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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/file.h> | |
13 | #include <linux/splice.h> | |
14 | #include <linux/xattr.h> | |
15 | #include <linux/security.h> | |
16 | #include <linux/uaccess.h> | |
17 | #include <linux/sched.h> | |
18 | #include <linux/namei.h> | |
19 | #include "overlayfs.h" | |
20 | ||
21 | #define OVL_COPY_UP_CHUNK_SIZE (1 << 20) | |
22 | ||
23 | int ovl_copy_xattr(struct dentry *old, struct dentry *new) | |
24 | { | |
25 | ssize_t list_size, size; | |
26 | char *buf, *name, *value; | |
27 | int error; | |
28 | ||
29 | if (!old->d_inode->i_op->getxattr || | |
30 | !new->d_inode->i_op->getxattr) | |
31 | return 0; | |
32 | ||
33 | list_size = vfs_listxattr(old, NULL, 0); | |
34 | if (list_size <= 0) { | |
35 | if (list_size == -EOPNOTSUPP) | |
36 | return 0; | |
37 | return list_size; | |
38 | } | |
39 | ||
40 | buf = kzalloc(list_size, GFP_KERNEL); | |
41 | if (!buf) | |
42 | return -ENOMEM; | |
43 | ||
44 | error = -ENOMEM; | |
45 | value = kmalloc(XATTR_SIZE_MAX, GFP_KERNEL); | |
46 | if (!value) | |
47 | goto out; | |
48 | ||
49 | list_size = vfs_listxattr(old, buf, list_size); | |
50 | if (list_size <= 0) { | |
51 | error = list_size; | |
52 | goto out_free_value; | |
53 | } | |
54 | ||
55 | for (name = buf; name < (buf + list_size); name += strlen(name) + 1) { | |
56 | size = vfs_getxattr(old, name, value, XATTR_SIZE_MAX); | |
57 | if (size <= 0) { | |
58 | error = size; | |
59 | goto out_free_value; | |
60 | } | |
61 | error = vfs_setxattr(new, name, value, size, 0); | |
62 | if (error) | |
63 | goto out_free_value; | |
64 | } | |
65 | ||
66 | out_free_value: | |
67 | kfree(value); | |
68 | out: | |
69 | kfree(buf); | |
70 | return error; | |
71 | } | |
72 | ||
73 | static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len) | |
74 | { | |
75 | struct file *old_file; | |
76 | struct file *new_file; | |
77 | loff_t old_pos = 0; | |
78 | loff_t new_pos = 0; | |
79 | int error = 0; | |
80 | ||
81 | if (len == 0) | |
82 | return 0; | |
83 | ||
84 | old_file = ovl_path_open(old, O_RDONLY); | |
85 | if (IS_ERR(old_file)) | |
86 | return PTR_ERR(old_file); | |
87 | ||
88 | new_file = ovl_path_open(new, O_WRONLY); | |
89 | if (IS_ERR(new_file)) { | |
90 | error = PTR_ERR(new_file); | |
91 | goto out_fput; | |
92 | } | |
93 | ||
94 | /* FIXME: copy up sparse files efficiently */ | |
95 | while (len) { | |
96 | size_t this_len = OVL_COPY_UP_CHUNK_SIZE; | |
97 | long bytes; | |
98 | ||
99 | if (len < this_len) | |
100 | this_len = len; | |
101 | ||
102 | if (signal_pending_state(TASK_KILLABLE, current)) { | |
103 | error = -EINTR; | |
104 | break; | |
105 | } | |
106 | ||
107 | bytes = do_splice_direct(old_file, &old_pos, | |
108 | new_file, &new_pos, | |
109 | this_len, SPLICE_F_MOVE); | |
110 | if (bytes <= 0) { | |
111 | error = bytes; | |
112 | break; | |
113 | } | |
114 | WARN_ON(old_pos != new_pos); | |
115 | ||
116 | len -= bytes; | |
117 | } | |
118 | ||
119 | fput(new_file); | |
120 | out_fput: | |
121 | fput(old_file); | |
122 | return error; | |
123 | } | |
124 | ||
