Commit | Line | Data |
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d2912cb1 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
8ed5eec9 AG |
2 | /* |
3 | * Overlayfs NFS export support. | |
4 | * | |
5 | * Amir Goldstein <amir73il@gmail.com> | |
6 | * | |
7 | * Copyright (C) 2017-2018 CTERA Networks. All Rights Reserved. | |
8ed5eec9 AG |
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 | ||
2ca3c148 AG |
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_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("overlayfs: 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 */ | |
77 | static 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 | */ | |
105 | static 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 | ||
b305e844 AG |
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 | |
05e1f118 AG |
170 | * Indexed upper | L (*) |
171 | * Non-upper | L (*) | |
b305e844 AG |
172 | * |
173 | * U = upper file handle | |
174 | * L = lower file handle | |
05e1f118 AG |
175 | * |
176 | * (*) Connecting an overlay dir from real lower dentry is not always | |
2ca3c148 AG |
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. | |
b305e844 | 182 | */ |
2ca3c148 | 183 | static int ovl_check_encode_origin(struct dentry *dentry) |
b305e844 | 184 | { |
05e1f118 AG |
185 | struct ovl_fs *ofs = dentry->d_sb->s_fs_info; |
186 | ||
2ca3c148 | 187 | /* Upper file handle for pure upper */ |
b305e844 | 188 | if (!ovl_dentry_lower(dentry)) |
2ca3c148 | 189 | return 0; |
b305e844 | 190 | |
05e1f118 | 191 | /* |
2ca3c148 | 192 | * Upper file handle for non-indexed upper. |
05e1f118 | 193 | * |
2ca3c148 AG |
194 | * Root is never indexed, so if there's an upper layer, encode upper for |
195 | * root. | |
05e1f118 | 196 | */ |
b305e844 AG |
197 | if (ovl_dentry_upper(dentry) && |
198 | !ovl_test_flag(OVL_INDEX, d_inode(dentry))) | |
05e1f118 AG |
199 | return 0; |
200 | ||
2ca3c148 AG |
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) && ofs->upper_mnt) | |
208 | return ovl_connect_layer(dentry); | |
05e1f118 | 209 | |
2ca3c148 AG |
210 | /* Lower file handle for indexed and non-upper dir/non-dir */ |
211 | return 1; | |
05e1f118 AG |
212 | } |
213 | ||
8ed5eec9 AG |
214 | static int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen) |
215 | { | |
8ed5eec9 | 216 | struct ovl_fh *fh = NULL; |
2ca3c148 | 217 | int err, enc_lower; |
8ed5eec9 | 218 | |
05e1f118 | 219 | /* |
2ca3c148 AG |
220 | * Check if we should encode a lower or upper file handle and maybe |
221 | * copy up an ancestor to make lower file handle connectable. | |
05e1f118 | 222 | */ |
2ca3c148 AG |
223 | err = enc_lower = ovl_check_encode_origin(dentry); |
224 | if (enc_lower < 0) | |
225 | goto fail; | |
8ed5eec9 | 226 | |
2ca3c148 | 227 | /* Encode an upper or lower file handle */ |
5b2cccd3 AG |
228 | fh = ovl_encode_real_fh(enc_lower ? ovl_dentry_lower(dentry) : |
229 | ovl_dentry_upper(dentry), !enc_lower); | |
9b6faee0 | 230 | if (IS_ERR(fh)) |
97f024b9 | 231 | return PTR_ERR(fh); |
8ed5eec9 AG |
232 | |
233 | err = -EOVERFLOW; | |
234 | if (fh->len > buflen) | |
235 | goto fail; | |
236 | ||
237 | memcpy(buf, (char *)fh, fh->len); | |
238 | err = fh->len; | |
239 | ||
240 | out: | |
241 | kfree(fh); | |
242 | return err; | |
243 | ||
244 | fail: | |
245 | pr_warn_ratelimited("overlayfs: failed to encode file handle (%pd2, err=%i, buflen=%d, len=%d, type=%d)\n", | |
246 | dentry, err, buflen, fh ? (int)fh->len : 0, | |
