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_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(flag: OVL_INDEX, inode: 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(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(dentry: 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(dentry: parent) < origin_layer) {
129 err = ovl_encode_maybe_copy_up(dentry: next);
130 break;
131 }
132
133 /* If @parent is connected or indexed we are done */
134 if (ovl_dentry_test_flag(flag: OVL_E_CONNECTED, dentry: parent) ||
135 ovl_test_flag(flag: OVL_INDEX, inode: d_inode(dentry: 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(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 dentry *dentry)
180{
181 struct ovl_fs *ofs = OVL_FS(sb: dentry->d_sb);
182 bool decodable = ofs->config.nfs_export;
183
184 /* Lower file handle for non-upper non-decodable */
185 if (!ovl_dentry_upper(dentry) && !decodable)
186 return 1;
187
188 /* Upper file handle for pure upper */
189 if (!ovl_dentry_lower(dentry))
190 return 0;
191
192 /*
193 * Root is never indexed, so if there's an upper layer, encode upper for
194 * root.
195 */
196 if (dentry == dentry->d_sb->s_root)
197 return 0;
198
199 /*
200 * Upper decodable file handle for non-indexed upper.
201 */
202 if (ovl_dentry_upper(dentry) && decodable &&
203 !ovl_test_flag(flag: OVL_INDEX, inode: d_inode(dentry)))
204 return 0;
205
206 /*
207 * Decoding a merge dir, whose origin's ancestor is under a redirected
208 * lower dir or under a non-indexed upper is not always possible.
209 * ovl_connect_layer() will try to make origin's layer "connected" by
210 * copying up a "connectable" ancestor.
211 */
212 if (d_is_dir(dentry) && ovl_upper_mnt(ofs) && decodable)
213 return ovl_connect_layer(dentry);
214
215 /* Lower file handle for indexed and non-upper dir/non-dir */
216 return 1;
217}
218
219static int ovl_dentry_to_fid(struct ovl_fs *ofs, struct dentry *dentry,
220 u32 *fid, int buflen)
221{
222 struct ovl_fh *fh = NULL;
223 int err, enc_lower;
224 int len;
225
226 /*
227 * Check if we should encode a lower or upper file handle and maybe
228 * copy up an ancestor to make lower file handle connectable.
229 */
230 err = enc_lower = ovl_check_encode_origin(dentry);
231 if (enc_lower < 0)
232 goto fail;
233
234 /* Encode an upper or lower file handle */
235 fh = ovl_encode_real_fh(ofs, real: enc_lower ? ovl_dentry_lower(dentry) :
236 ovl_dentry_upper(dentry), is_upper: !enc_lower);
237 if (IS_ERR(ptr: fh))
238 return PTR_ERR(ptr: fh);
239
240 len = OVL_FH_LEN(fh);
241 if (len <= buflen)
242 memcpy(fid, fh, len);
243 err = len;
244
245out:
246 kfree(objp: fh);
247 return err;
248
249fail:
250 pr_warn_ratelimited("failed to encode file handle (%pd2, err=%i)\n",
251 dentry, err);
252 goto out;
253}
254
255static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len,
256 struct inode *parent)
257{
258 struct ovl_fs *ofs = OVL_FS(sb: inode->i_sb);
259 struct dentry *dentry;
260 int bytes, buflen = *max_len << 2;
261
262 /* TODO: encode connectable file handles */
263 if (parent)
264 return FILEID_INVALID;
265
266 dentry = d_find_any_alias(inode);
267 if (!dentry)
268 return FILEID_INVALID;
269
270 bytes = ovl_dentry_to_fid(ofs, dentry, fid, buflen);
271 dput(dentry);
272 if (bytes <= 0)
273 return FILEID_INVALID;
274
275 *max_len = bytes >> 2;
276 if (bytes > buflen)
277 return FILEID_INVALID;
278
279 return OVL_FILEID_V1;
280}
281
282/*
283 * Find or instantiate an overlay dentry from real dentries and index.