125 | static char *ovl_read_symlink(struct dentry *realdentry) | |
126 | { | |
127 | int res; | |
128 | char *buf; | |
129 | struct inode *inode = realdentry->d_inode; | |
130 | mm_segment_t old_fs; | |
131 | ||
132 | res = -EINVAL; | |
133 | if (!inode->i_op->readlink) | |
134 | goto err; | |
135 | ||
136 | res = -ENOMEM; | |
137 | buf = (char *) __get_free_page(GFP_KERNEL); | |
138 | if (!buf) | |
139 | goto err; | |
140 | ||
141 | old_fs = get_fs(); | |
142 | set_fs(get_ds()); | |
143 | /* The cast to a user pointer is valid due to the set_fs() */ | |
144 | res = inode->i_op->readlink(realdentry, | |
145 | (char __user *)buf, PAGE_SIZE - 1); | |
146 | set_fs(old_fs); | |
147 | if (res < 0) { | |
148 | free_page((unsigned long) buf); | |
149 | goto err; | |
150 | } | |
151 | buf[res] = '\0'; | |
152 | ||
153 | return buf; | |
154 | ||
155 | err: | |
156 | return ERR_PTR(res); | |
157 | } | |
158 | ||
159 | static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat) | |
160 | { | |
161 | struct iattr attr = { | |
162 | .ia_valid = | |
163 | ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET, | |
164 | .ia_atime = stat->atime, | |
165 | .ia_mtime = stat->mtime, | |
166 | }; | |
167 | ||
168 | return notify_change(upperdentry, &attr, NULL); | |
169 | } | |
170 | ||
171 | int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat) | |
172 | { | |
173 | int err = 0; | |
174 | ||
175 | if (!S_ISLNK(stat->mode)) { | |
176 | struct iattr attr = { | |
177 | .ia_valid = ATTR_MODE, | |
178 | .ia_mode = stat->mode, | |
179 | }; | |
180 | err = notify_change(upperdentry, &attr, NULL); | |
181 | } | |
182 | if (!err) { | |
183 | struct iattr attr = { | |
184 | .ia_valid = ATTR_UID | ATTR_GID, | |
185 | .ia_uid = stat->uid, | |
186 | .ia_gid = stat->gid, | |
187 | }; | |
188 | err = notify_change(upperdentry, &attr, NULL); | |
189 | } | |
190 | if (!err) | |
191 | ovl_set_timestamps(upperdentry, stat); | |
192 | ||
193 | return err; | |
e9be9d5e MS |
194 | } |
195 | ||
196 | static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir, | |
197 | struct dentry *dentry, struct path *lowerpath, | |
198 | struct kstat *stat, struct iattr *attr, | |
199 | const char *link) | |
200 | { | |
201 | struct inode *wdir = workdir->d_inode; | |
202 | struct inode *udir = upperdir->d_inode; | |
203 | struct dentry *newdentry = NULL; | |
204 | struct dentry *upper = NULL; | |
205 | umode_t mode = stat->mode; | |
206 | int err; | |
207 | ||
208 | newdentry = ovl_lookup_temp(workdir, dentry); | |
209 | err = PTR_ERR(newdentry); | |
210 | if (IS_ERR(newdentry)) | |
211 | goto out; | |
212 | ||
213 | upper = lookup_one_len(dentry->d_name.name, upperdir, | |
214 | dentry->d_name.len); | |
215 | err = PTR_ERR(upper); | |
216 | if (IS_ERR(upper)) | |
217 | goto out1; | |
218 | ||
219 | /* Can't properly set mode on creation because of the umask */ | |
220 | stat->mode &= S_IFMT; | |
221 | err = ovl_create_real(wdir, newdentry, stat, link, NULL, true); | |
222 | stat->mode = mode; | |
223 | if (err) | |
224 | goto out2; | |
225 | ||
226 | if (S_ISREG(stat->mode)) { | |
