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TOMOYO Linux Cross Reference
Linux/fs/overlayfs/dir.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  *
  4  * Copyright (C) 2011 Novell Inc.
  5  */
  6 
  7 #include <linux/fs.h>
  8 #include <linux/namei.h>
  9 #include <linux/xattr.h>
 10 #include <linux/security.h>
 11 #include <linux/cred.h>
 12 #include <linux/module.h>
 13 #include <linux/posix_acl.h>
 14 #include <linux/posix_acl_xattr.h>
 15 #include <linux/atomic.h>
 16 #include <linux/ratelimit.h>
 17 #include "overlayfs.h"
 18 
 19 static unsigned short ovl_redirect_max = 256;
 20 module_param_named(redirect_max, ovl_redirect_max, ushort, 0644);
 21 MODULE_PARM_DESC(redirect_max,
 22                  "Maximum length of absolute redirect xattr value");
 23 
 24 static int ovl_set_redirect(struct dentry *dentry, bool samedir);
 25 
 26 int ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
 27 {
 28         int err;
 29 
 30         dget(wdentry);
 31         if (d_is_dir(wdentry))
 32                 err = ovl_do_rmdir(wdir, wdentry);
 33         else
 34                 err = ovl_do_unlink(wdir, wdentry);
 35         dput(wdentry);
 36 
 37         if (err) {
 38                 pr_err("overlayfs: cleanup of '%pd2' failed (%i)\n",
 39                        wdentry, err);
 40         }
 41 
 42         return err;
 43 }
 44 
 45 static struct dentry *ovl_lookup_temp(struct dentry *workdir)
 46 {
 47         struct dentry *temp;
 48         char name[20];
 49         static atomic_t temp_id = ATOMIC_INIT(0);
 50 
 51         /* counter is allowed to wrap, since temp dentries are ephemeral */
 52         snprintf(name, sizeof(name), "#%x", atomic_inc_return(&temp_id));
 53 
 54         temp = lookup_one_len(name, workdir, strlen(name));
 55         if (!IS_ERR(temp) && temp->d_inode) {
 56                 pr_err("overlayfs: workdir/%s already exists\n", name);
 57                 dput(temp);
 58                 temp = ERR_PTR(-EIO);
 59         }
 60 
 61         return temp;
 62 }
 63 
 64 /* caller holds i_mutex on workdir */
 65 static struct dentry *ovl_whiteout(struct dentry *workdir)
 66 {
 67         int err;
 68         struct dentry *whiteout;
 69         struct inode *wdir = workdir->d_inode;
 70 
 71         whiteout = ovl_lookup_temp(workdir);
 72         if (IS_ERR(whiteout))
 73                 return whiteout;
 74 
 75         err = ovl_do_whiteout(wdir, whiteout);
 76         if (err) {
 77                 dput(whiteout);
 78                 whiteout = ERR_PTR(err);
 79         }
 80 
 81         return whiteout;
 82 }
 83 
 84 /* Caller must hold i_mutex on both workdir and dir */
 85 int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
 86                              struct dentry *dentry)
 87 {
 88         struct inode *wdir = workdir->d_inode;
 89         struct dentry *whiteout;
 90         int err;
 91         int flags = 0;
 92 
 93         whiteout = ovl_whiteout(workdir);
 94         err = PTR_ERR(whiteout);
 95         if (IS_ERR(whiteout))
 96                 return err;
 97 
 98         if (d_is_dir(dentry))
 99                 flags = RENAME_EXCHANGE;
100 
101         err = ovl_do_rename(wdir, whiteout, dir, dentry, flags);
102         if (err)
103                 goto kill_whiteout;
104         if (flags)
105                 ovl_cleanup(wdir, dentry);
106 
107 out:
108         dput(whiteout);
109         return err;
110 
111 kill_whiteout:
112         ovl_cleanup(wdir, whiteout);
113         goto out;
114 }
115 
116 static int ovl_mkdir_real(struct inode *dir, struct dentry **newdentry,
117                           umode_t mode)
118 {
119         int err;
120         struct dentry *d, *dentry = *newdentry;
121 
122         err = ovl_do_mkdir(dir, dentry, mode);
123         if (err)
124                 return err;
125 
126         if (likely(!d_unhashed(dentry)))
127                 return 0;
128 
129         /*
130          * vfs_mkdir() may succeed and leave the dentry passed
131          * to it unhashed and negative. If that happens, try to
132          * lookup a new hashed and positive dentry.
