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Linux/fs/posix_acl.c

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  1 /*
  2  * Copyright (C) 2002,2003 by Andreas Gruenbacher <a.gruenbacher@computer.org>
  3  *
  4  * Fixes from William Schumacher incorporated on 15 March 2001.
  5  *    (Reported by Charles Bertsch, <CBertsch@microtest.com>).
  6  */
  7 
  8 /*
  9  *  This file contains generic functions for manipulating
 10  *  POSIX 1003.1e draft standard 17 ACLs.
 11  */
 12 
 13 #include <linux/kernel.h>
 14 #include <linux/slab.h>
 15 #include <linux/atomic.h>
 16 #include <linux/fs.h>
 17 #include <linux/sched.h>
 18 #include <linux/posix_acl.h>
 19 #include <linux/posix_acl_xattr.h>
 20 #include <linux/xattr.h>
 21 #include <linux/export.h>
 22 #include <linux/user_namespace.h>
 23 
 24 static struct posix_acl **acl_by_type(struct inode *inode, int type)
 25 {
 26         switch (type) {
 27         case ACL_TYPE_ACCESS:
 28                 return &inode->i_acl;
 29         case ACL_TYPE_DEFAULT:
 30                 return &inode->i_default_acl;
 31         default:
 32                 BUG();
 33         }
 34 }
 35 
 36 struct posix_acl *get_cached_acl(struct inode *inode, int type)
 37 {
 38         struct posix_acl **p = acl_by_type(inode, type);
 39         struct posix_acl *acl;
 40 
 41         for (;;) {
 42                 rcu_read_lock();
 43                 acl = rcu_dereference(*p);
 44                 if (!acl || is_uncached_acl(acl) ||
 45                     atomic_inc_not_zero(&acl->a_refcount))
 46                         break;
 47                 rcu_read_unlock();
 48                 cpu_relax();
 49         }
 50         rcu_read_unlock();
 51         return acl;
 52 }
 53 EXPORT_SYMBOL(get_cached_acl);
 54 
 55 struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
 56 {
 57         return rcu_dereference(*acl_by_type(inode, type));
 58 }
 59 EXPORT_SYMBOL(get_cached_acl_rcu);
 60 
 61 void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
 62 {
 63         struct posix_acl **p = acl_by_type(inode, type);
 64         struct posix_acl *old;
 65 
 66         old = xchg(p, posix_acl_dup(acl));
 67         if (!is_uncached_acl(old))
 68                 posix_acl_release(old);
 69 }
 70 EXPORT_SYMBOL(set_cached_acl);
 71 
 72 static void __forget_cached_acl(struct posix_acl **p)
 73 {
 74         struct posix_acl *old;
 75 
 76         old = xchg(p, ACL_NOT_CACHED);
 77         if (!is_uncached_acl(old))
 78                 posix_acl_release(old);
 79 }
 80 
 81 void forget_cached_acl(struct inode *inode, int type)
 82 {
 83         __forget_cached_acl(acl_by_type(inode, type));
 84 }
 85 EXPORT_SYMBOL(forget_cached_acl);
 86 
 87 void forget_all_cached_acls(struct inode *inode)
 88 {
 89         __forget_cached_acl(&inode->i_acl);
 90         __forget_cached_acl(&inode->i_default_acl);
 91 }
 92 EXPORT_SYMBOL(forget_all_cached_acls);
 93 
 94 struct posix_acl *get_acl(struct inode *inode, int type)
 95 {
 96         void *sentinel;
 97         struct posix_acl **p;
 98         struct posix_acl *acl;
 99 
100         /*
101          * The sentinel is used to detect when another operation like
102          * set_cached_acl() or forget_cached_acl() races with get_acl().
103          * It is guaranteed that is_uncached_acl(sentinel) is true.
104          */
105 
106         acl = get_cached_acl(inode, type);
107         if (!is_uncached_acl(acl))
108                 return acl;
109 
110         if (!IS_POSIXACL(inode))
111                 return NULL;
112 
113         sentinel = uncached_acl_sentinel(current);
114         p = acl_by_type(inode, type);
115 
116         /*
117          * If the ACL isn't being read yet, set our sentinel.  Otherwise, the
118          * current value of the ACL will not be ACL_NOT_CACHED and so our own
119          * sentinel will not be set; another task will update the cache.  We
120          * could wait for that other task to complete its job, but it's easier
121          * to just call ->get_acl to fetch the ACL ourself.  (This is going to
122          * be an unlikely race.)
123          */
124         if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED)
125                 /* fall through */ ;
126 
127         /*
128          * Normally, the ACL returned by ->get_acl will be cached.
