible.
215 * ovl_connect_layer() will try to make origin's layer "connected" by
216 * copying up a "connectable" ancestor.
217 */
218 if (!decodable || !S_ISDIR(inode->i_mode))
219 return 1;
220
221 dentry = d_find_any_alias(inode);
222 if (!dentry)
223 return -ENOENT;
224
225 err = ovl_connect_layer(dentry);
226 dput(dentry);
227 if (err < 0)
228 return err;
229
230 /* Lower file handle for indexed and non-upper dir/non-dir */
231 return 1;
232}
233
234static int ovl_dentry_to_fid(struct ovl_fs *ofs, struct inode *inode,
235 u32 *fid, int buflen)
236{
237 struct ovl_fh *fh = NULL;
238 int err, enc_lower;
239 int len;
240
241 /*
242 * Check if we should encode a lower or upper file handle and maybe
243 * copy up an ancestor to make lower file handle connectable.
244 */
245 err = enc_lower = ovl_check_encode_origin(inode);
246 if (enc_lower < 0)
247 goto fail;
248
249 /* Encode an upper or lower file handle */
250 fh = ovl_encode_real_fh(ofs, enc_lower ? ovl_inode_lower(inode) :
251 ovl_inode_upper(inode), !enc_lower);
252 if (IS_ERR(fh))
253 return PTR_ERR(fh);
254
255 len = OVL_FH_LEN(fh);
256 if (len <= buflen)
257 memcpy(fid, fh, len);
258 err = len;
259
260out:
261 kfree(fh);
262 return err;
263
264fail:
265 pr_warn_ratelimited("failed to encode file handle (ino=%llu, err=%i)\n",
266 inode->i_ino, err);
267 goto out;
268}
269
270static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len,
271 struct inode *parent)
272{
273 struct ovl_fs *ofs = OVL_FS(inode->i_sb);
274 int bytes, buflen = *max_len << 2;
275
276 /* TODO: encode connectable file handles */
277 if (parent)
278 return FILEID_INVALID;
279
280 bytes = ovl_dentry_to_fid(ofs, inode, fid, buflen);
281 if (bytes <= 0)
282 return FILEID_INVALID;
283
284 *max_len = bytes >> 2;
285 if (bytes > buflen)
286 return FILEID_INVALID;
287
288 return OVL_FILEID_V1;
289}
290
291/*
292 * Find or instantiate an overlay dentry from real dentries and index.
293 */
294static struct dentry *ovl_obtain_alias(struct super_block *sb,
295 struct dentry *upper_alias,
296 struct ovl_path *lowerpath,
297 struct dentry *index)
298{
299 struct dentry *lower = lowerpath ? lowerpath->dentry : NULL;
300 struct dentry *upper = upper_alias ?: index;
301 struct inode *inode = NULL;
302 struct ovl_entry *oe;
303 struct ovl_inode_params oip = {
304 .index = index,
305 };
306
307 /* We get overlay directory dentries with ovl_lookup_real() */
308 if (d_is_dir(upper ?: lower))
309 return ERR_PTR(-EIO);
310
311 oe = ovl_alloc_entry(!!lower);
312 if (!oe)
313 return ERR_PTR(-ENOMEM);
314
315 oip.upperdentry = dget(upper);
316 if (lower) {
317 ovl_lowerstack(oe)->dentry = dget(lower);
318 ovl_lowerstack(oe)->layer = lowerpath->layer;
319 }
320 oip.oe = oe;
321 inode = ovl_get_inode(sb, &oip);
322 if (IS_ERR(inode)) {
323 ovl_free_entry(oe);
324 dput(upper);
325 return ERR_CAST(inode);
326 }
327
328 if (upper)
329 ovl_set_flag(OVL_UPPERDATA, inode);
330
331 return d_obtain_alias(inode);
332}
333
334/* Get the upper or lower dentry in stack whose on layer @idx */
335static struct dentry *ovl_dentry_real_at(struct dentry *dentry, int idx)
336{
337 struct ovl_entry *oe = OVL_E(dentry);
338 struct ovl_path *lowerstack = ovl_lowerstack(oe);
339 int i;
340
341 if (!idx)
342 return ovl_dentry_upper(dentry);
343
344 for (i = 0; i < ovl_numlower(oe); i++) {
345 if (lowerstack[i].layer->idx == idx)
346 return lowerstack[i].dentry;
347 }
348
349 return NULL;
350}
351
352/**
353 * ovl_lookup_real_one - Lookup a child overlay dentry to get an overlay dentry whose real dentry is given
354 * @connected: parent overlay dentry
355 * @real: given child real dentry
356 * @layer: layer in which @real exists
357 *
358 *
359 * Lookup a child overlay dentry in @connected with the same name as the @real
360 * dentry. Then check that the parent of the result is the real dentry for
361 * @connected, and @real is the real dentry for the result.
