Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszer...
[sfrench/cifs-2.6.git] / fs / overlayfs / dir.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/fs.h>
11 #include <linux/namei.h>
12 #include <linux/xattr.h>
13 #include <linux/security.h>
14 #include <linux/cred.h>
15 #include <linux/module.h>
16 #include <linux/posix_acl.h>
17 #include <linux/posix_acl_xattr.h>
18 #include <linux/atomic.h>
19 #include <linux/ratelimit.h>
20 #include "overlayfs.h"
21
22 static unsigned short ovl_redirect_max = 256;
23 module_param_named(redirect_max, ovl_redirect_max, ushort, 0644);
24 MODULE_PARM_DESC(ovl_redirect_max,
25                  "Maximum length of absolute redirect xattr value");
26
27 int ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
28 {
29         int err;
30
31         dget(wdentry);
32         if (d_is_dir(wdentry))
33                 err = ovl_do_rmdir(wdir, wdentry);
34         else
35                 err = ovl_do_unlink(wdir, wdentry);
36         dput(wdentry);
37
38         if (err) {
39                 pr_err("overlayfs: cleanup of '%pd2' failed (%i)\n",
40                        wdentry, err);
41         }
42
43         return err;
44 }
45
46 struct dentry *ovl_lookup_temp(struct dentry *workdir)
47 {
48         struct dentry *temp;
49         char name[20];
50         static atomic_t temp_id = ATOMIC_INIT(0);
51
52         /* counter is allowed to wrap, since temp dentries are ephemeral */
53         snprintf(name, sizeof(name), "#%x", atomic_inc_return(&temp_id));
54
55         temp = lookup_one_len(name, workdir, strlen(name));
56         if (!IS_ERR(temp) && temp->d_inode) {
57                 pr_err("overlayfs: workdir/%s already exists\n", name);
58                 dput(temp);
59                 temp = ERR_PTR(-EIO);
60         }
61
62         return temp;
63 }
64
65 /* caller holds i_mutex on workdir */
66 static struct dentry *ovl_whiteout(struct dentry *workdir)
67 {
68         int err;
69         struct dentry *whiteout;
70         struct inode *wdir = workdir->d_inode;
71
72         whiteout = ovl_lookup_temp(workdir);
73         if (IS_ERR(whiteout))
74                 return whiteout;
75
76         err = ovl_do_whiteout(wdir, whiteout);
77         if (err) {
78                 dput(whiteout);
79                 whiteout = ERR_PTR(err);
80         }
81
82         return whiteout;
83 }
84
85 /* Caller must hold i_mutex on both workdir and dir */
86 int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
87                              struct dentry *dentry)
88 {
89         struct inode *wdir = workdir->d_inode;
90         struct dentry *whiteout;
91         int err;
92         int flags = 0;
93
94         whiteout = ovl_whiteout(workdir);
95         err = PTR_ERR(whiteout);
96         if (IS_ERR(whiteout))
97                 return err;
98
99         if (d_is_dir(dentry))
100                 flags = RENAME_EXCHANGE;
101
102         err = ovl_do_rename(wdir, whiteout, dir, dentry, flags);
103         if (err)
104                 goto kill_whiteout;
105         if (flags)
106                 ovl_cleanup(wdir, dentry);
107
108 out:
109         dput(whiteout);
110         return err;
111
112 kill_whiteout:
113         ovl_cleanup(wdir, whiteout);
114         goto out;
115 }
116
117 int ovl_create_real(struct inode *dir, struct dentry *newdentry,
118                     struct cattr *attr, struct dentry *hardlink, bool debug)
119 {
120         int err;
121
122         if (newdentry->d_inode)
123                 return -ESTALE;
124
125         if (hardlink) {
126                 err = ovl_do_link(hardlink, dir, newdentry, debug);
127         } else {
128                 switch (attr->mode & S_IFMT) {
129                 case S_IFREG:
130                         err = ovl_do_create(dir, newdentry, attr->mode, debug);
131                         break;
132
133                 case S_IFDIR:
134                         err = ovl_do_mkdir(dir, newdentry, attr->mode, debug);
135                         break;
136
137                 case S_IFCHR:
138                 case S_IFBLK:
139                 case S_IFIFO:
140                 case S_IFSOCK:
141                         err = ovl_do_mknod(dir, newdentry,
142                                            attr->mode, attr->rdev, debug);
143                         break;
144
145                 case S_IFLNK:
146                         err = ovl_do_symlink(dir, newdentry, attr->link, debug);
147                         break;
148
149                 default:
150                         err = -EPERM;
151                 }
152         }
153         if (!err && WARN_ON(!newdentry->d_inode)) {
154                 /*
155                  * Not quite sure if non-instantiated dentry is legal or not.
