Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszer...
[sfrench/cifs-2.6.git] / fs / overlayfs / copy_up.c
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/module.h>
11 #include <linux/fs.h>
12 #include <linux/slab.h>
13 #include <linux/file.h>
14 #include <linux/splice.h>
15 #include <linux/xattr.h>
16 #include <linux/security.h>
17 #include <linux/uaccess.h>
18 #include <linux/sched/signal.h>
19 #include <linux/cred.h>
20 #include <linux/namei.h>
21 #include <linux/fdtable.h>
22 #include <linux/ratelimit.h>
23 #include "overlayfs.h"
24 #include "ovl_entry.h"
25
26 #define OVL_COPY_UP_CHUNK_SIZE (1 << 20)
27
28 static bool __read_mostly ovl_check_copy_up;
29 module_param_named(check_copy_up, ovl_check_copy_up, bool,
30                    S_IWUSR | S_IRUGO);
31 MODULE_PARM_DESC(ovl_check_copy_up,
32                  "Warn on copy-up when causing process also has a R/O fd open");
33
34 static int ovl_check_fd(const void *data, struct file *f, unsigned int fd)
35 {
36         const struct dentry *dentry = data;
37
38         if (file_inode(f) == d_inode(dentry))
39                 pr_warn_ratelimited("overlayfs: Warning: Copying up %pD, but open R/O on fd %u which will cease to be coherent [pid=%d %s]\n",
40                                     f, fd, current->pid, current->comm);
41         return 0;
42 }
43
44 /*
45  * Check the fds open by this process and warn if something like the following
46  * scenario is about to occur:
47  *
48  *      fd1 = open("foo", O_RDONLY);
49  *      fd2 = open("foo", O_RDWR);
50  */
51 static void ovl_do_check_copy_up(struct dentry *dentry)
52 {
53         if (ovl_check_copy_up)
54                 iterate_fd(current->files, 0, ovl_check_fd, dentry);
55 }
56
57 int ovl_copy_xattr(struct dentry *old, struct dentry *new)
58 {
59         ssize_t list_size, size, value_size = 0;
60         char *buf, *name, *value = NULL;
61         int uninitialized_var(error);
62         size_t slen;
63
64         if (!(old->d_inode->i_opflags & IOP_XATTR) ||
65             !(new->d_inode->i_opflags & IOP_XATTR))
66                 return 0;
67
68         list_size = vfs_listxattr(old, NULL, 0);
69         if (list_size <= 0) {
70                 if (list_size == -EOPNOTSUPP)
71                         return 0;
72                 return list_size;
73         }
74
75         buf = kzalloc(list_size, GFP_KERNEL);
76         if (!buf)
77                 return -ENOMEM;
78
79         list_size = vfs_listxattr(old, buf, list_size);
80         if (list_size <= 0) {
81                 error = list_size;
82                 goto out;
83         }
84
85         for (name = buf; list_size; name += slen) {
86                 slen = strnlen(name, list_size) + 1;
87
88                 /* underlying fs providing us with an broken xattr list? */
89                 if (WARN_ON(slen > list_size)) {
90                         error = -EIO;
91                         break;
92                 }
93                 list_size -= slen;
94
95                 if (ovl_is_private_xattr(name))
96                         continue;
97 retry:
98                 size = vfs_getxattr(old, name, value, value_size);
99                 if (size == -ERANGE)
100                         size = vfs_getxattr(old, name, NULL, 0);
101
102                 if (size < 0) {
103                         error = size;
104                         break;
105                 }
106
107                 if (size > value_size) {
108                         void *new;
109
110                         new = krealloc(value, size, GFP_KERNEL);
111                         if (!new) {
112                                 error = -ENOMEM;
113                                 break;
114                         }
115                         value = new;
116                         value_size = size;
117                         goto retry;
118                 }
119
120                 error = security_inode_copy_up_xattr(name);
121                 if (error < 0 && error != -EOPNOTSUPP)
122                         break;
123                 if (error == 1) {
124                         error = 0;
125                         continue; /* Discard */
126                 }
127                 error = vfs_setxattr(new, name, value, size, 0);
128                 if (error)
129                         break;
130         }
131         kfree(value);
132 out:
133         kfree(buf);
134         return error;
135 }
136
137 static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
138 {
139         struct file *old_file;
140         struct file *new_file;
141         loff_t old_pos = 0;
142         loff_t new_pos = 0;
143         int error = 0;
144
145         if (len == 0)
146                 return 0;
147
148         old_file = ovl_path_open(old, O_LARGEFILE | O_RDONLY);
149         if (IS_ERR(old_file))
150                 return PTR_ERR(old_file);
151
152         new_file = ovl_path_open(new, O_LARGEFILE | O_WRONLY);
153         if (IS_ERR(new_file)) {
154                 error = PTR_ERR(new_file);
155                 goto out_fput;
156         }
157
158         /* Try to use clone_file_range to clone up within the same fs */
159         error = vfs_clone_file_range(old_file, 0, new_file, 0, len);
160         if (!error)
161                 goto out;
162         /* Couldn't clone, so now we try to copy the data */
163         error = 0;
164
165         /* FIXME: copy up sparse files efficiently */
166         while (len) {
167                 size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
168                 long bytes;
169
170                 if (len < this_len)
171                         this_len = len;
172
173                 if (signal_pending_state(TASK_KILLABLE, current)) {
174                         error = -EINTR;
175                         break;
176                 }
177
178                 bytes = do_splice_direct(old_file, &old_pos,
179                                          new_file, &new_pos,
