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5
6
7#include <linux/fs.h>
8#include <linux/mount.h>
9#include <linux/slab.h>
10#include <linux/cred.h>
11#include <linux/xattr.h>
12#include <linux/exportfs.h>
13#include <linux/uuid.h>
14#include <linux/namei.h>
15#include <linux/ratelimit.h>
16#include "overlayfs.h"
17
18int ovl_want_write(struct dentry *dentry)
19{
20 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
21 return mnt_want_write(ovl_upper_mnt(ofs));
22}
23
24void ovl_drop_write(struct dentry *dentry)
25{
26 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
27 mnt_drop_write(ovl_upper_mnt(ofs));
28}
29
30struct dentry *ovl_workdir(struct dentry *dentry)
31{
32 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
33 return ofs->workdir;
34}
35
36const struct cred *ovl_override_creds(struct super_block *sb)
37{
38 struct ovl_fs *ofs = sb->s_fs_info;
39
40 return override_creds(ofs->creator_cred);
41}
42
43
44
45
46
47
48
49
50
51int ovl_can_decode_fh(struct super_block *sb)
52{
53 if (!sb->s_export_op || !sb->s_export_op->fh_to_dentry)
54 return 0;
55
56 return sb->s_export_op->encode_fh ? -1 : FILEID_INO32_GEN;
57}
58
59struct dentry *ovl_indexdir(struct super_block *sb)
60{
61 struct ovl_fs *ofs = sb->s_fs_info;
62
63 return ofs->indexdir;
64}
65
66
67bool ovl_index_all(struct super_block *sb)
68{
69 struct ovl_fs *ofs = sb->s_fs_info;
70
71 return ofs->config.nfs_export && ofs->config.index;
72}
73
74
75bool ovl_verify_lower(struct super_block *sb)
76{
77 struct ovl_fs *ofs = sb->s_fs_info;
78
79 return ofs->config.nfs_export && ofs->config.index;
80}
81
82struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
83{
84 size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
85 struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
86
87 if (oe)
88 oe->numlower = numlower;
89
90 return oe;
91}
92
93bool ovl_dentry_remote(struct dentry *dentry)
94{
95 return dentry->d_flags &
96 (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
97}
98
99void ovl_dentry_update_reval(struct dentry *dentry, struct dentry *upperdentry,
100 unsigned int mask)
101{
102 struct ovl_entry *oe = OVL_E(dentry);
103 unsigned int i, flags = 0;
104
105 if (upperdentry)
106 flags |= upperdentry->d_flags;
107 for (i = 0; i < oe->numlower; i++)
108 flags |= oe->lowerstack[i].dentry->d_flags;
109
110 spin_lock(&dentry->d_lock);
111 dentry->d_flags &= ~mask;
112 dentry->d_flags |= flags & mask;
113 spin_unlock(&dentry->d_lock);
114}
115
116bool ovl_dentry_weird(struct dentry *dentry)
117{
118 return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
119 DCACHE_MANAGE_TRANSIT |
120 DCACHE_OP_HASH |
121 DCACHE_OP_COMPARE);
122}
123
124enum ovl_path_type ovl_path_type(struct dentry *dentry)
125{
126 struct ovl_entry *oe = dentry->d_fsdata;
127 enum ovl_path_type type = 0;
128
129 if (ovl_dentry_upper(dentry)) {
130 type = __OVL_PATH_UPPER;
131
132
133
134
135 if (oe->numlower) {
136 if (ovl_test_flag(OVL_CONST_INO, d_inode(dentry)))
137 type |= __OVL_PATH_ORIGIN;
138 if (d_is_dir(dentry) ||
139 !ovl_has_upperdata(d_inode(dentry)))
140 type |= __OVL_PATH_MERGE;
141 }
142 } else {
143 if (oe->numlower > 1)
144 type |= __OVL_PATH_MERGE;
145 }
146 return type;
147}
148
149void ovl_path_upper(struct dentry *dentry, struct path *path)
150{