156                  * VFS doesn't seem to care so check and warn here.
157                  */
158                 err = -ENOENT;
159         }
160         return err;
161 }
162
163 static int ovl_set_opaque_xerr(struct dentry *dentry, struct dentry *upper,
164                                int xerr)
165 {
166         int err;
167
168         err = ovl_check_setxattr(dentry, upper, OVL_XATTR_OPAQUE, "y", 1, xerr);
169         if (!err)
170                 ovl_dentry_set_opaque(dentry);
171
172         return err;
173 }
174
175 static int ovl_set_opaque(struct dentry *dentry, struct dentry *upperdentry)
176 {
177         /*
178          * Fail with -EIO when trying to create opaque dir and upper doesn't
179          * support xattrs. ovl_rename() calls ovl_set_opaque_xerr(-EXDEV) to
180          * return a specific error for noxattr case.
181          */
182         return ovl_set_opaque_xerr(dentry, upperdentry, -EIO);
183 }
184
185 /* Common operations required to be done after creation of file on upper */
186 static void ovl_instantiate(struct dentry *dentry, struct inode *inode,
187                             struct dentry *newdentry, bool hardlink)
188 {
189         ovl_dentry_version_inc(dentry->d_parent, false);
190         ovl_dentry_set_upper_alias(dentry);
191         if (!hardlink) {
192                 ovl_inode_update(inode, newdentry);
193                 ovl_copyattr(newdentry->d_inode, inode);
194         } else {
195                 WARN_ON(ovl_inode_real(inode) != d_inode(newdentry));
196                 dput(newdentry);
197                 inc_nlink(inode);
198         }
199         d_instantiate(dentry, inode);
200         /* Force lookup of new upper hardlink to find its lower */
201         if (hardlink)
202                 d_drop(dentry);
203 }
204
205 static bool ovl_type_merge(struct dentry *dentry)
206 {
207         return OVL_TYPE_MERGE(ovl_path_type(dentry));
208 }
209
210 static bool ovl_type_origin(struct dentry *dentry)
211 {
212         return OVL_TYPE_ORIGIN(ovl_path_type(dentry));
213 }
214
215 static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
216                             struct cattr *attr, struct dentry *hardlink)
217 {
218         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
219         struct inode *udir = upperdir->d_inode;
220         struct dentry *newdentry;
221         int err;
222
223         if (!hardlink && !IS_POSIXACL(udir))
224                 attr->mode &= ~current_umask();
225
226         inode_lock_nested(udir, I_MUTEX_PARENT);
227         newdentry = lookup_one_len(dentry->d_name.name, upperdir,
228                                    dentry->d_name.len);
229         err = PTR_ERR(newdentry);
230         if (IS_ERR(newdentry))
231                 goto out_unlock;
232         err = ovl_create_real(udir, newdentry, attr, hardlink, false);
233         if (err)
234                 goto out_dput;
235
236         if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry)) {
237                 /* Setting opaque here is just an optimization, allow to fail */
238                 ovl_set_opaque(dentry, newdentry);
239         }
240
241         ovl_instantiate(dentry, inode, newdentry, !!hardlink);
242         newdentry = NULL;
243 out_dput:
244         dput(newdentry);
245 out_unlock:
246         inode_unlock(udir);
247         return err;
248 }
249
250 static struct dentry *ovl_clear_empty(struct dentry *dentry,
251                                       struct list_head *list)
252 {
253         struct dentry *workdir = ovl_workdir(dentry);
254         struct inode *wdir = workdir->d_inode;
255         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
256         struct inode *udir = upperdir->d_inode;
257         struct path upperpath;
258         struct dentry *upper;
259         struct dentry *opaquedir;
260         struct kstat stat;
261         int err;
262
263         if (WARN_ON(!workdir))
264                 return ERR_PTR(-EROFS);
265
266         err = ovl_lock_rename_workdir(workdir, upperdir);
267         if (err)
268                 goto out;
269
270         ovl_path_upper(dentry, &upperpath);
271         err = vfs_getattr(&upperpath, &stat,
272                           STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
273         if (err)
274                 goto out_unlock;
275
276         err = -ESTALE;
277         if (!S_ISDIR(stat.mode))
278                 goto out_unlock;
279         upper = upperpath.dentry;
280         if (upper->d_parent->d_inode != udir)
281                 goto out_unlock;
282
283         opaquedir = ovl_lookup_temp(workdir);
284         err = PTR_ERR(opaquedir);
285         if (IS_ERR(opaquedir))
286                 goto out_unlock;
287
288         err = ovl_create_real(wdir, opaquedir,
