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> | |
12 | #include <linux/xattr.h> | |
13 | #include "overlayfs.h" | |
14 | ||
0f7ff2da | 15 | static int ovl_copy_up_truncate(struct dentry *dentry) |
e9be9d5e MS |
16 | { |
17 | int err; | |
18 | struct dentry *parent; | |
19 | struct kstat stat; | |
20 | struct path lowerpath; | |
21 | ||
22 | parent = dget_parent(dentry); | |
23 | err = ovl_copy_up(parent); | |
24 | if (err) | |
25 | goto out_dput_parent; | |
26 | ||
27 | ovl_path_lower(dentry, &lowerpath); | |
28 | err = vfs_getattr(&lowerpath, &stat); | |
29 | if (err) | |
30 | goto out_dput_parent; | |
31 | ||
0f7ff2da AV |
32 | stat.size = 0; |
33 | err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat); | |
e9be9d5e MS |
34 | |
35 | out_dput_parent: | |
36 | dput(parent); | |
37 | return err; | |
38 | } | |
39 | ||
40 | int ovl_setattr(struct dentry *dentry, struct iattr *attr) | |
41 | { | |
42 | int err; | |
43 | struct dentry *upperdentry; | |
44 | ||
cf9a6784 MS |
45 | /* |
46 | * Check for permissions before trying to copy-up. This is redundant | |
47 | * since it will be rechecked later by ->setattr() on upper dentry. But | |
48 | * without this, copy-up can be triggered by just about anybody. | |
49 | * | |
50 | * We don't initialize inode->size, which just means that | |
51 | * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not | |
52 | * check for a swapfile (which this won't be anyway). | |
53 | */ | |
54 | err = inode_change_ok(dentry->d_inode, attr); | |
55 | if (err) | |
56 | return err; | |
57 | ||
e9be9d5e MS |
58 | err = ovl_want_write(dentry); |
59 | if (err) | |
60 | goto out; | |
61 | ||
03bea604 MS |
62 | if (attr->ia_valid & ATTR_SIZE) { |
63 | struct inode *realinode = d_inode(ovl_dentry_real(dentry)); | |
64 | ||
65 | err = -ETXTBSY; | |
66 | if (atomic_read(&realinode->i_writecount) < 0) | |
67 | goto out_drop_write; | |
68 | } | |
69 | ||
acff81ec MS |
70 | err = ovl_copy_up(dentry); |
71 | if (!err) { | |
03bea604 MS |
72 | struct inode *winode = NULL; |
73 | ||
acff81ec MS |
74 | upperdentry = ovl_dentry_upper(dentry); |
75 | ||
03bea604 MS |
76 | if (attr->ia_valid & ATTR_SIZE) { |
77 | winode = d_inode(upperdentry); | |
78 | err = get_write_access(winode); | |
79 | if (err) | |
80 | goto out_drop_write; | |
81 | } | |
82 | ||
5955102c | 83 | inode_lock(upperdentry->d_inode); |
e9be9d5e | 84 | err = notify_change(upperdentry, attr, NULL); |
b81de061 KK |
85 | if (!err) |
86 | ovl_copyattr(upperdentry->d_inode, dentry->d_inode); | |
5955102c | 87 | inode_unlock(upperdentry->d_inode); |
03bea604 MS |
88 | |
89 | if (winode) | |
90 | put_write_access(winode); | |
e9be9d5e | 91 | } |
03bea604 | 92 | out_drop_write: |
e9be9d5e MS |
93 | ovl_drop_write(dentry); |
94 | out: | |
95 | return err; | |
96 | } | |
97 | ||
98 | static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry, | |
99 | struct kstat *stat) | |
100 | { | |
101 | struct path realpath; | |
102 | ||
103 | ovl_path_real(dentry, &realpath); | |
104 | return vfs_getattr(&realpath, stat); | |
105 | } | |
106 | ||
107 | int ovl_permission(struct inode *inode, int mask) | |
108 | { | |
109 | struct ovl_entry *oe; | |
110 | struct dentry *alias = NULL; | |
111 | struct inode *realinode; | |
112 | struct dentry *realdentry; | |
113 | bool is_upper; | |
114 | int err; | |
115 | ||
116 | if (S_ISDIR(inode->i_mode)) { | |
117 | oe = inode->i_private; | |
118 | } else if (mask & MAY_NOT_BLOCK) { | |