129          * A filesystem can prevent that by calling
130          * forget_cached_acl(inode, type) in ->get_acl.
131          *
132          * If the filesystem doesn't have a get_acl() function at all, we'll
133          * just create the negative cache entry.
134          */
135         if (!inode->i_op->get_acl) {
136                 set_cached_acl(inode, type, NULL);
137                 return NULL;
138         }
139         acl = inode->i_op->get_acl(inode, type);
140 
141         if (IS_ERR(acl)) {
142                 /*
143                  * Remove our sentinel so that we don't block future attempts
144                  * to cache the ACL.
145                  */
146                 cmpxchg(p, sentinel, ACL_NOT_CACHED);
147                 return acl;
148         }
149 
150         /*
151          * Cache the result, but only if our sentinel is still in place.
152          */
153         posix_acl_dup(acl);
154         if (unlikely(cmpxchg(p, sentinel, acl) != sentinel))
155                 posix_acl_release(acl);
156         return acl;
157 }
158 EXPORT_SYMBOL(get_acl);
159 
160 /*
161  * Init a fresh posix_acl
162  */
163 void
164 posix_acl_init(struct posix_acl *acl, int count)
165 {
166         atomic_set(&acl->a_refcount, 1);
167         acl->a_count = count;
168 }
169 EXPORT_SYMBOL(posix_acl_init);
170 
171 /*
172  * Allocate a new ACL with the specified number of entries.
173  */
174 struct posix_acl *
175 posix_acl_alloc(int count, gfp_t flags)
176 {
177         const size_t size = sizeof(struct posix_acl) +
178                             count * sizeof(struct posix_acl_entry);
179         struct posix_acl *acl = kmalloc(size, flags);
180         if (acl)
181                 posix_acl_init(acl, count);
182         return acl;
183 }
184 EXPORT_SYMBOL(posix_acl_alloc);
185 
186 /*
187  * Clone an ACL.
188  */
189 static struct posix_acl *
190 posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
191 {
192         struct posix_acl *clone = NULL;
193 
194         if (acl) {
195                 int size = sizeof(struct posix_acl) + acl->a_count *
196                            sizeof(struct posix_acl_entry);
197                 clone = kmemdup(acl, size, flags);
198                 if (clone)
199                         atomic_set(&clone->a_refcount, 1);
200         }
201         return clone;
202 }
203 
204 /*
205  * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
206  */
207 int
208 posix_acl_valid(struct user_namespace *user_ns, const struct posix_acl *acl)
209 {
210         const struct posix_acl_entry *pa, *pe;
211         int state = ACL_USER_OBJ;
212         int needs_mask = 0;
213 
214         FOREACH_ACL_ENTRY(pa, acl, pe) {
215                 if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
216                         return -EINVAL;
217                 switch (pa->e_tag) {
218                         case ACL_USER_OBJ:
219                                 if (state == ACL_USER_OBJ) {
220                                         state = ACL_USER;
221                                         break;
222                                 }
223                                 return -EINVAL;
224 
225                         case ACL_USER:
226                                 if (state != ACL_USER)
227                                         return -EINVAL;
228                                 if (!kuid_has_mapping(user_ns, pa->e_uid))
229                                         return -EINVAL;
230                                 needs_mask = 1;
231                                 break;
232 
233                         case ACL_GROUP_OBJ:
234                                 if (state == ACL_USER) {
235                                         state = ACL_GROUP;
236                                         break;
237                                 }
238                                 return -EINVAL;
239 
240                         case ACL_GROUP:
241                                 if (state != ACL_GROUP)
242                                         return -EINVAL;
243                                 if (!kgid_has_mapping(user_ns, pa->e_gid))
244                                         return -EINVAL;
245                                 needs_mask = 1;
246                                 break;
247 
248                         case ACL_MASK:
249                                 if (state != ACL_GROUP)
250                                         return -EINVAL;
251                                 state = ACL_OTHER;
252                                 break;
253 
254                         case ACL_OTHER:
255                                 if (state == ACL_OTHER ||
256                                     (state == ACL_GROUP && !needs_mask)) {
257                                         state = 0;
258                                         break;
259                                 }
260                                 return -EINVAL;
261 
262                         default:
263                                 return -EINVAL;
264                 }
265         }
266         if (state == 0)
267                 return 0;
268         return -EINVAL;
269 }
270 EXPORT_SYMBOL(posix_acl_valid);
271 
272 /*
273  * Returns 0 if the acl can be exactly represented in the traditional
274  * file mode permission bits, or else 1. Returns -E... on error.