133          */
134         d = lookup_one_len(dentry->d_name.name, dentry->d_parent,
135                            dentry->d_name.len);
136         if (IS_ERR(d)) {
137                 pr_warn("overlayfs: failed lookup after mkdir (%pd2, err=%i).\n",
138                         dentry, err);
139                 return PTR_ERR(d);
140         }
141         dput(dentry);
142         *newdentry = d;
143 
144         return 0;
145 }
146 
147 struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry,
148                                struct ovl_cattr *attr)
149 {
150         int err;
151 
152         if (IS_ERR(newdentry))
153                 return newdentry;
154 
155         err = -ESTALE;
156         if (newdentry->d_inode)
157                 goto out;
158 
159         if (attr->hardlink) {
160                 err = ovl_do_link(attr->hardlink, dir, newdentry);
161         } else {
162                 switch (attr->mode & S_IFMT) {
163                 case S_IFREG:
164                         err = ovl_do_create(dir, newdentry, attr->mode);
165                         break;
166 
167                 case S_IFDIR:
168                         /* mkdir is special... */
169                         err =  ovl_mkdir_real(dir, &newdentry, attr->mode);
170                         break;
171 
172                 case S_IFCHR:
173                 case S_IFBLK:
174                 case S_IFIFO:
175                 case S_IFSOCK:
176                         err = ovl_do_mknod(dir, newdentry, attr->mode,
177                                            attr->rdev);
178                         break;
179 
180                 case S_IFLNK:
181                         err = ovl_do_symlink(dir, newdentry, attr->link);
182                         break;
183 
184                 default:
185                         err = -EPERM;
186                 }
187         }
188         if (!err && WARN_ON(!newdentry->d_inode)) {
189                 /*
190                  * Not quite sure if non-instantiated dentry is legal or not.
191                  * VFS doesn't seem to care so check and warn here.
192                  */
193                 err = -EIO;
194         }
195 out:
196         if (err) {
197                 dput(newdentry);
198                 return ERR_PTR(err);
199         }
200         return newdentry;
201 }
202 
203 struct dentry *ovl_create_temp(struct dentry *workdir, struct ovl_cattr *attr)
204 {
205         return ovl_create_real(d_inode(workdir), ovl_lookup_temp(workdir),
206                                attr);
207 }
208 
209 static int ovl_set_opaque_xerr(struct dentry *dentry, struct dentry *upper,
210                                int xerr)
211 {
212         int err;
213 
214         err = ovl_check_setxattr(dentry, upper, OVL_XATTR_OPAQUE, "y", 1, xerr);
215         if (!err)
216                 ovl_dentry_set_opaque(dentry);
217 
218         return err;
219 }
220 
221 static int ovl_set_opaque(struct dentry *dentry, struct dentry *upperdentry)
222 {
223         /*
224          * Fail with -EIO when trying to create opaque dir and upper doesn't
225          * support xattrs. ovl_rename() calls ovl_set_opaque_xerr(-EXDEV) to
226          * return a specific error for noxattr case.
227          */
228         return ovl_set_opaque_xerr(dentry, upperdentry, -EIO);
229 }
230 
231 /*
232  * Common operations required to be done after creation of file on upper.
233  * If @hardlink is false, then @inode is a pre-allocated inode, we may or
234  * may not use to instantiate the new dentry.
235  */
236 static int ovl_instantiate(struct dentry *dentry, struct inode *inode,
237                            struct dentry *newdentry, bool hardlink)
238 {
239         struct ovl_inode_params oip = {
240                 .upperdentry = newdentry,
241                 .newinode = inode,
242         };
243 
244         ovl_dir_modified(dentry->d_parent, false);
245         ovl_dentry_set_upper_alias(dentry);
246         if (!hardlink) {
247                 /*
248                  * ovl_obtain_alias() can be called after ovl_create_real()
249                  * and before we get here, so we may get an inode from cache
250                  * with the same real upperdentry that is not the inode we
251                  * pre-allocated.  In this case we will use the cached inode
252                  * to instantiate the new dentry.
253                  *
254                  * XXX: if we ever use ovl_obtain_alias() to decode directory
255                  * file handles, need to use ovl_get_inode_locked() and
256                  * d_instantiate_new() here to prevent from creating two
257                  * hashed directory inode aliases.
258                  */
259                 inode = ovl_get_inode(dentry->d_sb, &oip);
260                 if (IS_ERR(inode))
261                         return PTR_ERR(inode);
262         } else {
263                 WARN_ON(ovl_inode_real(inode) != d_inode(newdentry));
264                 dput(newdentry);
265                 inc_nlink(inode);
266         }
267 
268         d_instantiate(dentry, inode);
269         if (inode != oip.newinode) {
270                 pr_warn_ratelimited("overlayfs: newly created inode found in cache (%pd2)\n",
271                                     dentry);
272         }
273 
274         /* Force lookup of new upper hardlink to find its lower */
275         if (hardlink)
276                 d_drop(dentry);
277 
278         return 0;
279 }
280 
281 static bool ovl_type_merge(struct dentry *dentry)
282 {
283         return OVL_TYPE_MERGE(ovl_path_type(dentry));
284 }
285 
286 static bool ovl_type_origin(struct dentry *dentry)
287 {
288         return OVL_TYPE_ORIGIN(ovl_path_type(dentry));
289 }
290 
291 static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
