Commit | Line | Data |
---|---|---|
e9be9d5e MS |
1 | /* |
2 | * | |
3 | * Copyright (C) 2011 Novell 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> | |
11 | #include <linux/slab.h> | |
5b825c3a | 12 | #include <linux/cred.h> |
e9be9d5e | 13 | #include <linux/xattr.h> |
5201dc44 | 14 | #include <linux/posix_acl.h> |
5f8415d6 | 15 | #include <linux/ratelimit.h> |
e9be9d5e MS |
16 | #include "overlayfs.h" |
17 | ||
ba1e563c CR |
18 | |
19 | static dev_t ovl_get_pseudo_dev(struct dentry *dentry) | |
20 | { | |
21 | struct ovl_entry *oe = dentry->d_fsdata; | |
22 | ||
23 | return oe->lowerstack[0].layer->pseudo_dev; | |
24 | } | |
25 | ||
e9be9d5e MS |
26 | int ovl_setattr(struct dentry *dentry, struct iattr *attr) |
27 | { | |
28 | int err; | |
29 | struct dentry *upperdentry; | |
1175b6b8 | 30 | const struct cred *old_cred; |
e9be9d5e | 31 | |
cf9a6784 MS |
32 | /* |
33 | * Check for permissions before trying to copy-up. This is redundant | |
34 | * since it will be rechecked later by ->setattr() on upper dentry. But | |
35 | * without this, copy-up can be triggered by just about anybody. | |
36 | * | |
37 | * We don't initialize inode->size, which just means that | |
38 | * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not | |
39 | * check for a swapfile (which this won't be anyway). | |
40 | */ | |
31051c85 | 41 | err = setattr_prepare(dentry, attr); |
cf9a6784 MS |
42 | if (err) |
43 | return err; | |
44 | ||
e9be9d5e MS |
45 | err = ovl_want_write(dentry); |
46 | if (err) | |
47 | goto out; | |
48 | ||
acff81ec MS |
49 | err = ovl_copy_up(dentry); |
50 | if (!err) { | |
51 | upperdentry = ovl_dentry_upper(dentry); | |
52 | ||
b99c2d91 MS |
53 | if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) |
54 | attr->ia_valid &= ~ATTR_MODE; | |
55 | ||
5955102c | 56 | inode_lock(upperdentry->d_inode); |
1175b6b8 | 57 | old_cred = ovl_override_creds(dentry->d_sb); |
e9be9d5e | 58 | err = notify_change(upperdentry, attr, NULL); |
1175b6b8 | 59 | revert_creds(old_cred); |
b81de061 KK |
60 | if (!err) |
61 | ovl_copyattr(upperdentry->d_inode, dentry->d_inode); | |
5955102c | 62 | inode_unlock(upperdentry->d_inode); |
e9be9d5e MS |
63 | } |
64 | ovl_drop_write(dentry); | |
65 | out: | |
66 | return err; | |
67 | } | |
68 | ||
5b712091 MS |
69 | int ovl_getattr(const struct path *path, struct kstat *stat, |
70 | u32 request_mask, unsigned int flags) | |
e9be9d5e | 71 | { |
a528d35e | 72 | struct dentry *dentry = path->dentry; |
72b608f0 | 73 | enum ovl_path_type type; |
e9be9d5e | 74 | struct path realpath; |
1175b6b8 | 75 | const struct cred *old_cred; |
5b712091 | 76 | bool is_dir = S_ISDIR(dentry->d_inode->i_mode); |
a0c5ad30 | 77 | bool samefs = ovl_same_sb(dentry->d_sb); |
1175b6b8 | 78 | int err; |
e9be9d5e | 79 | |
72b608f0 | 80 | type = ovl_path_real(dentry, &realpath); |
1175b6b8 | 81 | old_cred = ovl_override_creds(dentry->d_sb); |
a528d35e | 82 | err = vfs_getattr(&realpath, stat, request_mask, flags); |
72b608f0 AG |
83 | if (err) |
84 | goto out; | |
85 | ||
86 | /* | |
a0c5ad30 AG |
87 | * For non-dir or same fs, we use st_ino of the copy up origin, if we |
88 | * know it. This guaranties constant st_dev/st_ino across copy up. | |
72b608f0 AG |
89 | * |
90 | * If filesystem supports NFS export ops, this also guaranties | |
91 | * persistent st_ino across mount cycle. | |
92 | */ | |
a0c5ad30 | 93 | if (!is_dir || samefs) { |
72b608f0 AG |
94 | if (OVL_TYPE_ORIGIN(type)) { |