247 | fh ? fh->type : 0); | |
248 | goto out; | |
249 | } | |
250 | ||
251 | static int ovl_dentry_to_fh(struct dentry *dentry, u32 *fid, int *max_len) | |
252 | { | |
253 | int res, len = *max_len << 2; | |
254 | ||
255 | res = ovl_d_to_fh(dentry, (char *)fid, len); | |
256 | if (res <= 0) | |
257 | return FILEID_INVALID; | |
258 | ||
259 | len = res; | |
260 | ||
261 | /* Round up to dwords */ | |
262 | *max_len = (len + 3) >> 2; | |
263 | return OVL_FILEID; | |
264 | } | |
265 | ||
5b2cccd3 AG |
266 | static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len, |
267 | struct inode *parent) | |
8ed5eec9 AG |
268 | { |
269 | struct dentry *dentry; | |
270 | int type; | |
271 | ||
272 | /* TODO: encode connectable file handles */ | |
273 | if (parent) | |
274 | return FILEID_INVALID; | |
275 | ||
276 | dentry = d_find_any_alias(inode); | |
277 | if (WARN_ON(!dentry)) | |
278 | return FILEID_INVALID; | |
279 | ||
280 | type = ovl_dentry_to_fh(dentry, fid, max_len); | |
281 | ||
282 | dput(dentry); | |
283 | return type; | |
284 | } | |
285 | ||
8556a420 | 286 | /* |
f71bd9cf | 287 | * Find or instantiate an overlay dentry from real dentries and index. |
8556a420 AG |
288 | */ |
289 | static struct dentry *ovl_obtain_alias(struct super_block *sb, | |
f71bd9cf AG |
290 | struct dentry *upper_alias, |
291 | struct ovl_path *lowerpath, | |
292 | struct dentry *index) | |
8556a420 | 293 | { |
f941866f | 294 | struct dentry *lower = lowerpath ? lowerpath->dentry : NULL; |
f71bd9cf | 295 | struct dentry *upper = upper_alias ?: index; |
8556a420 | 296 | struct dentry *dentry; |
f941866f | 297 | struct inode *inode; |
8556a420 | 298 | struct ovl_entry *oe; |
ac6a52eb VG |
299 | struct ovl_inode_params oip = { |
300 | .lowerpath = lowerpath, | |
301 | .index = index, | |
302 | .numlower = !!lower | |
303 | }; | |
8556a420 | 304 | |
f71bd9cf AG |
305 | /* We get overlay directory dentries with ovl_lookup_real() */ |
306 | if (d_is_dir(upper ?: lower)) | |
8556a420 AG |
307 | return ERR_PTR(-EIO); |
308 | ||
ac6a52eb VG |
309 | oip.upperdentry = dget(upper); |
310 | inode = ovl_get_inode(sb, &oip); | |
8556a420 AG |
311 | if (IS_ERR(inode)) { |
312 | dput(upper); | |
313 | return ERR_CAST(inode); | |
314 | } | |
315 | ||
9d3dfea3 VG |
316 | if (upper) |
317 | ovl_set_flag(OVL_UPPERDATA, inode); | |
318 | ||
8556a420 AG |
319 | dentry = d_find_any_alias(inode); |
320 | if (!dentry) { | |
321 | dentry = d_alloc_anon(inode->i_sb); | |
322 | if (!dentry) | |
323 | goto nomem; | |
f941866f | 324 | oe = ovl_alloc_entry(lower ? 1 : 0); |
8556a420 AG |
325 | if (!oe) |
326 | goto nomem; | |
327 | ||
f941866f AG |
328 | if (lower) { |
329 | oe->lowerstack->dentry = dget(lower); | |
330 | oe->lowerstack->layer = lowerpath->layer; | |
331 | } | |
8556a420 | 332 | dentry->d_fsdata = oe; |
f71bd9cf | 333 | if (upper_alias) |
f941866f | 334 | ovl_dentry_set_upper_alias(dentry); |
8556a420 AG |
335 | } |
336 | ||
337 | return d_instantiate_anon(dentry, inode); | |
338 | ||
339 | nomem: | |
340 | iput(inode); | |
341 | dput(dentry); | |
342 | return ERR_PTR(-ENOMEM); | |
343 | } | |
344 | ||
98892516 AG |
345 | /* Get the upper or lower dentry in stach whose on layer @idx */ |
346 | static struct dentry *ovl_dentry_real_at(struct dentry *dentry, int idx) | |
347 | { | |
348 | struct ovl_entry *oe = dentry->d_fsdata; | |
349 | int i; | |
350 | ||
351 | if (!idx) | |
352 | return ovl_dentry_upper(dentry); | |
353 | ||
354 | for (i = 0; i < oe->numlower; i++) { | |