289                               &(struct cattr){.mode = stat.mode}, NULL, true);
290         if (err)
291                 goto out_dput;
292
293         err = ovl_copy_xattr(upper, opaquedir);
294         if (err)
295                 goto out_cleanup;
296
297         err = ovl_set_opaque(dentry, opaquedir);
298         if (err)
299                 goto out_cleanup;
300
301         inode_lock(opaquedir->d_inode);
302         err = ovl_set_attr(opaquedir, &stat);
303         inode_unlock(opaquedir->d_inode);
304         if (err)
305                 goto out_cleanup;
306
307         err = ovl_do_rename(wdir, opaquedir, udir, upper, RENAME_EXCHANGE);
308         if (err)
309                 goto out_cleanup;
310
311         ovl_cleanup_whiteouts(upper, list);
312         ovl_cleanup(wdir, upper);
313         unlock_rename(workdir, upperdir);
314
315         /* dentry's upper doesn't match now, get rid of it */
316         d_drop(dentry);
317
318         return opaquedir;
319
320 out_cleanup:
321         ovl_cleanup(wdir, opaquedir);
322 out_dput:
323         dput(opaquedir);
324 out_unlock:
325         unlock_rename(workdir, upperdir);
326 out:
327         return ERR_PTR(err);
328 }
329
330 static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
331                              const struct posix_acl *acl)
332 {
333         void *buffer;
334         size_t size;
335         int err;
336
337         if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
338                 return 0;
339
340         size = posix_acl_to_xattr(NULL, acl, NULL, 0);
341         buffer = kmalloc(size, GFP_KERNEL);
342         if (!buffer)
343                 return -ENOMEM;
344
345         size = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
346         err = size;
347         if (err < 0)
348                 goto out_free;
349
350         err = vfs_setxattr(upperdentry, name, buffer, size, XATTR_CREATE);
351 out_free:
352         kfree(buffer);
353         return err;
354 }
355
356 static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
357                                     struct cattr *cattr,
358                                     struct dentry *hardlink)
359 {
360         struct dentry *workdir = ovl_workdir(dentry);
361         struct inode *wdir = workdir->d_inode;
362         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
363         struct inode *udir = upperdir->d_inode;
364         struct dentry *upper;
365         struct dentry *newdentry;
366         int err;
367         struct posix_acl *acl, *default_acl;
368
369         if (WARN_ON(!workdir))
370                 return -EROFS;
371
372         if (!hardlink) {
373                 err = posix_acl_create(dentry->d_parent->d_inode,
374                                        &cattr->mode, &default_acl, &acl);
375                 if (err)
376                         return err;
377         }
378
379         err = ovl_lock_rename_workdir(workdir, upperdir);
380         if (err)
381                 goto out;
382
383         newdentry = ovl_lookup_temp(workdir);
384         err = PTR_ERR(newdentry);
385         if (IS_ERR(newdentry))
386                 goto out_unlock;
387
388         upper = lookup_one_len(dentry->d_name.name, upperdir,
389                                dentry->d_name.len);
390         err = PTR_ERR(upper);
391         if (IS_ERR(upper))
392                 goto out_dput;
393
394         err = ovl_create_real(wdir, newdentry, cattr, hardlink, true);
395         if (err)
396                 goto out_dput2;
397
398         /*
399          * mode could have been mutilated due to umask (e.g. sgid directory)
400          */
401         if (!hardlink &&
402             !S_ISLNK(cattr->mode) &&
403             newdentry->d_inode->i_mode != cattr->mode) {
404                 struct iattr attr = {
405                         .ia_valid = ATTR_MODE,
406                         .ia_mode = cattr->mode,
407                 };
408                 inode_lock(newdentry->d_inode);
409                 err = notify_change(newdentry, &attr, NULL);
410                 inode_unlock(newdentry->d_inode);
411                 if (err)
412                         goto out_cleanup;
413         }
414         if (!hardlink) {
415                 err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_ACCESS,
416                                         acl);
417                 if (err)
418                         goto out_cleanup;
419
420                 err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_DEFAULT,
421                                         default_acl);
422                 if (err)
423                         goto out_cleanup;
424         }
425
426         if (!hardlink && S_ISDIR(cattr->mode)) {
427                 err = ovl_set_opaque(dentry, newdentry);
