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

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  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 static int ovl_set_redirect(struct dentry *dentry, bool samedir);
 28 
 29 int ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
 30 {
 31         int err;
 32 
 33         dget(wdentry);
 34         if (d_is_dir(wdentry))
 35                 err = ovl_do_rmdir(wdir, wdentry);
 36         else
 37                 err = ovl_do_unlink(wdir, wdentry);
 38         dput(wdentry);
 39 
 40         if (err) {
 41                 pr_err("overlayfs: cleanup of '%pd2' failed (%i)\n",
 42                        wdentry, err);
 43         }
 44 
 45         return err;
 46 }
 47 
 48 static struct dentry *ovl_lookup_temp(struct dentry *workdir)
 49 {
 50         struct dentry *temp;
 51         char name[20];
 52         static atomic_t temp_id = ATOMIC_INIT(0);
 53 
 54         /* counter is allowed to wrap, since temp dentries are ephemeral */
 55         snprintf(name, sizeof(name), "#%x", atomic_inc_return(&temp_id));
 56 
 57         temp = lookup_one_len(name, workdir, strlen(name));
 58         if (!IS_ERR(temp) && temp->d_inode) {
 59                 pr_err("overlayfs: workdir/%s already exists\n", name);
 60                 dput(temp);
 61                 temp = ERR_PTR(-EIO);
 62         }
 63 
 64         return temp;
 65 }
 66 
 67 /* caller holds i_mutex on workdir */
 68 static struct dentry *ovl_whiteout(struct dentry *workdir)
 69 {
 70         int err;
 71         struct dentry *whiteout;
 72         struct inode *wdir = workdir->d_inode;
 73 
 74         whiteout = ovl_lookup_temp(workdir);
 75         if (IS_ERR(whiteout))
 76                 return whiteout;
 77 
 78         err = ovl_do_whiteout(wdir, whiteout);
 79         if (err) {
 80                 dput(whiteout);
 81                 whiteout = ERR_PTR(err);
 82         }
 83 
 84         return whiteout;
 85 }
 86 
 87 /* Caller must hold i_mutex on both workdir and dir */
 88 int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
 89                              struct dentry *dentry)
 90 {
 91         struct inode *wdir = workdir->d_inode;
 92         struct dentry *whiteout;
 93         int err;
 94         int flags = 0;
 95 
 96         whiteout = ovl_whiteout(workdir);
 97         err = PTR_ERR(whiteout);
 98         if (IS_ERR(whiteout))
 99                 return err;
100 
101         if (d_is_dir(dentry))
102                 flags = RENAME_EXCHANGE;
103 
104         err = ovl_do_rename(wdir, whiteout, dir, dentry, flags);
105         if (err)
106                 goto kill_whiteout;
107         if (flags)
108                 ovl_cleanup(wdir, dentry);
109 
110 out:
111         dput(whiteout);
112         return err;
113 
114 kill_whiteout:
115         ovl_cleanup(wdir, whiteout);
116         goto out;
117 }
118 
119 static int ovl_mkdir_real(struct inode *dir, struct dentry **newdentry,
120                           umode_t mode)
121 {
122         int err;
123         struct dentry *d, *dentry = *newdentry;
124 
125         err = ovl_do_mkdir(dir, dentry, mode);
126         if (err)
127                 return err;
128 
129         if (likely(!d_unhashed(dentry)))
130                 return 0;
131 
132         /*
133          * vfs_mkdir() may succeed and leave the dentry passed
134          * to it unhashed and negative. If that happens, try to
135          * lookup a new hashed and positive dentry.
136          */
137         d = lookup_one_len(dentry->d_name.name, dentry->d_parent,
138                            dentry->d_name.len);
139         if (IS_ERR(d)) {
140                 pr_warn("overlayfs: failed lookup after mkdir (%pd2, err=%i).\n",
141                         dentry, err);
142                 return PTR_ERR(d);
143         }
144         dput(dentry);
145         *newdentry = d;
146 
147         return 0;
148 }
149 
150 struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry,
151                                struct ovl_cattr *attr)
152 {
153         int err;
154 
155         if (IS_ERR(newdentry))
156                 return newdentry;
157 
158         err = -ESTALE;
159         if (newdentry->d_inode)
160                 goto out;
161 
162         if (attr->hardlink) {
163                 err = ovl_do_link(attr->hardlink, dir, newdentry);
164         } else {
165                 switch (attr->mode & S_IFMT) {
166                 case S_IFREG:
167                         err = ovl_do_create(dir, newdentry, attr->mode);
168                         break;
169 
170                 case S_IFDIR:
171                         /* mkdir is special... */
172                         err =  ovl_mkdir_real(dir, &newdentry, attr->mode);
173                         break;
174 
175                 case S_IFCHR:
176                 case S_IFBLK:
177                 case S_IFIFO:
178                 case S_IFSOCK:
179                         err = ovl_do_mknod(dir, newdentry, attr->mode,
180                                            attr->rdev);
181                         break;
182 
183                 case S_IFLNK:
184                         err = ovl_do_symlink(dir, newdentry, attr->link);
185                         break;
186 
187                 default:
188                         err = -EPERM;
189                 }
190         }
191         if (!err && WARN_ON(!newdentry->d_inode)) {
192                 /*
193                  * Not quite sure if non-instantiated dentry is legal or not.