95 | struct kstat lowerstat; | |
5b712091 | 96 | u32 lowermask = STATX_INO | (!is_dir ? STATX_NLINK : 0); |
72b608f0 AG |
97 | |
98 | ovl_path_lower(dentry, &realpath); | |
99 | err = vfs_getattr(&realpath, &lowerstat, | |
5b712091 | 100 | lowermask, flags); |
72b608f0 AG |
101 | if (err) |
102 | goto out; | |
103 | ||
72b608f0 | 104 | /* |
359f392c | 105 | * Lower hardlinks may be broken on copy up to different |
72b608f0 AG |
106 | * upper files, so we cannot use the lower origin st_ino |
107 | * for those different files, even for the same fs case. | |
86eaa130 AG |
108 | * |
109 | * Similarly, several redirected dirs can point to the | |
110 | * same dir on a lower layer. With the "verify_lower" | |
111 | * feature, we do not use the lower origin st_ino, if | |
112 | * we haven't verified that this redirect is unique. | |
113 | * | |
359f392c | 114 | * With inodes index enabled, it is safe to use st_ino |
86eaa130 AG |
115 | * of an indexed origin. The index validates that the |
116 | * upper hardlink is not broken and that a redirected | |
117 | * dir is the only redirect to that origin. | |
72b608f0 | 118 | */ |
86eaa130 AG |
119 | if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) || |
120 | (!ovl_verify_lower(dentry->d_sb) && | |
121 | (is_dir || lowerstat.nlink == 1))) | |
72b608f0 | 122 | stat->ino = lowerstat.ino; |
a0c5ad30 AG |
123 | |
124 | if (samefs) | |
125 | WARN_ON_ONCE(stat->dev != lowerstat.dev); | |
126 | else | |
127 | stat->dev = ovl_get_pseudo_dev(dentry); | |
72b608f0 | 128 | } |
a0c5ad30 AG |
129 | if (samefs) { |
130 | /* | |
131 | * When all layers are on the same fs, all real inode | |
132 | * number are unique, so we use the overlay st_dev, | |
133 | * which is friendly to du -x. | |
134 | */ | |
135 | stat->dev = dentry->d_sb->s_dev; | |
136 | } else if (!OVL_TYPE_UPPER(type)) { | |
137 | /* | |
138 | * For non-samefs setup, to make sure that st_dev/st_ino | |
139 | * pair is unique across the system, we use a unique | |
140 | * anonymous st_dev for lower layer inode. | |
141 | */ | |
142 | stat->dev = ovl_get_pseudo_dev(dentry); | |
143 | } | |
144 | } else { | |
5b712091 | 145 | /* |
5b712091 MS |
146 | * Always use the overlay st_dev for directories, so 'find |
147 | * -xdev' will scan the entire overlay mount and won't cross the | |
148 | * overlay mount boundaries. | |
a0c5ad30 AG |
149 | * |
150 | * If not all layers are on the same fs the pair {real st_ino; | |
151 | * overlay st_dev} is not unique, so use the non persistent | |
152 | * overlay st_ino for directories. | |
5b712091 MS |
153 | */ |
154 | stat->dev = dentry->d_sb->s_dev; | |
155 | stat->ino = dentry->d_inode->i_ino; | |
72b608f0 | 156 | } |
5b712091 MS |
157 | |
158 | /* | |
159 | * It's probably not worth it to count subdirs to get the | |
160 | * correct link count. nlink=1 seems to pacify 'find' and | |
161 | * other utilities. | |
162 | */ | |
163 | if (is_dir && OVL_TYPE_MERGE(type)) | |
164 | stat->nlink = 1; | |
165 | ||
5f8415d6 AG |
166 | /* |
167 | * Return the overlay inode nlinks for indexed upper inodes. | |
168 | * Overlay inode nlink counts the union of the upper hardlinks | |
169 | * and non-covered lower hardlinks. It does not include the upper | |
170 | * index hardlink. | |
171 | */ | |
172 | if (!is_dir && ovl_test_flag(OVL_INDEX, d_inode(dentry))) | |
173 | stat->nlink = dentry->d_inode->i_nlink; | |
174 | ||
72b608f0 | 175 | out: |
1175b6b8 | 176 | revert_creds(old_cred); |
72b608f0 | 177 | |