428                 if (err)
429                         goto out_cleanup;
430
431                 err = ovl_do_rename(wdir, newdentry, udir, upper,
432                                     RENAME_EXCHANGE);
433                 if (err)
434                         goto out_cleanup;
435
436                 ovl_cleanup(wdir, upper);
437         } else {
438                 err = ovl_do_rename(wdir, newdentry, udir, upper, 0);
439                 if (err)
440                         goto out_cleanup;
441         }
442         ovl_instantiate(dentry, inode, newdentry, !!hardlink);
443         newdentry = NULL;
444 out_dput2:
445         dput(upper);
446 out_dput:
447         dput(newdentry);
448 out_unlock:
449         unlock_rename(workdir, upperdir);
450 out:
451         if (!hardlink) {
452                 posix_acl_release(acl);
453                 posix_acl_release(default_acl);
454         }
455         return err;
456
457 out_cleanup:
458         ovl_cleanup(wdir, newdentry);
459         goto out_dput2;
460 }
461
462 static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
463                               struct cattr *attr, struct dentry *hardlink,
464                               bool origin)
465 {
466         int err;
467         const struct cred *old_cred;
468         struct cred *override_cred;
469         struct dentry *parent = dentry->d_parent;
470
471         err = ovl_copy_up(parent);
472         if (err)
473                 return err;
474
475         old_cred = ovl_override_creds(dentry->d_sb);
476
477         /*
478          * When linking a file with copy up origin into a new parent, mark the
479          * new parent dir "impure".
480          */
481         if (origin) {
482                 err = ovl_set_impure(parent, ovl_dentry_upper(parent));
483                 if (err)
484                         goto out_revert_creds;
485         }
486
487         err = -ENOMEM;
488         override_cred = prepare_creds();
489         if (override_cred) {
490                 override_cred->fsuid = inode->i_uid;
491                 override_cred->fsgid = inode->i_gid;
492                 if (!hardlink) {
493                         err = security_dentry_create_files_as(dentry,
494                                         attr->mode, &dentry->d_name, old_cred,
495                                         override_cred);
496                         if (err) {
497                                 put_cred(override_cred);
498                                 goto out_revert_creds;
499                         }
500                 }
501                 put_cred(override_creds(override_cred));
502                 put_cred(override_cred);
503
504                 if (!ovl_dentry_is_whiteout(dentry))
505                         err = ovl_create_upper(dentry, inode, attr,
506                                                 hardlink);
507                 else
508                         err = ovl_create_over_whiteout(dentry, inode, attr,
509                                                         hardlink);
510         }
511 out_revert_creds:
512         revert_creds(old_cred);
513         if (!err) {
514                 struct inode *realinode = d_inode(ovl_dentry_upper(dentry));
515
516                 WARN_ON(inode->i_mode != realinode->i_mode);
517                 WARN_ON(!uid_eq(inode->i_uid, realinode->i_uid));
518                 WARN_ON(!gid_eq(inode->i_gid, realinode->i_gid));
519         }
520         return err;
521 }
522
523 static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
524                              const char *link)
525 {
526         int err;
527         struct inode *inode;
528         struct cattr attr = {
529                 .rdev = rdev,
530                 .link = link,
531         };
532
533         err = ovl_want_write(dentry);
534         if (err)
535                 goto out;
536
537         err = -ENOMEM;
538         inode = ovl_new_inode(dentry->d_sb, mode, rdev);
539         if (!inode)
540                 goto out_drop_write;
541
542         inode_init_owner(inode, dentry->d_parent->d_inode, mode);
543         attr.mode = inode->i_mode;
544
545         err = ovl_create_or_link(dentry, inode, &attr, NULL, false);
546         if (err)
547                 iput(inode);
548
549 out_drop_write:
550         ovl_drop_write(dentry);
551 out:
552         return err;
553 }
554
555 static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
556                       bool excl)
557 {
558         return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
559 }
560
561 static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
562 {
563         return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
564 }
565
566 static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
567                      dev_t rdev)