194                  * VFS doesn't seem to care so check and warn here.
195                  */
196                 err = -EIO;
197         }
198 out:
199         if (err) {
200                 dput(newdentry);
201                 return ERR_PTR(err);
202         }
203         return newdentry;
204 }
205 
206 struct dentry *ovl_create_temp(struct dentry *workdir, struct ovl_cattr *attr)
207 {
208         return ovl_create_real(d_inode(workdir), ovl_lookup_temp(workdir),
209                                attr);
210 }
211 
212 static int ovl_set_opaque_xerr(struct dentry *dentry, struct dentry *upper,
213                                int xerr)
214 {
215         int err;
216 
217         err = ovl_check_setxattr(dentry, upper, OVL_XATTR_OPAQUE, "y", 1, xerr);
218         if (!err)
219                 ovl_dentry_set_opaque(dentry);
220 
221         return err;
222 }
223 
224 static int ovl_set_opaque(struct dentry *dentry, struct dentry *upperdentry)
225 {
226         /*
227          * Fail with -EIO when trying to create opaque dir and upper doesn't
228          * support xattrs. ovl_rename() calls ovl_set_opaque_xerr(-EXDEV) to
229          * return a specific error for noxattr case.
230          */
231         return ovl_set_opaque_xerr(dentry, upperdentry, -EIO);
232 }
233 
234 /*
235  * Common operations required to be done after creation of file on upper.
236  * If @hardlink is false, then @inode is a pre-allocated inode, we may or
237  * may not use to instantiate the new dentry.
238  */
239 static int ovl_instantiate(struct dentry *dentry, struct inode *inode,
240                            struct dentry *newdentry, bool hardlink)
241 {
242         struct ovl_inode_params oip = {
243                 .upperdentry = newdentry,
244                 .newinode = inode,
245         };
246 
247         ovl_dir_modified(dentry->d_parent, false);
248         ovl_dentry_set_upper_alias(dentry);
249         if (!hardlink) {
250                 /*
251                  * ovl_obtain_alias() can be called after ovl_create_real()
252                  * and before we get here, so we may get an inode from cache
253                  * with the same real upperdentry that is not the inode we
254                  * pre-allocated.  In this case we will use the cached inode
255                  * to instantiate the new dentry.
256                  *
257                  * XXX: if we ever use ovl_obtain_alias() to decode directory
258                  * file handles, need to use ovl_get_inode_locked() and
259                  * d_instantiate_new() here to prevent from creating two
260                  * hashed directory inode aliases.
261                  */
262                 inode = ovl_get_inode(dentry->d_sb, &oip);
263                 if (WARN_ON(IS_ERR(inode)))
264                         return PTR_ERR(inode);
265         } else {
266                 WARN_ON(ovl_inode_real(inode) != d_inode(newdentry));
267                 dput(newdentry);
268                 inc_nlink(inode);
269         }
270 
271         d_instantiate(dentry, inode);
272         if (inode != oip.newinode) {
273                 pr_warn_ratelimited("overlayfs: newly created inode found in cache (%pd2)\n",
274                                     dentry);
275         }
276 
277         /* Force lookup of new upper hardlink to find its lower */
278         if (hardlink)
279                 d_drop(dentry);
280 
281         return 0;
282 }
283 
284 static bool ovl_type_merge(struct dentry *dentry)
285 {
286         return OVL_TYPE_MERGE(ovl_path_type(dentry));
287 }
288 
289 static bool ovl_type_origin(struct dentry *dentry)
290 {
291         return OVL_TYPE_ORIGIN(ovl_path_type(dentry));
292 }
293 
294 static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
295                             struct ovl_cattr *attr)
296 {
297         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
298         struct inode *udir = upperdir->d_inode;
299         struct dentry *newdentry;
300         int err;
301 
302         if (!attr->hardlink && !IS_POSIXACL(udir))
303                 attr->mode &= ~current_umask();
304 
305         inode_lock_nested(udir, I_MUTEX_PARENT);
306         newdentry = ovl_create_real(udir,
307                                     lookup_one_len(dentry->d_name.name,
308                                                    upperdir,
309                                                    dentry->d_name.len),
310                                     attr);
311         err = PTR_ERR(newdentry);
312         if (IS_ERR(newdentry))
313                 goto out_unlock;
314 
315         if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry)) {
316                 /* Setting opaque here is just an optimization, allow to fail */
317                 ovl_set_opaque(dentry, newdentry);
318         }
319 
320         err = ovl_instantiate(dentry, inode, newdentry, !!attr->hardlink);
321         if (err)
322                 goto out_cleanup;
323 out_unlock:
324         inode_unlock(udir);
325         return err;
326 
327 out_cleanup:
328         ovl_cleanup(udir, newdentry);
329         dput(newdentry);
330         goto out_unlock;
331 }
332 
333 static struct dentry *ovl_clear_empty(struct dentry *dentry,
334                                       struct list_head *list)