151 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
152
153 path->mnt = ovl_upper_mnt(ofs);
154 path->dentry = ovl_dentry_upper(dentry);
155}
156
157void ovl_path_lower(struct dentry *dentry, struct path *path)
158{
159 struct ovl_entry *oe = dentry->d_fsdata;
160
161 if (oe->numlower) {
162 path->mnt = oe->lowerstack[0].layer->mnt;
163 path->dentry = oe->lowerstack[0].dentry;
164 } else {
165 *path = (struct path) { };
166 }
167}
168
169void ovl_path_lowerdata(struct dentry *dentry, struct path *path)
170{
171 struct ovl_entry *oe = dentry->d_fsdata;
172
173 if (oe->numlower) {
174 path->mnt = oe->lowerstack[oe->numlower - 1].layer->mnt;
175 path->dentry = oe->lowerstack[oe->numlower - 1].dentry;
176 } else {
177 *path = (struct path) { };
178 }
179}
180
181enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
182{
183 enum ovl_path_type type = ovl_path_type(dentry);
184
185 if (!OVL_TYPE_UPPER(type))
186 ovl_path_lower(dentry, path);
187 else
188 ovl_path_upper(dentry, path);
189
190 return type;
191}
192
193struct dentry *ovl_dentry_upper(struct dentry *dentry)
194{
195 return ovl_upperdentry_dereference(OVL_I(d_inode(dentry)));
196}
197
198struct dentry *ovl_dentry_lower(struct dentry *dentry)
199{
200 struct ovl_entry *oe = dentry->d_fsdata;
201
202 return oe->numlower ? oe->lowerstack[0].dentry : NULL;
203}
204
205const struct ovl_layer *ovl_layer_lower(struct dentry *dentry)
206{
207 struct ovl_entry *oe = dentry->d_fsdata;
208
209 return oe->numlower ? oe->lowerstack[0].layer : NULL;
210}
211
212
213
214
215
216
217
218struct dentry *ovl_dentry_lowerdata(struct dentry *dentry)
219{
220 struct ovl_entry *oe = dentry->d_fsdata;
221
222 return oe->numlower ? oe->lowerstack[oe->numlower - 1].dentry : NULL;
223}
224
225struct dentry *ovl_dentry_real(struct dentry *dentry)
226{
227 return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry);
228}
229
230struct dentry *ovl_i_dentry_upper(struct inode *inode)
231{
232 return ovl_upperdentry_dereference(OVL_I(inode));
233}
234
235struct inode *ovl_inode_upper(struct inode *inode)
236{
237 struct dentry *upperdentry = ovl_i_dentry_upper(inode);
238
239 return upperdentry ? d_inode(upperdentry) : NULL;
240}
241
242struct inode *ovl_inode_lower(struct inode *inode)
243{
244 return OVL_I(inode)->lower;
245}
246
247struct inode *ovl_inode_real(struct inode *inode)
248{
249 return ovl_inode_upper(inode) ?: ovl_inode_lower(inode);
250}
251
252
253struct inode *ovl_inode_lowerdata(struct inode *inode)
254{
255 if (WARN_ON(!S_ISREG(inode->i_mode)))
256 return NULL;
257
258 return OVL_I(inode)->lowerdata ?: ovl_inode_lower(inode);
259}
260
261
262struct inode *ovl_inode_realdata(struct inode *inode)
263{
264 struct inode *upperinode;
265
266 upperinode = ovl_inode_upper(inode);
267 if (upperinode && ovl_has_upperdata(inode))
268 return upperinode;
269
270 return ovl_inode_lowerdata(inode);
271}
272
273struct ovl_dir_cache *ovl_dir_cache(struct inode *inode)
274{
275 return OVL_I(inode)->cache;
276}
277
278void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache)
279{
280 OVL_I(inode)->cache = cache;
281}
282
283void ovl_dentry_set_flag(unsigned long flag, struct dentry *dentry)
284{
285 set_bit(flag, &OVL_E(dentry)->flags);
286}
287
288void ovl_dentry_clear_flag(unsigned long flag, struct dentry *dentry)