568 {
569         /* Don't allow creation of "whiteout" on overlay */
570         if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
571                 return -EPERM;
572
573         return ovl_create_object(dentry, mode, rdev, NULL);
574 }
575
576 static int ovl_symlink(struct inode *dir, struct dentry *dentry,
577                        const char *link)
578 {
579         return ovl_create_object(dentry, S_IFLNK, 0, link);
580 }
581
582 static int ovl_link(struct dentry *old, struct inode *newdir,
583                     struct dentry *new)
584 {
585         int err;
586         bool locked = false;
587         struct inode *inode;
588
589         err = ovl_want_write(old);
590         if (err)
591                 goto out;
592
593         err = ovl_copy_up(old);
594         if (err)
595                 goto out_drop_write;
596
597         err = ovl_nlink_start(old, &locked);
598         if (err)
599                 goto out_drop_write;
600
601         inode = d_inode(old);
602         ihold(inode);
603
604         err = ovl_create_or_link(new, inode, NULL, ovl_dentry_upper(old),
605                                  ovl_type_origin(old));
606         if (err)
607                 iput(inode);
608
609         ovl_nlink_end(old, locked);
610 out_drop_write:
611         ovl_drop_write(old);
612 out:
613         return err;
614 }
615
616 static bool ovl_matches_upper(struct dentry *dentry, struct dentry *upper)
617 {
618         return d_inode(ovl_dentry_upper(dentry)) == d_inode(upper);
619 }
620
621 static int ovl_remove_and_whiteout(struct dentry *dentry,
622                                    struct list_head *list)
623 {
624         struct dentry *workdir = ovl_workdir(dentry);
625         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
626         struct dentry *upper;
627         struct dentry *opaquedir = NULL;
628         int err;
629
630         if (WARN_ON(!workdir))
631                 return -EROFS;
632
633         if (!list_empty(list)) {
634                 opaquedir = ovl_clear_empty(dentry, list);
635                 err = PTR_ERR(opaquedir);
636                 if (IS_ERR(opaquedir))
637                         goto out;
638         }
639
640         err = ovl_lock_rename_workdir(workdir, upperdir);
641         if (err)
642                 goto out_dput;
643
644         upper = lookup_one_len(dentry->d_name.name, upperdir,
645                                dentry->d_name.len);
646         err = PTR_ERR(upper);
647         if (IS_ERR(upper))
648                 goto out_unlock;
649
650         err = -ESTALE;
651         if ((opaquedir && upper != opaquedir) ||
652             (!opaquedir && ovl_dentry_upper(dentry) &&
653              !ovl_matches_upper(dentry, upper))) {
654                 goto out_dput_upper;
655         }
656
657         err = ovl_cleanup_and_whiteout(workdir, d_inode(upperdir), upper);
658         if (err)
659                 goto out_d_drop;
660
661         ovl_dentry_version_inc(dentry->d_parent, true);
662 out_d_drop:
663         d_drop(dentry);
664 out_dput_upper:
665         dput(upper);
666 out_unlock:
667         unlock_rename(workdir, upperdir);
668 out_dput:
669         dput(opaquedir);
670 out:
671         return err;
672 }
673
674 static int ovl_remove_upper(struct dentry *dentry, bool is_dir,
675                             struct list_head *list)
676 {
677         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
678         struct inode *dir = upperdir->d_inode;
679         struct dentry *upper;
680         struct dentry *opaquedir = NULL;
681         int err;
682
683         if (!list_empty(list)) {
684                 opaquedir = ovl_clear_empty(dentry, list);
685                 err = PTR_ERR(opaquedir);
686                 if (IS_ERR(opaquedir))
687                         goto out;
688         }
689
690         inode_lock_nested(dir, I_MUTEX_PARENT);
691         upper = lookup_one_len(dentry->d_name.name, upperdir,
692                                dentry->d_name.len);
693         err = PTR_ERR(upper);
694         if (IS_ERR(upper))
695                 goto out_unlock;
696
697         err = -ESTALE;
698         if ((opaquedir && upper != opaquedir) ||
699             (!opaquedir && !ovl_matches_upper(dentry, upper)))
700                 goto out_dput_upper;
701
702         if (is_dir)
703                 err = vfs_rmdir(dir, upper);
704         else
705                 err = vfs_unlink(dir, upper, NULL);
706         ovl_dentry_version_inc(dentry->d_parent, ovl_type_origin(dentry));
707
708         /*
709          * Keeping this dentry hashed would mean having to release
710          * upperpath/lowerpath, which could only be done if we are the
711          * sole user of this dentry.  Too tricky...  Just unhash for
712          * now.