335 {
336         struct dentry *workdir = ovl_workdir(dentry);
337         struct inode *wdir = workdir->d_inode;
338         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
339         struct inode *udir = upperdir->d_inode;
340         struct path upperpath;
341         struct dentry *upper;
342         struct dentry *opaquedir;
343         struct kstat stat;
344         int err;
345 
346         if (WARN_ON(!workdir))
347                 return ERR_PTR(-EROFS);
348 
349         err = ovl_lock_rename_workdir(workdir, upperdir);
350         if (err)
351                 goto out;
352 
353         ovl_path_upper(dentry, &upperpath);
354         err = vfs_getattr(&upperpath, &stat,
355                           STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
356         if (err)
357                 goto out_unlock;
358 
359         err = -ESTALE;
360         if (!S_ISDIR(stat.mode))
361                 goto out_unlock;
362         upper = upperpath.dentry;
363         if (upper->d_parent->d_inode != udir)
364                 goto out_unlock;
365 
366         opaquedir = ovl_create_temp(workdir, OVL_CATTR(stat.mode));
367         err = PTR_ERR(opaquedir);
368         if (IS_ERR(opaquedir))
369                 goto out_unlock;
370 
371         err = ovl_copy_xattr(upper, opaquedir);
372         if (err)
373                 goto out_cleanup;
374 
375         err = ovl_set_opaque(dentry, opaquedir);
376         if (err)
377                 goto out_cleanup;
378 
379         inode_lock(opaquedir->d_inode);
380         err = ovl_set_attr(opaquedir, &stat);
381         inode_unlock(opaquedir->d_inode);
382         if (err)
383                 goto out_cleanup;
384 
385         err = ovl_do_rename(wdir, opaquedir, udir, upper, RENAME_EXCHANGE);
386         if (err)
387                 goto out_cleanup;
388 
389         ovl_cleanup_whiteouts(upper, list);
390         ovl_cleanup(wdir, upper);
391         unlock_rename(workdir, upperdir);
392 
393         /* dentry's upper doesn't match now, get rid of it */
394         d_drop(dentry);
395 
396         return opaquedir;
397 
398 out_cleanup:
399         ovl_cleanup(wdir, opaquedir);
400         dput(opaquedir);
401 out_unlock:
402         unlock_rename(workdir, upperdir);
403 out:
404         return ERR_PTR(err);
405 }
406 
407 static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
408                              const struct posix_acl *acl)
409 {
410         void *buffer;
411         size_t size;
412         int err;
413 
414         if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
415                 return 0;
416 
417         size = posix_acl_xattr_size(acl->a_count);
418         buffer = kmalloc(size, GFP_KERNEL);
419         if (!buffer)
420                 return -ENOMEM;
421 
422         err = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
423         if (err < 0)
424                 goto out_free;
425 
426         err = vfs_setxattr(upperdentry, name, buffer, size, XATTR_CREATE);
427 out_free:
428         kfree(buffer);
429         return err;
430 }
431 
432 static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
433                                     struct ovl_cattr *cattr)
434 {
435         struct dentry *workdir = ovl_workdir(dentry);
436         struct inode *wdir = workdir->d_inode;
437         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
438         struct inode *udir = upperdir->d_inode;
439         struct dentry *upper;
440         struct dentry *newdentry;
441         int err;
442         struct posix_acl *acl, *default_acl;
443         bool hardlink = !!cattr->hardlink;
444 
445         if (WARN_ON(!workdir))
446                 return -EROFS;
447 
448         if (!hardlink) {
449                 err = posix_acl_create(dentry->d_parent->d_inode,
450                                        &cattr->mode, &default_acl, &acl);
451                 if (err)
452                         return err;
453         }
454 
455         err = ovl_lock_rename_workdir(workdir, upperdir);
456         if (err)
457                 goto out;
458 
459         upper = lookup_one_len(dentry->d_name.name, upperdir,
460                                dentry->d_name.len);
461         err = PTR_ERR(upper);
462         if (IS_ERR(upper))
463                 goto out_unlock;
464 
465         err = -ESTALE;
466         if (d_is_negative(upper) || !IS_WHITEOUT(d_inode(upper)))
467                 goto out_dput;
468 
469         newdentry = ovl_create_temp(workdir, cattr);
470         err = PTR_ERR(newdentry);
471         if (IS_ERR(newdentry))
472                 goto out_dput;
473 
474         /*
475          * mode could have been mutilated due to umask (e.g. sgid directory)
476          */
477         if (!hardlink &&
478             !S_ISLNK(cattr->mode) &&
479             newdentry->d_inode->i_mode != cattr->mode) {
480                 struct iattr attr = {
481                         .ia_valid = ATTR_MODE,
482                         .ia_mode = cattr->mode,
483                 };
484                 inode_lock(newdentry->d_inode);
485                 err = notify_change(newdentry, &attr, NULL);
486                 inode_unlock(newdentry->d_inode);
487                 if (err)
488                         goto out_cleanup;
489         }