119 | return -ECHILD; | |
120 | } else { | |
121 | /* | |
122 | * For non-directories find an alias and get the info | |
123 | * from there. | |
124 | */ | |
125 | alias = d_find_any_alias(inode); | |
126 | if (WARN_ON(!alias)) | |
127 | return -ENOENT; | |
128 | ||
129 | oe = alias->d_fsdata; | |
130 | } | |
131 | ||
132 | realdentry = ovl_entry_real(oe, &is_upper); | |
133 | ||
8d3095f4 MS |
134 | if (ovl_is_default_permissions(inode)) { |
135 | struct kstat stat; | |
136 | struct path realpath = { .dentry = realdentry }; | |
137 | ||
138 | if (mask & MAY_NOT_BLOCK) | |
139 | return -ECHILD; | |
140 | ||
141 | realpath.mnt = ovl_entry_mnt_real(oe, inode, is_upper); | |
142 | ||
143 | err = vfs_getattr(&realpath, &stat); | |
144 | if (err) | |
a4859d75 | 145 | goto out_dput; |
8d3095f4 | 146 | |
a4859d75 | 147 | err = -ESTALE; |
8d3095f4 | 148 | if ((stat.mode ^ inode->i_mode) & S_IFMT) |
a4859d75 | 149 | goto out_dput; |
8d3095f4 MS |
150 | |
151 | inode->i_mode = stat.mode; | |
152 | inode->i_uid = stat.uid; | |
153 | inode->i_gid = stat.gid; | |
154 | ||
a4859d75 MS |
155 | err = generic_permission(inode, mask); |
156 | goto out_dput; | |
8d3095f4 MS |
157 | } |
158 | ||
e9be9d5e MS |
159 | /* Careful in RCU walk mode */ |
160 | realinode = ACCESS_ONCE(realdentry->d_inode); | |
161 | if (!realinode) { | |
162 | WARN_ON(!(mask & MAY_NOT_BLOCK)); | |
163 | err = -ENOENT; | |
164 | goto out_dput; | |
165 | } | |
166 | ||
167 | if (mask & MAY_WRITE) { | |
168 | umode_t mode = realinode->i_mode; | |
169 | ||
170 | /* | |
171 | * Writes will always be redirected to upper layer, so | |
172 | * ignore lower layer being read-only. | |
173 | * | |
174 | * If the overlay itself is read-only then proceed | |
175 | * with the permission check, don't return EROFS. | |
176 | * This will only happen if this is the lower layer of | |
177 | * another overlayfs. | |
178 | * | |
179 | * If upper fs becomes read-only after the overlay was | |
180 | * constructed return EROFS to prevent modification of | |
181 | * upper layer. | |
182 | */ | |
183 | err = -EROFS; | |
184 | if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) && | |
185 | (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) | |
186 | goto out_dput; | |
187 | } | |
188 | ||
189 | err = __inode_permission(realinode, mask); | |
190 | out_dput: | |
191 | dput(alias); | |
192 | return err; | |
193 | } | |
194 | ||
6b255391 | 195 | static const char *ovl_get_link(struct dentry *dentry, |
fceef393 AV |
196 | struct inode *inode, |
197 | struct delayed_call *done) | |
e9be9d5e | 198 | { |
e9be9d5e MS |
199 | struct dentry *realdentry; |
200 | struct inode *realinode; | |
201 | ||
6b255391 AV |
202 | if (!dentry) |
203 | return ERR_PTR(-ECHILD); | |
204 | ||
e9be9d5e MS |
205 | realdentry = ovl_dentry_real(dentry); |
206 | realinode = realdentry->d_inode; | |
207 | ||
6b255391 | 208 | if (WARN_ON(!realinode->i_op->get_link)) |
e9be9d5e MS |
209 | return ERR_PTR(-EPERM); |
210 | ||
fceef393 | 211 | return realinode->i_op->get_link(realdentry, realinode, done); |
e9be9d5e MS |
212 | } |
213 | ||
214 | static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz) | |
215 | { | |
216 | struct path realpath; | |
217 | struct inode *realinode; | |
218 | ||
219 | ovl_path_real(dentry, &realpath); | |
220 | realinode = realpath.dentry->d_inode; | |
221 | ||
222 | if (!realinode->i_op->readlink) | |
223 | return -EINVAL; | |
224 | ||
