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Miklos Szeredie9be9d52014-10-24 00:14:38 +02001/*
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
23int 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
66out_free_value:
67 kfree(value);
68out:
69 kfree(buf);
70 return error;
71}
72
73static 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);
120out_fput:
121 fput(old_file);
122 return error;
123}
124
125static 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
155err:
156 return ERR_PTR(res);
157}
158
159static 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
171int 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;
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200194}
195
196static 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);
261out2:
262 dput(upper);
263out1:
264 dput(newdentry);
265out:
266 return err;
267
268out_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 */
288int 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 }
362out_unlock:
363 unlock_rename(workdir, upperdir);
364out_put_cred:
365 revert_creds(old_cred);
366 put_cred(override_cred);
367
368out_free_link:
369 if (link)
370 free_page((unsigned long) link);
371
372 return err;
373}
374
375int 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
Miklos Szeredi1afaba12014-12-13 00:59:42 +0100387 if (OVL_TYPE_UPPER(type))
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200388 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);
Miklos Szeredi1afaba12014-12-13 00:59:42 +0100396 if (OVL_TYPE_UPPER(type))
Miklos Szeredie9be9d52014-10-24 00:14:38 +0200397 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}