490         if (!hardlink) {
491                 err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_ACCESS,
492                                         acl);
493                 if (err)
494                         goto out_cleanup;
495 
496                 err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_DEFAULT,
497                                         default_acl);
498                 if (err)
499                         goto out_cleanup;
500         }
501 
502         if (!hardlink && S_ISDIR(cattr->mode)) {
503                 err = ovl_set_opaque(dentry, newdentry);
504                 if (err)
505                         goto out_cleanup;
506 
507                 err = ovl_do_rename(wdir, newdentry, udir, upper,
508                                     RENAME_EXCHANGE);
509                 if (err)
510                         goto out_cleanup;
511 
512                 ovl_cleanup(wdir, upper);
513         } else {
514                 err = ovl_do_rename(wdir, newdentry, udir, upper, 0);
515                 if (err)
516                         goto out_cleanup;
517         }
518         err = ovl_instantiate(dentry, inode, newdentry, hardlink);
519         if (err)
520                 goto out_cleanup;
521 out_dput:
522         dput(upper);
523 out_unlock:
524         unlock_rename(workdir, upperdir);
525 out:
526         if (!hardlink) {
527                 posix_acl_release(acl);
528                 posix_acl_release(default_acl);
529         }
530         return err;
531 
532 out_cleanup:
533         ovl_cleanup(wdir, newdentry);
534         dput(newdentry);
535         goto out_dput;
536 }
537 
538 static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
539                               struct ovl_cattr *attr, bool origin)
540 {
541         int err;
542         const struct cred *old_cred;
543         struct cred *override_cred;
544         struct dentry *parent = dentry->d_parent;
545 
546         err = ovl_copy_up(parent);
547         if (err)
548                 return err;
549 
550         old_cred = ovl_override_creds(dentry->d_sb);
551 
552         /*
553          * When linking a file with copy up origin into a new parent, mark the
554          * new parent dir "impure".
555          */
556         if (origin) {
557                 err = ovl_set_impure(parent, ovl_dentry_upper(parent));
558                 if (err)
559                         goto out_revert_creds;
560         }
561 
562         err = -ENOMEM;
563         override_cred = prepare_creds();
564         if (override_cred) {
565                 override_cred->fsuid = inode->i_uid;
566                 override_cred->fsgid = inode->i_gid;
567                 if (!attr->hardlink) {
568                         err = security_dentry_create_files_as(dentry,
569                                         attr->mode, &dentry->d_name, old_cred,
570                                         override_cred);
571                         if (err) {
572                                 put_cred(override_cred);
573                                 goto out_revert_creds;
574                         }
575                 }
576                 put_cred(override_creds(override_cred));
577                 put_cred(override_cred);
578 
579                 if (!ovl_dentry_is_whiteout(dentry))
580                         err = ovl_create_upper(dentry, inode, attr);
581                 else
582                         err = ovl_create_over_whiteout(dentry, inode, attr);
583         }
584 out_revert_creds:
585         revert_creds(old_cred);
586         return err;
587 }
588 
589 static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
590                              const char *link)
591 {
592         int err;
593         struct inode *inode;
594         struct ovl_cattr attr = {
595                 .rdev = rdev,
596                 .link = link,
597         };
598 
599         err = ovl_want_write(dentry);
600         if (err)
601                 goto out;
602 
603         /* Preallocate inode to be used by ovl_get_inode() */
604         err = -ENOMEM;
605         inode = ovl_new_inode(dentry->d_sb, mode, rdev);
606         if (!inode)
607                 goto out_drop_write;
608 
609         spin_lock(&inode->i_lock);
610         inode->i_state |= I_CREATING;
611         spin_unlock(&inode->i_lock);
612 
613         inode_init_owner(inode, dentry->d_parent->d_inode, mode);
614         attr.mode = inode->i_mode;
615 
616         err = ovl_create_or_link(dentry, inode, &attr, false);
617         /* Did we end up using the preallocated inode? */
618         if (inode != d_inode(dentry))
619                 iput(inode);
620 
621 out_drop_write:
622         ovl_drop_write(dentry);
623 out:
624         return err;
625 }
626 
627 static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
628                       bool excl)
629 {
630         return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
631 }
632 
633 static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
634 {
635         return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
636 }
637 
638 static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
639                      dev_t rdev)
640 {
641         /* Don't allow creation of "whiteout" on overlay */
642         if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