275  */
276 int
277 posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
278 {
279         const struct posix_acl_entry *pa, *pe;
280         umode_t mode = 0;
281         int not_equiv = 0;
282 
283         /*
284          * A null ACL can always be presented as mode bits.
285          */
286         if (!acl)
287                 return 0;
288 
289         FOREACH_ACL_ENTRY(pa, acl, pe) {
290                 switch (pa->e_tag) {
291                         case ACL_USER_OBJ:
292                                 mode |= (pa->e_perm & S_IRWXO) << 6;
293                                 break;
294                         case ACL_GROUP_OBJ:
295                                 mode |= (pa->e_perm & S_IRWXO) << 3;
296                                 break;
297                         case ACL_OTHER:
298                                 mode |= pa->e_perm & S_IRWXO;
299                                 break;
300                         case ACL_MASK:
301                                 mode = (mode & ~S_IRWXG) |
302                                        ((pa->e_perm & S_IRWXO) << 3);
303                                 not_equiv = 1;
304                                 break;
305                         case ACL_USER:
306                         case ACL_GROUP:
307                                 not_equiv = 1;
308                                 break;
309                         default:
310                                 return -EINVAL;
311                 }
312         }
313         if (mode_p)
314                 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
315         return not_equiv;
316 }
317 EXPORT_SYMBOL(posix_acl_equiv_mode);
318 
319 /*
320  * Create an ACL representing the file mode permission bits of an inode.
321  */
322 struct posix_acl *
323 posix_acl_from_mode(umode_t mode, gfp_t flags)
324 {
325         struct posix_acl *acl = posix_acl_alloc(3, flags);
326         if (!acl)
327                 return ERR_PTR(-ENOMEM);
328 
329         acl->a_entries[0].e_tag  = ACL_USER_OBJ;
330         acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
331 
332         acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;
333         acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
334 
335         acl->a_entries[2].e_tag  = ACL_OTHER;
336         acl->a_entries[2].e_perm = (mode & S_IRWXO);
337         return acl;
338 }
339 EXPORT_SYMBOL(posix_acl_from_mode);
340 
341 /*
342  * Return 0 if current is granted want access to the inode
343  * by the acl. Returns -E... otherwise.
344  */
345 int
346 posix_acl_permission(struct inode *inode, const struct posix_acl *acl, int want)
347 {
348         const struct posix_acl_entry *pa, *pe, *mask_obj;
349         int found = 0;
350 
351         want &= MAY_READ | MAY_WRITE | MAY_EXEC | MAY_NOT_BLOCK;
352 
353         FOREACH_ACL_ENTRY(pa, acl, pe) {
354                 switch(pa->e_tag) {
355                         case ACL_USER_OBJ:
356                                 /* (May have been checked already) */
357                                 if (uid_eq(inode->i_uid, current_fsuid()))
358                                         goto check_perm;
359                                 break;
360                         case ACL_USER:
361                                 if (uid_eq(pa->e_uid, current_fsuid()))
362                                         goto mask;
363                                 break;
364                         case ACL_GROUP_OBJ:
365                                 if (in_group_p(inode->i_gid)) {
366                                         found = 1;
367                                         if ((pa->e_perm & want) == want)
368                                                 goto mask;
369                                 }
370                                 break;
371                         case ACL_GROUP:
372                                 if (in_group_p(pa->e_gid)) {
373                                         found = 1;
374                                         if ((pa->e_perm & want) == want)
375                                                 goto mask;
376                                 }
377                                 break;
378                         case ACL_MASK:
379                                 break;
380                         case ACL_OTHER:
381                                 if (found)
382                                         return -EACCES;
383                                 else
384                                         goto check_perm;
385                         default:
386                                 return -EIO;
387                 }
388         }
389         return -EIO;
390 
391 mask:
392         for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
393                 if (mask_obj->e_tag == ACL_MASK) {
394                         if ((pa->e_perm & mask_obj->e_perm & want) == want)
395                                 return 0;
396                         return -EACCES;
397                 }
398         }
399 
400 check_perm:
401         if ((pa->e_perm & want) == want)
402                 return 0;
403         return -EACCES;
404 }
405 
406 /*
407  * Modify acl when creating a new inode. The caller must ensure the acl is
408  * only referenced once.
409  *
410  * mode_p initially must contain the mode parameter to the open() / creat()
411  * system calls. All permissions that are not granted by the acl are removed.
412  * The permissions in the acl are changed to reflect the mode_p parameter.