1175b6b8 | 178 | return err; |
e9be9d5e MS |
179 | } |
180 | ||
181 | int ovl_permission(struct inode *inode, int mask) | |
182 | { | |
09d8b586 MS |
183 | struct inode *upperinode = ovl_inode_upper(inode); |
184 | struct inode *realinode = upperinode ?: ovl_inode_lower(inode); | |
c0ca3d70 | 185 | const struct cred *old_cred; |
e9be9d5e MS |
186 | int err; |
187 | ||
e9be9d5e | 188 | /* Careful in RCU walk mode */ |
e9be9d5e MS |
189 | if (!realinode) { |
190 | WARN_ON(!(mask & MAY_NOT_BLOCK)); | |
a999d7e1 | 191 | return -ECHILD; |
e9be9d5e MS |
192 | } |
193 | ||
c0ca3d70 VG |
194 | /* |
195 | * Check overlay inode with the creds of task and underlying inode | |
196 | * with creds of mounter | |
197 | */ | |
198 | err = generic_permission(inode, mask); | |
199 | if (err) | |
200 | return err; | |
201 | ||
202 | old_cred = ovl_override_creds(inode->i_sb); | |
09d8b586 MS |
203 | if (!upperinode && |
204 | !special_file(realinode->i_mode) && mask & MAY_WRITE) { | |
754f8cb7 | 205 | mask &= ~(MAY_WRITE | MAY_APPEND); |
500cac3c VG |
206 | /* Make sure mounter can read file for copy up later */ |
207 | mask |= MAY_READ; | |
208 | } | |
9c630ebe | 209 | err = inode_permission(realinode, mask); |
c0ca3d70 VG |
210 | revert_creds(old_cred); |
211 | ||
212 | return err; | |
e9be9d5e MS |
213 | } |
214 | ||
6b255391 | 215 | static const char *ovl_get_link(struct dentry *dentry, |
fceef393 AV |
216 | struct inode *inode, |
217 | struct delayed_call *done) | |
e9be9d5e | 218 | { |
1175b6b8 VG |
219 | const struct cred *old_cred; |
220 | const char *p; | |
e9be9d5e | 221 | |
6b255391 AV |
222 | if (!dentry) |
223 | return ERR_PTR(-ECHILD); | |
224 | ||
1175b6b8 | 225 | old_cred = ovl_override_creds(dentry->d_sb); |
7764235b | 226 | p = vfs_get_link(ovl_dentry_real(dentry), done); |
1175b6b8 VG |
227 | revert_creds(old_cred); |
228 | return p; | |
e9be9d5e MS |
229 | } |
230 | ||
0956254a | 231 | bool ovl_is_private_xattr(const char *name) |
e9be9d5e | 232 | { |
fe2b7595 AG |
233 | return strncmp(name, OVL_XATTR_PREFIX, |
234 | sizeof(OVL_XATTR_PREFIX) - 1) == 0; | |
e9be9d5e MS |
235 | } |
236 | ||
1d88f183 MS |
237 | int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name, |
238 | const void *value, size_t size, int flags) | |
e9be9d5e MS |
239 | { |
240 | int err; | |
1d88f183 MS |
241 | struct dentry *upperdentry = ovl_i_dentry_upper(inode); |
242 | struct dentry *realdentry = upperdentry ?: ovl_dentry_lower(dentry); | |
1175b6b8 | 243 | const struct cred *old_cred; |
e9be9d5e MS |
244 | |
245 | err = ovl_want_write(dentry); | |
246 | if (err) | |
247 | goto out; | |
248 | ||
1d88f183 MS |
249 | if (!value && !upperdentry) { |
250 | err = vfs_getxattr(realdentry, name, NULL, 0); | |
0e585ccc AG |
251 | if (err < 0) |
252 | goto out_drop_write; | |
253 | } | |
254 | ||
1d88f183 MS |
255 | if (!upperdentry) { |
256 | err = ovl_copy_up(dentry); | |
257 | if (err) | |
258 | goto out_drop_write; | |
e9be9d5e | 259 | |
1d88f183 MS |
260 | realdentry = ovl_dentry_upper(dentry); |
261 | } | |
0e585ccc | 262 | |
1175b6b8 | 263 | old_cred = ovl_override_creds(dentry->d_sb); |
0e585ccc | 264 | if (value) |
1d88f183 | 265 | err = vfs_setxattr(realdentry, name, value, size, flags); |
0e585ccc AG |
266 | else { |
267 | WARN_ON(flags != XATTR_REPLACE); | |
1d88f183 | 268 | err = vfs_removexattr(realdentry, name); |
0e585ccc | 269 | } |
1175b6b8 | 270 | revert_creds(old_cred); |
e9be9d5e MS |
271 | |
272 | out_drop_write: | |