643                 return -EPERM;
644 
645         return ovl_create_object(dentry, mode, rdev, NULL);
646 }
647 
648 static int ovl_symlink(struct inode *dir, struct dentry *dentry,
649                        const char *link)
650 {
651         return ovl_create_object(dentry, S_IFLNK, 0, link);
652 }
653 
654 static int ovl_set_link_redirect(struct dentry *dentry)
655 {
656         const struct cred *old_cred;
657         int err;
658 
659         old_cred = ovl_override_creds(dentry->d_sb);
660         err = ovl_set_redirect(dentry, false);
661         revert_creds(old_cred);
662 
663         return err;
664 }
665 
666 static int ovl_link(struct dentry *old, struct inode *newdir,
667                     struct dentry *new)
668 {
669         int err;
670         struct inode *inode;
671 
672         err = ovl_want_write(old);
673         if (err)
674                 goto out;
675 
676         err = ovl_copy_up(old);
677         if (err)
678                 goto out_drop_write;
679 
680         err = ovl_copy_up(new->d_parent);
681         if (err)
682                 goto out_drop_write;
683 
684         if (ovl_is_metacopy_dentry(old)) {
685                 err = ovl_set_link_redirect(old);
686                 if (err)
687                         goto out_drop_write;
688         }
689 
690         err = ovl_nlink_start(old);
691         if (err)
692                 goto out_drop_write;
693 
694         inode = d_inode(old);
695         ihold(inode);
696 
697         err = ovl_create_or_link(new, inode,
698                         &(struct ovl_cattr) {.hardlink = ovl_dentry_upper(old)},
699                         ovl_type_origin(old));
700         if (err)
701                 iput(inode);
702 
703         ovl_nlink_end(old);
704 out_drop_write:
705         ovl_drop_write(old);
706 out:
707         return err;
708 }
709 
710 static bool ovl_matches_upper(struct dentry *dentry, struct dentry *upper)
711 {
712         return d_inode(ovl_dentry_upper(dentry)) == d_inode(upper);
713 }
714 
715 static int ovl_remove_and_whiteout(struct dentry *dentry,
716                                    struct list_head *list)
717 {
718         struct dentry *workdir = ovl_workdir(dentry);
719         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
720         struct dentry *upper;
721         struct dentry *opaquedir = NULL;
722         int err;
723 
724         if (WARN_ON(!workdir))
725                 return -EROFS;
726 
727         if (!list_empty(list)) {
728                 opaquedir = ovl_clear_empty(dentry, list);
729                 err = PTR_ERR(opaquedir);
730                 if (IS_ERR(opaquedir))
731                         goto out;
732         }
733 
734         err = ovl_lock_rename_workdir(workdir, upperdir);
735         if (err)
736                 goto out_dput;
737 
738         upper = lookup_one_len(dentry->d_name.name, upperdir,
739                                dentry->d_name.len);
740         err = PTR_ERR(upper);
741         if (IS_ERR(upper))
742                 goto out_unlock;
743 
744         err = -ESTALE;
745         if ((opaquedir && upper != opaquedir) ||
746             (!opaquedir && ovl_dentry_upper(dentry) &&
747              !ovl_matches_upper(dentry, upper))) {
748                 goto out_dput_upper;
749         }
750 
751         err = ovl_cleanup_and_whiteout(workdir, d_inode(upperdir), upper);
752         if (err)
753                 goto out_d_drop;
754 
755         ovl_dir_modified(dentry->d_parent, true);
756 out_d_drop:
757         d_drop(dentry);
758 out_dput_upper:
759         dput(upper);
760 out_unlock:
761         unlock_rename(workdir, upperdir);
762 out_dput:
763         dput(opaquedir);
764 out:
765         return err;
766 }
767 
768 static int ovl_remove_upper(struct dentry *dentry, bool is_dir,
769                             struct list_head *list)
770 {
771         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
772         struct inode *dir = upperdir->d_inode;
773         struct dentry *upper;
774         struct dentry *opaquedir = NULL;
775         int err;
776 
777         if (!list_empty(list)) {
778                 opaquedir = ovl_clear_empty(dentry, list);
779                 err = PTR_ERR(opaquedir);
780                 if (IS_ERR(opaquedir))
781                         goto out;
782         }
783 
784         inode_lock_nested(dir, I_MUTEX_PARENT);
785         upper = lookup_one_len(dentry->d_name.name, upperdir,
786                                dentry->d_name.len);
787         err = PTR_ERR(upper);
788         if (IS_ERR(upper))
789                 goto out_unlock;
790 
791         err = -ESTALE;
792         if ((opaquedir && upper != opaquedir) ||
793             (!opaquedir && !ovl_matches_upper(dentry, upper)))
794                 goto out_dput_upper;
795 
796         if (is_dir)
797                 err = vfs_rmdir(dir, upper);
798         else
799                 err = vfs_unlink(dir, upper, NULL);
800         ovl_dir_modified(dentry->d_parent, ovl_type_origin(dentry));
801 
802         /*
803          * Keeping this dentry hashed would mean having to release
804          * upperpath/lowerpath, which could only be done if we are the
805          * sole user of this dentry.  Too tricky...  Just unhash for
806          * now.
