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-rw-r--r--fs/overlayfs/copy_up.c414
1 files changed, 414 insertions, 0 deletions
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
new file mode 100644
index 000000000000..ea10a8719107
--- /dev/null
+++ b/fs/overlayfs/copy_up.c
@@ -0,0 +1,414 @@
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
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;
194
195}
196
197static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
198 struct dentry *dentry, struct path *lowerpath,
199 struct kstat *stat, struct iattr *attr,
200 const char *link)
201{
202 struct inode *wdir = workdir->d_inode;
203 struct inode *udir = upperdir->d_inode;
204 struct dentry *newdentry = NULL;
205 struct dentry *upper = NULL;
206 umode_t mode = stat->mode;
207 int err;
208
209 newdentry = ovl_lookup_temp(workdir, dentry);
210 err = PTR_ERR(newdentry);
211 if (IS_ERR(newdentry))
212 goto out;
213
214 upper = lookup_one_len(dentry->d_name.name, upperdir,
215 dentry->d_name.len);
216 err = PTR_ERR(upper);
217 if (IS_ERR(upper))
218 goto out1;
219
220 /* Can't properly set mode on creation because of the umask */
221 stat->mode &= S_IFMT;
222 err = ovl_create_real(wdir, newdentry, stat, link, NULL, true);
223 stat->mode = mode;
224 if (err)
225 goto out2;
226
227 if (S_ISREG(stat->mode)) {
228 struct path upperpath;
229 ovl_path_upper(dentry, &upperpath);
230 BUG_ON(upperpath.dentry != NULL);
231 upperpath.dentry = newdentry;
232
233 err = ovl_copy_up_data(lowerpath, &upperpath, stat->size);
234 if (err)
235 goto out_cleanup;
236 }
237
238 err = ovl_copy_xattr(lowerpath->dentry, newdentry);
239 if (err)
240 goto out_cleanup;
241
242 mutex_lock(&newdentry->d_inode->i_mutex);
243 err = ovl_set_attr(newdentry, stat);
244 if (!err && attr)
245 err = notify_change(newdentry, attr, NULL);
246 mutex_unlock(&newdentry->d_inode->i_mutex);
247 if (err)
248 goto out_cleanup;
249
250 err = ovl_do_rename(wdir, newdentry, udir, upper, 0);
251 if (err)
252 goto out_cleanup;
253
254 ovl_dentry_update(dentry, newdentry);
255 newdentry = NULL;
256
257 /*
258 * Non-directores become opaque when copied up.
259 */
260 if (!S_ISDIR(stat->mode))
261 ovl_dentry_set_opaque(dentry, true);
262out2:
263 dput(upper);
264out1:
265 dput(newdentry);
266out:
267 return err;
268
269out_cleanup:
270 ovl_cleanup(wdir, newdentry);
271 goto out;
272}
273
274/*
275 * Copy up a single dentry
276 *
277 * Directory renames only allowed on "pure upper" (already created on
278 * upper filesystem, never copied up). Directories which are on lower or
279 * are merged may not be renamed. For these -EXDEV is returned and
280 * userspace has to deal with it. This means, when copying up a
281 * directory we can rely on it and ancestors being stable.
282 *
283 * Non-directory renames start with copy up of source if necessary. The
284 * actual rename will only proceed once the copy up was successful. Copy
285 * up uses upper parent i_mutex for exclusion. Since rename can change
286 * d_parent it is possible that the copy up will lock the old parent. At
287 * that point the file will have already been copied up anyway.
288 */
289int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
290 struct path *lowerpath, struct kstat *stat,
291 struct iattr *attr)
292{
293 struct dentry *workdir = ovl_workdir(dentry);
294 int err;
295 struct kstat pstat;
296 struct path parentpath;
297 struct dentry *upperdir;
298 struct dentry *upperdentry;
299 const struct cred *old_cred;
300 struct cred *override_cred;
301 char *link = NULL;
302
303 ovl_path_upper(parent, &parentpath);
304 upperdir = parentpath.dentry;
305
306 err = vfs_getattr(&parentpath, &pstat);
307 if (err)
308 return err;
309
310 if (S_ISLNK(stat->mode)) {
311 link = ovl_read_symlink(lowerpath->dentry);
312 if (IS_ERR(link))
313 return PTR_ERR(link);
314 }
315
316 err = -ENOMEM;
317 override_cred = prepare_creds();
318 if (!override_cred)
319 goto out_free_link;
320
321 override_cred->fsuid = stat->uid;
322 override_cred->fsgid = stat->gid;
323 /*
324 * CAP_SYS_ADMIN for copying up extended attributes
325 * CAP_DAC_OVERRIDE for create
326 * CAP_FOWNER for chmod, timestamp update
327 * CAP_FSETID for chmod
328 * CAP_CHOWN for chown
329 * CAP_MKNOD for mknod
330 */
331 cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
332 cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
333 cap_raise(override_cred->cap_effective, CAP_FOWNER);
334 cap_raise(override_cred->cap_effective, CAP_FSETID);
335 cap_raise(override_cred->cap_effective, CAP_CHOWN);
336 cap_raise(override_cred->cap_effective, CAP_MKNOD);
337 old_cred = override_creds(override_cred);
338
339 err = -EIO;
340 if (lock_rename(workdir, upperdir) != NULL) {
341 pr_err("overlayfs: failed to lock workdir+upperdir\n");
342 goto out_unlock;
343 }
344 upperdentry = ovl_dentry_upper(dentry);
345 if (upperdentry) {
346 unlock_rename(workdir, upperdir);
347 err = 0;
348 /* Raced with another copy-up? Do the setattr here */
349 if (attr) {
350 mutex_lock(&upperdentry->d_inode->i_mutex);
351 err = notify_change(upperdentry, attr, NULL);
352 mutex_unlock(&upperdentry->d_inode->i_mutex);
353 }
354 goto out_put_cred;
355 }
356
357 err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath,
358 stat, attr, link);
359 if (!err) {
360 /* Restore timestamps on parent (best effort) */
361 ovl_set_timestamps(upperdir, &pstat);
362 }
363out_unlock:
364 unlock_rename(workdir, upperdir);
365out_put_cred:
366 revert_creds(old_cred);
367 put_cred(override_cred);
368
369out_free_link:
370 if (link)
371 free_page((unsigned long) link);
372
373 return err;
374}
375
376int ovl_copy_up(struct dentry *dentry)
377{
378 int err;
379
380 err = 0;
381 while (!err) {
382 struct dentry *next;
383 struct dentry *parent;
384 struct path lowerpath;
385 struct kstat stat;
386 enum ovl_path_type type = ovl_path_type(dentry);
387
388 if (type != OVL_PATH_LOWER)
389 break;
390
391 next = dget(dentry);
392 /* find the topmost dentry not yet copied up */
393 for (;;) {
394 parent = dget_parent(next);
395
396 type = ovl_path_type(parent);
397 if (type != OVL_PATH_LOWER)
398 break;
399
400 dput(next);
401 next = parent;
402 }
403
404 ovl_path_lower(next, &lowerpath);
405 err = vfs_getattr(&lowerpath, &stat);
406 if (!err)
407 err = ovl_copy_up_one(parent, next, &lowerpath, &stat, NULL);
408
409 dput(parent);
410 dput(next);
411 }
412
413 return err;
414}
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