284 */
285static struct dentry *ovl_obtain_alias(struct super_block *sb,
286 struct dentry *upper_alias,
287 struct ovl_path *lowerpath,
288 struct dentry *index)
289{
290 struct dentry *lower = lowerpath ? lowerpath->dentry : NULL;
291 struct dentry *upper = upper_alias ?: index;
292 struct dentry *dentry;
293 struct inode *inode = NULL;
294 struct ovl_entry *oe;
295 struct ovl_inode_params oip = {
296 .index = index,
297 };
298
299 /* We get overlay directory dentries with ovl_lookup_real() */
300 if (d_is_dir(dentry: upper ?: lower))
301 return ERR_PTR(error: -EIO);
302
303 oe = ovl_alloc_entry(numlower: !!lower);
304 if (!oe)
305 return ERR_PTR(error: -ENOMEM);
306
307 oip.upperdentry = dget(dentry: upper);
308 if (lower) {
309 ovl_lowerstack(oe)->dentry = dget(dentry: lower);
310 ovl_lowerstack(oe)->layer = lowerpath->layer;
311 }
312 oip.oe = oe;
313 inode = ovl_get_inode(sb, oip: &oip);
314 if (IS_ERR(ptr: inode)) {
315 ovl_free_entry(oe);
316 dput(upper);
317 return ERR_CAST(ptr: inode);
318 }
319
320 if (upper)
321 ovl_set_flag(flag: OVL_UPPERDATA, inode);
322
323 dentry = d_find_any_alias(inode);
324 if (dentry)
325 goto out_iput;
326
327 dentry = d_alloc_anon(inode->i_sb);
328 if (unlikely(!dentry))
329 goto nomem;
330
331 if (upper_alias)
332 ovl_dentry_set_upper_alias(dentry);
333
334 ovl_dentry_init_reval(dentry, upperdentry: upper, oe: OVL_I_E(inode));
335
336 return d_instantiate_anon(dentry, inode);
337
338nomem:
339 dput(dentry);
340 dentry = ERR_PTR(error: -ENOMEM);
341out_iput:
342 iput(inode);
343 return dentry;
344}
345
346/* Get the upper or lower dentry in stack whose on layer @idx */
347static struct dentry *ovl_dentry_real_at(struct dentry *dentry, int idx)
348{
349 struct ovl_entry *oe = OVL_E(dentry);
350 struct ovl_path *lowerstack = ovl_lowerstack(oe);
351 int i;
352
353 if (!idx)
354 return ovl_dentry_upper(dentry);
355
356 for (i = 0; i < ovl_numlower(oe); i++) {
357 if (lowerstack[i].layer->idx == idx)
358 return lowerstack[i].dentry;
359 }
360
361 return NULL;
362}
363
364/*
365 * Lookup a child overlay dentry to get a connected overlay dentry whose real
366 * dentry is @real. If @real is on upper layer, we lookup a child overlay
367 * dentry with the same name as the real dentry. Otherwise, we need to consult
368 * index for lookup.
369 */
370static struct dentry *ovl_lookup_real_one(struct dentry *connected,
371 struct dentry *real,
372 const struct ovl_layer *layer)
373{
374 struct inode *dir = d_inode(dentry: connected);
375 struct dentry *this, *parent = NULL;
376 struct name_snapshot name;
377 int err;
378
379 /*
380 * Lookup child overlay dentry by real name. The dir mutex protects us
381 * from racing with overlay rename. If the overlay dentry that is above
382 * real has already been moved to a parent that is not under the
383 * connected overlay dir, we return -ECHILD and restart the lookup of
384 * connected real path from the top.
385 */
386 inode_lock_nested(inode: dir, subclass: I_MUTEX_PARENT);
387 err = -ECHILD;
388 parent = dget_parent(dentry: real);
389 if (ovl_dentry_real_at(dentry: connected, idx: layer->idx) != parent)
390 goto fail;
391
392 /*
393 * We also need to take a snapshot of real dentry name to protect us
394 * from racing with underlying layer rename. In this case, we don't
395 * care about returning ESTALE, only from dereferencing a free name
396 * pointer because we hold no lock on the real dentry.