292                             struct ovl_cattr *attr)
293 {
294         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
295         struct inode *udir = upperdir->d_inode;
296         struct dentry *newdentry;
297         int err;
298 
299         if (!attr->hardlink && !IS_POSIXACL(udir))
300                 attr->mode &= ~current_umask();
301 
302         inode_lock_nested(udir, I_MUTEX_PARENT);
303         newdentry = ovl_create_real(udir,
304                                     lookup_one_len(dentry->d_name.name,
305                                                    upperdir,
306                                                    dentry->d_name.len),
307                                     attr);
308         err = PTR_ERR(newdentry);
309         if (IS_ERR(newdentry))
310                 goto out_unlock;
311 
312         if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry)) {
313                 /* Setting opaque here is just an optimization, allow to fail */
314                 ovl_set_opaque(dentry, newdentry);
315         }
316 
317         err = ovl_instantiate(dentry, inode, newdentry, !!attr->hardlink);
318         if (err)
319                 goto out_cleanup;
320 out_unlock:
321         inode_unlock(udir);
322         return err;
323 
324 out_cleanup:
325         ovl_cleanup(udir, newdentry);
326         dput(newdentry);
327         goto out_unlock;
328 }
329 
330 static struct dentry *ovl_clear_empty(struct dentry *dentry,
331                                       struct list_head *list)
332 {
333         struct dentry *workdir = ovl_workdir(dentry);
334         struct inode *wdir = workdir->d_inode;
335         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
336         struct inode *udir = upperdir->d_inode;
337         struct path upperpath;
338         struct dentry *upper;
339         struct dentry *opaquedir;
340         struct kstat stat;
341         int err;
342 
343         if (WARN_ON(!workdir))
344                 return ERR_PTR(-EROFS);
345 
346         err = ovl_lock_rename_workdir(workdir, upperdir);
347         if (err)
348                 goto out;
349 
350         ovl_path_upper(dentry, &upperpath);
351         err = vfs_getattr(&upperpath, &stat,
352                           STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
353         if (err)
354                 goto out_unlock;
355 
356         err = -ESTALE;
357         if (!S_ISDIR(stat.mode))
358                 goto out_unlock;
359         upper = upperpath.dentry;
360         if (upper->d_parent->d_inode != udir)
361                 goto out_unlock;
362 
363         opaquedir = ovl_create_temp(workdir, OVL_CATTR(stat.mode));
364         err = PTR_ERR(opaquedir);
365         if (IS_ERR(opaquedir))
366                 goto out_unlock;
367 
368         err = ovl_copy_xattr(upper, opaquedir);
369         if (err)
370                 goto out_cleanup;
371 
372         err = ovl_set_opaque(dentry, opaquedir);
373         if (err)
374                 goto out_cleanup;
375 
376         inode_lock(opaquedir->d_inode);
377         err = ovl_set_attr(opaquedir, &stat);
378         inode_unlock(opaquedir->d_inode);
379         if (err)
380                 goto out_cleanup;
381 
382         err = ovl_do_rename(wdir, opaquedir, udir, upper, RENAME_EXCHANGE);
383         if (err)
384                 goto out_cleanup;
385 
386         ovl_cleanup_whiteouts(upper, list);
387         ovl_cleanup(wdir, upper);
388         unlock_rename(workdir, upperdir);
389 
390         /* dentry's upper doesn't match now, get rid of it */
391         d_drop(dentry);
392 
393         return opaquedir;
394 
395 out_cleanup:
396         ovl_cleanup(wdir, opaquedir);
397         dput(opaquedir);
398 out_unlock:
399         unlock_rename(workdir, upperdir);
400 out:
401         return ERR_PTR(err);
402 }
403 
404 static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
405                              const struct posix_acl *acl)
406 {
407         void *buffer;
408         size_t size;
409         int err;
410 
411         if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
412                 return 0;
413 
414         size = posix_acl_xattr_size(acl->a_count);
415         buffer = kmalloc(size, GFP_KERNEL);
416         if (!buffer)
417                 return -ENOMEM;
418 
419         err = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
420         if (err < 0)
421                 goto out_free;
422 
423         err = vfs_setxattr(upperdentry, name, buffer, size, XATTR_CREATE);
424 out_free:
425         kfree(buffer);
426         return err;
427 }
428 
429 static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
430                                     struct ovl_cattr *cattr)
431 {
432         struct dentry *workdir = ovl_workdir(dentry);
433         struct inode *wdir = workdir->d_inode;
434         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
435         struct inode *udir = upperdir->d_inode;
436         struct dentry *upper;
437         struct dentry *newdentry;
438         int err;
439         struct posix_acl *acl, *default_acl;
440         bool hardlink = !!cattr->hardlink;
441 
442         if (WARN_ON(!workdir))
443                 return -EROFS;
444 
445         if (!hardlink) {
446                 err = posix_acl_create(dentry->d_parent->d_inode,
447                                        &cattr->mode, &default_acl, &acl);
448                 if (err)
449                         return err;
450         }
451 
452         err = ovl_lock_rename_workdir(workdir, upperdir);
453         if (err)
454                 goto out;
455 
456         upper = lookup_one_len(dentry->d_name.name, upperdir,
457                                dentry->d_name.len);
458         err = PTR_ERR(upper);
459         if (IS_ERR(upper))
