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 | ||
15 | static int ovl_copy_up_last(struct dentry *dentry, struct iattr *attr, | |
16 | bool no_data) | |
17 | { | |
18 | int err; | |
19 | struct dentry *parent; | |
20 | struct kstat stat; | |
21 | struct path lowerpath; | |
22 | ||
23 | parent = dget_parent(dentry); | |
24 | err = ovl_copy_up(parent); | |
25 | if (err) | |
26 | goto out_dput_parent; | |
27 | ||
28 | ovl_path_lower(dentry, &lowerpath); | |
29 | err = vfs_getattr(&lowerpath, &stat); | |
30 | if (err) | |
31 | goto out_dput_parent; | |
32 | ||
33 | if (no_data) | |
34 | stat.size = 0; | |
35 | ||
36 | err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat, attr); | |
37 | ||
38 | out_dput_parent: | |
39 | dput(parent); | |
40 | return err; | |
41 | } | |
42 | ||
43 | int ovl_setattr(struct dentry *dentry, struct iattr *attr) | |
44 | { | |
45 | int err; | |
46 | struct dentry *upperdentry; | |
47 | ||
48 | err = ovl_want_write(dentry); | |
49 | if (err) | |
50 | goto out; | |
51 | ||
52 | upperdentry = ovl_dentry_upper(dentry); | |
53 | if (upperdentry) { | |
54 | mutex_lock(&upperdentry->d_inode->i_mutex); | |
55 | err = notify_change(upperdentry, attr, NULL); | |
56 | mutex_unlock(&upperdentry->d_inode->i_mutex); | |
57 | } else { | |
58 | err = ovl_copy_up_last(dentry, attr, false); | |
59 | } | |
60 | ovl_drop_write(dentry); | |
61 | out: | |
62 | return err; | |
63 | } | |
64 | ||
65 | static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry, | |
66 | struct kstat *stat) | |
67 | { | |
68 | struct path realpath; | |
69 | ||
70 | ovl_path_real(dentry, &realpath); | |
71 | return vfs_getattr(&realpath, stat); | |
72 | } | |
73 | ||
74 | int ovl_permission(struct inode *inode, int mask) | |
75 | { | |
76 | struct ovl_entry *oe; | |
77 | struct dentry *alias = NULL; | |
78 | struct inode *realinode; | |
79 | struct dentry *realdentry; | |
80 | bool is_upper; | |
81 | int err; | |
82 | ||
83 | if (S_ISDIR(inode->i_mode)) { | |
84 | oe = inode->i_private; | |
85 | } else if (mask & MAY_NOT_BLOCK) { | |
86 | return -ECHILD; | |
87 | } else { | |
88 | /* | |
89 | * For non-directories find an alias and get the info | |
90 | * from there. | |
91 | */ | |
92 | alias = d_find_any_alias(inode); | |
93 | if (WARN_ON(!alias)) | |
94 | return -ENOENT; | |
95 | ||
96 | oe = alias->d_fsdata; | |
97 | } | |
98 | ||
99 | realdentry = ovl_entry_real(oe, &is_upper); | |
100 | ||
101 | /* Careful in RCU walk mode */ | |
102 | realinode = ACCESS_ONCE(realdentry->d_inode); | |
103 | if (!realinode) { | |
104 | WARN_ON(!(mask & MAY_NOT_BLOCK)); | |
105 | err = -ENOENT; | |
106 | goto out_dput; | |
107 | } | |
108 | ||
109 | if (mask & MAY_WRITE) { | |
110 | umode_t mode = realinode->i_mode; | |
111 | ||
112 | /* | |
113 | * Writes will always be redirected to upper layer, so | |
114 | * ignore lower layer being read-only. | |
115 | * | |
116 | * If the overlay itself is read-only then proceed | |
117 | * with the permission check, don't return EROFS. | |
118 | * This will only happen if this is the lower layer of | |
119 | * another overlayfs. | |
120 | * | |
121 | * If upper fs becomes read-only after the overlay was | |
122 | * constructed return EROFS to prevent modification of | |