807          */
808         if (!err)
809                 d_drop(dentry);
810 out_dput_upper:
811         dput(upper);
812 out_unlock:
813         inode_unlock(dir);
814         dput(opaquedir);
815 out:
816         return err;
817 }
818 
819 static bool ovl_pure_upper(struct dentry *dentry)
820 {
821         return !ovl_dentry_lower(dentry) &&
822                !ovl_test_flag(OVL_WHITEOUTS, d_inode(dentry));
823 }
824 
825 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
826 {
827         int err;
828         const struct cred *old_cred;
829         struct dentry *upperdentry;
830         bool lower_positive = ovl_lower_positive(dentry);
831         LIST_HEAD(list);
832 
833         /* No need to clean pure upper removed by vfs_rmdir() */
834         if (is_dir && (lower_positive || !ovl_pure_upper(dentry))) {
835                 err = ovl_check_empty_dir(dentry, &list);
836                 if (err)
837                         goto out;
838         }
839 
840         err = ovl_want_write(dentry);
841         if (err)
842                 goto out;
843 
844         err = ovl_copy_up(dentry->d_parent);
845         if (err)
846                 goto out_drop_write;
847 
848         err = ovl_nlink_start(dentry);
849         if (err)
850                 goto out_drop_write;
851 
852         old_cred = ovl_override_creds(dentry->d_sb);
853         if (!lower_positive)
854                 err = ovl_remove_upper(dentry, is_dir, &list);
855         else
856                 err = ovl_remove_and_whiteout(dentry, &list);
857         revert_creds(old_cred);
858         if (!err) {
859                 if (is_dir)
860                         clear_nlink(dentry->d_inode);
861                 else
862                         drop_nlink(dentry->d_inode);
863         }
864         ovl_nlink_end(dentry);
865 
866         /*
867          * Copy ctime
868          *
869          * Note: we fail to update ctime if there was no copy-up, only a
870          * whiteout
871          */
872         upperdentry = ovl_dentry_upper(dentry);
873         if (upperdentry)
874                 ovl_copyattr(d_inode(upperdentry), d_inode(dentry));
875 
876 out_drop_write:
877         ovl_drop_write(dentry);
878 out:
879         ovl_cache_free(&list);
880         return err;
881 }
882 
883 static int ovl_unlink(struct inode *dir, struct dentry *dentry)
884 {
885         return ovl_do_remove(dentry, false);
886 }
887 
888 static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
889 {
890         return ovl_do_remove(dentry, true);
891 }
892 
893 static bool ovl_type_merge_or_lower(struct dentry *dentry)
894 {
895         enum ovl_path_type type = ovl_path_type(dentry);
896 
897         return OVL_TYPE_MERGE(type) || !OVL_TYPE_UPPER(type);
898 }
899 
900 static bool ovl_can_move(struct dentry *dentry)
901 {
902         return ovl_redirect_dir(dentry->d_sb) ||
903                 !d_is_dir(dentry) || !ovl_type_merge_or_lower(dentry);
904 }
905 
906 static char *ovl_get_redirect(struct dentry *dentry, bool abs_redirect)
907 {
908         char *buf, *ret;
909         struct dentry *d, *tmp;
910         int buflen = ovl_redirect_max + 1;
911 
912         if (!abs_redirect) {
913                 ret = kstrndup(dentry->d_name.name, dentry->d_name.len,
914                                GFP_KERNEL);
915                 goto out;
916         }
917 
918         buf = ret = kmalloc(buflen, GFP_KERNEL);
919         if (!buf)
920                 goto out;
921 
922         buflen--;
923         buf[buflen] = '\0';
924         for (d = dget(dentry); !IS_ROOT(d);) {
925                 const char *name;
926                 int thislen;
927 
928                 spin_lock(&d->d_lock);
929                 name = ovl_dentry_get_redirect(d);
930                 if (name) {
931                         thislen = strlen(name);
932                 } else {
933                         name = d->d_name.name;
934                         thislen = d->d_name.len;
935                 }
936 
937                 /* If path is too long, fall back to userspace move */
938                 if (thislen + (name[0] != '/') > buflen) {
939                         ret = ERR_PTR(-EXDEV);
940                         spin_unlock(&d->d_lock);
941                         goto out_put;
942                 }
943 
944                 buflen -= thislen;
945                 memcpy(&buf[buflen], name, thislen);
946                 tmp = dget_dlock(d->d_parent);
947                 spin_unlock(&d->d_lock);
948 
949                 dput(d);
950                 d = tmp;
951 
952                 /* Absolute redirect: finished */
953                 if (buf[buflen] == '/')
954                         break;
955                 buflen--;
956                 buf[buflen] = '/';
957         }
958         ret = kstrdup(&buf[buflen], GFP_KERNEL);
959 out_put:
960         dput(d);
961         kfree(buf);
962 out:
963         return ret ? ret : ERR_PTR(-ENOMEM);
964 }
965 
966 static bool ovl_need_absolute_redirect(struct dentry *dentry, bool samedir)
967 {
968         struct dentry *lowerdentry;
969 
970         if (!samedir)
971                 return true;
972 
973         if (d_is_dir(dentry))
974                 return false;
975 
976         /*
977          * For non-dir hardlinked files, we need absolute redirects
978          * in general as two upper hardlinks could be in different
979          * dirs. We could put a relative redirect now and convert
980          * it to absolute redirect later. But when nlink > 1 and
981          * indexing is on, that means relative redirect needs to be
982          * converted to absolute during copy up of another lower
983          * hardllink as well.
984          *
985          * So without optimizing too much, just check if lower is
986          * a hard link or not. If lower is hard link, put absolute
987          * redirect.