460                 goto out_unlock;
461 
462         err = -ESTALE;
463         if (d_is_negative(upper) || !IS_WHITEOUT(d_inode(upper)))
464                 goto out_dput;
465 
466         newdentry = ovl_create_temp(workdir, cattr);
467         err = PTR_ERR(newdentry);
468         if (IS_ERR(newdentry))
469                 goto out_dput;
470 
471         /*
472          * mode could have been mutilated due to umask (e.g. sgid directory)
473          */
474         if (!hardlink &&
475             !S_ISLNK(cattr->mode) &&
476             newdentry->d_inode->i_mode != cattr->mode) {
477                 struct iattr attr = {
478                         .ia_valid = ATTR_MODE,
479                         .ia_mode = cattr->mode,
480                 };
481                 inode_lock(newdentry->d_inode);
482                 err = notify_change(newdentry, &attr, NULL);
483                 inode_unlock(newdentry->d_inode);
484                 if (err)
485                         goto out_cleanup;
486         }
487         if (!hardlink) {
488                 err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_ACCESS,
489                                         acl);
490                 if (err)
491                         goto out_cleanup;
492 
493                 err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_DEFAULT,
494                                         default_acl);
495                 if (err)
496                         goto out_cleanup;
497         }
498 
499         if (!hardlink && S_ISDIR(cattr->mode)) {
500                 err = ovl_set_opaque(dentry, newdentry);
501                 if (err)
502                         goto out_cleanup;
503 
504                 err = ovl_do_rename(wdir, newdentry, udir, upper,
505                                     RENAME_EXCHANGE);
506                 if (err)
507                         goto out_cleanup;
508 
509                 ovl_cleanup(wdir, upper);
510         } else {
511                 err = ovl_do_rename(wdir, newdentry, udir, upper, 0);
512                 if (err)
513                         goto out_cleanup;
514         }
515         err = ovl_instantiate(dentry, inode, newdentry, hardlink);
516         if (err)
517                 goto out_cleanup;
518 out_dput:
519         dput(upper);
520 out_unlock:
521         unlock_rename(workdir, upperdir);
522 out:
523         if (!hardlink) {
524                 posix_acl_release(acl);
525                 posix_acl_release(default_acl);
526         }
527         return err;
528 
529 out_cleanup:
530         ovl_cleanup(wdir, newdentry);
531         dput(newdentry);
532         goto out_dput;
533 }
534 
535 static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
536                               struct ovl_cattr *attr, bool origin)
537 {
538         int err;
539         const struct cred *old_cred;
540         struct cred *override_cred;
541         struct dentry *parent = dentry->d_parent;
542 
543         err = ovl_copy_up(parent);
544         if (err)
545                 return err;
546 
547         old_cred = ovl_override_creds(dentry->d_sb);
548 
549         /*
550          * When linking a file with copy up origin into a new parent, mark the
551          * new parent dir "impure".
552          */
553         if (origin) {
554                 err = ovl_set_impure(parent, ovl_dentry_upper(parent));
555                 if (err)
556                         goto out_revert_creds;
557         }
558 
559         err = -ENOMEM;
560         override_cred = prepare_creds();
561         if (override_cred) {
562                 override_cred->fsuid = inode->i_uid;
563                 override_cred->fsgid = inode->i_gid;
564                 if (!attr->hardlink) {
565                         err = security_dentry_create_files_as(dentry,
566                                         attr->mode, &dentry->d_name, old_cred,
567                                         override_cred);
568                         if (err) {
569                                 put_cred(override_cred);
570                                 goto out_revert_creds;
571                         }
572                 }
573                 put_cred(override_creds(override_cred));
574                 put_cred(override_cred);
575 
576                 if (!ovl_dentry_is_whiteout(dentry))
577                         err = ovl_create_upper(dentry, inode, attr);
578                 else
579                         err = ovl_create_over_whiteout(dentry, inode, attr);
580         }
581 out_revert_creds:
582         revert_creds(old_cred);
583         return err;
584 }
585 
586 static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
587                              const char *link)
588 {
589         int err;
590         struct inode *inode;
591         struct ovl_cattr attr = {
592                 .rdev = rdev,
593                 .link = link,
594         };
595 
596         err = ovl_want_write(dentry);
597         if (err)
598                 goto out;
599 
600         /* Preallocate inode to be used by ovl_get_inode() */
601         err = -ENOMEM;
602         inode = ovl_new_inode(dentry->d_sb, mode, rdev);
603         if (!inode)
604                 goto out_drop_write;
605 
606         spin_lock(&inode->i_lock);
607         inode->i_state |= I_CREATING;
608         spin_unlock(&inode->i_lock);
609 
610         inode_init_owner(inode, dentry->d_parent->d_inode, mode);
611         attr.mode = inode->i_mode;
612 
613         err = ovl_create_or_link(dentry, inode, &attr, false);
614         /* Did we end up using the preallocated inode? */
615         if (inode != d_inode(dentry))
616                 iput(inode);
617 
618 out_drop_write:
619         ovl_drop_write(dentry);
620 out:
621         return err;
622 }
623 
624 static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