397 */
398 take_dentry_name_snapshot(&name, real);
399 /*
400 * No idmap handling here: it's an internal lookup. Could skip
401 * permission checking altogether, but for now just use non-idmap
402 * transformed ids.
403 */
404 this = lookup_one_len(name.name.name, connected, name.name.len);
405 release_dentry_name_snapshot(&name);
406 err = PTR_ERR(ptr: this);
407 if (IS_ERR(ptr: this)) {
408 goto fail;
409 } else if (!this || !this->d_inode) {
410 dput(this);
411 err = -ENOENT;
412 goto fail;
413 } else if (ovl_dentry_real_at(dentry: this, idx: layer->idx) != real) {
414 dput(this);
415 err = -ESTALE;
416 goto fail;
417 }
418
419out:
420 dput(parent);
421 inode_unlock(inode: dir);
422 return this;
423
424fail:
425 pr_warn_ratelimited("failed to lookup one by real (%pd2, layer=%d, connected=%pd2, err=%i)\n",
426 real, layer->idx, connected, err);
427 this = ERR_PTR(error: err);
428 goto out;
429}
430
431static struct dentry *ovl_lookup_real(struct super_block *sb,
432 struct dentry *real,
433 const struct ovl_layer *layer);
434
435/*
436 * Lookup an indexed or hashed overlay dentry by real inode.
437 */
438static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
439 struct dentry *real,
440 const struct ovl_layer *layer)
441{
442 struct ovl_fs *ofs = OVL_FS(sb);
443 struct dentry *index = NULL;
444 struct dentry *this = NULL;
445 struct inode *inode;
446
447 /*
448 * Decoding upper dir from index is expensive, so first try to lookup
449 * overlay dentry in inode/dcache.
450 */
451 inode = ovl_lookup_inode(sb, real, is_upper: !layer->idx);
452 if (IS_ERR(ptr: inode))
453 return ERR_CAST(ptr: inode);
454 if (inode) {
455 this = d_find_any_alias(inode);
456 iput(inode);
457 }
458
459 /*
460 * For decoded lower dir file handle, lookup index by origin to check
461 * if lower dir was copied up and and/or removed.
462 */
463 if (!this && layer->idx && ofs->indexdir && !WARN_ON(!d_is_dir(real))) {
464 index = ovl_lookup_index(ofs, NULL, origin: real, verify: false);
465 if (IS_ERR(ptr: index))
466 return index;
467 }
468
469 /* Get connected upper overlay dir from index */
470 if (index) {
471 struct dentry *upper = ovl_index_upper(ofs, index, connected: true);
472
473 dput(index);
474 if (IS_ERR_OR_NULL(ptr: upper))
475 return upper;
476
477 /*
478 * ovl_lookup_real() in lower layer may call recursively once to
479 * ovl_lookup_real() in upper layer. The first level call walks
480 * back lower parents to the topmost indexed parent. The second
481 * recursive call walks back from indexed upper to the topmost
482 * connected/hashed upper parent (or up to root).
483 */
484 this = ovl_lookup_real(sb, real: upper, layer: &ofs->layers[0]);
485 dput(upper);
486 }
487
488 if (IS_ERR_OR_NULL(ptr: this))
489 return this;
490
491 if (ovl_dentry_real_at(dentry: this, idx: layer->idx) != real) {
492 dput(this);
493 this = ERR_PTR(error: -EIO);
494 }
495
496 return this;
497}
498
499/*
500 * Lookup an indexed or hashed overlay dentry, whose real dentry is an
501 * ancestor of @real.
502 */
503static struct dentry *ovl_lookup_real_ancestor(struct super_block *sb,
504 struct dentry *real,
505 const struct ovl_layer *layer)
506{
507 struct dentry *next, *parent = NULL;
508 struct dentry *ancestor = ERR_PTR(error: -EIO);
509
510 if (real == layer->mnt->mnt_root)
511 return dget(dentry: sb->s_root);
512
513 /* Find the topmost indexed or hashed ancestor */
514 next = dget(dentry: real);
515 for (;;) {
516 parent = dget_parent(dentry: next);
517
518 /*
519 * Lookup a matching overlay dentry in inode/dentry
520 * cache or in index by real inode.
