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Commit | Line | Data |
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bbb1e54d MS |
1 | /* |
2 | * Copyright (C) 2011 Novell Inc. | |
3 | * Copyright (C) 2016 Red Hat, Inc. | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify it | |
6 | * under the terms of the GNU General Public License version 2 as published by | |
7 | * the Free Software Foundation. | |
8 | */ | |
9 | ||
10 | #include <linux/fs.h> | |
5b825c3a | 11 | #include <linux/cred.h> |
bbb1e54d MS |
12 | #include <linux/namei.h> |
13 | #include <linux/xattr.h> | |
02b69b28 | 14 | #include <linux/ratelimit.h> |
a9d01957 AG |
15 | #include <linux/mount.h> |
16 | #include <linux/exportfs.h> | |
bbb1e54d MS |
17 | #include "overlayfs.h" |
18 | #include "ovl_entry.h" | |
19 | ||
e28edc46 MS |
20 | struct ovl_lookup_data { |
21 | struct qstr name; | |
22 | bool is_dir; | |
23 | bool opaque; | |
24 | bool stop; | |
25 | bool last; | |
02b69b28 | 26 | char *redirect; |
e28edc46 | 27 | }; |
bbb1e54d | 28 | |
02b69b28 MS |
29 | static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d, |
30 | size_t prelen, const char *post) | |
31 | { | |
32 | int res; | |
33 | char *s, *next, *buf = NULL; | |
34 | ||
35 | res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, NULL, 0); | |
36 | if (res < 0) { | |
37 | if (res == -ENODATA || res == -EOPNOTSUPP) | |
38 | return 0; | |
39 | goto fail; | |
40 | } | |
41 | buf = kzalloc(prelen + res + strlen(post) + 1, GFP_TEMPORARY); | |
42 | if (!buf) | |
43 | return -ENOMEM; | |
44 | ||
45 | if (res == 0) | |
46 | goto invalid; | |
47 | ||
48 | res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, buf, res); | |
49 | if (res < 0) | |
50 | goto fail; | |
51 | if (res == 0) | |
52 | goto invalid; | |
53 | if (buf[0] == '/') { | |
54 | for (s = buf; *s++ == '/'; s = next) { | |
55 | next = strchrnul(s, '/'); | |
56 | if (s == next) | |
57 | goto invalid; | |
58 | } | |
59 | } else { | |
60 | if (strchr(buf, '/') != NULL) | |
61 | goto invalid; | |
62 | ||
63 | memmove(buf + prelen, buf, res); | |
64 | memcpy(buf, d->name.name, prelen); | |
65 | } | |
66 | ||
67 | strcat(buf, post); | |
68 | kfree(d->redirect); | |
69 | d->redirect = buf; | |
70 | d->name.name = d->redirect; | |
71 | d->name.len = strlen(d->redirect); | |
72 | ||
73 | return 0; | |
74 | ||
75 | err_free: | |
76 | kfree(buf); | |
77 | return 0; | |
78 | fail: | |
79 | pr_warn_ratelimited("overlayfs: failed to get redirect (%i)\n", res); | |
80 | goto err_free; | |
81 | invalid: | |
82 | pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf); | |
83 | goto err_free; | |
84 | } | |
85 | ||
a9d01957 AG |
86 | static int ovl_acceptable(void *ctx, struct dentry *dentry) |
87 | { | |
88 | return 1; | |
89 | } | |
90 | ||
91 | static struct dentry *ovl_get_origin(struct dentry *dentry, | |
92 | struct vfsmount *mnt) | |
93 | { | |
94 | int res; | |
95 | struct ovl_fh *fh = NULL; | |
96 | struct dentry *origin = NULL; | |
97 | int bytes; | |
98 | ||
99 | res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0); | |
100 | if (res < 0) { | |
101 | if (res == -ENODATA || res == -EOPNOTSUPP) | |
102 | return NULL; | |
103 | goto fail; | |
104 | } | |
105 | /* Zero size value means "copied up but origin unknown" */ | |
106 | if (res == 0) | |
107 | return NULL; | |
108 | ||
109 | fh = kzalloc(res, GFP_TEMPORARY); | |
110 | if (!fh) | |
111 | return ERR_PTR(-ENOMEM); | |
112 | ||