180                                          this_len, SPLICE_F_MOVE);
181                 if (bytes <= 0) {
182                         error = bytes;
183                         break;
184                 }
185                 WARN_ON(old_pos != new_pos);
186
187                 len -= bytes;
188         }
189 out:
190         if (!error)
191                 error = vfs_fsync(new_file, 0);
192         fput(new_file);
193 out_fput:
194         fput(old_file);
195         return error;
196 }
197
198 static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat)
199 {
200         struct iattr attr = {
201                 .ia_valid =
202                      ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET,
203                 .ia_atime = stat->atime,
204                 .ia_mtime = stat->mtime,
205         };
206
207         return notify_change(upperdentry, &attr, NULL);
208 }
209
210 int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat)
211 {
212         int err = 0;
213
214         if (!S_ISLNK(stat->mode)) {
215                 struct iattr attr = {
216                         .ia_valid = ATTR_MODE,
217                         .ia_mode = stat->mode,
218                 };
219                 err = notify_change(upperdentry, &attr, NULL);
220         }
221         if (!err) {
222                 struct iattr attr = {
223                         .ia_valid = ATTR_UID | ATTR_GID,
224                         .ia_uid = stat->uid,
225                         .ia_gid = stat->gid,
226                 };
227                 err = notify_change(upperdentry, &attr, NULL);
228         }
229         if (!err)
230                 ovl_set_timestamps(upperdentry, stat);
231
232         return err;
233 }
234
235 static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
236                               struct dentry *dentry, struct path *lowerpath,
237                               struct kstat *stat, const char *link,
238                               struct kstat *pstat, bool tmpfile)
239 {
240         struct inode *wdir = workdir->d_inode;
241         struct inode *udir = upperdir->d_inode;
242         struct dentry *newdentry = NULL;
243         struct dentry *upper = NULL;
244         struct dentry *temp = NULL;
245         int err;
246         const struct cred *old_creds = NULL;
247         struct cred *new_creds = NULL;
248         struct cattr cattr = {
249                 /* Can't properly set mode on creation because of the umask */
250                 .mode = stat->mode & S_IFMT,
251                 .rdev = stat->rdev,
252                 .link = link
253         };
254
255         upper = lookup_one_len(dentry->d_name.name, upperdir,
256                                dentry->d_name.len);
257         err = PTR_ERR(upper);
258         if (IS_ERR(upper))
259                 goto out;
260
261         err = security_inode_copy_up(dentry, &new_creds);
262         if (err < 0)
263                 goto out1;
264
265         if (new_creds)
266                 old_creds = override_creds(new_creds);
267
268         if (tmpfile)
269                 temp = ovl_do_tmpfile(upperdir, stat->mode);
270         else
271                 temp = ovl_lookup_temp(workdir, dentry);
272         err = PTR_ERR(temp);
273         if (IS_ERR(temp))
274                 goto out1;
275
276         err = 0;
277         if (!tmpfile)
278                 err = ovl_create_real(wdir, temp, &cattr, NULL, true);
279
280         if (new_creds) {
281                 revert_creds(old_creds);
282                 put_cred(new_creds);
283         }
284
285         if (err)
286                 goto out2;
287
288         if (S_ISREG(stat->mode)) {
289                 struct path upperpath;
290
291                 ovl_path_upper(dentry, &upperpath);
292                 BUG_ON(upperpath.dentry != NULL);
293                 upperpath.dentry = temp;
294
295                 if (tmpfile) {
296                         inode_unlock(udir);
297                         err = ovl_copy_up_data(lowerpath, &upperpath,
298                                                stat->size);
299                         inode_lock_nested(udir, I_MUTEX_PARENT);
300                 } else {
301                         err = ovl_copy_up_data(lowerpath, &upperpath,
302                                                stat->size);
303                 }
304
305                 if (err)
306                         goto out_cleanup;
307         }
308
309         err = ovl_copy_xattr(lowerpath->dentry, temp);
310         if (err)
311                 goto out_cleanup;
312
313         inode_lock(temp->d_inode);
314         err = ovl_set_attr(temp, stat);
315         inode_unlock(temp->d_inode);
316         if (err)
317                 goto out_cleanup;
318
319         if (tmpfile)
320                 err = ovl_do_link(temp, udir, upper, true);
321         else
322                 err = ovl_do_rename(wdir, temp, udir, upper, 0);
323         if (err)
324                 goto out_cleanup;
325
326         newdentry = dget(tmpfile ? upper : temp);
327         ovl_dentry_update(dentry, newdentry);
328         ovl_inode_update(d_inode(dentry), d_inode(newdentry));
329
330         /* Restore timestamps on parent (best effort) */
331         ovl_set_timestamps(upperdir, pstat);
332 out2:
333         dput(temp);
334 out1:
335         dput(upper);
336 out:
337         return err;
338
339 out_cleanup:
340         if (!tmpfile)
341                 ovl_cleanup(wdir, temp);
342         goto out2;
343 }
344
345 /*
346  * Copy up a single dentry
347  *
348  * All renames start with copy up of source if necessary.  The actual
349  * rename will only proceed once the copy up was successful.  Copy up uses
350  * upper parent i_mutex for exclusion.  Since rename can change d_parent it
351  * is possible that the copy up will lock the old parent.  At that point
352  * the file will have already been copied up anyway.