713          */
714         if (!err)
715                 d_drop(dentry);
716 out_dput_upper:
717         dput(upper);
718 out_unlock:
719         inode_unlock(dir);
720         dput(opaquedir);
721 out:
722         return err;
723 }
724
725 static bool ovl_pure_upper(struct dentry *dentry)
726 {
727         return !ovl_dentry_lower(dentry) &&
728                !ovl_test_flag(OVL_WHITEOUTS, d_inode(dentry));
729 }
730
731 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
732 {
733         int err;
734         bool locked = false;
735         const struct cred *old_cred;
736         bool lower_positive = ovl_lower_positive(dentry);
737         LIST_HEAD(list);
738
739         /* No need to clean pure upper removed by vfs_rmdir() */
740         if (is_dir && (lower_positive || !ovl_pure_upper(dentry))) {
741                 err = ovl_check_empty_dir(dentry, &list);
742                 if (err)
743                         goto out;
744         }
745
746         err = ovl_want_write(dentry);
747         if (err)
748                 goto out;
749
750         err = ovl_copy_up(dentry->d_parent);
751         if (err)
752                 goto out_drop_write;
753
754         err = ovl_nlink_start(dentry, &locked);
755         if (err)
756                 goto out_drop_write;
757
758         old_cred = ovl_override_creds(dentry->d_sb);
759         if (!lower_positive)
760                 err = ovl_remove_upper(dentry, is_dir, &list);
761         else
762                 err = ovl_remove_and_whiteout(dentry, &list);
763         revert_creds(old_cred);
764         if (!err) {
765                 if (is_dir)
766                         clear_nlink(dentry->d_inode);
767                 else
768                         drop_nlink(dentry->d_inode);
769         }
770         ovl_nlink_end(dentry, locked);
771 out_drop_write:
772         ovl_drop_write(dentry);
773 out:
774         ovl_cache_free(&list);
775         return err;
776 }
777
778 static int ovl_unlink(struct inode *dir, struct dentry *dentry)
779 {
780         return ovl_do_remove(dentry, false);
781 }
782
783 static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
784 {
785         return ovl_do_remove(dentry, true);
786 }
787
788 static bool ovl_type_merge_or_lower(struct dentry *dentry)
789 {
790         enum ovl_path_type type = ovl_path_type(dentry);
791
792         return OVL_TYPE_MERGE(type) || !OVL_TYPE_UPPER(type);
793 }
794
795 static bool ovl_can_move(struct dentry *dentry)
796 {
797         return ovl_redirect_dir(dentry->d_sb) ||
798                 !d_is_dir(dentry) || !ovl_type_merge_or_lower(dentry);
799 }
800
801 static char *ovl_get_redirect(struct dentry *dentry, bool samedir)
802 {
803         char *buf, *ret;
804         struct dentry *d, *tmp;
805         int buflen = ovl_redirect_max + 1;
806
807         if (samedir) {
808                 ret = kstrndup(dentry->d_name.name, dentry->d_name.len,
809                                GFP_KERNEL);
810                 goto out;
811         }
812
813         buf = ret = kmalloc(buflen, GFP_KERNEL);
814         if (!buf)
815                 goto out;
816
817         buflen--;
818         buf[buflen] = '\0';
819         for (d = dget(dentry); !IS_ROOT(d);) {
820                 const char *name;
821                 int thislen;
822
823                 spin_lock(&d->d_lock);
824                 name = ovl_dentry_get_redirect(d);
825                 if (name) {
826                         thislen = strlen(name);
827                 } else {
828                         name = d->d_name.name;
829                         thislen = d->d_name.len;
830                 }
831
832                 /* If path is too long, fall back to userspace move */
833                 if (thislen + (name[0] != '/') > buflen) {
834                         ret = ERR_PTR(-EXDEV);
835                         spin_unlock(&d->d_lock);
836                         goto out_put;
837                 }
838
839                 buflen -= thislen;
840                 memcpy(&buf[buflen], name, thislen);
841                 tmp = dget_dlock(d->d_parent);
842                 spin_unlock(&d->d_lock);
843
844                 dput(d);
845                 d = tmp;
846
847                 /* Absolute redirect: finished */
848                 if (buf[buflen] == '/')
849                         break;
850                 buflen--;
851                 buf[buflen] = '/';
852         }
853         ret = kstrdup(&buf[buflen], GFP_KERNEL);
854 out_put:
855         dput(d);
856         kfree(buf);
857 out:
858         return ret ? ret : ERR_PTR(-ENOMEM);
859 }
860
861 static int ovl_set_redirect(struct dentry *dentry, bool samedir)
862 {