113 | res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, fh, res); | |
114 | if (res < 0) | |
115 | goto fail; | |
116 | ||
117 | if (res < sizeof(struct ovl_fh) || res < fh->len) | |
118 | goto invalid; | |
119 | ||
120 | if (fh->magic != OVL_FH_MAGIC) | |
121 | goto invalid; | |
122 | ||
123 | /* Treat larger version and unknown flags as "origin unknown" */ | |
124 | if (fh->version > OVL_FH_VERSION || fh->flags & ~OVL_FH_FLAG_ALL) | |
125 | goto out; | |
126 | ||
127 | /* Treat endianness mismatch as "origin unknown" */ | |
128 | if (!(fh->flags & OVL_FH_FLAG_ANY_ENDIAN) && | |
129 | (fh->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN) | |
130 | goto out; | |
131 | ||
132 | bytes = (fh->len - offsetof(struct ovl_fh, fid)); | |
133 | ||
134 | /* | |
135 | * Make sure that the stored uuid matches the uuid of the lower | |
136 | * layer where file handle will be decoded. | |
137 | */ | |
138 | if (uuid_be_cmp(fh->uuid, *(uuid_be *) &mnt->mnt_sb->s_uuid)) | |
139 | goto out; | |
140 | ||
141 | origin = exportfs_decode_fh(mnt, (struct fid *)fh->fid, | |
142 | bytes >> 2, (int)fh->type, | |
143 | ovl_acceptable, NULL); | |
144 | if (IS_ERR(origin)) { | |
145 | /* Treat stale file handle as "origin unknown" */ | |
146 | if (origin == ERR_PTR(-ESTALE)) | |
147 | origin = NULL; | |
148 | goto out; | |
149 | } | |
150 | ||
151 | if (ovl_dentry_weird(origin) || | |
152 | ((d_inode(origin)->i_mode ^ d_inode(dentry)->i_mode) & S_IFMT)) { | |
153 | dput(origin); | |
154 | origin = NULL; | |
155 | goto invalid; | |
156 | } | |
157 | ||
158 | out: | |
159 | kfree(fh); | |
160 | return origin; | |
161 | ||
162 | fail: | |
163 | pr_warn_ratelimited("overlayfs: failed to get origin (%i)\n", res); | |
164 | goto out; | |
165 | invalid: | |
166 | pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n", res, fh); | |
167 | goto out; | |
168 | } | |
169 | ||
ee1d6d37 AG |
170 | static bool ovl_is_opaquedir(struct dentry *dentry) |
171 | { | |
172 | return ovl_check_dir_xattr(dentry, OVL_XATTR_OPAQUE); | |
173 | } | |
174 | ||
e28edc46 MS |
175 | static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d, |
176 | const char *name, unsigned int namelen, | |
02b69b28 | 177 | size_t prelen, const char *post, |
e28edc46 MS |
178 | struct dentry **ret) |
179 | { | |
180 | struct dentry *this; | |
181 | int err; | |
182 | ||
183 | this = lookup_one_len_unlocked(name, base, namelen); | |
184 | if (IS_ERR(this)) { | |
185 | err = PTR_ERR(this); | |
186 | this = NULL; | |
187 | if (err == -ENOENT || err == -ENAMETOOLONG) | |
188 | goto out; | |
189 | goto out_err; | |
190 | } | |
191 | if (!this->d_inode) | |
192 | goto put_and_out; | |
193 | ||
194 | if (ovl_dentry_weird(this)) { | |
195 | /* Don't support traversing automounts and other weirdness */ | |
196 | err = -EREMOTE; | |
197 | goto out_err; | |
198 | } | |
199 | if (ovl_is_whiteout(this)) { | |
200 | d->stop = d->opaque = true; | |
201 | goto put_and_out; | |
202 | } | |
203 | if (!d_can_lookup(this)) { | |
204 | d->stop = true; | |
205 | if (d->is_dir) | |
206 | goto put_and_out; | |
207 | goto out; | |
208 | } | |
209 | d->is_dir = true; | |
210 | if (!d->last && ovl_is_opaquedir(this)) { | |
211 | d->stop = d->opaque = true; | |
212 | goto out; | |
213 | } | |
02b69b28 MS |
214 | err = ovl_check_redirect(this, d, prelen, post); |
215 | if (err) | |
216 | goto out_err; | |
e28edc46 MS |
217 | out: |
218 | *ret = this; | |
219 | return 0; | |
220 | ||
221 | put_and_out: | |
222 | dput(this); | |
223 | this = NULL; | |