227 | struct path upperpath; | |
228 | ovl_path_upper(dentry, &upperpath); | |
229 | BUG_ON(upperpath.dentry != NULL); | |
230 | upperpath.dentry = newdentry; | |
231 | ||
232 | err = ovl_copy_up_data(lowerpath, &upperpath, stat->size); | |
233 | if (err) | |
234 | goto out_cleanup; | |
235 | } | |
236 | ||
237 | err = ovl_copy_xattr(lowerpath->dentry, newdentry); | |
238 | if (err) | |
239 | goto out_cleanup; | |
240 | ||
241 | mutex_lock(&newdentry->d_inode->i_mutex); | |
242 | err = ovl_set_attr(newdentry, stat); | |
243 | if (!err && attr) | |
244 | err = notify_change(newdentry, attr, NULL); | |
245 | mutex_unlock(&newdentry->d_inode->i_mutex); | |
246 | if (err) | |
247 | goto out_cleanup; | |
248 | ||
249 | err = ovl_do_rename(wdir, newdentry, udir, upper, 0); | |
250 | if (err) | |
251 | goto out_cleanup; | |
252 | ||
253 | ovl_dentry_update(dentry, newdentry); | |
254 | newdentry = NULL; | |
255 | ||
256 | /* | |
257 | * Non-directores become opaque when copied up. | |
258 | */ | |
259 | if (!S_ISDIR(stat->mode)) | |
260 | ovl_dentry_set_opaque(dentry, true); | |
261 | out2: | |
262 | dput(upper); | |
263 | out1: | |
264 | dput(newdentry); | |
265 | out: | |
266 | return err; | |
267 | ||
268 | out_cleanup: | |
269 | ovl_cleanup(wdir, newdentry); | |
270 | goto out; | |
271 | } | |
272 | ||
273 | /* | |
274 | * Copy up a single dentry | |
275 | * | |
276 | * Directory renames only allowed on "pure upper" (already created on | |
277 | * upper filesystem, never copied up). Directories which are on lower or | |
278 | * are merged may not be renamed. For these -EXDEV is returned and | |
279 | * userspace has to deal with it. This means, when copying up a | |
280 | * directory we can rely on it and ancestors being stable. | |
281 | * | |
282 | * Non-directory renames start with copy up of source if necessary. The | |
283 | * actual rename will only proceed once the copy up was successful. Copy | |
284 | * up uses upper parent i_mutex for exclusion. Since rename can change | |
285 | * d_parent it is possible that the copy up will lock the old parent. At | |
286 | * that point the file will have already been copied up anyway. | |
287 | */ | |
288 | int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry, | |
289 | struct path *lowerpath, struct kstat *stat, | |
290 | struct iattr *attr) | |
291 | { | |
292 | struct dentry *workdir = ovl_workdir(dentry); | |
293 | int err; | |
294 | struct kstat pstat; | |
295 | struct path parentpath; | |
296 | struct dentry *upperdir; | |
297 | struct dentry *upperdentry; | |
298 | const struct cred *old_cred; | |
299 | struct cred *override_cred; | |
300 | char *link = NULL; | |
301 | ||
302 | ovl_path_upper(parent, &parentpath); | |
303 | upperdir = parentpath.dentry; | |
304 | ||
305 | err = vfs_getattr(&parentpath, &pstat); | |
306 | if (err) | |
307 | return err; | |
308 | ||
309 | if (S_ISLNK(stat->mode)) { | |
310 | link = ovl_read_symlink(lowerpath->dentry); | |
311 | if (IS_ERR(link)) | |
312 | return PTR_ERR(link); | |
313 | } | |
314 | ||
315 | err = -ENOMEM; | |
316 | override_cred = prepare_creds(); | |