273 | ovl_drop_write(dentry); | |
274 | out: | |
275 | return err; | |
276 | } | |
277 | ||
1d88f183 | 278 | int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name, |
0eb45fc3 | 279 | void *value, size_t size) |
e9be9d5e | 280 | { |
1175b6b8 VG |
281 | ssize_t res; |
282 | const struct cred *old_cred; | |
1d88f183 MS |
283 | struct dentry *realdentry = |
284 | ovl_i_dentry_upper(inode) ?: ovl_dentry_lower(dentry); | |
52148463 | 285 | |
1175b6b8 VG |
286 | old_cred = ovl_override_creds(dentry->d_sb); |
287 | res = vfs_getxattr(realdentry, name, value, size); | |
288 | revert_creds(old_cred); | |
289 | return res; | |
e9be9d5e MS |
290 | } |
291 | ||
a082c6f6 MS |
292 | static bool ovl_can_list(const char *s) |
293 | { | |
294 | /* List all non-trusted xatts */ | |
295 | if (strncmp(s, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) != 0) | |
296 | return true; | |
297 | ||
298 | /* Never list trusted.overlay, list other trusted for superuser only */ | |
299 | return !ovl_is_private_xattr(s) && capable(CAP_SYS_ADMIN); | |
300 | } | |
301 | ||
e9be9d5e MS |
302 | ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) |
303 | { | |
b581755b | 304 | struct dentry *realdentry = ovl_dentry_real(dentry); |
e9be9d5e | 305 | ssize_t res; |
7cb35119 MS |
306 | size_t len; |
307 | char *s; | |
1175b6b8 | 308 | const struct cred *old_cred; |
e9be9d5e | 309 | |
1175b6b8 | 310 | old_cred = ovl_override_creds(dentry->d_sb); |
b581755b | 311 | res = vfs_listxattr(realdentry, list, size); |
1175b6b8 | 312 | revert_creds(old_cred); |
e9be9d5e MS |
313 | if (res <= 0 || size == 0) |
314 | return res; | |
315 | ||
e9be9d5e | 316 | /* filter out private xattrs */ |
7cb35119 MS |
317 | for (s = list, len = res; len;) { |
318 | size_t slen = strnlen(s, len) + 1; | |
e9be9d5e | 319 | |
7cb35119 MS |
320 | /* underlying fs providing us with an broken xattr list? */ |
321 | if (WARN_ON(slen > len)) | |
322 | return -EIO; | |
e9be9d5e | 323 | |
7cb35119 | 324 | len -= slen; |
a082c6f6 | 325 | if (!ovl_can_list(s)) { |
e9be9d5e | 326 | res -= slen; |
7cb35119 | 327 | memmove(s, s + slen, len); |
e9be9d5e | 328 | } else { |
7cb35119 | 329 | s += slen; |
e9be9d5e MS |
330 | } |
331 | } | |
332 | ||
333 | return res; | |
334 | } | |
335 | ||
39a25b2b VG |
336 | struct posix_acl *ovl_get_acl(struct inode *inode, int type) |
337 | { | |
09d8b586 | 338 | struct inode *realinode = ovl_inode_real(inode); |
1175b6b8 VG |
339 | const struct cred *old_cred; |
340 | struct posix_acl *acl; | |
39a25b2b | 341 | |
5201dc44 | 342 | if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode)) |
39a25b2b VG |
343 | return NULL; |
344 | ||
1175b6b8 | 345 | old_cred = ovl_override_creds(inode->i_sb); |
5201dc44 | 346 | acl = get_acl(realinode, type); |
1175b6b8 VG |
347 | revert_creds(old_cred); |
348 | ||
349 | return acl; | |
39a25b2b VG |
350 | } |
351 | ||
59be0971 | 352 | static bool ovl_open_need_copy_up(struct dentry *dentry, int flags) |
e9be9d5e | 353 | { |
59be0971 AG |
354 | if (ovl_dentry_upper(dentry) && |
355 | ovl_dentry_has_upper_alias(dentry)) | |
e9be9d5e MS |
356 | return false; |
357 | ||
59be0971 | 358 | if (special_file(d_inode(dentry)->i_mode)) |
e9be9d5e MS |
359 | return false; |
360 | ||
361 | if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) | |
362 | return false; | |
363 | ||
364 | return true; | |
365 | } | |
366 | ||
2d902671 | 367 | int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags) |
e9be9d5e | 368 | { |