355 | if (oe->lowerstack[i].layer->idx == idx) | |
356 | return oe->lowerstack[i].dentry; | |
357 | } | |
358 | ||
359 | return NULL; | |
360 | } | |
361 | ||
3985b70a AG |
362 | /* |
363 | * Lookup a child overlay dentry to get a connected overlay dentry whose real | |
364 | * dentry is @real. If @real is on upper layer, we lookup a child overlay | |
365 | * dentry with the same name as the real dentry. Otherwise, we need to consult | |
366 | * index for lookup. | |
367 | */ | |
368 | static struct dentry *ovl_lookup_real_one(struct dentry *connected, | |
369 | struct dentry *real, | |
370 | struct ovl_layer *layer) | |
371 | { | |
372 | struct inode *dir = d_inode(connected); | |
373 | struct dentry *this, *parent = NULL; | |
374 | struct name_snapshot name; | |
375 | int err; | |
376 | ||
3985b70a AG |
377 | /* |
378 | * Lookup child overlay dentry by real name. The dir mutex protects us | |
379 | * from racing with overlay rename. If the overlay dentry that is above | |
380 | * real has already been moved to a parent that is not under the | |
381 | * connected overlay dir, we return -ECHILD and restart the lookup of | |
382 | * connected real path from the top. | |
383 | */ | |
384 | inode_lock_nested(dir, I_MUTEX_PARENT); | |
385 | err = -ECHILD; | |
386 | parent = dget_parent(real); | |
98892516 | 387 | if (ovl_dentry_real_at(connected, layer->idx) != parent) |
3985b70a AG |
388 | goto fail; |
389 | ||
390 | /* | |
391 | * We also need to take a snapshot of real dentry name to protect us | |
392 | * from racing with underlying layer rename. In this case, we don't | |
393 | * care about returning ESTALE, only from dereferencing a free name | |
394 | * pointer because we hold no lock on the real dentry. | |
395 | */ | |
396 | take_dentry_name_snapshot(&name, real); | |
230c6402 | 397 | this = lookup_one_len(name.name.name, connected, name.name.len); |
3985b70a AG |
398 | err = PTR_ERR(this); |
399 | if (IS_ERR(this)) { | |
400 | goto fail; | |
401 | } else if (!this || !this->d_inode) { | |
402 | dput(this); | |
403 | err = -ENOENT; | |
404 | goto fail; | |
98892516 | 405 | } else if (ovl_dentry_real_at(this, layer->idx) != real) { |
3985b70a AG |
406 | dput(this); |
407 | err = -ESTALE; | |
408 | goto fail; | |
409 | } | |
410 | ||
411 | out: | |
412 | release_dentry_name_snapshot(&name); | |
413 | dput(parent); | |
414 | inode_unlock(dir); | |
415 | return this; | |
416 | ||
417 | fail: | |
418 | pr_warn_ratelimited("overlayfs: failed to lookup one by real (%pd2, layer=%d, connected=%pd2, err=%i)\n", | |
419 | real, layer->idx, connected, err); | |
420 | this = ERR_PTR(err); | |
421 | goto out; | |
422 | } | |
423 | ||
06170154 AG |
424 | static struct dentry *ovl_lookup_real(struct super_block *sb, |
425 | struct dentry *real, | |
426 | struct ovl_layer *layer); | |
427 | ||
4b91c30a AG |
428 | /* |
429 | * Lookup an indexed or hashed overlay dentry by real inode. | |
430 | */ | |
431 | static struct dentry *ovl_lookup_real_inode(struct super_block *sb, | |
432 | struct dentry *real, | |
433 | struct ovl_layer *layer) | |
434 | { | |
06170154 AG |
435 | struct ovl_fs *ofs = sb->s_fs_info; |
436 | struct ovl_layer upper_layer = { .mnt = ofs->upper_mnt }; | |
437 | struct dentry *index = NULL; | |
4b91c30a AG |
438 | struct dentry *this = NULL; |
439 | struct inode *inode; | |
440 | ||
06170154 AG |
441 | /* |
442 | * Decoding upper dir from index is expensive, so first try to lookup | |