521 */
522 ancestor = ovl_lookup_real_inode(sb, real: next, layer);
523 if (ancestor)
524 break;
525
526 if (parent == layer->mnt->mnt_root) {
527 ancestor = dget(dentry: sb->s_root);
528 break;
529 }
530
531 /*
532 * If @real has been moved out of the layer root directory,
533 * we will eventully hit the real fs root. This cannot happen
534 * by legit overlay rename, so we return error in that case.
535 */
536 if (parent == next) {
537 ancestor = ERR_PTR(error: -EXDEV);
538 break;
539 }
540
541 dput(next);
542 next = parent;
543 }
544
545 dput(parent);
546 dput(next);
547
548 return ancestor;
549}
550
551/*
552 * Lookup a connected overlay dentry whose real dentry is @real.
553 * If @real is on upper layer, we lookup a child overlay dentry with the same
554 * path the real dentry. Otherwise, we need to consult index for lookup.
555 */
556static struct dentry *ovl_lookup_real(struct super_block *sb,
557 struct dentry *real,
558 const struct ovl_layer *layer)
559{
560 struct dentry *connected;
561 int err = 0;
562
563 connected = ovl_lookup_real_ancestor(sb, real, layer);
564 if (IS_ERR(ptr: connected))
565 return connected;
566
567 while (!err) {
568 struct dentry *next, *this;
569 struct dentry *parent = NULL;
570 struct dentry *real_connected = ovl_dentry_real_at(dentry: connected,
571 idx: layer->idx);
572
573 if (real_connected == real)
574 break;
575
576 /* Find the topmost dentry not yet connected */
577 next = dget(dentry: real);
578 for (;;) {
579 parent = dget_parent(dentry: next);
580
581 if (parent == real_connected)
582 break;
583
584 /*
585 * If real has been moved out of 'real_connected',
586 * we will not find 'real_connected' and hit the layer
587 * root. In that case, we need to restart connecting.
588 * This game can go on forever in the worst case. We
589 * may want to consider taking s_vfs_rename_mutex if
590 * this happens more than once.
591 */
592 if (parent == layer->mnt->mnt_root) {
593 dput(connected);
594 connected = dget(dentry: sb->s_root);
595 break;
596 }
597
598 /*
599 * If real file has been moved out of the layer root
600 * directory, we will eventully hit the real fs root.
601 * This cannot happen by legit overlay rename, so we
602 * return error in that case.
603 */
604 if (parent == next) {
605 err = -EXDEV;
606 break;
607 }
608
609 dput(next);
610 next = parent;
611 }
612
613 if (!err) {
614 this = ovl_lookup_real_one(connected, real: next, layer);
615 if (IS_ERR(ptr: this))
616 err = PTR_ERR(ptr: this);
617
618 /*
619 * Lookup of child in overlay can fail when racing with
620 * overlay rename of child away from 'connected' parent.
621 * In this case, we need to restart the lookup from the
622 * top, because we cannot trust that 'real_connected' is
623 * still an ancestor of 'real'. There is a good chance
624 * that the renamed overlay ancestor is now in cache, so
625 * ovl_lookup_real_ancestor() will find it and we can
626 * continue to connect exactly from where lookup failed.
627 */
628 if (err == -ECHILD) {
629 this = ovl_lookup_real_ancestor(sb, real,
630 layer);
631 err = PTR_ERR_OR_ZERO(ptr: this);
632 }
633 if (!err) {
634 dput(connected);
635 connected = this;
636 }
637 }
638
639 dput(parent);
640 dput(next);
641 }
642
643 if (err)
644 goto fail;
645
646 return connected;
647
648fail:
649 pr_warn_ratelimited("failed to lookup by real (%pd2, layer=%d, connected=%pd2, err=%i)\n",
650 real, layer->idx, connected, err);
651 dput(connected);
652 return ERR_PTR(error: err);
653}
654
655/*
656 * Get an overlay dentry from upper/lower real dentries and index.