625                       bool excl)
626 {
627         return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
628 }
629 
630 static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
631 {
632         return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
633 }
634 
635 static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
636                      dev_t rdev)
637 {
638         /* Don't allow creation of "whiteout" on overlay */
639         if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
640                 return -EPERM;
641 
642         return ovl_create_object(dentry, mode, rdev, NULL);
643 }
644 
645 static int ovl_symlink(struct inode *dir, struct dentry *dentry,
646                        const char *link)
647 {
648         return ovl_create_object(dentry, S_IFLNK, 0, link);
649 }
650 
651 static int ovl_set_link_redirect(struct dentry *dentry)
652 {
653         const struct cred *old_cred;
654         int err;
655 
656         old_cred = ovl_override_creds(dentry->d_sb);
657         err = ovl_set_redirect(dentry, false);
658         revert_creds(old_cred);
659 
660         return err;
661 }
662 
663 static int ovl_link(struct dentry *old, struct inode *newdir,
664                     struct dentry *new)
665 {
666         int err;
667         struct inode *inode;
668 
669         err = ovl_want_write(old);
670         if (err)
671                 goto out;
672 
673         err = ovl_copy_up(old);
674         if (err)
675                 goto out_drop_write;
676 
677         err = ovl_copy_up(new->d_parent);
678         if (err)
679                 goto out_drop_write;
680 
681         if (ovl_is_metacopy_dentry(old)) {
682                 err = ovl_set_link_redirect(old);
683                 if (err)
684                         goto out_drop_write;
685         }
686 
687         err = ovl_nlink_start(old);
688         if (err)
689                 goto out_drop_write;
690 
691         inode = d_inode(old);
692         ihold(inode);
693 
694         err = ovl_create_or_link(new, inode,
695                         &(struct ovl_cattr) {.hardlink = ovl_dentry_upper(old)},
696                         ovl_type_origin(old));
697         if (err)
698                 iput(inode);
699 
700         ovl_nlink_end(old);
701 out_drop_write:
702         ovl_drop_write(old);
703 out:
704         return err;
705 }
706 
707 static bool ovl_matches_upper(struct dentry *dentry, struct dentry *upper)
708 {
709         return d_inode(ovl_dentry_upper(dentry)) == d_inode(upper);
710 }
711 
712 static int ovl_remove_and_whiteout(struct dentry *dentry,
713                                    struct list_head *list)
714 {
715         struct dentry *workdir = ovl_workdir(dentry);
716         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
717         struct dentry *upper;
718         struct dentry *opaquedir = NULL;
719         int err;
720 
721         if (WARN_ON(!workdir))
722                 return -EROFS;
723 
724         if (!list_empty(list)) {
725                 opaquedir = ovl_clear_empty(dentry, list);
726                 err = PTR_ERR(opaquedir);
727                 if (IS_ERR(opaquedir))
728                         goto out;
729         }
730 
731         err = ovl_lock_rename_workdir(workdir, upperdir);
732         if (err)
733                 goto out_dput;
734 
735         upper = lookup_one_len(dentry->d_name.name, upperdir,
736                                dentry->d_name.len);
737         err = PTR_ERR(upper);
738         if (IS_ERR(upper))
739                 goto out_unlock;
740 
741         err = -ESTALE;
742         if ((opaquedir && upper != opaquedir) ||
743             (!opaquedir && ovl_dentry_upper(dentry) &&
744              !ovl_matches_upper(dentry, upper))) {
745                 goto out_dput_upper;
746         }
747 
748         err = ovl_cleanup_and_whiteout(workdir, d_inode(upperdir), upper);
749         if (err)
750                 goto out_d_drop;
751 
752         ovl_dir_modified(dentry->d_parent, true);
753 out_d_drop:
754         d_drop(dentry);
755 out_dput_upper:
756         dput(upper);
757 out_unlock:
758         unlock_rename(workdir, upperdir);
759 out_dput:
760         dput(opaquedir);
761 out:
762         return err;
763 }
764 
765 static int ovl_remove_upper(struct dentry *dentry, bool is_dir,
766                             struct list_head *list)
767 {
768         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
769         struct inode *dir = upperdir->d_inode;
770         struct dentry *upper;
771         struct dentry *opaquedir = NULL;
772         int err;
773 
774         if (!list_empty(list)) {
775                 opaquedir = ovl_clear_empty(dentry, list);
776                 err = PTR_ERR(opaquedir);
777                 if (IS_ERR(opaquedir))
778                         goto out;
779         }
780 
781         inode_lock_nested(dir, I_MUTEX_PARENT);
782         upper = lookup_one_len(dentry->d_name.name, upperdir,
783                                dentry->d_name.len);
784         err = PTR_ERR(upper);
785         if (IS_ERR(upper))
786                 goto out_unlock;
787 
788         err = -ESTALE;
789         if ((opaquedir && upper != opaquedir) ||
790             (!opaquedir && !ovl_matches_upper(dentry, upper)))
791                 goto out_dput_upper;
792 
793         if (is_dir)
794                 err = vfs_rmdir(dir, upper);
795         else
796                 err = vfs_unlink(dir, upper, NULL);
797         ovl_dir_modified(dentry->d_parent, ovl_type_origin(dentry));
798 
799         /*
800          * Keeping this dentry hashed would mean having to release
801          * upperpath/lowerpath, which could only be done if we are the
802          * sole user of this dentry.  Too tricky...  Just unhash for
803          * now.