224 | goto out; | |
225 | ||
226 | out_err: | |
227 | dput(this); | |
228 | return err; | |
229 | } | |
230 | ||
231 | static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d, | |
232 | struct dentry **ret) | |
233 | { | |
4c7d0c9c AG |
234 | /* Counting down from the end, since the prefix can change */ |
235 | size_t rem = d->name.len - 1; | |
02b69b28 MS |
236 | struct dentry *dentry = NULL; |
237 | int err; | |
238 | ||
4c7d0c9c | 239 | if (d->name.name[0] != '/') |
02b69b28 MS |
240 | return ovl_lookup_single(base, d, d->name.name, d->name.len, |
241 | 0, "", ret); | |
242 | ||
4c7d0c9c AG |
243 | while (!IS_ERR_OR_NULL(base) && d_can_lookup(base)) { |
244 | const char *s = d->name.name + d->name.len - rem; | |
02b69b28 | 245 | const char *next = strchrnul(s, '/'); |
4c7d0c9c AG |
246 | size_t thislen = next - s; |
247 | bool end = !next[0]; | |
02b69b28 | 248 | |
4c7d0c9c AG |
249 | /* Verify we did not go off the rails */ |
250 | if (WARN_ON(s[-1] != '/')) | |
02b69b28 MS |
251 | return -EIO; |
252 | ||
4c7d0c9c AG |
253 | err = ovl_lookup_single(base, d, s, thislen, |
254 | d->name.len - rem, next, &base); | |
02b69b28 MS |
255 | dput(dentry); |
256 | if (err) | |
257 | return err; | |
258 | dentry = base; | |
4c7d0c9c AG |
259 | if (end) |
260 | break; | |
261 | ||
262 | rem -= thislen + 1; | |
263 | ||
264 | if (WARN_ON(rem >= d->name.len)) | |
265 | return -EIO; | |
02b69b28 MS |
266 | } |
267 | *ret = dentry; | |
268 | return 0; | |
e28edc46 MS |
269 | } |
270 | ||
a9d01957 AG |
271 | |
272 | static int ovl_check_origin(struct dentry *dentry, struct dentry *upperdentry, | |
273 | struct path **stackp, unsigned int *ctrp) | |
274 | { | |
275 | struct super_block *same_sb = ovl_same_sb(dentry->d_sb); | |
276 | struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata; | |
277 | struct vfsmount *mnt; | |
278 | struct dentry *origin; | |
279 | ||
280 | if (!same_sb || !roe->numlower) | |
281 | return 0; | |
282 | ||
283 | /* | |
284 | * Since all layers are on the same fs, we use the first layer for | |
285 | * decoding the file handle. We may get a disconnected dentry, | |
286 | * which is fine, because we only need to hold the origin inode in | |
287 | * cache and use its inode number. We may even get a connected dentry, | |
288 | * that is not under the first layer's root. That is also fine for | |
289 | * using it's inode number - it's the same as if we held a reference | |
290 | * to a dentry in first layer that was moved under us. | |
291 | */ | |
292 | mnt = roe->lowerstack[0].mnt; | |
293 | ||
294 | origin = ovl_get_origin(upperdentry, mnt); | |
295 | if (IS_ERR_OR_NULL(origin)) | |
296 | return PTR_ERR(origin); | |
297 | ||
298 | BUG_ON(*stackp || *ctrp); | |
299 | *stackp = kmalloc(sizeof(struct path), GFP_TEMPORARY); | |
300 | if (!*stackp) { | |
301 | dput(origin); | |
302 | return -ENOMEM; | |
303 | } | |
304 | **stackp = (struct path) { .dentry = origin, .mnt = mnt }; | |
305 | *ctrp = 1; | |
306 | ||
307 | return 0; | |
308 | } | |
309 | ||
bbb1e54d MS |
310 | /* |
311 | * Returns next layer in stack starting from top. | |
312 | * Returns -1 if this is the last layer. | |
313 | */ | |
314 | int ovl_path_next(int idx, struct dentry *dentry, struct path *path) | |
315 | { | |
316 | struct ovl_entry *oe = dentry->d_fsdata; | |
317 | ||
318 | BUG_ON(idx < 0); | |
319 | if (idx == 0) { | |
320 | ovl_path_upper(dentry, path); | |
321 | if (path->dentry) | |
322 | return oe->numlower ? 1 : -1; | |