362 *
363 * Returns:
364 * %-ECHILD if the parent of @real is no longer the real dentry for @connected.
365 * %-ESTALE if @real is not the real dentry of the found dentry.
366 * Otherwise the found dentry is returned.
367 */
368static struct dentry *ovl_lookup_real_one(struct dentry *connected,
369 struct dentry *real,
370 const struct ovl_layer *layer)
371{
372 struct dentry *this;
373 struct name_snapshot name;
374 int err;
375
376 /*
377 * We need to take a snapshot of real dentry name to protect us
378 * from racing with underlying layer rename. In this case, we don't
379 * care about returning ESTALE, only from dereferencing a free name
380 * pointer because we hold no lock on the real dentry.
381 */
382 take_dentry_name_snapshot(&name, real);
383 this = lookup_noperm_unlocked(&name.name, connected);
384 release_dentry_name_snapshot(&name);
385
386 err = -ECHILD;
387 if (ovl_dentry_real_at(connected, layer->idx) != real->d_parent)
388 goto fail;
389
390 err = PTR_ERR(this);
391 if (IS_ERR(this))
392 goto fail;
393
394 err = -ENOENT;
395 if (!this || !this->d_inode)
396 goto fail;
397
398 err = -ESTALE;
399 if (ovl_dentry_real_at(this, layer->idx) != real)
400 goto fail;
401
402 return this;
403
404fail:
405 pr_warn_ratelimited("failed to lookup one by real (%pd2, layer=%d, connected=%pd2, err=%i)\n",
406 real, layer->idx, connected, err);
407 if (!IS_ERR(this))
408 dput(this);
409 return ERR_PTR(err);
410}
411
412static struct dentry *ovl_lookup_real(struct super_block *sb,
413 struct dentry *real,
414 const struct ovl_layer *layer);
415
416/*
417 * Lookup an indexed or hashed overlay dentry by real inode.
418 */
419static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
420 struct dentry *real,
421 const struct ovl_layer *layer)
422{
423 struct ovl_fs *ofs = OVL_FS(sb);
424 struct dentry *index = NULL;
425 struct dentry *this = NULL;
426 struct inode *inode;
427
428 /*
429 * Decoding upper dir from index is expensive, so first try to lookup
430 * overlay dentry in inode/dcache.
431 */
432 inode = ovl_lookup_inode(sb, real, !layer->idx);
433 if (IS_ERR(inode))
434 return ERR_CAST(inode);
435 if (inode) {
436 this = d_find_any_alias(inode);
437 iput(inode);
438 }
439
440 /*
441 * For decoded lower dir file handle, lookup index by origin to check
442 * if lower dir was copied up and and/or removed.
443 */
444 if (!this && layer->idx && ovl_indexdir(sb) && !WARN_ON(!d_is_dir(real))) {
445 index = ovl_lookup_index(ofs, NULL, real, false);
446 if (IS_ERR(index))
447 return index;
448 }
449
450 /* Get connected upper overlay dir from index */
451 if (index) {
452 struct dentry *upper = ovl_index_upper(ofs, index, true);
453
454 dput(index);
455 if (IS_ERR_OR_NULL(upper))
456 return upper;
457
458 /*
459 * ovl_lookup_real() in lower layer may call recursively once to
460 * ovl_lookup_real() in upper layer. The first level call walks
461 * back lower parents to the topmost indexed parent. The second
462 * recursive call walks back from indexed upper to the topmost
463 * connected/hashed upper parent (or up to root).