443 | * overlay dentry in inode/dcache. | |
444 | */ | |
4b91c30a AG |
445 | inode = ovl_lookup_inode(sb, real, !layer->idx); |
446 | if (IS_ERR(inode)) | |
447 | return ERR_CAST(inode); | |
448 | if (inode) { | |
449 | this = d_find_any_alias(inode); | |
450 | iput(inode); | |
451 | } | |
452 | ||
06170154 AG |
453 | /* |
454 | * For decoded lower dir file handle, lookup index by origin to check | |
455 | * if lower dir was copied up and and/or removed. | |
456 | */ | |
457 | if (!this && layer->idx && ofs->indexdir && !WARN_ON(!d_is_dir(real))) { | |
458 | index = ovl_lookup_index(ofs, NULL, real, false); | |
459 | if (IS_ERR(index)) | |
460 | return index; | |
461 | } | |
462 | ||
463 | /* Get connected upper overlay dir from index */ | |
464 | if (index) { | |
465 | struct dentry *upper = ovl_index_upper(ofs, index); | |
466 | ||
467 | dput(index); | |
468 | if (IS_ERR_OR_NULL(upper)) | |
469 | return upper; | |
470 | ||
471 | /* | |
472 | * ovl_lookup_real() in lower layer may call recursively once to | |
473 | * ovl_lookup_real() in upper layer. The first level call walks | |
474 | * back lower parents to the topmost indexed parent. The second | |
475 | * recursive call walks back from indexed upper to the topmost | |
476 | * connected/hashed upper parent (or up to root). | |
477 | */ | |
478 | this = ovl_lookup_real(sb, upper, &upper_layer); | |
479 | dput(upper); | |
480 | } | |
481 | ||
7168179f AG |
482 | if (IS_ERR_OR_NULL(this)) |
483 | return this; | |
4b91c30a AG |
484 | |
485 | if (WARN_ON(ovl_dentry_real_at(this, layer->idx) != real)) { | |
486 | dput(this); | |
487 | this = ERR_PTR(-EIO); | |
488 | } | |
489 | ||
490 | return this; | |
491 | } | |
492 | ||
493 | /* | |
494 | * Lookup an indexed or hashed overlay dentry, whose real dentry is an | |
495 | * ancestor of @real. | |
496 | */ | |
497 | static struct dentry *ovl_lookup_real_ancestor(struct super_block *sb, | |
498 | struct dentry *real, | |
499 | struct ovl_layer *layer) | |
500 | { | |
501 | struct dentry *next, *parent = NULL; | |
502 | struct dentry *ancestor = ERR_PTR(-EIO); | |
503 | ||
504 | if (real == layer->mnt->mnt_root) | |
505 | return dget(sb->s_root); | |
506 | ||
507 | /* Find the topmost indexed or hashed ancestor */ | |
508 | next = dget(real); | |
509 | for (;;) { | |
510 | parent = dget_parent(next); | |
511 | ||
512 | /* | |
513 | * Lookup a matching overlay dentry in inode/dentry | |
514 | * cache or in index by real inode. | |
515 | */ | |
516 | ancestor = ovl_lookup_real_inode(sb, next, layer); | |
517 | if (ancestor) | |
518 | break; | |
519 | ||
520 | if (parent == layer->mnt->mnt_root) { | |
521 | ancestor = dget(sb->s_root); | |
522 | break; | |
523 | } | |
524 | ||
525 | /* | |
526 | * If @real has been moved out of the layer root directory, | |
527 | * we will eventully hit the real fs root. This cannot happen | |
528 | * by legit overlay rename, so we return error in that case. | |
529 | */ | |
530 | if (parent == next) { | |
531 | ancestor = ERR_PTR(-EXDEV); | |
532 | break; | |
533 | } | |
534 | ||
535 | dput(next); | |
536 | next = parent; | |
537 | } | |
538 | ||
539 | dput(parent); | |
540 | dput(next); | |
541 | ||
542 | return ancestor; | |
543 | } | |
544 | ||
3985b70a AG |
545 | /* |
546 | * Lookup a connected overlay dentry whose real dentry is @real. | |
547 | * If @real is on upper layer, we lookup a child overlay dentry with the same | |
548 | * path the real dentry. Otherwise, we need to consult index for lookup. | |