123 | * upper layer. | |
124 | */ | |
125 | err = -EROFS; | |
126 | if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) && | |
127 | (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) | |
128 | goto out_dput; | |
129 | } | |
130 | ||
131 | err = __inode_permission(realinode, mask); | |
132 | out_dput: | |
133 | dput(alias); | |
134 | return err; | |
135 | } | |
136 | ||
137 | ||
138 | struct ovl_link_data { | |
139 | struct dentry *realdentry; | |
140 | void *cookie; | |
141 | }; | |
142 | ||
6e77137b | 143 | static const char *ovl_follow_link(struct dentry *dentry, void **cookie) |
e9be9d5e | 144 | { |
e9be9d5e MS |
145 | struct dentry *realdentry; |
146 | struct inode *realinode; | |
3188b295 | 147 | struct ovl_link_data *data = NULL; |
680baacb | 148 | const char *ret; |
e9be9d5e MS |
149 | |
150 | realdentry = ovl_dentry_real(dentry); | |
151 | realinode = realdentry->d_inode; | |
152 | ||
153 | if (WARN_ON(!realinode->i_op->follow_link)) | |
154 | return ERR_PTR(-EPERM); | |
155 | ||
e9be9d5e | 156 | if (realinode->i_op->put_link) { |
e9be9d5e | 157 | data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL); |
3188b295 | 158 | if (!data) |
e9be9d5e | 159 | return ERR_PTR(-ENOMEM); |
e9be9d5e | 160 | data->realdentry = realdentry; |
3188b295 | 161 | } |
e9be9d5e | 162 | |
6e77137b | 163 | ret = realinode->i_op->follow_link(realdentry, cookie); |
680baacb | 164 | if (IS_ERR_OR_NULL(ret)) { |
3188b295 N |
165 | kfree(data); |
166 | return ret; | |
e9be9d5e | 167 | } |
3188b295 N |
168 | |
169 | if (data) | |
680baacb | 170 | data->cookie = *cookie; |
3188b295 | 171 | |
680baacb AV |
172 | *cookie = data; |
173 | ||
174 | return ret; | |
e9be9d5e MS |
175 | } |
176 | ||
5f2c4179 | 177 | static void ovl_put_link(struct inode *unused, void *c) |
e9be9d5e MS |
178 | { |
179 | struct inode *realinode; | |
180 | struct ovl_link_data *data = c; | |
181 | ||
182 | if (!data) | |
183 | return; | |
184 | ||
185 | realinode = data->realdentry->d_inode; | |
5f2c4179 | 186 | realinode->i_op->put_link(realinode, data->cookie); |
e9be9d5e MS |
187 | kfree(data); |
188 | } | |
189 | ||
190 | static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz) | |
191 | { | |
192 | struct path realpath; | |
193 | struct inode *realinode; | |
194 | ||
195 | ovl_path_real(dentry, &realpath); | |
196 | realinode = realpath.dentry->d_inode; | |
197 | ||
198 | if (!realinode->i_op->readlink) | |
199 | return -EINVAL; | |
200 | ||
201 | touch_atime(&realpath); | |
202 | ||
203 | return realinode->i_op->readlink(realpath.dentry, buf, bufsiz); | |
204 | } | |
205 | ||
206 | ||
207 | static bool ovl_is_private_xattr(const char *name) | |
208 | { | |
cead89bb | 209 | return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0; |
e9be9d5e MS |
210 | } |
211 | ||
212 | int ovl_setxattr(struct dentry *dentry, const char *name, | |
213 | const void *value, size_t size, int flags) | |
214 | { | |
215 | int err; | |
216 | struct dentry *upperdentry; | |
217 | ||
218 | err = ovl_want_write(dentry); | |
219 | if (err) | |
220 | goto out; | |
221 | ||
222 | err = -EPERM; | |
223 | if (ovl_is_private_xattr(name)) | |
224 | goto out_drop_write; | |
225 | ||
226 | err = ovl_copy_up(dentry); | |