988          */
989         lowerdentry = ovl_dentry_lower(dentry);
990         return (d_inode(lowerdentry)->i_nlink > 1);
991 }
992 
993 static int ovl_set_redirect(struct dentry *dentry, bool samedir)
994 {
995         int err;
996         const char *redirect = ovl_dentry_get_redirect(dentry);
997         bool absolute_redirect = ovl_need_absolute_redirect(dentry, samedir);
998 
999         if (redirect && (!absolute_redirect || redirect[0] == '/'))
1000                 return 0;
1001 
1002         redirect = ovl_get_redirect(dentry, absolute_redirect);
1003         if (IS_ERR(redirect))
1004                 return PTR_ERR(redirect);
1005 
1006         err = ovl_check_setxattr(dentry, ovl_dentry_upper(dentry),
1007                                  OVL_XATTR_REDIRECT,
1008                                  redirect, strlen(redirect), -EXDEV);
1009         if (!err) {
1010                 spin_lock(&dentry->d_lock);
1011                 ovl_dentry_set_redirect(dentry, redirect);
1012                 spin_unlock(&dentry->d_lock);
1013         } else {
1014                 kfree(redirect);
1015                 pr_warn_ratelimited("overlayfs: failed to set redirect (%i)\n",
1016                                     err);
1017                 /* Fall back to userspace copy-up */
1018                 err = -EXDEV;
1019         }
1020         return err;
1021 }
1022 
1023 static int ovl_rename(struct inode *olddir, struct dentry *old,
1024                       struct inode *newdir, struct dentry *new,
1025                       unsigned int flags)
1026 {
1027         int err;
1028         struct dentry *old_upperdir;
1029         struct dentry *new_upperdir;
1030         struct dentry *olddentry;
1031         struct dentry *newdentry;
1032         struct dentry *trap;
1033         bool old_opaque;
1034         bool new_opaque;
1035         bool cleanup_whiteout = false;
1036         bool update_nlink = false;
1037         bool overwrite = !(flags & RENAME_EXCHANGE);
1038         bool is_dir = d_is_dir(old);
1039         bool new_is_dir = d_is_dir(new);
1040         bool samedir = olddir == newdir;
1041         struct dentry *opaquedir = NULL;
1042         const struct cred *old_cred = NULL;
1043         LIST_HEAD(list);
1044 
1045         err = -EINVAL;
1046         if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
1047                 goto out;
1048 
1049         flags &= ~RENAME_NOREPLACE;
1050 
1051         /* Don't copy up directory trees */
1052         err = -EXDEV;
1053         if (!ovl_can_move(old))
1054                 goto out;
1055         if (!overwrite && !ovl_can_move(new))
1056                 goto out;
1057 
1058         if (overwrite && new_is_dir && !ovl_pure_upper(new)) {
1059                 err = ovl_check_empty_dir(new, &list);
1060                 if (err)
1061                         goto out;
1062         }
1063 
1064         if (overwrite) {
1065                 if (ovl_lower_positive(old)) {
1066                         if (!ovl_dentry_is_whiteout(new)) {
1067                                 /* Whiteout source */
1068                                 flags |= RENAME_WHITEOUT;
1069                         } else {
1070                                 /* Switch whiteouts */
1071                                 flags |= RENAME_EXCHANGE;
1072                         }
1073                 } else if (is_dir && ovl_dentry_is_whiteout(new)) {
1074                         flags |= RENAME_EXCHANGE;
1075                         cleanup_whiteout = true;
1076                 }
1077         }
1078 
1079         err = ovl_want_write(old);
1080         if (err)
1081                 goto out;
1082 
1083         err = ovl_copy_up(old);
1084         if (err)
1085                 goto out_drop_write;
1086 
1087         err = ovl_copy_up(new->d_parent);
1088         if (err)
1089                 goto out_drop_write;
1090         if (!overwrite) {
1091                 err = ovl_copy_up(new);
1092                 if (err)
1093                         goto out_drop_write;
1094         } else if (d_inode(new)) {
1095                 err = ovl_nlink_start(new);
1096                 if (err)
1097                         goto out_drop_write;
1098 
1099                 update_nlink = true;
1100         }
1101 
1102         old_cred = ovl_override_creds(old->d_sb);
1103 
1104         if (!list_empty(&list)) {
1105                 opaquedir = ovl_clear_empty(new, &list);
1106                 err = PTR_ERR(opaquedir);
1107                 if (IS_ERR(opaquedir)) {
1108                         opaquedir = NULL;
1109                         goto out_revert_creds;
1110                 }
1111         }
1112 
1113         old_upperdir = ovl_dentry_upper(old->d_parent);
1114         new_upperdir = ovl_dentry_upper(new->d_parent);
1115 
1116         if (!samedir) {
1117                 /*
1118                  * When moving a merge dir or non-dir with copy up origin into
1119                  * a new parent, we are marking the new parent dir "impure".
1120                  * When ovl_iterate() iterates an "impure" upper dir, it will
1121                  * lookup the origin inodes of the entries to fill d_ino.