413  */
414 static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
415 {
416         struct posix_acl_entry *pa, *pe;
417         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
418         umode_t mode = *mode_p;
419         int not_equiv = 0;
420 
421         /* assert(atomic_read(acl->a_refcount) == 1); */
422 
423         FOREACH_ACL_ENTRY(pa, acl, pe) {
424                 switch(pa->e_tag) {
425                         case ACL_USER_OBJ:
426                                 pa->e_perm &= (mode >> 6) | ~S_IRWXO;
427                                 mode &= (pa->e_perm << 6) | ~S_IRWXU;
428                                 break;
429 
430                         case ACL_USER:
431                         case ACL_GROUP:
432                                 not_equiv = 1;
433                                 break;
434 
435                         case ACL_GROUP_OBJ:
436                                 group_obj = pa;
437                                 break;
438 
439                         case ACL_OTHER:
440                                 pa->e_perm &= mode | ~S_IRWXO;
441                                 mode &= pa->e_perm | ~S_IRWXO;
442                                 break;
443 
444                         case ACL_MASK:
445                                 mask_obj = pa;
446                                 not_equiv = 1;
447                                 break;
448 
449                         default:
450                                 return -EIO;
451                 }
452         }
453 
454         if (mask_obj) {
455                 mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
456                 mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
457         } else {
458                 if (!group_obj)
459                         return -EIO;
460                 group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
461                 mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
462         }
463 
464         *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
465         return not_equiv;
466 }
467 
468 /*
469  * Modify the ACL for the chmod syscall.
470  */
471 static int __posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)
472 {
473         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
474         struct posix_acl_entry *pa, *pe;
475 
476         /* assert(atomic_read(acl->a_refcount) == 1); */
477 
478         FOREACH_ACL_ENTRY(pa, acl, pe) {
479                 switch(pa->e_tag) {
480                         case ACL_USER_OBJ:
481                                 pa->e_perm = (mode & S_IRWXU) >> 6;
482                                 break;
483 
484                         case ACL_USER:
485                         case ACL_GROUP:
486                                 break;
487 
488                         case ACL_GROUP_OBJ:
489                                 group_obj = pa;
490                                 break;
491 
492                         case ACL_MASK:
493                                 mask_obj = pa;
494                                 break;
495 
496                         case ACL_OTHER:
497                                 pa->e_perm = (mode & S_IRWXO);
498                                 break;
499 
500                         default:
501                                 return -EIO;
502                 }
503         }
504 
505         if (mask_obj) {
506                 mask_obj->e_perm = (mode & S_IRWXG) >> 3;
507         } else {
508                 if (!group_obj)
509                         return -EIO;
510                 group_obj->e_perm = (mode & S_IRWXG) >> 3;
511         }
512 
513         return 0;
514 }
515 
516 int
517 __posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)
518 {
519         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
520         int err = -ENOMEM;
521         if (clone) {
522                 err = posix_acl_create_masq(clone, mode_p);
523                 if (err < 0) {
524                         posix_acl_release(clone);
525                         clone = NULL;
526                 }
527         }
528         posix_acl_release(*acl);
529         *acl = clone;
530         return err;
531 }
532 EXPORT_SYMBOL(__posix_acl_create);
533 
534 int
535 __posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
536 {
537         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
538         int err = -ENOMEM;
539         if (clone) {
540                 err = __posix_acl_chmod_masq(clone, mode);
541                 if (err) {
542                         posix_acl_release(clone);
543                         clone = NULL;
544                 }
545         }
546         posix_acl_release(*acl);
547         *acl = clone;
548         return err;
549 }
550 EXPORT_SYMBOL(__posix_acl_chmod);
551 
552 int
553 posix_acl_chmod(struct inode *inode, umode_t mode)
554 {
555         struct posix_acl *acl;
556         int ret = 0;
557 
558         if (!IS_POSIXACL(inode))
559                 return 0;
560         if (!inode->i_op->set_acl)
561                 return -EOPNOTSUPP;
562 
563         acl = get_acl(inode, ACL_TYPE_ACCESS);
564         if (IS_ERR_OR_NULL(acl)) {