227 | if (err) | |
228 | goto out_drop_write; | |
229 | ||
230 | upperdentry = ovl_dentry_upper(dentry); | |
231 | err = vfs_setxattr(upperdentry, name, value, size, flags); | |
232 | ||
233 | out_drop_write: | |
234 | ovl_drop_write(dentry); | |
235 | out: | |
236 | return err; | |
237 | } | |
238 | ||
52148463 MS |
239 | static bool ovl_need_xattr_filter(struct dentry *dentry, |
240 | enum ovl_path_type type) | |
241 | { | |
1afaba1e MS |
242 | if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER) |
243 | return S_ISDIR(dentry->d_inode->i_mode); | |
244 | else | |
245 | return false; | |
52148463 MS |
246 | } |
247 | ||
e9be9d5e MS |
248 | ssize_t ovl_getxattr(struct dentry *dentry, const char *name, |
249 | void *value, size_t size) | |
250 | { | |
52148463 MS |
251 | struct path realpath; |
252 | enum ovl_path_type type = ovl_path_real(dentry, &realpath); | |
253 | ||
254 | if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) | |
e9be9d5e MS |
255 | return -ENODATA; |
256 | ||
52148463 | 257 | return vfs_getxattr(realpath.dentry, name, value, size); |
e9be9d5e MS |
258 | } |
259 | ||
260 | ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) | |
261 | { | |
52148463 MS |
262 | struct path realpath; |
263 | enum ovl_path_type type = ovl_path_real(dentry, &realpath); | |
e9be9d5e MS |
264 | ssize_t res; |
265 | int off; | |
266 | ||
52148463 | 267 | res = vfs_listxattr(realpath.dentry, list, size); |
e9be9d5e MS |
268 | if (res <= 0 || size == 0) |
269 | return res; | |
270 | ||
52148463 | 271 | if (!ovl_need_xattr_filter(dentry, type)) |
e9be9d5e MS |
272 | return res; |
273 | ||
274 | /* filter out private xattrs */ | |
275 | for (off = 0; off < res;) { | |
276 | char *s = list + off; | |
277 | size_t slen = strlen(s) + 1; | |
278 | ||
279 | BUG_ON(off + slen > res); | |
280 | ||
281 | if (ovl_is_private_xattr(s)) { | |
282 | res -= slen; | |
283 | memmove(s, s + slen, res - off); | |
284 | } else { | |
285 | off += slen; | |
286 | } | |
287 | } | |
288 | ||
289 | return res; | |
290 | } | |
291 | ||
292 | int ovl_removexattr(struct dentry *dentry, const char *name) | |
293 | { | |
294 | int err; | |
295 | struct path realpath; | |
52148463 | 296 | enum ovl_path_type type = ovl_path_real(dentry, &realpath); |
e9be9d5e MS |
297 | |
298 | err = ovl_want_write(dentry); | |
299 | if (err) | |
300 | goto out; | |
301 | ||
52148463 MS |
302 | err = -ENODATA; |
303 | if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name)) | |
e9be9d5e MS |
304 | goto out_drop_write; |
305 | ||
1afaba1e | 306 | if (!OVL_TYPE_UPPER(type)) { |
e9be9d5e MS |
307 | err = vfs_getxattr(realpath.dentry, name, NULL, 0); |
308 | if (err < 0) | |
309 | goto out_drop_write; | |
310 | ||
311 | err = ovl_copy_up(dentry); | |
312 | if (err) | |
313 | goto out_drop_write; | |
314 | ||
315 | ovl_path_upper(dentry, &realpath); | |
316 | } | |
317 | ||
318 | err = vfs_removexattr(realpath.dentry, name); | |
319 | out_drop_write: | |
320 | ovl_drop_write(dentry); | |
321 | out: | |
322 | return err; | |
323 | } | |
324 | ||
325 | static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type, | |
326 | struct dentry *realdentry) | |
327 | { | |
1afaba1e | 328 | if (OVL_TYPE_UPPER(type)) |