2d902671 | 369 | int err = 0; |
e9be9d5e | 370 | |
59be0971 | 371 | if (ovl_open_need_copy_up(dentry, file_flags)) { |
e9be9d5e | 372 | err = ovl_want_write(dentry); |
2d902671 | 373 | if (!err) { |
9aba6521 | 374 | err = ovl_copy_up_flags(dentry, file_flags); |
2d902671 MS |
375 | ovl_drop_write(dentry); |
376 | } | |
e9be9d5e MS |
377 | } |
378 | ||
2d902671 | 379 | return err; |
e9be9d5e MS |
380 | } |
381 | ||
d719e8f2 MS |
382 | int ovl_update_time(struct inode *inode, struct timespec *ts, int flags) |
383 | { | |
384 | struct dentry *alias; | |
385 | struct path upperpath; | |
386 | ||
387 | if (!(flags & S_ATIME)) | |
388 | return 0; | |
389 | ||
390 | alias = d_find_any_alias(inode); | |
391 | if (!alias) | |
392 | return 0; | |
393 | ||
394 | ovl_path_upper(alias, &upperpath); | |
395 | if (upperpath.dentry) { | |
396 | touch_atime(&upperpath); | |
397 | inode->i_atime = d_inode(upperpath.dentry)->i_atime; | |
398 | } | |
399 | ||
400 | dput(alias); | |
401 | ||
402 | return 0; | |
403 | } | |
404 | ||
e9be9d5e MS |
405 | static const struct inode_operations ovl_file_inode_operations = { |
406 | .setattr = ovl_setattr, | |
407 | .permission = ovl_permission, | |
408 | .getattr = ovl_getattr, | |
e9be9d5e | 409 | .listxattr = ovl_listxattr, |
39a25b2b | 410 | .get_acl = ovl_get_acl, |
d719e8f2 | 411 | .update_time = ovl_update_time, |
e9be9d5e MS |
412 | }; |
413 | ||
414 | static const struct inode_operations ovl_symlink_inode_operations = { | |
415 | .setattr = ovl_setattr, | |
6b255391 | 416 | .get_link = ovl_get_link, |
e9be9d5e | 417 | .getattr = ovl_getattr, |
e9be9d5e | 418 | .listxattr = ovl_listxattr, |
d719e8f2 | 419 | .update_time = ovl_update_time, |
e9be9d5e MS |
420 | }; |
421 | ||
b1eaa950 AG |
422 | /* |
423 | * It is possible to stack overlayfs instance on top of another | |
424 | * overlayfs instance as lower layer. We need to annonate the | |
425 | * stackable i_mutex locks according to stack level of the super | |
426 | * block instance. An overlayfs instance can never be in stack | |
427 | * depth 0 (there is always a real fs below it). An overlayfs | |
428 | * inode lock will use the lockdep annotaion ovl_i_mutex_key[depth]. | |
429 | * | |
430 | * For example, here is a snip from /proc/lockdep_chains after | |
431 | * dir_iterate of nested overlayfs: | |
432 | * | |
433 | * [...] &ovl_i_mutex_dir_key[depth] (stack_depth=2) | |
434 | * [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1) | |
435 | * [...] &type->i_mutex_dir_key (stack_depth=0) | |
436 | */ | |
437 | #define OVL_MAX_NESTING FILESYSTEM_MAX_STACK_DEPTH | |
438 | ||
439 | static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode) | |
440 | { | |
441 | #ifdef CONFIG_LOCKDEP | |
442 | static struct lock_class_key ovl_i_mutex_key[OVL_MAX_NESTING]; | |
443 | static struct lock_class_key ovl_i_mutex_dir_key[OVL_MAX_NESTING]; | |
4eae06de | 444 | static struct lock_class_key ovl_i_lock_key[OVL_MAX_NESTING]; |
b1eaa950 AG |
445 | |
446 | int depth = inode->i_sb->s_stack_depth - 1; | |
447 | ||
448 | if (WARN_ON_ONCE(depth < 0 || depth >= OVL_MAX_NESTING)) | |
449 | depth = 0; | |
450 | ||
451 | if (S_ISDIR(inode->i_mode)) | |
452 | lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_dir_key[depth]); | |
453 | else | |
454 | lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_key[depth]); | |
4eae06de AG |
455 | |
456 | lockdep_set_class(&OVL_I(inode)->lock, &ovl_i_lock_key[depth]); | |
b1eaa950 AG |