323 | idx++; | |
324 | } | |
325 | BUG_ON(idx > oe->numlower); | |
326 | *path = oe->lowerstack[idx - 1]; | |
327 | ||
328 | return (idx < oe->numlower) ? idx + 1 : -1; | |
329 | } | |
330 | ||
331 | struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, | |
332 | unsigned int flags) | |
333 | { | |
334 | struct ovl_entry *oe; | |
335 | const struct cred *old_cred; | |
6b2d5fe4 | 336 | struct ovl_fs *ofs = dentry->d_sb->s_fs_info; |
bbb1e54d | 337 | struct ovl_entry *poe = dentry->d_parent->d_fsdata; |
c22205d0 | 338 | struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata; |
bbb1e54d MS |
339 | struct path *stack = NULL; |
340 | struct dentry *upperdir, *upperdentry = NULL; | |
341 | unsigned int ctr = 0; | |
342 | struct inode *inode = NULL; | |
343 | bool upperopaque = false; | |
ee1d6d37 | 344 | bool upperimpure = false; |
02b69b28 | 345 | char *upperredirect = NULL; |
bbb1e54d MS |
346 | struct dentry *this; |
347 | unsigned int i; | |
348 | int err; | |
e28edc46 MS |
349 | struct ovl_lookup_data d = { |
350 | .name = dentry->d_name, | |
351 | .is_dir = false, | |
352 | .opaque = false, | |
353 | .stop = false, | |
354 | .last = !poe->numlower, | |
02b69b28 | 355 | .redirect = NULL, |
e28edc46 | 356 | }; |
bbb1e54d | 357 | |
6b2d5fe4 MS |
358 | if (dentry->d_name.len > ofs->namelen) |
359 | return ERR_PTR(-ENAMETOOLONG); | |
360 | ||
bbb1e54d MS |
361 | old_cred = ovl_override_creds(dentry->d_sb); |
362 | upperdir = ovl_upperdentry_dereference(poe); | |
363 | if (upperdir) { | |
e28edc46 MS |
364 | err = ovl_lookup_layer(upperdir, &d, &upperdentry); |
365 | if (err) | |
bbb1e54d MS |
366 | goto out; |
367 | ||
e28edc46 MS |
368 | if (upperdentry && unlikely(ovl_dentry_remote(upperdentry))) { |
369 | dput(upperdentry); | |
370 | err = -EREMOTE; | |
371 | goto out; | |
bbb1e54d | 372 | } |
a9d01957 AG |
373 | if (upperdentry && !d.is_dir) { |
374 | BUG_ON(!d.stop || d.redirect); | |
375 | err = ovl_check_origin(dentry, upperdentry, | |
376 | &stack, &ctr); | |
377 | if (err) | |
378 | goto out; | |
379 | } | |
02b69b28 MS |
380 | |
381 | if (d.redirect) { | |
382 | upperredirect = kstrdup(d.redirect, GFP_KERNEL); | |
383 | if (!upperredirect) | |
384 | goto out_put_upper; | |
385 | if (d.redirect[0] == '/') | |
c22205d0 | 386 | poe = roe; |
02b69b28 | 387 | } |
e28edc46 | 388 | upperopaque = d.opaque; |
ee1d6d37 AG |
389 | if (upperdentry && d.is_dir) |
390 | upperimpure = ovl_is_impuredir(upperdentry); | |
bbb1e54d MS |
391 | } |
392 | ||
e28edc46 | 393 | if (!d.stop && poe->numlower) { |
bbb1e54d | 394 | err = -ENOMEM; |
02b69b28 | 395 | stack = kcalloc(ofs->numlower, sizeof(struct path), |
e28edc46 | 396 | GFP_TEMPORARY); |
bbb1e54d MS |
397 | if (!stack) |
398 | goto out_put_upper; | |
399 | } | |
400 | ||
e28edc46 | 401 | for (i = 0; !d.stop && i < poe->numlower; i++) { |
bbb1e54d MS |
402 | struct path lowerpath = poe->lowerstack[i]; |
403 | ||
e28edc46 MS |
404 | d.last = i == poe->numlower - 1; |
405 | err = ovl_lookup_layer(lowerpath.dentry, &d, &this); | |
406 | if (err) | |
bbb1e54d | 407 | goto out_put; |
6b2d5fe4 | 408 | |
bbb1e54d MS |
409 | if (!this) |
410 | continue; | |
bbb1e54d MS |
411 | |
412 | stack[ctr].dentry = this; | |
413 | stack[ctr].mnt = lowerpath.mnt; | |
414 | ctr++; | |
02b69b28 MS |
415 | |
416 | if (d.stop) | |
417 | break; | |
418 | ||
c22205d0 AG |
419 | if (d.redirect && d.redirect[0] == '/' && poe != roe) { |
420 | poe = roe; | |
02b69b28 MS |
421 | |