863         int err;
864         const char *redirect = ovl_dentry_get_redirect(dentry);
865
866         if (redirect && (samedir || redirect[0] == '/'))
867                 return 0;
868
869         redirect = ovl_get_redirect(dentry, samedir);
870         if (IS_ERR(redirect))
871                 return PTR_ERR(redirect);
872
873         err = ovl_check_setxattr(dentry, ovl_dentry_upper(dentry),
874                                  OVL_XATTR_REDIRECT,
875                                  redirect, strlen(redirect), -EXDEV);
876         if (!err) {
877                 spin_lock(&dentry->d_lock);
878                 ovl_dentry_set_redirect(dentry, redirect);
879                 spin_unlock(&dentry->d_lock);
880         } else {
881                 kfree(redirect);
882                 pr_warn_ratelimited("overlayfs: failed to set redirect (%i)\n",
883                                     err);
884                 /* Fall back to userspace copy-up */
885                 err = -EXDEV;
886         }
887         return err;
888 }
889
890 static int ovl_rename(struct inode *olddir, struct dentry *old,
891                       struct inode *newdir, struct dentry *new,
892                       unsigned int flags)
893 {
894         int err;
895         bool locked = false;
896         struct dentry *old_upperdir;
897         struct dentry *new_upperdir;
898         struct dentry *olddentry;
899         struct dentry *newdentry;
900         struct dentry *trap;
901         bool old_opaque;
902         bool new_opaque;
903         bool cleanup_whiteout = false;
904         bool overwrite = !(flags & RENAME_EXCHANGE);
905         bool is_dir = d_is_dir(old);
906         bool new_is_dir = d_is_dir(new);
907         bool samedir = olddir == newdir;
908         struct dentry *opaquedir = NULL;
909         const struct cred *old_cred = NULL;
910         LIST_HEAD(list);
911
912         err = -EINVAL;
913         if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
914                 goto out;
915
916         flags &= ~RENAME_NOREPLACE;
917
918         /* Don't copy up directory trees */
919         err = -EXDEV;
920         if (!ovl_can_move(old))
921                 goto out;
922         if (!overwrite && !ovl_can_move(new))
923                 goto out;
924
925         if (overwrite && new_is_dir && !ovl_pure_upper(new)) {
926                 err = ovl_check_empty_dir(new, &list);
927                 if (err)
928                         goto out;
929         }
930
931         if (overwrite) {
932                 if (ovl_lower_positive(old)) {
933                         if (!ovl_dentry_is_whiteout(new)) {
934                                 /* Whiteout source */
935                                 flags |= RENAME_WHITEOUT;
936                         } else {
937                                 /* Switch whiteouts */
938                                 flags |= RENAME_EXCHANGE;
939                         }
940                 } else if (is_dir && ovl_dentry_is_whiteout(new)) {
941                         flags |= RENAME_EXCHANGE;
942                         cleanup_whiteout = true;
943                 }
944         }
945
946         err = ovl_want_write(old);
947         if (err)
948                 goto out;
949
950         err = ovl_copy_up(old);
951         if (err)
952                 goto out_drop_write;
953
954         err = ovl_copy_up(new->d_parent);
955         if (err)
956                 goto out_drop_write;
957         if (!overwrite) {
958                 err = ovl_copy_up(new);
959                 if (err)
960                         goto out_drop_write;
961         } else {
962                 err = ovl_nlink_start(new, &locked);
963                 if (err)
964                         goto out_drop_write;
965         }
966
967         old_cred = ovl_override_creds(old->d_sb);
968
969         if (!list_empty(&list)) {
970                 opaquedir = ovl_clear_empty(new, &list);
971                 err = PTR_ERR(opaquedir);
972                 if (IS_ERR(opaquedir)) {
973                         opaquedir = NULL;
974                         goto out_revert_creds;
975                 }
976         }
977
978         old_upperdir = ovl_dentry_upper(old->d_parent);
979         new_upperdir = ovl_dentry_upper(new->d_parent);
980
981         if (!samedir) {
982                 /*
983                  * When moving a merge dir or non-dir with copy up origin into
984                  * a new parent, we are marking the new parent dir "impure".
985                  * When ovl_iterate() iterates an "impure" upper dir, it will
986                  * lookup the origin inodes of the entries to fill d_ino.