289{
290 clear_bit(flag, &OVL_E(dentry)->flags);
291}
292
293bool ovl_dentry_test_flag(unsigned long flag, struct dentry *dentry)
294{
295 return test_bit(flag, &OVL_E(dentry)->flags);
296}
297
298bool ovl_dentry_is_opaque(struct dentry *dentry)
299{
300 return ovl_dentry_test_flag(OVL_E_OPAQUE, dentry);
301}
302
303bool ovl_dentry_is_whiteout(struct dentry *dentry)
304{
305 return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
306}
307
308void ovl_dentry_set_opaque(struct dentry *dentry)
309{
310 ovl_dentry_set_flag(OVL_E_OPAQUE, dentry);
311}
312
313
314
315
316
317
318
319bool ovl_dentry_has_upper_alias(struct dentry *dentry)
320{
321 return ovl_dentry_test_flag(OVL_E_UPPER_ALIAS, dentry);
322}
323
324void ovl_dentry_set_upper_alias(struct dentry *dentry)
325{
326 ovl_dentry_set_flag(OVL_E_UPPER_ALIAS, dentry);
327}
328
329static bool ovl_should_check_upperdata(struct inode *inode)
330{
331 if (!S_ISREG(inode->i_mode))
332 return false;
333
334 if (!ovl_inode_lower(inode))
335 return false;
336
337 return true;
338}
339
340bool ovl_has_upperdata(struct inode *inode)
341{
342 if (!ovl_should_check_upperdata(inode))
343 return true;
344
345 if (!ovl_test_flag(OVL_UPPERDATA, inode))
346 return false;
347
348
349
350
351
352
353 smp_rmb();
354 return true;
355}
356
357void ovl_set_upperdata(struct inode *inode)
358{
359
360
361
362
363
364 smp_wmb();
365 ovl_set_flag(OVL_UPPERDATA, inode);
366}
367
368
369bool ovl_dentry_needs_data_copy_up_locked(struct dentry *dentry, int flags)
370{
371 if (!ovl_open_flags_need_copy_up(flags))
372 return false;
373
374 return !ovl_test_flag(OVL_UPPERDATA, d_inode(dentry));
375}
376
377bool ovl_dentry_needs_data_copy_up(struct dentry *dentry, int flags)
378{
379 if (!ovl_open_flags_need_copy_up(flags))
380 return false;
381
382 return !ovl_has_upperdata(d_inode(dentry));
383}
384
385bool ovl_redirect_dir(struct super_block *sb)
386{
387 struct ovl_fs *ofs = sb->s_fs_info;
388
389 return ofs->config.redirect_dir && !ofs->noxattr;
390}
391
392const char *ovl_dentry_get_redirect(struct dentry *dentry)
393{
394 return OVL_I(d_inode(dentry))->redirect;
395}
396
397void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
398{
399 struct ovl_inode *oi = OVL_I(d_inode(dentry));
400
401 kfree(oi->redirect);
402 oi->redirect = redirect;
403}
404
405void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
406{
407 struct inode *upperinode = d_inode(upperdentry);
408
409 WARN_ON(OVL_I(inode)->__upperdentry);
410
411
412
413
414 smp_wmb();
415 OVL_I(inode)->__upperdentry = upperdentry;
416 if (inode_unhashed(inode)) {
417 inode->i_private = upperinode;
418 __insert_inode_hash(inode, (unsigned long) upperinode);
419 }
420}
421
422static void ovl_dentry_version_inc(struct dentry *dentry, bool impurity)
423{
424 struct inode *inode = d_inode(dentry);
425
426 WARN_ON(!inode_is_locked(inode));
427
428
429
430
431
432
433 if (OVL_TYPE_MERGE(ovl_path_type(dentry)) || impurity)
434 OVL_I(inode)->version++;
435}
436
437void ovl_dir_modified(struct dentry *dentry, bool impurity)
438{
439
440 ovl_copyattr(d_inode(ovl_dentry_upper(dentry)), d_inode(dentry));
441
442 ovl_dentry_version_inc(dentry, impurity);
443}
444
445u64 ovl_dentry_version_get(struct dentry *dentry)
446{
447 struct inode *inode = d_inode(dentry);