422 | /* Find the current layer on the root dentry */ | |
423 | for (i = 0; i < poe->numlower; i++) | |
424 | if (poe->lowerstack[i].mnt == lowerpath.mnt) | |
425 | break; | |
426 | if (WARN_ON(i == poe->numlower)) | |
427 | break; | |
428 | } | |
bbb1e54d MS |
429 | } |
430 | ||
431 | oe = ovl_alloc_entry(ctr); | |
432 | err = -ENOMEM; | |
433 | if (!oe) | |
434 | goto out_put; | |
435 | ||
436 | if (upperdentry || ctr) { | |
437 | struct dentry *realdentry; | |
438 | struct inode *realinode; | |
439 | ||
440 | realdentry = upperdentry ? upperdentry : stack[0].dentry; | |
441 | realinode = d_inode(realdentry); | |
442 | ||
443 | err = -ENOMEM; | |
444 | if (upperdentry && !d_is_dir(upperdentry)) { | |
445 | inode = ovl_get_inode(dentry->d_sb, realinode); | |
446 | } else { | |
447 | inode = ovl_new_inode(dentry->d_sb, realinode->i_mode, | |
448 | realinode->i_rdev); | |
449 | if (inode) | |
450 | ovl_inode_init(inode, realinode, !!upperdentry); | |
451 | } | |
452 | if (!inode) | |
453 | goto out_free_oe; | |
454 | ovl_copyattr(realdentry->d_inode, inode); | |
455 | } | |
456 | ||
457 | revert_creds(old_cred); | |
458 | oe->opaque = upperopaque; | |
ee1d6d37 | 459 | oe->impure = upperimpure; |
02b69b28 | 460 | oe->redirect = upperredirect; |
bbb1e54d MS |
461 | oe->__upperdentry = upperdentry; |
462 | memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr); | |
463 | kfree(stack); | |
02b69b28 | 464 | kfree(d.redirect); |
bbb1e54d MS |
465 | dentry->d_fsdata = oe; |
466 | d_add(dentry, inode); | |
467 | ||
468 | return NULL; | |
469 | ||
470 | out_free_oe: | |
471 | kfree(oe); | |
472 | out_put: | |
473 | for (i = 0; i < ctr; i++) | |
474 | dput(stack[i].dentry); | |
475 | kfree(stack); | |
476 | out_put_upper: | |
477 | dput(upperdentry); | |
02b69b28 | 478 | kfree(upperredirect); |
bbb1e54d | 479 | out: |
02b69b28 | 480 | kfree(d.redirect); |
bbb1e54d MS |
481 | revert_creds(old_cred); |
482 | return ERR_PTR(err); | |
483 | } | |
484 | ||
485 | bool ovl_lower_positive(struct dentry *dentry) | |
486 | { | |
487 | struct ovl_entry *oe = dentry->d_fsdata; | |
488 | struct ovl_entry *poe = dentry->d_parent->d_fsdata; | |
489 | const struct qstr *name = &dentry->d_name; | |
490 | unsigned int i; | |
491 | bool positive = false; | |
492 | bool done = false; | |
493 | ||
494 | /* | |
495 | * If dentry is negative, then lower is positive iff this is a | |
496 | * whiteout. | |
497 | */ | |
498 | if (!dentry->d_inode) | |
499 | return oe->opaque; | |
500 | ||
501 | /* Negative upper -> positive lower */ | |
502 | if (!oe->__upperdentry) | |
503 | return true; | |
504 | ||
505 | /* Positive upper -> have to look up lower to see whether it exists */ | |
506 | for (i = 0; !done && !positive && i < poe->numlower; i++) { | |
507 | struct dentry *this; | |
508 | struct dentry *lowerdir = poe->lowerstack[i].dentry; | |
509 | ||
510 | this = lookup_one_len_unlocked(name->name, lowerdir, | |
511 | name->len); | |
512 | if (IS_ERR(this)) { | |
513 | switch (PTR_ERR(this)) { | |
514 | case -ENOENT: | |
515 | case -ENAMETOOLONG: | |
516 | break; | |
517 | ||
518 | default: | |
519 | /* | |
520 | * Assume something is there, we just couldn't | |
521 | * access it. | |
522 | */ | |
523 | positive = true; | |
524 | break; | |
525 | } | |
526 | } else { | |
527 | if (this->d_inode) { | |
528 | positive = !ovl_is_whiteout(this); | |
529 | done = true; | |
530 | } | |
531 | dput(this); | |
532 | } | |
533 | } | |
534 | ||
535 | return positive; | |
536 | } |