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