804          */
805         if (!err)
806                 d_drop(dentry);
807 out_dput_upper:
808         dput(upper);
809 out_unlock:
810         inode_unlock(dir);
811         dput(opaquedir);
812 out:
813         return err;
814 }
815 
816 static bool ovl_pure_upper(struct dentry *dentry)
817 {
818         return !ovl_dentry_lower(dentry) &&
819                !ovl_test_flag(OVL_WHITEOUTS, d_inode(dentry));
820 }
821 
822 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
823 {
824         int err;
825         const struct cred *old_cred;
826         struct dentry *upperdentry;
827         bool lower_positive = ovl_lower_positive(dentry);
828         LIST_HEAD(list);
829 
830         /* No need to clean pure upper removed by vfs_rmdir() */
831         if (is_dir && (lower_positive || !ovl_pure_upper(dentry))) {
832                 err = ovl_check_empty_dir(dentry, &list);
833                 if (err)
834                         goto out;
835         }
836 
837         err = ovl_want_write(dentry);
838         if (err)
839                 goto out;
840 
841         err = ovl_copy_up(dentry->d_parent);
842         if (err)
843                 goto out_drop_write;
844 
845         err = ovl_nlink_start(dentry);
846         if (err)
847                 goto out_drop_write;
848 
849         old_cred = ovl_override_creds(dentry->d_sb);
850         if (!lower_positive)
851                 err = ovl_remove_upper(dentry, is_dir, &list);
852         else
853                 err = ovl_remove_and_whiteout(dentry, &list);
854         revert_creds(old_cred);
855         if (!err) {
856                 if (is_dir)
857                         clear_nlink(dentry->d_inode);
858                 else
859                         drop_nlink(dentry->d_inode);
860         }
861         ovl_nlink_end(dentry);
862 
863         /*
864          * Copy ctime
865          *
866          * Note: we fail to update ctime if there was no copy-up, only a
867          * whiteout
868          */
869         upperdentry = ovl_dentry_upper(dentry);
870         if (upperdentry)
871                 ovl_copyattr(d_inode(upperdentry), d_inode(dentry));
872 
873 out_drop_write:
874         ovl_drop_write(dentry);
875 out:
876         ovl_cache_free(&list);
877         return err;
878 }
879 
880 static int ovl_unlink(struct inode *dir, struct dentry *dentry)
881 {
882         return ovl_do_remove(dentry, false);
883 }
884 
885 static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
886 {
887         return ovl_do_remove(dentry, true);
888 }
889 
890 static bool ovl_type_merge_or_lower(struct dentry *dentry)
891 {
892         enum ovl_path_type type = ovl_path_type(dentry);
893 
894         return OVL_TYPE_MERGE(type) || !OVL_TYPE_UPPER(type);
895 }
896 
897 static bool ovl_can_move(struct dentry *dentry)
898 {
899         return ovl_redirect_dir(dentry->d_sb) ||
900                 !d_is_dir(dentry) || !ovl_type_merge_or_lower(dentry);
901 }
902 
903 static char *ovl_get_redirect(struct dentry *dentry, bool abs_redirect)
904 {
905         char *buf, *ret;
906         struct dentry *d, *tmp;
907         int buflen = ovl_redirect_max + 1;
908 
909         if (!abs_redirect) {
910                 ret = kstrndup(dentry->d_name.name, dentry->d_name.len,
911                                GFP_KERNEL);
912                 goto out;
913         }
914 
915         buf = ret = kmalloc(buflen, GFP_KERNEL);
916         if (!buf)
917                 goto out;
918 
919         buflen--;
920         buf[buflen] = '\0';
921         for (d = dget(dentry); !IS_ROOT(d);) {
922                 const char *name;
923                 int thislen;
924 
925                 spin_lock(&d->d_lock);
926                 name = ovl_dentry_get_redirect(d);
927                 if (name) {
928                         thislen = strlen(name);
929                 } else {
930                         name = d->d_name.name;
931                         thislen = d->d_name.len;
932                 }
933 
934                 /* If path is too long, fall back to userspace move */
935                 if (thislen + (name[0] != '/') > buflen) {
936                         ret = ERR_PTR(-EXDEV);
937                         spin_unlock(&d->d_lock);
938                         goto out_put;
939                 }
940 
941                 buflen -= thislen;
942                 memcpy(&buf[buflen], name, thislen);
943                 tmp = dget_dlock(d->d_parent);
944                 spin_unlock(&d->d_lock);
945 
946                 dput(d);
947                 d = tmp;
948 
949                 /* Absolute redirect: finished */
950                 if (buf[buflen] == '/')
951                         break;
952                 buflen--;
953                 buf[buflen] = '/';
954         }
955         ret = kstrdup(&buf[buflen], GFP_KERNEL);
956 out_put:
957         dput(d);
958         kfree(buf);
959 out:
960         return ret ? ret : ERR_PTR(-ENOMEM);
961 }
962 
963 static bool ovl_need_absolute_redirect(struct dentry *dentry, bool samedir)
964 {
965         struct dentry *lowerdentry;
966 
967         if (!samedir)
968                 return true;
969 
970         if (d_is_dir(dentry))
971                 return false;
972 
973         /*
974          * For non-dir hardlinked files, we need absolute redirects
975          * in general as two upper hardlinks could be in different
976          * dirs. We could put a relative redirect now and convert
977          * it to absolute redirect later. But when nlink > 1 and
978          * indexing is on, that means relative redirect needs to be
979          * converted to absolute during copy up of another lower
980          * hardllink as well.