448
449 WARN_ON(!inode_is_locked(inode));
450 return OVL_I(inode)->version;
451}
452
453bool ovl_is_whiteout(struct dentry *dentry)
454{
455 struct inode *inode = dentry->d_inode;
456
457 return inode && IS_WHITEOUT(inode);
458}
459
460struct file *ovl_path_open(struct path *path, int flags)
461{
462 struct inode *inode = d_inode(path->dentry);
463 int err, acc_mode;
464
465 if (flags & ~(O_ACCMODE | O_LARGEFILE))
466 BUG();
467
468 switch (flags & O_ACCMODE) {
469 case O_RDONLY:
470 acc_mode = MAY_READ;
471 break;
472 case O_WRONLY:
473 acc_mode = MAY_WRITE;
474 break;
475 default:
476 BUG();
477 }
478
479 err = inode_permission(inode, acc_mode | MAY_OPEN);
480 if (err)
481 return ERR_PTR(err);
482
483
484 if (inode_owner_or_capable(inode))
485 flags |= O_NOATIME;
486
487 return dentry_open(path, flags, current_cred());
488}
489
490
491static bool ovl_already_copied_up_locked(struct dentry *dentry, int flags)
492{
493 bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED;
494
495 if (ovl_dentry_upper(dentry) &&
496 (ovl_dentry_has_upper_alias(dentry) || disconnected) &&
497 !ovl_dentry_needs_data_copy_up_locked(dentry, flags))
498 return true;
499
500 return false;
501}
502
503bool ovl_already_copied_up(struct dentry *dentry, int flags)
504{
505 bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED;
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520 if (ovl_dentry_upper(dentry) &&
521 (ovl_dentry_has_upper_alias(dentry) || disconnected) &&
522 !ovl_dentry_needs_data_copy_up(dentry, flags))
523 return true;
524
525 return false;
526}
527
528int ovl_copy_up_start(struct dentry *dentry, int flags)
529{
530 struct inode *inode = d_inode(dentry);
531 int err;
532
533 err = ovl_inode_lock_interruptible(inode);
534 if (!err && ovl_already_copied_up_locked(dentry, flags)) {
535 err = 1;
536 ovl_inode_unlock(inode);
537 }
538
539 return err;
540}
541
542void ovl_copy_up_end(struct dentry *dentry)
543{
544 ovl_inode_unlock(d_inode(dentry));
545}
546
547bool ovl_check_origin_xattr(struct dentry *dentry)
548{
549 int res;
550
551 res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
552
553
554 if (res >= 0)
555 return true;
556
557 return false;
558}
559
560bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)
561{
562 int res;
563 char val;
564
565 if (!d_is_dir(dentry))
566 return false;
567
568 res = vfs_getxattr(dentry, name, &val, 1);
569 if (res == 1 && val == 'y')
570 return true;
571
572 return false;
573}
574
575int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
576 const char *name, const void *value, size_t size,
577 int xerr)
578{
579 int err;
580 struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
581
582 if (ofs->noxattr)
583 return xerr;
584
585 err = ovl_do_setxattr(upperdentry, name, value, size, 0);
586
587 if (err == -EOPNOTSUPP) {
588 pr_warn("cannot set %s xattr on upper\n", name);
589 ofs->noxattr = true;
590 return xerr;
591 }
592
593 return err;
594}
595
596int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry)
597{
598 int err;
599
600 if (ovl_test_flag(OVL_IMPURE, d_inode(dentry)))
601 return 0;
602
603
604
605
606
607 err = ovl_check_setxattr(dentry, upperdentry, OVL_XATTR_IMPURE,
608 "y", 1, 0);
609 if (!err)
610 ovl_set_flag(OVL_IMPURE, d_inode(dentry));
611
612 return err;