464 */
465 this = ovl_lookup_real(sb, upper, &ofs->layers[0]);
466 dput(upper);
467 }
468
469 if (IS_ERR_OR_NULL(this))
470 return this;
471
472 if (ovl_dentry_real_at(this, layer->idx) != real) {
473 dput(this);
474 this = ERR_PTR(-EIO);
475 }
476
477 return this;
478}
479
480/*
481 * Lookup an indexed or hashed overlay dentry, whose real dentry is an
482 * ancestor of @real.
483 */
484static struct dentry *ovl_lookup_real_ancestor(struct super_block *sb,
485 struct dentry *real,
486 const struct ovl_layer *layer)
487{
488 struct dentry *next, *parent = NULL;
489 struct dentry *ancestor = ERR_PTR(-EIO);
490
491 if (real == layer->mnt->mnt_root)
492 return dget(sb->s_root);
493
494 /* Find the topmost indexed or hashed ancestor */
495 next = dget(real);
496 for (;;) {
497 parent = dget_parent(next);
498
499 /*
500 * Lookup a matching overlay dentry in inode/dentry
501 * cache or in index by real inode.
502 */
503 ancestor = ovl_lookup_real_inode(sb, next, layer);
504 if (ancestor)
505 break;
506
507 if (parent == layer->mnt->mnt_root) {
508 ancestor = dget(sb->s_root);
509 break;
510 }
511
512 /*
513 * If @real has been moved out of the layer root directory,
514 * we will eventully hit the real fs root. This cannot happen
515 * by legit overlay rename, so we return error in that case.
516 */
517 if (parent == next) {
518 ancestor = ERR_PTR(-EXDEV);
519 break;
520 }
521
522 dput(next);
523 next = parent;
524 }
525
526 dput(parent);
527 dput(next);
528
529 return ancestor;
530}
531
532/*
533 * Lookup a connected overlay dentry whose real dentry is @real.
534 * If @real is on upper layer, we lookup a child overlay dentry with the same
535 * path the real dentry. Otherwise, we need to consult index for lookup.
536 */
537static struct dentry *ovl_lookup_real(struct super_block *sb,
538 struct dentry *real,
539 const struct ovl_layer *layer)
540{
541 struct dentry *connected;
542 int err = 0;
543
544 connected = ovl_lookup_real_ancestor(sb, real, layer);
545 if (IS_ERR(connected))
546 return connected;
547
548 while (!err) {
549 struct dentry *next, *this;
550 struct dentry *parent = NULL;
551 struct dentry *real_connected = ovl_dentry_real_at(connected,
552 layer->idx);
553
554 if (real_connected == real)
555 break;
556
557 /* Find the topmost dentry not yet connected */
558 next = dget(real);
559 for (;;) {
560 parent = dget_parent(next);
561
562 if (parent == real_connected)
563 break;
564
565 /*
566 * If real has been moved out of 'real_connected',
567 * we will not find 'real_connected' and hit the layer
568 * root. In that case, we need to restart connecting.
569 * This game can go on forever in the worst case. We
570 * may want to consider taking s_vfs_rename_mutex if
571 * this happens more than once.
572 */
573 if (parent == layer->mnt->mnt_root) {
574 dput(connected);
575 connected = dget(sb->s_root);
576 break;
577 }
578
579 /*
580 * If real file has been moved out of the layer root
581 * directory, we will eventully hit the real fs root.
582 * This cannot happen by legit overlay rename, so we
583 * return error in that case.
584 */
585 if (parent == next) {
586 err = -EXDEV;
587 break;
588 }
589
590 dput(next);
591 next = parent;
592 }
593
594 if (!err) {
595 this = ovl_lookup_real_one(connected, next, layer);
596 if (IS_ERR(this))
597 err = PTR_ERR(this);
598
599 /*
600 * Lookup of child in overlay can fail when racing with
601 * overlay rename of child away from 'connected' parent.
602 * In this case, we need to restart the lookup from the
603 * top, because we cannot trust that 'real_connected' is
604 * still an ancestor of 'real'. There is a good chance
605 * that the renamed overlay ancestor is now in cache, so
606 * ovl_lookup_real_ancestor() will find it and we can
607 * continue to connect exactly from where lookup failed.