981          *
982          * So without optimizing too much, just check if lower is
983          * a hard link or not. If lower is hard link, put absolute
984          * redirect.
985          */
986         lowerdentry = ovl_dentry_lower(dentry);
987         return (d_inode(lowerdentry)->i_nlink > 1);
988 }
989 
990 static int ovl_set_redirect(struct dentry *dentry, bool samedir)
991 {
992         int err;
993         const char *redirect = ovl_dentry_get_redirect(dentry);
994         bool absolute_redirect = ovl_need_absolute_redirect(dentry, samedir);
995 
996         if (redirect && (!absolute_redirect || redirect[0] == '/'))
997                 return 0;
998 
999         redirect = ovl_get_redirect(dentry, absolute_redirect);
1000         if (IS_ERR(redirect))
1001                 return PTR_ERR(redirect);
1002 
1003         err = ovl_check_setxattr(dentry, ovl_dentry_upper(dentry),
1004                                  OVL_XATTR_REDIRECT,
1005                                  redirect, strlen(redirect), -EXDEV);
1006         if (!err) {
1007                 spin_lock(&dentry->d_lock);
1008                 ovl_dentry_set_redirect(dentry, redirect);
1009                 spin_unlock(&dentry->d_lock);
1010         } else {
1011                 kfree(redirect);
1012                 pr_warn_ratelimited("overlayfs: failed to set redirect (%i)\n",
1013                                     err);
1014                 /* Fall back to userspace copy-up */
1015                 err = -EXDEV;
1016         }
1017         return err;
1018 }
1019 
1020 static int ovl_rename(struct inode *olddir, struct dentry *old,
1021                       struct inode *newdir, struct dentry *new,
1022                       unsigned int flags)
1023 {
1024         int err;
1025         struct dentry *old_upperdir;
1026         struct dentry *new_upperdir;
1027         struct dentry *olddentry;
1028         struct dentry *newdentry;
1029         struct dentry *trap;
1030         bool old_opaque;
1031         bool new_opaque;
1032         bool cleanup_whiteout = false;
1033         bool update_nlink = false;
1034         bool overwrite = !(flags & RENAME_EXCHANGE);
1035         bool is_dir = d_is_dir(old);
1036         bool new_is_dir = d_is_dir(new);
1037         bool samedir = olddir == newdir;
1038         struct dentry *opaquedir = NULL;
1039         const struct cred *old_cred = NULL;
1040         LIST_HEAD(list);
1041 
1042         err = -EINVAL;
1043         if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
1044                 goto out;
1045 
1046         flags &= ~RENAME_NOREPLACE;
1047 
1048         /* Don't copy up directory trees */
1049         err = -EXDEV;
1050         if (!ovl_can_move(old))
1051                 goto out;
1052         if (!overwrite && !ovl_can_move(new))
1053                 goto out;
1054 
1055         if (overwrite && new_is_dir && !ovl_pure_upper(new)) {
1056                 err = ovl_check_empty_dir(new, &list);
1057                 if (err)
1058                         goto out;
1059         }
1060 
1061         if (overwrite) {
1062                 if (ovl_lower_positive(old)) {
1063                         if (!ovl_dentry_is_whiteout(new)) {
1064                                 /* Whiteout source */
1065                                 flags |= RENAME_WHITEOUT;
1066                         } else {
1067                                 /* Switch whiteouts */
1068                                 flags |= RENAME_EXCHANGE;
1069                         }
1070                 } else if (is_dir && ovl_dentry_is_whiteout(new)) {
1071                         flags |= RENAME_EXCHANGE;
1072                         cleanup_whiteout = true;
1073                 }
1074         }
1075 
1076         err = ovl_want_write(old);
1077         if (err)
1078                 goto out;
1079 
1080         err = ovl_copy_up(old);
1081         if (err)
1082                 goto out_drop_write;
1083 
1084         err = ovl_copy_up(new->d_parent);
1085         if (err)
1086                 goto out_drop_write;
1087         if (!overwrite) {
1088                 err = ovl_copy_up(new);
1089                 if (err)
1090                         goto out_drop_write;
1091         } else if (d_inode(new)) {
1092                 err = ovl_nlink_start(new);
1093                 if (err)
1094                         goto out_drop_write;
1095 
1096                 update_nlink = true;
1097         }
1098 
1099         old_cred = ovl_override_creds(old->d_sb);
1100 
1101         if (!list_empty(&list)) {
1102                 opaquedir = ovl_clear_empty(new, &list);
1103                 err = PTR_ERR(opaquedir);
1104                 if (IS_ERR(opaquedir)) {
1105                         opaquedir = NULL;
1106                         goto out_revert_creds;
1107                 }
1108         }
1109 
1110         old_upperdir = ovl_dentry_upper(old->d_parent);
1111         new_upperdir = ovl_dentry_upper(new->d_parent);
1112 
1113         if (!samedir) {
1114                 /*
1115                  * When moving a merge dir or non-dir with copy up origin into
1116                  * a new parent, we are marking the new parent dir "impure".
1117                  * When ovl_iterate() iterates an "impure" upper dir, it will
1118                  * lookup the origin inodes of the entries to fill d_ino.