457 | #endif |
458 | } | |
459 | ||
ca4c8a3a | 460 | static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev) |
e9be9d5e | 461 | { |
e9be9d5e MS |
462 | inode->i_ino = get_next_ino(); |
463 | inode->i_mode = mode; | |
d719e8f2 | 464 | inode->i_flags |= S_NOCMTIME; |
2a3a2a3f MS |
465 | #ifdef CONFIG_FS_POSIX_ACL |
466 | inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE; | |
467 | #endif | |
e9be9d5e | 468 | |
b1eaa950 AG |
469 | ovl_lockdep_annotate_inode_mutex_key(inode); |
470 | ||
ca4c8a3a MS |
471 | switch (mode & S_IFMT) { |
472 | case S_IFREG: | |
473 | inode->i_op = &ovl_file_inode_operations; | |
474 | break; | |
475 | ||
e9be9d5e | 476 | case S_IFDIR: |
e9be9d5e MS |
477 | inode->i_op = &ovl_dir_inode_operations; |
478 | inode->i_fop = &ovl_dir_operations; | |
479 | break; | |
480 | ||
481 | case S_IFLNK: | |
482 | inode->i_op = &ovl_symlink_inode_operations; | |
483 | break; | |
484 | ||
51f7e52d | 485 | default: |
e9be9d5e | 486 | inode->i_op = &ovl_file_inode_operations; |
ca4c8a3a | 487 | init_special_inode(inode, mode, rdev); |
e9be9d5e | 488 | break; |
51f7e52d MS |
489 | } |
490 | } | |
e9be9d5e | 491 | |
5f8415d6 AG |
492 | /* |
493 | * With inodes index enabled, an overlay inode nlink counts the union of upper | |
494 | * hardlinks and non-covered lower hardlinks. During the lifetime of a non-pure | |
495 | * upper inode, the following nlink modifying operations can happen: | |
496 | * | |
497 | * 1. Lower hardlink copy up | |
498 | * 2. Upper hardlink created, unlinked or renamed over | |
499 | * 3. Lower hardlink whiteout or renamed over | |
500 | * | |
501 | * For the first, copy up case, the union nlink does not change, whether the | |
502 | * operation succeeds or fails, but the upper inode nlink may change. | |
503 | * Therefore, before copy up, we store the union nlink value relative to the | |
504 | * lower inode nlink in the index inode xattr trusted.overlay.nlink. | |
505 | * | |
506 | * For the second, upper hardlink case, the union nlink should be incremented | |
507 | * or decremented IFF the operation succeeds, aligned with nlink change of the | |
508 | * upper inode. Therefore, before link/unlink/rename, we store the union nlink | |
509 | * value relative to the upper inode nlink in the index inode. | |
510 | * | |
511 | * For the last, lower cover up case, we simplify things by preceding the | |
512 | * whiteout or cover up with copy up. This makes sure that there is an index | |
513 | * upper inode where the nlink xattr can be stored before the copied up upper | |
514 | * entry is unlink. | |
515 | */ | |
516 | #define OVL_NLINK_ADD_UPPER (1 << 0) | |
517 | ||
518 | /* | |
519 | * On-disk format for indexed nlink: | |
520 | * | |
521 | * nlink relative to the upper inode - "U[+-]NUM" | |
522 | * nlink relative to the lower inode - "L[+-]NUM" | |
523 | */ | |
524 | ||
525 | static int ovl_set_nlink_common(struct dentry *dentry, | |
526 | struct dentry *realdentry, const char *format) | |
527 | { | |
528 | struct inode *inode = d_inode(dentry); | |
529 | struct inode *realinode = d_inode(realdentry); | |
530 | char buf[13]; | |
531 | int len; | |
532 | ||
533 | len = snprintf(buf, sizeof(buf), format, | |
534 | (int) (inode->i_nlink - realinode->i_nlink)); | |
535 | ||
6787341a MS |
536 | if (WARN_ON(len >= sizeof(buf))) |
537 | return -EIO; | |
538 | ||
5f8415d6 AG |
539 | return ovl_do_setxattr(ovl_dentry_upper(dentry), |
540 | OVL_XATTR_NLINK, buf, len, 0); | |