608 */
609 if (err == -ECHILD) {
610 this = ovl_lookup_real_ancestor(sb, real,
611 layer);
612 err = PTR_ERR_OR_ZERO(this);
613 }
614 if (!err) {
615 dput(connected);
616 connected = this;
617 }
618 }
619
620 dput(parent);
621 dput(next);
622 }
623
624 if (err)
625 goto fail;
626
627 return connected;
628
629fail:
630 pr_warn_ratelimited("failed to lookup by real (%pd2, layer=%d, connected=%pd2, err=%i)\n",
631 real, layer->idx, connected, err);
632 dput(connected);
633 return ERR_PTR(err);
634}
635
636/*
637 * Get an overlay dentry from upper/lower real dentries and index.
638 */
639static struct dentry *ovl_get_dentry(struct super_block *sb,
640 struct dentry *upper,
641 struct ovl_path *lowerpath,
642 struct dentry *index)
643{
644 struct ovl_fs *ofs = OVL_FS(sb);
645 const struct ovl_layer *layer = upper ? &ofs->layers[0] : lowerpath->layer;
646 struct dentry *real = upper ?: (index ?: lowerpath->dentry);
647
648 /*
649 * Obtain a disconnected overlay dentry from a non-dir real dentry
650 * and index.
651 */
652 if (!d_is_dir(real))
653 return ovl_obtain_alias(sb, upper, lowerpath, index);
654
655 /* Removed empty directory? */
656 if ((real->d_flags & DCACHE_DISCONNECTED) || d_unhashed(real))
657 return ERR_PTR(-ENOENT);
658
659 /*
660 * If real dentry is connected and hashed, get a connected overlay
661 * dentry whose real dentry is @real.
662 */
663 return ovl_lookup_real(sb, real, layer);
664}
665
666static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
667 struct ovl_fh *fh)
668{
669 struct ovl_fs *ofs = OVL_FS(sb);
670 struct dentry *dentry;
671 struct dentry *upper;
672
673 if (!ovl_upper_mnt(ofs))
674 return ERR_PTR(-EACCES);
675
676 upper = ovl_decode_real_fh(ofs, fh, ovl_upper_mnt(ofs), true);
677 if (IS_ERR_OR_NULL(upper))
678 return upper;
679
680 dentry = ovl_get_dentry(sb, upper, NULL, NULL);
681 dput(upper);
682
683 return dentry;
684}
685
686static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
687 struct ovl_fh *fh)
688{
689 struct ovl_fs *ofs = OVL_FS(sb);
690 struct ovl_path origin = { };
691 struct ovl_path *stack = &origin;
692 struct dentry *dentry = NULL;
693 struct dentry *index = NULL;
694 struct inode *inode;
695 int err;
696
697 /* First lookup overlay inode in inode cache by origin fh */
698 err = ovl_check_origin_fh(ofs, fh, false, NULL, &stack);
699 if (err)
700 return ERR_PTR(err);
701
702 if (!d_is_dir(origin.dentry) ||
703 !(origin.dentry->d_flags & DCACHE_DISCONNECTED)) {
704 inode = ovl_lookup_inode(sb, origin.dentry, false);
705 err = PTR_ERR(inode);
706 if (IS_ERR(inode))
707 goto out_err;
708 if (inode) {
709 dentry = d_find_any_alias(inode);
710 iput(inode);
711 if (dentry)
712 goto out;
713 }
714 }
715
716 /* Then lookup indexed upper/whiteout by origin fh */
717 if (ovl_indexdir(sb)) {
718 index = ovl_get_index_fh(ofs, fh);
719 err = PTR_ERR(index);
720 if (IS_ERR(index)) {
721 index = NULL;
722 goto out_err;
723 }
724 }
725
726 /* Then try to get a connected upper dir by index */
727 if (index && d_is_dir(index)) {
728 struct dentry *upper = ovl_index_upper(ofs, index, true);
729
730 err = PTR_ERR(upper);
731 if (IS_ERR_OR_NULL(upper))
732 goto out_err;
733
734 dentry = ovl_get_dentry(sb, upper, NULL, NULL);
735 dput(upper);
736 goto out;
737 }
738
739 /* Find origin.dentry again with ovl_acceptable() layer check */