1122                  */
1123                 if (ovl_type_origin(old)) {
1124                         err = ovl_set_impure(new->d_parent, new_upperdir);
1125                         if (err)
1126                                 goto out_revert_creds;
1127                 }
1128                 if (!overwrite && ovl_type_origin(new)) {
1129                         err = ovl_set_impure(old->d_parent, old_upperdir);
1130                         if (err)
1131                                 goto out_revert_creds;
1132                 }
1133         }
1134 
1135         trap = lock_rename(new_upperdir, old_upperdir);
1136 
1137         olddentry = lookup_one_len(old->d_name.name, old_upperdir,
1138                                    old->d_name.len);
1139         err = PTR_ERR(olddentry);
1140         if (IS_ERR(olddentry))
1141                 goto out_unlock;
1142 
1143         err = -ESTALE;
1144         if (!ovl_matches_upper(old, olddentry))
1145                 goto out_dput_old;
1146 
1147         newdentry = lookup_one_len(new->d_name.name, new_upperdir,
1148                                    new->d_name.len);
1149         err = PTR_ERR(newdentry);
1150         if (IS_ERR(newdentry))
1151                 goto out_dput_old;
1152 
1153         old_opaque = ovl_dentry_is_opaque(old);
1154         new_opaque = ovl_dentry_is_opaque(new);
1155 
1156         err = -ESTALE;
1157         if (d_inode(new) && ovl_dentry_upper(new)) {
1158                 if (opaquedir) {
1159                         if (newdentry != opaquedir)
1160                                 goto out_dput;
1161                 } else {
1162                         if (!ovl_matches_upper(new, newdentry))
1163                                 goto out_dput;
1164                 }
1165         } else {
1166                 if (!d_is_negative(newdentry) &&
1167                     (!new_opaque || !ovl_is_whiteout(newdentry)))
1168                         goto out_dput;
1169         }
1170 
1171         if (olddentry == trap)
1172                 goto out_dput;
1173         if (newdentry == trap)
1174                 goto out_dput;
1175 
1176         if (WARN_ON(olddentry->d_inode == newdentry->d_inode))
1177                 goto out_dput;
1178 
1179         err = 0;
1180         if (ovl_type_merge_or_lower(old))
1181                 err = ovl_set_redirect(old, samedir);
1182         else if (is_dir && !old_opaque && ovl_type_merge(new->d_parent))
1183                 err = ovl_set_opaque_xerr(old, olddentry, -EXDEV);
1184         if (err)
1185                 goto out_dput;
1186 
1187         if (!overwrite && ovl_type_merge_or_lower(new))
1188                 err = ovl_set_redirect(new, samedir);
1189         else if (!overwrite && new_is_dir && !new_opaque &&
1190                  ovl_type_merge(old->d_parent))
1191                 err = ovl_set_opaque_xerr(new, newdentry, -EXDEV);
1192         if (err)
1193                 goto out_dput;
1194 
1195         err = ovl_do_rename(old_upperdir->d_inode, olddentry,
1196                             new_upperdir->d_inode, newdentry, flags);
1197         if (err)
1198                 goto out_dput;
1199 
1200         if (cleanup_whiteout)
1201                 ovl_cleanup(old_upperdir->d_inode, newdentry);
1202 
1203         if (overwrite && d_inode(new)) {
1204                 if (new_is_dir)
1205                         clear_nlink(d_inode(new));
1206                 else
1207                         drop_nlink(d_inode(new));
1208         }
1209 
1210         ovl_dir_modified(old->d_parent, ovl_type_origin(old) ||
1211                          (!overwrite && ovl_type_origin(new)));
1212         ovl_dir_modified(new->d_parent, ovl_type_origin(old) ||
1213                          (d_inode(new) && ovl_type_origin(new)));
1214 
1215         /* copy ctime: */
1216         ovl_copyattr(d_inode(olddentry), d_inode(old));
1217         if (d_inode(new) && ovl_dentry_upper(new))
1218                 ovl_copyattr(d_inode(newdentry), d_inode(new));
1219 
1220 out_dput:
1221         dput(newdentry);
1222 out_dput_old:
1223         dput(olddentry);
1224 out_unlock:
1225         unlock_rename(new_upperdir, old_upperdir);
1226 out_revert_creds:
1227         revert_creds(old_cred);
1228         if (update_nlink)
1229                 ovl_nlink_end(new);
1230 out_drop_write:
1231         ovl_drop_write(old);
1232 out:
1233         dput(opaquedir);
1234         ovl_cache_free(&list);
1235         return err;
1236 }
1237 
1238 const struct inode_operations ovl_dir_inode_operations = {
1239         .lookup         = ovl_lookup,
1240         .mkdir          = ovl_mkdir,
1241         .symlink        = ovl_symlink,
1242         .unlink         = ovl_unlink,
1243         .rmdir          = ovl_rmdir,
1244         .rename         = ovl_rename,
1245         .link           = ovl_link,
1246         .setattr        = ovl_setattr,
1247         .create         = ovl_create,
1248         .mknod          = ovl_mknod,
1249         .permission     = ovl_permission,
1250         .getattr        = ovl_getattr,
1251         .listxattr      = ovl_listxattr,
1252         .get_acl        = ovl_get_acl,
1253         .update_time    = ovl_update_time,
1254 };
1255 

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