613}
614
615void ovl_set_flag(unsigned long flag, struct inode *inode)
616{
617 set_bit(flag, &OVL_I(inode)->flags);
618}
619
620void ovl_clear_flag(unsigned long flag, struct inode *inode)
621{
622 clear_bit(flag, &OVL_I(inode)->flags);
623}
624
625bool ovl_test_flag(unsigned long flag, struct inode *inode)
626{
627 return test_bit(flag, &OVL_I(inode)->flags);
628}
629
630
631
632
633
634bool ovl_inuse_trylock(struct dentry *dentry)
635{
636 struct inode *inode = d_inode(dentry);
637 bool locked = false;
638
639 spin_lock(&inode->i_lock);
640 if (!(inode->i_state & I_OVL_INUSE)) {
641 inode->i_state |= I_OVL_INUSE;
642 locked = true;
643 }
644 spin_unlock(&inode->i_lock);
645
646 return locked;
647}
648
649void ovl_inuse_unlock(struct dentry *dentry)
650{
651 if (dentry) {
652 struct inode *inode = d_inode(dentry);
653
654 spin_lock(&inode->i_lock);
655 WARN_ON(!(inode->i_state & I_OVL_INUSE));
656 inode->i_state &= ~I_OVL_INUSE;
657 spin_unlock(&inode->i_lock);
658 }
659}
660
661bool ovl_is_inuse(struct dentry *dentry)
662{
663 struct inode *inode = d_inode(dentry);
664 bool inuse;
665
666 spin_lock(&inode->i_lock);
667 inuse = (inode->i_state & I_OVL_INUSE);
668 spin_unlock(&inode->i_lock);
669
670 return inuse;
671}
672
673
674
675
676bool ovl_need_index(struct dentry *dentry)
677{
678 struct dentry *lower = ovl_dentry_lower(dentry);
679
680 if (!lower || !ovl_indexdir(dentry->d_sb))
681 return false;
682
683
684 if (ovl_index_all(dentry->d_sb))
685 return true;
686
687
688 if (!d_is_dir(lower) && d_inode(lower)->i_nlink > 1)
689 return true;
690
691 return false;
692}
693
694
695static void ovl_cleanup_index(struct dentry *dentry)
696{
697 struct dentry *indexdir = ovl_indexdir(dentry->d_sb);
698 struct inode *dir = indexdir->d_inode;
699 struct dentry *lowerdentry = ovl_dentry_lower(dentry);
700 struct dentry *upperdentry = ovl_dentry_upper(dentry);
701 struct dentry *index = NULL;
702 struct inode *inode;
703 struct qstr name = { };
704 int err;
705
706 err = ovl_get_index_name(lowerdentry, &name);
707 if (err)
708 goto fail;
709
710 inode = d_inode(upperdentry);
711 if (!S_ISDIR(inode->i_mode) && inode->i_nlink != 1) {
712 pr_warn_ratelimited("cleanup linked index (%pd2, ino=%lu, nlink=%u)\n",
713 upperdentry, inode->i_ino, inode->i_nlink);
714
715
716
717
718
719
720
721
722
723 set_nlink(d_inode(dentry), inode->i_nlink - 1);
724 ovl_set_nlink_upper(dentry);
725 goto out;
726 }
727
728 inode_lock_nested(dir, I_MUTEX_PARENT);
729 index = lookup_one_len(name.name, indexdir, name.len);
730 err = PTR_ERR(index);
731 if (IS_ERR(index)) {
732 index = NULL;
733 } else if (ovl_index_all(dentry->d_sb)) {
734
735 err = ovl_cleanup_and_whiteout(OVL_FS(dentry->d_sb),
736 dir, index);
737 } else {
738
739 err = ovl_cleanup(dir, index);
740 }
741
742 inode_unlock(dir);
743 if (err)
744 goto fail;
745
746out:
747 kfree(name.name);
748 dput(index);
749 return;
750
751fail:
752 pr_err("cleanup index of '%pd2' failed (%i)\n", dentry, err);
753 goto out;
754}
755
756
757
758
759
760int ovl_nlink_start(struct dentry *dentry)
761{
762 struct inode *inode = d_inode(dentry);
763 const struct cred *old_cred;
764 int err;
765
766 if (WARN_ON(!inode))
767 return -ENOENT;
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783 if (ovl_need_index(dentry) && !ovl_dentry_has_upper_alias(dentry)) {