740 if (d_is_dir(origin.dentry)) {
741 dput(origin.dentry);
742 origin.dentry = NULL;
743 err = ovl_check_origin_fh(ofs, fh, true, NULL, &stack);
744 if (err)
745 goto out_err;
746 }
747 if (index) {
748 err = ovl_verify_origin(ofs, index, origin.dentry, false);
749 if (err)
750 goto out_err;
751 }
752
753 /* Get a connected non-upper dir or disconnected non-dir */
754 dentry = ovl_get_dentry(sb, NULL, &origin, index);
755
756out:
757 dput(origin.dentry);
758 dput(index);
759 return dentry;
760
761out_err:
762 dentry = ERR_PTR(err);
763 goto out;
764}
765
766static struct ovl_fh *ovl_fid_to_fh(struct fid *fid, int buflen, int fh_type)
767{
768 struct ovl_fh *fh;
769
770 /* If on-wire inner fid is aligned - nothing to do */
771 if (fh_type == OVL_FILEID_V1)
772 return (struct ovl_fh *)fid;
773
774 if (fh_type != OVL_FILEID_V0)
775 return ERR_PTR(-EINVAL);
776
777 if (buflen <= OVL_FH_WIRE_OFFSET)
778 return ERR_PTR(-EINVAL);
779
780 fh = kzalloc(buflen, GFP_KERNEL);
781 if (!fh)
782 return ERR_PTR(-ENOMEM);
783
784 /* Copy unaligned inner fh into aligned buffer */
785 memcpy(fh->buf, fid, buflen - OVL_FH_WIRE_OFFSET);
786 return fh;
787}
788
789static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid,
790 int fh_len, int fh_type)
791{
792 struct dentry *dentry = NULL;
793 struct ovl_fh *fh = NULL;
794 int len = fh_len << 2;
795 unsigned int flags = 0;
796 int err;
797
798 fh = ovl_fid_to_fh(fid, len, fh_type);
799 err = PTR_ERR(fh);
800 if (IS_ERR(fh))
801 goto out_err;
802
803 err = ovl_check_fh_len(fh, len);
804 if (err)
805 goto out_err;
806
807 flags = fh->fb.flags;
808 dentry = (flags & OVL_FH_FLAG_PATH_UPPER) ?
809 ovl_upper_fh_to_d(sb, fh) :
810 ovl_lower_fh_to_d(sb, fh);
811 err = PTR_ERR(dentry);
812 if (IS_ERR(dentry) && err != -ESTALE)
813 goto out_err;
814
815out:
816 /* We may have needed to re-align OVL_FILEID_V0 */
817 if (!IS_ERR_OR_NULL(fh) && fh != (void *)fid)
818 kfree(fh);
819
820 return dentry;
821
822out_err:
823 pr_warn_ratelimited("failed to decode file handle (len=%d, type=%d, flags=%x, err=%i)\n",
824 fh_len, fh_type, flags, err);
825 dentry = ERR_PTR(err);
826 goto out;
827}
828
829static struct dentry *ovl_fh_to_parent(struct super_block *sb, struct fid *fid,
830 int fh_len, int fh_type)
831{
832 pr_warn_ratelimited("connectable file handles not supported; use 'no_subtree_check' exportfs option.\n");
833 return ERR_PTR(-EACCES);
834}
835
836static int ovl_get_name(struct dentry *parent, char *name,
837 struct dentry *child)
838{
839 /*
840 * ovl_fh_to_dentry() returns connected dir overlay dentries and
841 * ovl_fh_to_parent() is not implemented, so we should not get here.
842 */
843 WARN_ON_ONCE(1);
844 return -EIO;
845}
846
847static struct dentry *ovl_get_parent(struct dentry *dentry)
848{
849 /*
850 * ovl_fh_to_dentry() returns connected dir overlay dentries, so we
851 * should not get here.
852 */
853 WARN_ON_ONCE(1);
854 return ERR_PTR(-EIO);
855}
856
857const struct export_operations ovl_export_operations = {
858 .encode_fh = ovl_encode_fh,
859 .fh_to_dentry = ovl_fh_to_dentry,
860 .fh_to_parent = ovl_fh_to_parent,
861 .get_name = ovl_get_name,
862 .get_parent = ovl_get_parent,
863};
864
865/* encode_fh() encodes non-decodable file handles with nfs_export=off */
866const struct export_operations ovl_export_fid_operations = {
867 .encode_fh = ovl_encode_fh,
868};