353  */
354 static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
355                            struct path *lowerpath, struct kstat *stat)
356 {
357         DEFINE_DELAYED_CALL(done);
358         struct dentry *workdir = ovl_workdir(dentry);
359         int err;
360         struct kstat pstat;
361         struct path parentpath;
362         struct dentry *lowerdentry = lowerpath->dentry;
363         struct dentry *upperdir;
364         const char *link = NULL;
365         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
366
367         if (WARN_ON(!workdir))
368                 return -EROFS;
369
370         ovl_do_check_copy_up(lowerdentry);
371
372         ovl_path_upper(parent, &parentpath);
373         upperdir = parentpath.dentry;
374
375         err = vfs_getattr(&parentpath, &pstat,
376                           STATX_ATIME | STATX_MTIME, AT_STATX_SYNC_AS_STAT);
377         if (err)
378                 return err;
379
380         if (S_ISLNK(stat->mode)) {
381                 link = vfs_get_link(lowerdentry, &done);
382                 if (IS_ERR(link))
383                         return PTR_ERR(link);
384         }
385
386         /* Should we copyup with O_TMPFILE or with workdir? */
387         if (S_ISREG(stat->mode) && ofs->tmpfile) {
388                 err = ovl_copy_up_start(dentry);
389                 /* err < 0: interrupted, err > 0: raced with another copy-up */
390                 if (unlikely(err)) {
391                         pr_debug("ovl_copy_up_start(%pd2) = %i\n", dentry, err);
392                         if (err > 0)
393                                 err = 0;
394                         goto out_done;
395                 }
396
397                 inode_lock_nested(upperdir->d_inode, I_MUTEX_PARENT);
398                 err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath,
399                                          stat, link, &pstat, true);
400                 inode_unlock(upperdir->d_inode);
401                 ovl_copy_up_end(dentry);
402                 goto out_done;
403         }
404
405         err = -EIO;
406         if (lock_rename(workdir, upperdir) != NULL) {
407                 pr_err("overlayfs: failed to lock workdir+upperdir\n");
408                 goto out_unlock;
409         }
410         if (ovl_dentry_upper(dentry)) {
411                 /* Raced with another copy-up?  Nothing to do, then... */
412                 err = 0;
413                 goto out_unlock;
414         }
415
416         err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath,
417                                  stat, link, &pstat, false);
418 out_unlock:
419         unlock_rename(workdir, upperdir);
420 out_done:
421         do_delayed_call(&done);
422
423         return err;
424 }
425
426 int ovl_copy_up_flags(struct dentry *dentry, int flags)
427 {
428         int err = 0;
429         const struct cred *old_cred = ovl_override_creds(dentry->d_sb);
430
431         while (!err) {
432                 struct dentry *next;
433                 struct dentry *parent;
434                 struct path lowerpath;
435                 struct kstat stat;
436                 enum ovl_path_type type = ovl_path_type(dentry);
437
438                 if (OVL_TYPE_UPPER(type))
439                         break;
440
441                 next = dget(dentry);
442                 /* find the topmost dentry not yet copied up */
443                 for (;;) {
444                         parent = dget_parent(next);
445
446                         type = ovl_path_type(parent);
447                         if (OVL_TYPE_UPPER(type))
448                                 break;
449
450                         dput(next);
451                         next = parent;
452                 }
453
454                 ovl_path_lower(next, &lowerpath);
455                 err = vfs_getattr(&lowerpath, &stat,
456                                   STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
457                 /* maybe truncate regular file. this has no effect on dirs */
458                 if (flags & O_TRUNC)
459                         stat.size = 0;
460                 if (!err)
461                         err = ovl_copy_up_one(parent, next, &lowerpath, &stat);
462
463                 dput(parent);
464                 dput(next);
465         }
466         revert_creds(old_cred);
467
468         return err;
469 }
470
471 int ovl_copy_up(struct dentry *dentry)
472 {
473         return ovl_copy_up_flags(dentry, 0);
474 }