549 | */ | |
550 | static struct dentry *ovl_lookup_real(struct super_block *sb, | |
551 | struct dentry *real, | |
552 | struct ovl_layer *layer) | |
553 | { | |
554 | struct dentry *connected; | |
555 | int err = 0; | |
556 | ||
4b91c30a AG |
557 | connected = ovl_lookup_real_ancestor(sb, real, layer); |
558 | if (IS_ERR(connected)) | |
559 | return connected; | |
3985b70a | 560 | |
3985b70a AG |
561 | while (!err) { |
562 | struct dentry *next, *this; | |
563 | struct dentry *parent = NULL; | |
98892516 AG |
564 | struct dentry *real_connected = ovl_dentry_real_at(connected, |
565 | layer->idx); | |
3985b70a AG |
566 | |
567 | if (real_connected == real) | |
568 | break; | |
569 | ||
570 | /* Find the topmost dentry not yet connected */ | |
571 | next = dget(real); | |
572 | for (;;) { | |
573 | parent = dget_parent(next); | |
574 | ||
575 | if (parent == real_connected) | |
576 | break; | |
577 | ||
578 | /* | |
579 | * If real has been moved out of 'real_connected', | |
580 | * we will not find 'real_connected' and hit the layer | |
581 | * root. In that case, we need to restart connecting. | |
582 | * This game can go on forever in the worst case. We | |
583 | * may want to consider taking s_vfs_rename_mutex if | |
584 | * this happens more than once. | |
585 | */ | |
586 | if (parent == layer->mnt->mnt_root) { | |
587 | dput(connected); | |
588 | connected = dget(sb->s_root); | |
589 | break; | |
590 | } | |
591 | ||
592 | /* | |
593 | * If real file has been moved out of the layer root | |
594 | * directory, we will eventully hit the real fs root. | |
595 | * This cannot happen by legit overlay rename, so we | |
596 | * return error in that case. | |
597 | */ | |
598 | if (parent == next) { | |
599 | err = -EXDEV; | |
600 | break; | |
601 | } | |
602 | ||
603 | dput(next); | |
604 | next = parent; | |
605 | } | |
606 | ||
607 | if (!err) { | |
608 | this = ovl_lookup_real_one(connected, next, layer); | |
609 | if (IS_ERR(this)) | |
610 | err = PTR_ERR(this); | |
611 | ||
612 | /* | |
613 | * Lookup of child in overlay can fail when racing with | |
614 | * overlay rename of child away from 'connected' parent. | |
615 | * In this case, we need to restart the lookup from the | |
616 | * top, because we cannot trust that 'real_connected' is | |
4b91c30a AG |
617 | * still an ancestor of 'real'. There is a good chance |
618 | * that the renamed overlay ancestor is now in cache, so | |
619 | * ovl_lookup_real_ancestor() will find it and we can | |
620 | * continue to connect exactly from where lookup failed. | |
3985b70a AG |
621 | */ |
622 | if (err == -ECHILD) { | |
4b91c30a AG |
623 | this = ovl_lookup_real_ancestor(sb, real, |
624 | layer); | |
b5095f24 | 625 | err = PTR_ERR_OR_ZERO(this); |
3985b70a AG |
626 | } |
627 | if (!err) { | |
628 | dput(connected); | |
629 | connected = this; | |
630 | } | |
631 | } | |
632 | ||
633 | dput(parent); | |
634 | dput(next); | |
635 | } | |
636 | ||
637 | if (err) | |
638 | goto fail; | |
639 | ||
640 | return connected; | |
641 | ||
642 | fail: | |
643 | pr_warn_ratelimited("overlayfs: failed to lookup by real (%pd2, layer=%d, connected=%pd2, err=%i)\n", | |
644 | real, layer->idx, connected, err); | |
645 | dput(connected); | |
646 | return ERR_PTR(err); | |
647 | } | |
648 | ||
649 | /* | |
f71bd9cf | 650 | * Get an overlay dentry from upper/lower real dentries and index. |
3985b70a AG |
651 | */ |
652 | static struct dentry *ovl_get_dentry(struct super_block *sb, | |