784 err = ovl_copy_up(dentry);
785 if (err)
786 return err;
787 }
788
789 err = ovl_inode_lock_interruptible(inode);
790 if (err)
791 return err;
792
793 if (d_is_dir(dentry) || !ovl_test_flag(OVL_INDEX, inode))
794 goto out;
795
796 old_cred = ovl_override_creds(dentry->d_sb);
797
798
799
800
801
802
803 err = ovl_set_nlink_upper(dentry);
804 revert_creds(old_cred);
805
806out:
807 if (err)
808 ovl_inode_unlock(inode);
809
810 return err;
811}
812
813void ovl_nlink_end(struct dentry *dentry)
814{
815 struct inode *inode = d_inode(dentry);
816
817 if (ovl_test_flag(OVL_INDEX, inode) && inode->i_nlink == 0) {
818 const struct cred *old_cred;
819
820 old_cred = ovl_override_creds(dentry->d_sb);
821 ovl_cleanup_index(dentry);
822 revert_creds(old_cred);
823 }
824
825 ovl_inode_unlock(inode);
826}
827
828int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir)
829{
830
831 if (workdir == upperdir)
832 goto err;
833
834
835 if (lock_rename(workdir, upperdir) != NULL)
836 goto err_unlock;
837
838 return 0;
839
840err_unlock:
841 unlock_rename(workdir, upperdir);
842err:
843 pr_err("failed to lock workdir+upperdir\n");
844 return -EIO;
845}
846
847
848int ovl_check_metacopy_xattr(struct dentry *dentry)
849{
850 int res;
851
852
853 if (!S_ISREG(d_inode(dentry)->i_mode))
854 return 0;
855
856 res = vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0);
857 if (res < 0) {
858 if (res == -ENODATA || res == -EOPNOTSUPP)
859 return 0;
860 goto out;
861 }
862
863 return 1;
864out:
865 pr_warn_ratelimited("failed to get metacopy (%i)\n", res);
866 return res;
867}
868
869bool ovl_is_metacopy_dentry(struct dentry *dentry)
870{
871 struct ovl_entry *oe = dentry->d_fsdata;
872
873 if (!d_is_reg(dentry))
874 return false;
875
876 if (ovl_dentry_upper(dentry)) {
877 if (!ovl_has_upperdata(d_inode(dentry)))
878 return true;
879 return false;
880 }
881
882 return (oe->numlower > 1);
883}
884
885ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value,
886 size_t padding)
887{
888 ssize_t res;
889 char *buf = NULL;
890
891 res = vfs_getxattr(dentry, name, NULL, 0);
892 if (res < 0) {
893 if (res == -ENODATA || res == -EOPNOTSUPP)
894 return -ENODATA;
895 goto fail;
896 }
897
898 if (res != 0) {
899 buf = kzalloc(res + padding, GFP_KERNEL);
900 if (!buf)
901 return -ENOMEM;
902
903 res = vfs_getxattr(dentry, name, buf, res);
904 if (res < 0)
905 goto fail;
906 }
907 *value = buf;
908
909 return res;
910
911fail:
912 pr_warn_ratelimited("failed to get xattr %s: err=%zi)\n",
913 name, res);
914 kfree(buf);
915 return res;
916}
917
918char *ovl_get_redirect_xattr(struct dentry *dentry, int padding)
919{
920 int res;
921 char *s, *next, *buf = NULL;
922
923 res = ovl_getxattr(dentry, OVL_XATTR_REDIRECT, &buf, padding + 1);
924 if (res == -ENODATA)
925 return NULL;
926 if (res < 0)
927 return ERR_PTR(res);
928 if (res == 0)
929 goto invalid;
930
931 if (buf[0] == '/') {
932 for (s = buf; *s++ == '/'; s = next) {
933 next = strchrnul(s, '/');
934 if (s == next)
935 goto invalid;
936 }
937 } else {
938 if (strchr(buf, '/') != NULL)
939 goto invalid;
940 }
941
942 return buf;
943invalid:
944 pr_warn_ratelimited("invalid redirect (%s)\n", buf);
945 res = -EINVAL;
946 kfree(buf);
947 return ERR_PTR(res);
948}
949