225 | touch_atime(&realpath); | |
226 | ||
227 | return realinode->i_op->readlink(realpath.dentry, buf, bufsiz); | |
228 | } | |
229 | ||
230 | ||
231 | static bool ovl_is_private_xattr(const char *name) | |
232 | { | |
cead89bb | 233 | return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0; |
e9be9d5e MS |
234 | } |
235 | ||
3767e255 AV |
236 | int ovl_setxattr(struct dentry *dentry, struct inode *inode, |
237 | const char *name, const void *value, | |
238 | size_t size, int flags) | |
e9be9d5e MS |
239 | { |
240 | int err; | |
241 | struct dentry *upperdentry; | |
242 | ||
243 | err = ovl_want_write(dentry); | |
244 | if (err) | |
245 | goto out; | |
246 | ||
247 | err = -EPERM; | |
248 | if (ovl_is_private_xattr(name)) | |
249 | goto out_drop_write; | |
250 | ||
251 | err = ovl_copy_up(dentry); | |
252 | if (err) | |
253 | goto out_drop_write; | |
254 | ||
255 | upperdentry = ovl_dentry_upper(dentry); | |
256 | err = vfs_setxattr(upperdentry, name, value, size, flags); | |
257 | ||
258 | out_drop_write: | |
259 | ovl_drop_write(dentry); | |
260 | out: | |
261 | return err; | |
262 | } | |
263 | ||
ce23e640 AV |
264 | ssize_t ovl_getxattr(struct dentry *dentry, struct inode *inode, |
265 | const char *name, void *value, size_t size) | |
e9be9d5e | 266 | { |
b581755b | 267 | struct dentry *realdentry = ovl_dentry_real(dentry); |
52148463 | 268 | |
b581755b | 269 | if (ovl_is_private_xattr(name)) |
e9be9d5e MS |
270 | return -ENODATA; |
271 | ||
b581755b | 272 | return vfs_getxattr(realdentry, name, value, size); |
e9be9d5e MS |
273 | } |
274 | ||
275 | ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) | |
276 | { | |
b581755b | 277 | struct dentry *realdentry = ovl_dentry_real(dentry); |
e9be9d5e MS |
278 | ssize_t res; |
279 | int off; | |
280 | ||
b581755b | 281 | res = vfs_listxattr(realdentry, list, size); |
e9be9d5e MS |
282 | if (res <= 0 || size == 0) |
283 | return res; | |
284 | ||
e9be9d5e MS |
285 | /* filter out private xattrs */ |
286 | for (off = 0; off < res;) { | |
287 | char *s = list + off; | |
288 | size_t slen = strlen(s) + 1; | |
289 | ||
290 | BUG_ON(off + slen > res); | |
291 | ||
292 | if (ovl_is_private_xattr(s)) { | |
293 | res -= slen; | |
294 | memmove(s, s + slen, res - off); | |
295 | } else { | |
296 | off += slen; | |
297 | } | |
298 | } | |
299 | ||
300 | return res; | |
301 | } | |
302 | ||
303 | int ovl_removexattr(struct dentry *dentry, const char *name) | |
304 | { | |
305 | int err; | |
306 | struct path realpath; | |
52148463 | 307 | enum ovl_path_type type = ovl_path_real(dentry, &realpath); |
e9be9d5e MS |
308 | |
309 | err = ovl_want_write(dentry); | |
310 | if (err) | |
311 | goto out; | |
312 | ||
52148463 | 313 | err = -ENODATA; |
b581755b | 314 | if (ovl_is_private_xattr(name)) |
e9be9d5e MS |
315 | goto out_drop_write; |
316 | ||
1afaba1e | 317 | if (!OVL_TYPE_UPPER(type)) { |
e9be9d5e MS |
318 | err = vfs_getxattr(realpath.dentry, name, NULL, 0); |
319 | if (err < 0) | |
320 | goto out_drop_write; | |
321 | ||
322 | err = ovl_copy_up(dentry); | |
323 | if (err) | |
324 | goto out_drop_write; | |
325 | ||
326 | ovl_path_upper(dentry, &realpath); | |
327 | } | |
328 | ||
329 | err = vfs_removexattr(realpath.dentry, name); | |
330 | out_drop_write: | |
331 | ovl_drop_write(dentry); | |
332 | out: | |
333 | return err; | |
334 | } | |
335 | ||
336 | static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type, | |