657 */
658static struct dentry *ovl_get_dentry(struct super_block *sb,
659 struct dentry *upper,
660 struct ovl_path *lowerpath,
661 struct dentry *index)
662{
663 struct ovl_fs *ofs = OVL_FS(sb);
664 const struct ovl_layer *layer = upper ? &ofs->layers[0] : lowerpath->layer;
665 struct dentry *real = upper ?: (index ?: lowerpath->dentry);
666
667 /*
668 * Obtain a disconnected overlay dentry from a non-dir real dentry
669 * and index.
670 */
671 if (!d_is_dir(dentry: real))
672 return ovl_obtain_alias(sb, upper_alias: upper, lowerpath, index);
673
674 /* Removed empty directory? */
675 if ((real->d_flags & DCACHE_DISCONNECTED) || d_unhashed(dentry: real))
676 return ERR_PTR(error: -ENOENT);
677
678 /*
679 * If real dentry is connected and hashed, get a connected overlay
680 * dentry whose real dentry is @real.
681 */
682 return ovl_lookup_real(sb, real, layer);
683}
684
685static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
686 struct ovl_fh *fh)
687{
688 struct ovl_fs *ofs = OVL_FS(sb);
689 struct dentry *dentry;
690 struct dentry *upper;
691
692 if (!ovl_upper_mnt(ofs))
693 return ERR_PTR(error: -EACCES);
694
695 upper = ovl_decode_real_fh(ofs, fh, mnt: ovl_upper_mnt(ofs), connected: true);
696 if (IS_ERR_OR_NULL(ptr: upper))
697 return upper;
698
699 dentry = ovl_get_dentry(sb, upper, NULL, NULL);
700 dput(upper);
701
702 return dentry;
703}
704
705static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
706 struct ovl_fh *fh)
707{
708 struct ovl_fs *ofs = OVL_FS(sb);
709 struct ovl_path origin = { };
710 struct ovl_path *stack = &origin;
711 struct dentry *dentry = NULL;
712 struct dentry *index = NULL;
713 struct inode *inode;
714 int err;
715
716 /* First lookup overlay inode in inode cache by origin fh */
717 err = ovl_check_origin_fh(ofs, fh, connected: false, NULL, stackp: &stack);
718 if (err)
719 return ERR_PTR(error: err);
720
721 if (!d_is_dir(dentry: origin.dentry) ||
722 !(origin.dentry->d_flags & DCACHE_DISCONNECTED)) {
723 inode = ovl_lookup_inode(sb, real: origin.dentry, is_upper: false);
724 err = PTR_ERR(ptr: inode);
725 if (IS_ERR(ptr: inode))
726 goto out_err;
727 if (inode) {
728 dentry = d_find_any_alias(inode);
729 iput(inode);
730 if (dentry)
731 goto out;
732 }
733 }
734
735 /* Then lookup indexed upper/whiteout by origin fh */
736 if (ofs->indexdir) {
737 index = ovl_get_index_fh(ofs, fh);
738 err = PTR_ERR(ptr: index);
739 if (IS_ERR(ptr: index)) {
740 index = NULL;
741 goto out_err;
742 }
743 }
744
745 /* Then try to get a connected upper dir by index */
746 if (index && d_is_dir(dentry: index)) {
747 struct dentry *upper = ovl_index_upper(ofs, index, connected: true);
748
749 err = PTR_ERR(ptr: upper);
750 if (IS_ERR_OR_NULL(ptr: upper))
751 goto out_err;
752
753 dentry = ovl_get_dentry(sb, upper, NULL, NULL);
754 dput(upper);
755 goto out;
756 }
757
758 /* Find origin.dentry again with ovl_acceptable() layer check */
759 if (d_is_dir(dentry: origin.dentry)) {
760 dput(origin.dentry);
761 origin.dentry = NULL;
762 err = ovl_check_origin_fh(ofs, fh, connected: true, NULL, stackp: &stack);
763 if (err)
764 goto out_err;
765 }
766 if (index) {
767 err = ovl_verify_origin(ofs, upper: index, origin: origin.dentry, set: false);
768 if (err)