541 | } | |
542 | ||
543 | int ovl_set_nlink_upper(struct dentry *dentry) | |
544 | { | |
545 | return ovl_set_nlink_common(dentry, ovl_dentry_upper(dentry), "U%+i"); | |
546 | } | |
547 | ||
548 | int ovl_set_nlink_lower(struct dentry *dentry) | |
549 | { | |
550 | return ovl_set_nlink_common(dentry, ovl_dentry_lower(dentry), "L%+i"); | |
551 | } | |
552 | ||
caf70cb2 AG |
553 | unsigned int ovl_get_nlink(struct dentry *lowerdentry, |
554 | struct dentry *upperdentry, | |
555 | unsigned int fallback) | |
5f8415d6 AG |
556 | { |
557 | int nlink_diff; | |
558 | int nlink; | |
559 | char buf[13]; | |
560 | int err; | |
561 | ||
562 | if (!lowerdentry || !upperdentry || d_inode(lowerdentry)->i_nlink == 1) | |
563 | return fallback; | |
564 | ||
565 | err = vfs_getxattr(upperdentry, OVL_XATTR_NLINK, &buf, sizeof(buf) - 1); | |
566 | if (err < 0) | |
567 | goto fail; | |
568 | ||
569 | buf[err] = '\0'; | |
570 | if ((buf[0] != 'L' && buf[0] != 'U') || | |
571 | (buf[1] != '+' && buf[1] != '-')) | |
572 | goto fail; | |
573 | ||
574 | err = kstrtoint(buf + 1, 10, &nlink_diff); | |
575 | if (err < 0) | |
576 | goto fail; | |
577 | ||
578 | nlink = d_inode(buf[0] == 'L' ? lowerdentry : upperdentry)->i_nlink; | |
579 | nlink += nlink_diff; | |
580 | ||
581 | if (nlink <= 0) | |
582 | goto fail; | |
583 | ||
584 | return nlink; | |
585 | ||
586 | fail: | |
587 | pr_warn_ratelimited("overlayfs: failed to get index nlink (%pd2, err=%i)\n", | |
588 | upperdentry, err); | |
589 | return fallback; | |
590 | } | |
591 | ||
ca4c8a3a | 592 | struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev) |
51f7e52d MS |
593 | { |
594 | struct inode *inode; | |
595 | ||
596 | inode = new_inode(sb); | |
597 | if (inode) | |
ca4c8a3a | 598 | ovl_fill_inode(inode, mode, rdev); |
51f7e52d MS |
599 | |
600 | return inode; | |
601 | } | |
602 | ||
603 | static int ovl_inode_test(struct inode *inode, void *data) | |
604 | { | |
25b7713a | 605 | return inode->i_private == data; |
51f7e52d MS |
606 | } |
607 | ||
608 | static int ovl_inode_set(struct inode *inode, void *data) | |
609 | { | |
25b7713a | 610 | inode->i_private = data; |
51f7e52d MS |
611 | return 0; |
612 | } | |
613 | ||
b9ac5c27 MS |
614 | static bool ovl_verify_inode(struct inode *inode, struct dentry *lowerdentry, |
615 | struct dentry *upperdentry) | |
616 | { | |
31747eda AG |
617 | if (S_ISDIR(inode->i_mode)) { |
618 | /* Real lower dir moved to upper layer under us? */ | |
619 | if (!lowerdentry && ovl_inode_lower(inode)) | |
620 | return false; | |
621 | ||
622 | /* Lookup of an uncovered redirect origin? */ | |
623 | if (!upperdentry && ovl_inode_upper(inode)) | |
624 | return false; | |
625 | } | |
626 | ||
939ae4ef AG |
627 | /* |
628 | * Allow non-NULL lower inode in ovl_inode even if lowerdentry is NULL. | |
629 | * This happens when finding a copied up overlay inode for a renamed | |
630 | * or hardlinked overlay dentry and lower dentry cannot be followed | |
631 | * by origin because lower fs does not support file handles. | |
632 | */ | |
633 | if (lowerdentry && ovl_inode_lower(inode) != d_inode(lowerdentry)) | |
b9ac5c27 MS |
634 | return false; |
635 | ||
636 | /* | |
637 | * Allow non-NULL __upperdentry in inode even if upperdentry is NULL. | |
638 | * This happens when finding a lower alias for a copied up hard link. | |
639 | */ | |
640 | if (upperdentry && ovl_inode_upper(inode) != d_inode(upperdentry)) | |
641 | return false; | |
642 | ||