1119                  */
1120                 if (ovl_type_origin(old)) {
1121                         err = ovl_set_impure(new->d_parent, new_upperdir);
1122                         if (err)
1123                                 goto out_revert_creds;
1124                 }
1125                 if (!overwrite && ovl_type_origin(new)) {
1126                         err = ovl_set_impure(old->d_parent, old_upperdir);
1127                         if (err)
1128                                 goto out_revert_creds;
1129                 }
1130         }
1131 
1132         trap = lock_rename(new_upperdir, old_upperdir);
1133 
1134         olddentry = lookup_one_len(old->d_name.name, old_upperdir,
1135                                    old->d_name.len);
1136         err = PTR_ERR(olddentry);
1137         if (IS_ERR(olddentry))
1138                 goto out_unlock;
1139 
1140         err = -ESTALE;
1141         if (!ovl_matches_upper(old, olddentry))
1142                 goto out_dput_old;
1143 
1144         newdentry = lookup_one_len(new->d_name.name, new_upperdir,
1145                                    new->d_name.len);
1146         err = PTR_ERR(newdentry);
1147         if (IS_ERR(newdentry))
1148                 goto out_dput_old;
1149 
1150         old_opaque = ovl_dentry_is_opaque(old);
1151         new_opaque = ovl_dentry_is_opaque(new);
1152 
1153         err = -ESTALE;
1154         if (d_inode(new) && ovl_dentry_upper(new)) {
1155                 if (opaquedir) {
1156                         if (newdentry != opaquedir)
1157                                 goto out_dput;
1158                 } else {
1159                         if (!ovl_matches_upper(new, newdentry))
1160                                 goto out_dput;
1161                 }
1162         } else {
1163                 if (!d_is_negative(newdentry) &&
1164                     (!new_opaque || !ovl_is_whiteout(newdentry)))
1165                         goto out_dput;
1166         }
1167 
1168         if (olddentry == trap)
1169                 goto out_dput;
1170         if (newdentry == trap)
1171                 goto out_dput;
1172 
1173         if (olddentry->d_inode == newdentry->d_inode)
1174                 goto out_dput;
1175 
1176         err = 0;
1177         if (ovl_type_merge_or_lower(old))
1178                 err = ovl_set_redirect(old, samedir);
1179         else if (is_dir && !old_opaque && ovl_type_merge(new->d_parent))
1180                 err = ovl_set_opaque_xerr(old, olddentry, -EXDEV);
1181         if (err)
1182                 goto out_dput;
1183 
1184         if (!overwrite && ovl_type_merge_or_lower(new))
1185                 err = ovl_set_redirect(new, samedir);
1186         else if (!overwrite && new_is_dir && !new_opaque &&
1187                  ovl_type_merge(old->d_parent))
1188                 err = ovl_set_opaque_xerr(new, newdentry, -EXDEV);
1189         if (err)
1190                 goto out_dput;
1191 
1192         err = ovl_do_rename(old_upperdir->d_inode, olddentry,
1193                             new_upperdir->d_inode, newdentry, flags);
1194         if (err)
1195                 goto out_dput;
1196 
1197         if (cleanup_whiteout)
1198                 ovl_cleanup(old_upperdir->d_inode, newdentry);
1199 
1200         if (overwrite && d_inode(new)) {
1201                 if (new_is_dir)
1202                         clear_nlink(d_inode(new));
1203                 else
1204                         drop_nlink(d_inode(new));
1205         }
1206 
1207         ovl_dir_modified(old->d_parent, ovl_type_origin(old) ||
1208                          (!overwrite && ovl_type_origin(new)));
1209         ovl_dir_modified(new->d_parent, ovl_type_origin(old) ||
1210                          (d_inode(new) && ovl_type_origin(new)));
1211 
1212         /* copy ctime: */
1213         ovl_copyattr(d_inode(olddentry), d_inode(old));
1214         if (d_inode(new) && ovl_dentry_upper(new))
1215                 ovl_copyattr(d_inode(newdentry), d_inode(new));
1216 
1217 out_dput:
1218         dput(newdentry);
1219 out_dput_old:
1220         dput(olddentry);
1221 out_unlock:
1222         unlock_rename(new_upperdir, old_upperdir);
1223 out_revert_creds:
1224         revert_creds(old_cred);
1225         if (update_nlink)
1226                 ovl_nlink_end(new);
1227 out_drop_write:
1228         ovl_drop_write(old);
1229 out:
1230         dput(opaquedir);
1231         ovl_cache_free(&list);
1232         return err;
1233 }
1234 
1235 const struct inode_operations ovl_dir_inode_operations = {
1236         .lookup         = ovl_lookup,
1237         .mkdir          = ovl_mkdir,
1238         .symlink        = ovl_symlink,
1239         .unlink         = ovl_unlink,
1240         .rmdir          = ovl_rmdir,
1241         .rename         = ovl_rename,
1242         .link           = ovl_link,
1243         .setattr        = ovl_setattr,
1244         .create         = ovl_create,
1245         .mknod          = ovl_mknod,
1246         .permission     = ovl_permission,
1247         .getattr        = ovl_getattr,
1248         .listxattr      = ovl_listxattr,
1249         .get_acl        = ovl_get_acl,
1250         .update_time    = ovl_update_time,
1251 };
1252 

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