769 goto out_err;
770 }
771
772 /* Get a connected non-upper dir or disconnected non-dir */
773 dentry = ovl_get_dentry(sb, NULL, lowerpath: &origin, index);
774
775out:
776 dput(origin.dentry);
777 dput(index);
778 return dentry;
779
780out_err:
781 dentry = ERR_PTR(error: err);
782 goto out;
783}
784
785static struct ovl_fh *ovl_fid_to_fh(struct fid *fid, int buflen, int fh_type)
786{
787 struct ovl_fh *fh;
788
789 /* If on-wire inner fid is aligned - nothing to do */
790 if (fh_type == OVL_FILEID_V1)
791 return (struct ovl_fh *)fid;
792
793 if (fh_type != OVL_FILEID_V0)
794 return ERR_PTR(error: -EINVAL);
795
796 if (buflen <= OVL_FH_WIRE_OFFSET)
797 return ERR_PTR(error: -EINVAL);
798
799 fh = kzalloc(size: buflen, GFP_KERNEL);
800 if (!fh)
801 return ERR_PTR(error: -ENOMEM);
802
803 /* Copy unaligned inner fh into aligned buffer */
804 memcpy(fh->buf, fid, buflen - OVL_FH_WIRE_OFFSET);
805 return fh;
806}
807
808static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid,
809 int fh_len, int fh_type)
810{
811 struct dentry *dentry = NULL;
812 struct ovl_fh *fh = NULL;
813 int len = fh_len << 2;
814 unsigned int flags = 0;
815 int err;
816
817 fh = ovl_fid_to_fh(fid, buflen: len, fh_type);
818 err = PTR_ERR(ptr: fh);
819 if (IS_ERR(ptr: fh))
820 goto out_err;
821
822 err = ovl_check_fh_len(fh, fh_len: len);
823 if (err)
824 goto out_err;
825
826 flags = fh->fb.flags;
827 dentry = (flags & OVL_FH_FLAG_PATH_UPPER) ?
828 ovl_upper_fh_to_d(sb, fh) :
829 ovl_lower_fh_to_d(sb, fh);
830 err = PTR_ERR(ptr: dentry);
831 if (IS_ERR(ptr: dentry) && err != -ESTALE)
832 goto out_err;
833
834out:
835 /* We may have needed to re-align OVL_FILEID_V0 */
836 if (!IS_ERR_OR_NULL(ptr: fh) && fh != (void *)fid)
837 kfree(objp: fh);
838
839 return dentry;
840
841out_err:
842 pr_warn_ratelimited("failed to decode file handle (len=%d, type=%d, flags=%x, err=%i)\n",
843 fh_len, fh_type, flags, err);
844 dentry = ERR_PTR(error: err);
845 goto out;
846}
847
848static struct dentry *ovl_fh_to_parent(struct super_block *sb, struct fid *fid,
849 int fh_len, int fh_type)
850{
851 pr_warn_ratelimited("connectable file handles not supported; use 'no_subtree_check' exportfs option.\n");
852 return ERR_PTR(error: -EACCES);
853}
854
855static int ovl_get_name(struct dentry *parent, char *name,
856 struct dentry *child)
857{
858 /*
859 * ovl_fh_to_dentry() returns connected dir overlay dentries and
860 * ovl_fh_to_parent() is not implemented, so we should not get here.
861 */
862 WARN_ON_ONCE(1);
863 return -EIO;
864}
865
866static struct dentry *ovl_get_parent(struct dentry *dentry)
867{
868 /*
869 * ovl_fh_to_dentry() returns connected dir overlay dentries, so we
870 * should not get here.
871 */
872 WARN_ON_ONCE(1);
873 return ERR_PTR(error: -EIO);
874}
875
876const struct export_operations ovl_export_operations = {
877 .encode_fh = ovl_encode_fh,
878 .fh_to_dentry = ovl_fh_to_dentry,
879 .fh_to_parent = ovl_fh_to_parent,
880 .get_name = ovl_get_name,
881 .get_parent = ovl_get_parent,
882};
883
884/* encode_fh() encodes non-decodable file handles with nfs_export=off */
885const struct export_operations ovl_export_fid_operations = {
886 .encode_fh = ovl_encode_fh,
887};
888

source code of linux/fs/overlayfs/export.c