643 | return true; | |
644 | } | |
645 | ||
6eaf0111 AG |
646 | struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry, |
647 | struct dentry *index) | |
51f7e52d | 648 | { |
09d8b586 MS |
649 | struct dentry *lowerdentry = ovl_dentry_lower(dentry); |
650 | struct inode *realinode = upperdentry ? d_inode(upperdentry) : NULL; | |
51f7e52d | 651 | struct inode *inode; |
6eaf0111 AG |
652 | /* Already indexed or could be indexed on copy up? */ |
653 | bool indexed = (index || (ovl_indexdir(dentry->d_sb) && !upperdentry)); | |
31747eda AG |
654 | struct dentry *origin = indexed ? lowerdentry : NULL; |
655 | bool is_dir; | |
6eaf0111 AG |
656 | |
657 | if (WARN_ON(upperdentry && indexed && !lowerdentry)) | |
658 | return ERR_PTR(-EIO); | |
51f7e52d | 659 | |
09d8b586 MS |
660 | if (!realinode) |
661 | realinode = d_inode(lowerdentry); | |
662 | ||
6eaf0111 | 663 | /* |
31747eda AG |
664 | * Copy up origin (lower) may exist for non-indexed non-dir upper, but |
665 | * we must not use lower as hash key in that case. | |
666 | * Hash non-dir that is or could be indexed by origin inode. | |
667 | * Hash dir that is or could be merged by origin inode. | |
668 | * Hash pure upper and non-indexed non-dir by upper inode. | |
6eaf0111 | 669 | */ |
31747eda AG |
670 | is_dir = S_ISDIR(realinode->i_mode); |
671 | if (is_dir) | |
672 | origin = lowerdentry; | |
673 | ||
674 | if (upperdentry || origin) { | |
675 | struct inode *key = d_inode(origin ?: upperdentry); | |
676 | unsigned int nlink = is_dir ? 1 : realinode->i_nlink; | |
b9ac5c27 MS |
677 | |
678 | inode = iget5_locked(dentry->d_sb, (unsigned long) key, | |
679 | ovl_inode_test, ovl_inode_set, key); | |
09d8b586 | 680 | if (!inode) |
b9ac5c27 | 681 | goto out_nomem; |
09d8b586 | 682 | if (!(inode->i_state & I_NEW)) { |
b9ac5c27 MS |
683 | /* |
684 | * Verify that the underlying files stored in the inode | |
685 | * match those in the dentry. | |
686 | */ | |
687 | if (!ovl_verify_inode(inode, lowerdentry, upperdentry)) { | |
688 | iput(inode); | |
689 | inode = ERR_PTR(-ESTALE); | |
690 | goto out; | |
691 | } | |
692 | ||
09d8b586 MS |
693 | dput(upperdentry); |
694 | goto out; | |
695 | } | |
e6d2ebdd | 696 | |
31747eda AG |
697 | /* Recalculate nlink for non-dir due to indexing */ |
698 | if (!is_dir) | |
699 | nlink = ovl_get_nlink(lowerdentry, upperdentry, nlink); | |
5f8415d6 | 700 | set_nlink(inode, nlink); |
e6d2ebdd MS |
701 | } else { |
702 | inode = new_inode(dentry->d_sb); | |
703 | if (!inode) | |
b9ac5c27 | 704 | goto out_nomem; |
e9be9d5e | 705 | } |
e6d2ebdd | 706 | ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev); |
09d8b586 | 707 | ovl_inode_init(inode, upperdentry, lowerdentry); |
13c72075 MS |
708 | |
709 | if (upperdentry && ovl_is_impuredir(upperdentry)) | |
710 | ovl_set_flag(OVL_IMPURE, inode); | |
711 | ||
b79e05aa | 712 | /* Check for non-merge dir that may have whiteouts */ |
31747eda | 713 | if (is_dir) { |
b79e05aa AG |
714 | struct ovl_entry *oe = dentry->d_fsdata; |
715 | ||
716 | if (((upperdentry && lowerdentry) || oe->numlower > 1) || | |
717 | ovl_check_origin_xattr(upperdentry ?: lowerdentry)) { | |
718 | ovl_set_flag(OVL_WHITEOUTS, inode); | |
719 | } | |
720 | } | |
721 | ||
e6d2ebdd MS |
722 | if (inode->i_state & I_NEW) |
723 | unlock_new_inode(inode); | |
724 | out: | |
e9be9d5e | 725 | return inode; |
b9ac5c27 MS |
726 | |
727 | out_nomem: | |
728 | inode = ERR_PTR(-ENOMEM); | |
729 | goto out; | |
e9be9d5e | 730 | } |