317 | if (!override_cred) | |
318 | goto out_free_link; | |
319 | ||
320 | override_cred->fsuid = stat->uid; | |
321 | override_cred->fsgid = stat->gid; | |
322 | /* | |
323 | * CAP_SYS_ADMIN for copying up extended attributes | |
324 | * CAP_DAC_OVERRIDE for create | |
325 | * CAP_FOWNER for chmod, timestamp update | |
326 | * CAP_FSETID for chmod | |
327 | * CAP_CHOWN for chown | |
328 | * CAP_MKNOD for mknod | |
329 | */ | |
330 | cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN); | |
331 | cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE); | |
332 | cap_raise(override_cred->cap_effective, CAP_FOWNER); | |
333 | cap_raise(override_cred->cap_effective, CAP_FSETID); | |
334 | cap_raise(override_cred->cap_effective, CAP_CHOWN); | |
335 | cap_raise(override_cred->cap_effective, CAP_MKNOD); | |
336 | old_cred = override_creds(override_cred); | |
337 | ||
338 | err = -EIO; | |
339 | if (lock_rename(workdir, upperdir) != NULL) { | |
340 | pr_err("overlayfs: failed to lock workdir+upperdir\n"); | |
341 | goto out_unlock; | |
342 | } | |
343 | upperdentry = ovl_dentry_upper(dentry); | |
344 | if (upperdentry) { | |
345 | unlock_rename(workdir, upperdir); | |
346 | err = 0; | |
347 | /* Raced with another copy-up? Do the setattr here */ | |
348 | if (attr) { | |
349 | mutex_lock(&upperdentry->d_inode->i_mutex); | |
350 | err = notify_change(upperdentry, attr, NULL); | |
351 | mutex_unlock(&upperdentry->d_inode->i_mutex); | |
352 | } | |
353 | goto out_put_cred; | |
354 | } | |
355 | ||
356 | err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath, | |
357 | stat, attr, link); | |
358 | if (!err) { | |
359 | /* Restore timestamps on parent (best effort) */ | |
360 | ovl_set_timestamps(upperdir, &pstat); | |
361 | } | |
362 | out_unlock: | |
363 | unlock_rename(workdir, upperdir); | |
364 | out_put_cred: | |
365 | revert_creds(old_cred); | |
366 | put_cred(override_cred); | |
367 | ||
368 | out_free_link: | |
369 | if (link) | |
370 | free_page((unsigned long) link); | |
371 | ||
372 | return err; | |
373 | } | |
374 | ||
375 | int ovl_copy_up(struct dentry *dentry) | |
376 | { | |
377 | int err; | |
378 | ||
379 | err = 0; | |
380 | while (!err) { | |
381 | struct dentry *next; | |
382 | struct dentry *parent; | |
383 | struct path lowerpath; | |
384 | struct kstat stat; | |
385 | enum ovl_path_type type = ovl_path_type(dentry); | |
386 | ||
1afaba1e | 387 | if (OVL_TYPE_UPPER(type)) |
e9be9d5e MS |
388 | break; |
389 | ||
390 | next = dget(dentry); | |
391 | /* find the topmost dentry not yet copied up */ | |
392 | for (;;) { | |
393 | parent = dget_parent(next); | |
394 | ||
395 | type = ovl_path_type(parent); | |
1afaba1e | 396 | if (OVL_TYPE_UPPER(type)) |
e9be9d5e MS |
397 | break; |
398 | ||
399 | dput(next); | |
400 | next = parent; | |
401 | } | |
402 | ||
403 | ovl_path_lower(next, &lowerpath); | |
404 | err = vfs_getattr(&lowerpath, &stat); | |
405 | if (!err) | |
406 | err = ovl_copy_up_one(parent, next, &lowerpath, &stat, NULL); | |
407 | ||
408 | dput(parent); | |
409 | dput(next); | |
410 | } | |
411 | ||
412 | return err; | |
413 | } |