337 | struct dentry *realdentry) | |
338 | { | |
1afaba1e | 339 | if (OVL_TYPE_UPPER(type)) |
e9be9d5e MS |
340 | return false; |
341 | ||
342 | if (special_file(realdentry->d_inode->i_mode)) | |
343 | return false; | |
344 | ||
345 | if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) | |
346 | return false; | |
347 | ||
348 | return true; | |
349 | } | |
350 | ||
4bacc9c9 | 351 | struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags) |
e9be9d5e MS |
352 | { |
353 | int err; | |
354 | struct path realpath; | |
355 | enum ovl_path_type type; | |
e9be9d5e | 356 | |
9391dd00 AV |
357 | if (d_is_dir(dentry)) |
358 | return d_backing_inode(dentry); | |
359 | ||
e9be9d5e | 360 | type = ovl_path_real(dentry, &realpath); |
4bacc9c9 | 361 | if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) { |
e9be9d5e MS |
362 | err = ovl_want_write(dentry); |
363 | if (err) | |
4bacc9c9 | 364 | return ERR_PTR(err); |
e9be9d5e | 365 | |
4bacc9c9 | 366 | if (file_flags & O_TRUNC) |
0f7ff2da | 367 | err = ovl_copy_up_truncate(dentry); |
e9be9d5e MS |
368 | else |
369 | err = ovl_copy_up(dentry); | |
f25801ee | 370 | ovl_drop_write(dentry); |
e9be9d5e | 371 | if (err) |
4bacc9c9 | 372 | return ERR_PTR(err); |
e9be9d5e MS |
373 | |
374 | ovl_path_upper(dentry, &realpath); | |
375 | } | |
376 | ||
1c8a47df MS |
377 | if (realpath.dentry->d_flags & DCACHE_OP_SELECT_INODE) |
378 | return realpath.dentry->d_op->d_select_inode(realpath.dentry, file_flags); | |
379 | ||
4bacc9c9 | 380 | return d_backing_inode(realpath.dentry); |
e9be9d5e MS |
381 | } |
382 | ||
383 | static const struct inode_operations ovl_file_inode_operations = { | |
384 | .setattr = ovl_setattr, | |
385 | .permission = ovl_permission, | |
386 | .getattr = ovl_getattr, | |
387 | .setxattr = ovl_setxattr, | |
388 | .getxattr = ovl_getxattr, | |
389 | .listxattr = ovl_listxattr, | |
390 | .removexattr = ovl_removexattr, | |
e9be9d5e MS |
391 | }; |
392 | ||
393 | static const struct inode_operations ovl_symlink_inode_operations = { | |
394 | .setattr = ovl_setattr, | |
6b255391 | 395 | .get_link = ovl_get_link, |
e9be9d5e MS |
396 | .readlink = ovl_readlink, |
397 | .getattr = ovl_getattr, | |
398 | .setxattr = ovl_setxattr, | |
399 | .getxattr = ovl_getxattr, | |
400 | .listxattr = ovl_listxattr, | |
401 | .removexattr = ovl_removexattr, | |
402 | }; | |
403 | ||
404 | struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, | |
405 | struct ovl_entry *oe) | |
406 | { | |
407 | struct inode *inode; | |
408 | ||
409 | inode = new_inode(sb); | |
410 | if (!inode) | |
411 | return NULL; | |
412 | ||
413 | mode &= S_IFMT; | |
414 | ||
415 | inode->i_ino = get_next_ino(); | |
416 | inode->i_mode = mode; | |
417 | inode->i_flags |= S_NOATIME | S_NOCMTIME; | |
418 | ||
419 | switch (mode) { | |
420 | case S_IFDIR: | |
421 | inode->i_private = oe; | |
422 | inode->i_op = &ovl_dir_inode_operations; | |
423 | inode->i_fop = &ovl_dir_operations; | |
424 | break; | |
425 | ||
426 | case S_IFLNK: | |
427 | inode->i_op = &ovl_symlink_inode_operations; | |
428 | break; | |
429 | ||
430 | case S_IFREG: | |
431 | case S_IFSOCK: | |
432 | case S_IFBLK: | |
433 | case S_IFCHR: | |
434 | case S_IFIFO: | |
435 | inode->i_op = &ovl_file_inode_operations; | |
436 | break; | |
437 | ||
438 | default: | |
439 | WARN(1, "illegal file type: %i\n", mode); | |
440 | iput(inode); | |
441 | inode = NULL; | |
442 | } | |
443 | ||
444 | return inode; | |
e9be9d5e | 445 | } |