653 | struct dentry *upper, | |
f71bd9cf AG |
654 | struct ovl_path *lowerpath, |
655 | struct dentry *index) | |
3985b70a AG |
656 | { |
657 | struct ovl_fs *ofs = sb->s_fs_info; | |
658 | struct ovl_layer upper_layer = { .mnt = ofs->upper_mnt }; | |
98892516 | 659 | struct ovl_layer *layer = upper ? &upper_layer : lowerpath->layer; |
f71bd9cf | 660 | struct dentry *real = upper ?: (index ?: lowerpath->dentry); |
3985b70a | 661 | |
f941866f | 662 | /* |
f71bd9cf AG |
663 | * Obtain a disconnected overlay dentry from a non-dir real dentry |
664 | * and index. | |
f941866f | 665 | */ |
f71bd9cf AG |
666 | if (!d_is_dir(real)) |
667 | return ovl_obtain_alias(sb, upper, lowerpath, index); | |
f941866f | 668 | |
3985b70a | 669 | /* Removed empty directory? */ |
98892516 | 670 | if ((real->d_flags & DCACHE_DISCONNECTED) || d_unhashed(real)) |
3985b70a AG |
671 | return ERR_PTR(-ENOENT); |
672 | ||
673 | /* | |
98892516 AG |
674 | * If real dentry is connected and hashed, get a connected overlay |
675 | * dentry whose real dentry is @real. | |
3985b70a | 676 | */ |
98892516 | 677 | return ovl_lookup_real(sb, real, layer); |
3985b70a AG |
678 | } |
679 | ||
8556a420 AG |
680 | static struct dentry *ovl_upper_fh_to_d(struct super_block *sb, |
681 | struct ovl_fh *fh) | |
682 | { | |
683 | struct ovl_fs *ofs = sb->s_fs_info; | |
684 | struct dentry *dentry; | |
685 | struct dentry *upper; | |
686 | ||
687 | if (!ofs->upper_mnt) | |
688 | return ERR_PTR(-EACCES); | |
689 | ||
8a22efa1 | 690 | upper = ovl_decode_real_fh(fh, ofs->upper_mnt, true); |
8556a420 AG |
691 | if (IS_ERR_OR_NULL(upper)) |
692 | return upper; | |
693 | ||
f71bd9cf | 694 | dentry = ovl_get_dentry(sb, upper, NULL, NULL); |
8556a420 AG |
695 | dput(upper); |
696 | ||
697 | return dentry; | |
698 | } | |
699 | ||
f941866f AG |
700 | static struct dentry *ovl_lower_fh_to_d(struct super_block *sb, |
701 | struct ovl_fh *fh) | |
702 | { | |
703 | struct ovl_fs *ofs = sb->s_fs_info; | |
704 | struct ovl_path origin = { }; | |
705 | struct ovl_path *stack = &origin; | |
706 | struct dentry *dentry = NULL; | |
f71bd9cf | 707 | struct dentry *index = NULL; |
8b58924a | 708 | struct inode *inode; |
f941866f AG |
709 | int err; |
710 | ||
8b58924a AG |
711 | /* First lookup overlay inode in inode cache by origin fh */ |
712 | err = ovl_check_origin_fh(ofs, fh, false, NULL, &stack); | |
713 | if (err) | |
714 | return ERR_PTR(err); | |
715 | ||
716 | if (!d_is_dir(origin.dentry) || | |
717 | !(origin.dentry->d_flags & DCACHE_DISCONNECTED)) { | |
718 | inode = ovl_lookup_inode(sb, origin.dentry, false); | |
719 | err = PTR_ERR(inode); | |
720 | if (IS_ERR(inode)) | |
721 | goto out_err; | |
722 | if (inode) { | |
723 | dentry = d_find_any_alias(inode); | |
724 | iput(inode); | |
725 | if (dentry) | |
726 | goto out; | |
727 | } | |
728 | } | |
729 | ||
730 | /* Then lookup indexed upper/whiteout by origin fh */ | |
f71bd9cf AG |
731 | if (ofs->indexdir) { |
732 | index = ovl_get_index_fh(ofs, fh); | |
733 | err = PTR_ERR(index); | |
9436a1a3 | 734 | if (IS_ERR(index)) { |
9436a1a3 | 735 | index = NULL; |
8b58924a | 736 | goto out_err; |
9436a1a3 | 737 | } |
f71bd9cf AG |
738 | } |
739 | ||
8b58924a | 740 | /* Then try to get a connected upper dir by index */ |
3b0bfc6e AG |
741 | if (index && d_is_dir(index)) { |
742 | struct dentry *upper = ovl_index_upper(ofs, index); | |
743 | ||
744 | err = PTR_ERR(upper); | |
745 | if (IS_ERR_OR_NULL(upper)) | |