e9be9d5e MS |
329 | return false; |
330 | ||
331 | if (special_file(realdentry->d_inode->i_mode)) | |
332 | return false; | |
333 | ||
334 | if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC)) | |
335 | return false; | |
336 | ||
337 | return true; | |
338 | } | |
339 | ||
4bacc9c9 | 340 | struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags) |
e9be9d5e MS |
341 | { |
342 | int err; | |
343 | struct path realpath; | |
344 | enum ovl_path_type type; | |
e9be9d5e | 345 | |
9391dd00 AV |
346 | if (d_is_dir(dentry)) |
347 | return d_backing_inode(dentry); | |
348 | ||
e9be9d5e | 349 | type = ovl_path_real(dentry, &realpath); |
4bacc9c9 | 350 | if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) { |
e9be9d5e MS |
351 | err = ovl_want_write(dentry); |
352 | if (err) | |
4bacc9c9 | 353 | return ERR_PTR(err); |
e9be9d5e | 354 | |
4bacc9c9 | 355 | if (file_flags & O_TRUNC) |
e9be9d5e MS |
356 | err = ovl_copy_up_last(dentry, NULL, true); |
357 | else | |
358 | err = ovl_copy_up(dentry); | |
f25801ee | 359 | ovl_drop_write(dentry); |
e9be9d5e | 360 | if (err) |
4bacc9c9 | 361 | return ERR_PTR(err); |
e9be9d5e MS |
362 | |
363 | ovl_path_upper(dentry, &realpath); | |
364 | } | |
365 | ||
4bacc9c9 | 366 | return d_backing_inode(realpath.dentry); |
e9be9d5e MS |
367 | } |
368 | ||
369 | static const struct inode_operations ovl_file_inode_operations = { | |
370 | .setattr = ovl_setattr, | |
371 | .permission = ovl_permission, | |
372 | .getattr = ovl_getattr, | |
373 | .setxattr = ovl_setxattr, | |
374 | .getxattr = ovl_getxattr, | |
375 | .listxattr = ovl_listxattr, | |
376 | .removexattr = ovl_removexattr, | |
e9be9d5e MS |
377 | }; |
378 | ||
379 | static const struct inode_operations ovl_symlink_inode_operations = { | |
380 | .setattr = ovl_setattr, | |
381 | .follow_link = ovl_follow_link, | |
382 | .put_link = ovl_put_link, | |
383 | .readlink = ovl_readlink, | |
384 | .getattr = ovl_getattr, | |
385 | .setxattr = ovl_setxattr, | |
386 | .getxattr = ovl_getxattr, | |
387 | .listxattr = ovl_listxattr, | |
388 | .removexattr = ovl_removexattr, | |
389 | }; | |
390 | ||
391 | struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, | |
392 | struct ovl_entry *oe) | |
393 | { | |
394 | struct inode *inode; | |
395 | ||
396 | inode = new_inode(sb); | |
397 | if (!inode) | |
398 | return NULL; | |
399 | ||
400 | mode &= S_IFMT; | |
401 | ||
402 | inode->i_ino = get_next_ino(); | |
403 | inode->i_mode = mode; | |
404 | inode->i_flags |= S_NOATIME | S_NOCMTIME; | |
405 | ||
406 | switch (mode) { | |
407 | case S_IFDIR: | |
408 | inode->i_private = oe; | |
409 | inode->i_op = &ovl_dir_inode_operations; | |
410 | inode->i_fop = &ovl_dir_operations; | |
411 | break; | |
412 | ||
413 | case S_IFLNK: | |
414 | inode->i_op = &ovl_symlink_inode_operations; | |
415 | break; | |
416 | ||
417 | case S_IFREG: | |
418 | case S_IFSOCK: | |
419 | case S_IFBLK: | |
420 | case S_IFCHR: | |
421 | case S_IFIFO: | |
422 | inode->i_op = &ovl_file_inode_operations; | |
423 | break; | |
424 | ||
425 | default: | |
426 | WARN(1, "illegal file type: %i\n", mode); | |
427 | iput(inode); | |
428 | inode = NULL; | |
429 | } | |
430 | ||
431 | return inode; | |
e9be9d5e | 432 | } |