987                  */
988                 if (ovl_type_origin(old)) {
989                         err = ovl_set_impure(new->d_parent, new_upperdir);
990                         if (err)
991                                 goto out_revert_creds;
992                 }
993                 if (!overwrite && ovl_type_origin(new)) {
994                         err = ovl_set_impure(old->d_parent, old_upperdir);
995                         if (err)
996                                 goto out_revert_creds;
997                 }
998         }
999
1000         trap = lock_rename(new_upperdir, old_upperdir);
1001
1002         olddentry = lookup_one_len(old->d_name.name, old_upperdir,
1003                                    old->d_name.len);
1004         err = PTR_ERR(olddentry);
1005         if (IS_ERR(olddentry))
1006                 goto out_unlock;
1007
1008         err = -ESTALE;
1009         if (!ovl_matches_upper(old, olddentry))
1010                 goto out_dput_old;
1011
1012         newdentry = lookup_one_len(new->d_name.name, new_upperdir,
1013                                    new->d_name.len);
1014         err = PTR_ERR(newdentry);
1015         if (IS_ERR(newdentry))
1016                 goto out_dput_old;
1017
1018         old_opaque = ovl_dentry_is_opaque(old);
1019         new_opaque = ovl_dentry_is_opaque(new);
1020
1021         err = -ESTALE;
1022         if (d_inode(new) && ovl_dentry_upper(new)) {
1023                 if (opaquedir) {
1024                         if (newdentry != opaquedir)
1025                                 goto out_dput;
1026                 } else {
1027                         if (!ovl_matches_upper(new, newdentry))
1028                                 goto out_dput;
1029                 }
1030         } else {
1031                 if (!d_is_negative(newdentry) &&
1032                     (!new_opaque || !ovl_is_whiteout(newdentry)))
1033                         goto out_dput;
1034         }
1035
1036         if (olddentry == trap)
1037                 goto out_dput;
1038         if (newdentry == trap)
1039                 goto out_dput;
1040
1041         if (WARN_ON(olddentry->d_inode == newdentry->d_inode))
1042                 goto out_dput;
1043
1044         err = 0;
1045         if (is_dir) {
1046                 if (ovl_type_merge_or_lower(old))
1047                         err = ovl_set_redirect(old, samedir);
1048                 else if (!old_opaque && ovl_type_merge(new->d_parent))
1049                         err = ovl_set_opaque_xerr(old, olddentry, -EXDEV);
1050                 if (err)
1051                         goto out_dput;
1052         }
1053         if (!overwrite && new_is_dir) {
1054                 if (ovl_type_merge_or_lower(new))
1055                         err = ovl_set_redirect(new, samedir);
1056                 else if (!new_opaque && ovl_type_merge(old->d_parent))
1057                         err = ovl_set_opaque_xerr(new, newdentry, -EXDEV);
1058                 if (err)
1059                         goto out_dput;
1060         }
1061
1062         err = ovl_do_rename(old_upperdir->d_inode, olddentry,
1063                             new_upperdir->d_inode, newdentry, flags);
1064         if (err)
1065                 goto out_dput;
1066
1067         if (cleanup_whiteout)
1068                 ovl_cleanup(old_upperdir->d_inode, newdentry);
1069
1070         if (overwrite && d_inode(new)) {
1071                 if (new_is_dir)
1072                         clear_nlink(d_inode(new));
1073                 else
1074                         drop_nlink(d_inode(new));
1075         }
1076
1077         ovl_dentry_version_inc(old->d_parent, ovl_type_origin(old) ||
1078                                (!overwrite && ovl_type_origin(new)));
1079         ovl_dentry_version_inc(new->d_parent, ovl_type_origin(old) ||
1080                                (d_inode(new) && ovl_type_origin(new)));
1081
1082 out_dput:
1083         dput(newdentry);
1084 out_dput_old:
1085         dput(olddentry);
1086 out_unlock:
1087         unlock_rename(new_upperdir, old_upperdir);
1088 out_revert_creds:
1089         revert_creds(old_cred);
1090         ovl_nlink_end(new, locked);
1091 out_drop_write:
1092         ovl_drop_write(old);
1093 out:
1094         dput(opaquedir);
1095         ovl_cache_free(&list);
1096         return err;
1097 }
1098
1099 const struct inode_operations ovl_dir_inode_operations = {
1100         .lookup         = ovl_lookup,
1101         .mkdir          = ovl_mkdir,
1102         .symlink        = ovl_symlink,
1103         .unlink         = ovl_unlink,
1104         .rmdir          = ovl_rmdir,
1105         .rename         = ovl_rename,
1106         .link           = ovl_link,
1107         .setattr        = ovl_setattr,
1108         .create         = ovl_create,
1109         .mknod          = ovl_mknod,
1110         .permission     = ovl_permission,
1111         .getattr        = ovl_getattr,
1112         .listxattr      = ovl_listxattr,
1113         .get_acl        = ovl_get_acl,
1114         .update_time    = ovl_update_time,
1115 };