746 | goto out_err; | |
747 | ||
748 | dentry = ovl_get_dentry(sb, upper, NULL, NULL); | |
749 | dput(upper); | |
750 | goto out; | |
751 | } | |
752 | ||
155b8a04 AG |
753 | /* Find origin.dentry again with ovl_acceptable() layer check */ |
754 | if (d_is_dir(origin.dentry)) { | |
8b58924a AG |
755 | dput(origin.dentry); |
756 | origin.dentry = NULL; | |
757 | err = ovl_check_origin_fh(ofs, fh, true, NULL, &stack); | |
f71bd9cf AG |
758 | if (err) |
759 | goto out_err; | |
8b58924a AG |
760 | } |
761 | if (index) { | |
762 | err = ovl_verify_origin(index, origin.dentry, false); | |
763 | if (err) | |
9436a1a3 | 764 | goto out_err; |
f71bd9cf | 765 | } |
f941866f | 766 | |
155b8a04 | 767 | /* Get a connected non-upper dir or disconnected non-dir */ |
f71bd9cf | 768 | dentry = ovl_get_dentry(sb, NULL, &origin, index); |
f941866f | 769 | |
f71bd9cf AG |
770 | out: |
771 | dput(origin.dentry); | |
772 | dput(index); | |
f941866f | 773 | return dentry; |
f71bd9cf AG |
774 | |
775 | out_err: | |
776 | dentry = ERR_PTR(err); | |
777 | goto out; | |
f941866f AG |
778 | } |
779 | ||
8556a420 AG |
780 | static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid, |
781 | int fh_len, int fh_type) | |
782 | { | |
783 | struct dentry *dentry = NULL; | |
784 | struct ovl_fh *fh = (struct ovl_fh *) fid; | |
785 | int len = fh_len << 2; | |
786 | unsigned int flags = 0; | |
787 | int err; | |
788 | ||
789 | err = -EINVAL; | |
790 | if (fh_type != OVL_FILEID) | |
791 | goto out_err; | |
792 | ||
793 | err = ovl_check_fh_len(fh, len); | |
794 | if (err) | |
795 | goto out_err; | |
796 | ||
8556a420 | 797 | flags = fh->flags; |
f941866f AG |
798 | dentry = (flags & OVL_FH_FLAG_PATH_UPPER) ? |
799 | ovl_upper_fh_to_d(sb, fh) : | |
800 | ovl_lower_fh_to_d(sb, fh); | |
8556a420 AG |
801 | err = PTR_ERR(dentry); |
802 | if (IS_ERR(dentry) && err != -ESTALE) | |
803 | goto out_err; | |
804 | ||
805 | return dentry; | |
806 | ||
807 | out_err: | |
808 | pr_warn_ratelimited("overlayfs: failed to decode file handle (len=%d, type=%d, flags=%x, err=%i)\n", | |
809 | len, fh_type, flags, err); | |
810 | return ERR_PTR(err); | |
811 | } | |
812 | ||
3985b70a AG |
813 | static struct dentry *ovl_fh_to_parent(struct super_block *sb, struct fid *fid, |
814 | int fh_len, int fh_type) | |
815 | { | |
816 | pr_warn_ratelimited("overlayfs: connectable file handles not supported; use 'no_subtree_check' exportfs option.\n"); | |
817 | return ERR_PTR(-EACCES); | |
818 | } | |
819 | ||
820 | static int ovl_get_name(struct dentry *parent, char *name, | |
821 | struct dentry *child) | |
822 | { | |
823 | /* | |
824 | * ovl_fh_to_dentry() returns connected dir overlay dentries and | |
825 | * ovl_fh_to_parent() is not implemented, so we should not get here. | |
826 | */ | |
827 | WARN_ON_ONCE(1); | |
828 | return -EIO; | |
829 | } | |
830 | ||
831 | static struct dentry *ovl_get_parent(struct dentry *dentry) | |
832 | { | |
833 | /* | |
834 | * ovl_fh_to_dentry() returns connected dir overlay dentries, so we | |
835 | * should not get here. | |
836 | */ | |
837 | WARN_ON_ONCE(1); | |
838 | return ERR_PTR(-EIO); | |
839 | } | |
840 | ||
8ed5eec9 | 841 | const struct export_operations ovl_export_operations = { |
5b2cccd3 | 842 | .encode_fh = ovl_encode_fh, |
8556a420 | 843 | .fh_to_dentry = ovl_fh_to_dentry, |
3985b70a AG |
844 | .fh_to_parent = ovl_fh_to_parent, |
845 | .get_name = ovl_get_name, | |
846 | .get_parent = ovl_get_parent, | |
8ed5eec9 | 847 | }; |