565                 if (acl == ERR_PTR(-EOPNOTSUPP))
566                         return 0;
567                 return PTR_ERR(acl);
568         }
569 
570         ret = __posix_acl_chmod(&acl, GFP_KERNEL, mode);
571         if (ret)
572                 return ret;
573         ret = inode->i_op->set_acl(inode, acl, ACL_TYPE_ACCESS);
574         posix_acl_release(acl);
575         return ret;
576 }
577 EXPORT_SYMBOL(posix_acl_chmod);
578 
579 int
580 posix_acl_create(struct inode *dir, umode_t *mode,
581                 struct posix_acl **default_acl, struct posix_acl **acl)
582 {
583         struct posix_acl *p;
584         struct posix_acl *clone;
585         int ret;
586 
587         *acl = NULL;
588         *default_acl = NULL;
589 
590         if (S_ISLNK(*mode) || !IS_POSIXACL(dir))
591                 return 0;
592 
593         p = get_acl(dir, ACL_TYPE_DEFAULT);
594         if (!p || p == ERR_PTR(-EOPNOTSUPP)) {
595                 *mode &= ~current_umask();
596                 return 0;
597         }
598         if (IS_ERR(p))
599                 return PTR_ERR(p);
600 
601         clone = posix_acl_clone(p, GFP_NOFS);
602         if (!clone)
603                 goto no_mem;
604 
605         ret = posix_acl_create_masq(clone, mode);
606         if (ret < 0)
607                 goto no_mem_clone;
608 
609         if (ret == 0)
610                 posix_acl_release(clone);
611         else
612                 *acl = clone;
613 
614         if (!S_ISDIR(*mode))
615                 posix_acl_release(p);
616         else
617                 *default_acl = p;
618 
619         return 0;
620 
621 no_mem_clone:
622         posix_acl_release(clone);
623 no_mem:
624         posix_acl_release(p);
625         return -ENOMEM;
626 }
627 EXPORT_SYMBOL_GPL(posix_acl_create);
628 
629 /**
630  * posix_acl_update_mode  -  update mode in set_acl
631  *
632  * Update the file mode when setting an ACL: compute the new file permission
633  * bits based on the ACL.  In addition, if the ACL is equivalent to the new
634  * file mode, set *acl to NULL to indicate that no ACL should be set.
635  *
636  * As with chmod, clear the setgit bit if the caller is not in the owning group
637  * or capable of CAP_FSETID (see inode_change_ok).
638  *
639  * Called from set_acl inode operations.
640  */
641 int posix_acl_update_mode(struct inode *inode, umode_t *mode_p,
642                           struct posix_acl **acl)
643 {
644         umode_t mode = inode->i_mode;
645         int error;
646 
647         error = posix_acl_equiv_mode(*acl, &mode);
648         if (error < 0)
649                 return error;
650         if (error == 0)
651                 *acl = NULL;
652         if (!in_group_p(inode->i_gid) &&
653             !capable_wrt_inode_uidgid(inode, CAP_FSETID))
654                 mode &= ~S_ISGID;
655         *mode_p = mode;
656         return 0;
657 }
658 EXPORT_SYMBOL(posix_acl_update_mode);
659 
660 /*
661  * Fix up the uids and gids in posix acl extended attributes in place.
662  */
663 static void posix_acl_fix_xattr_userns(
664         struct user_namespace *to, struct user_namespace *from,
665         void *value, size_t size)
666 {
667         posix_acl_xattr_header *header = (posix_acl_xattr_header *)value;
668         posix_acl_xattr_entry *entry = (posix_acl_xattr_entry *)(header+1), *end;
669         int count;
670         kuid_t uid;
671         kgid_t gid;
672 
673         if (!value)
674                 return;
675         if (size < sizeof(posix_acl_xattr_header))
676                 return;
677         if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
678                 return;
679 
680         count = posix_acl_xattr_count(size);
681         if (count < 0)
682                 return;
683         if (count == 0)
684                 return;
685 
686         for (end = entry + count; entry != end; entry++) {
687                 switch(le16_to_cpu(entry->e_tag)) {
688                 case ACL_USER:
689                         uid = make_kuid(from, le32_to_cpu(entry->e_id));
690                         entry->e_id = cpu_to_le32(from_kuid(to, uid));
691                         break;
692                 case ACL_GROUP:
693                         gid = make_kgid(from, le32_to_cpu(entry->e_id));
694                         entry->e_id = cpu_to_le32(from_kgid(to, gid));
695                         break;
696                 default:
697                         break;
698                 }
699         }
700 }
701 
702 void posix_acl_fix_xattr_from_user(void *value, size_t size)
703 {
704         struct user_namespace *user_ns = current_user_ns();
705         if (user_ns == &init_user_ns)
706                 return;
707         posix_acl_fix_xattr_userns(&init_user_ns, user_ns, value, size);
708 }
709 
710 void posix_acl_fix_xattr_to_user(void *value, size_t size)
711 {
712         struct user_namespace *user_ns = current_user_ns();
713         if (user_ns == &init_user_ns)
714                 return;
715         posix_acl_fix_xattr_userns(user_ns, &init_user_ns, value, size);
716 }
717 
718 /*
719  * Convert from extended attribute to in-memory representation.
720  */
721 struct posix_acl *
722 posix_acl_from_xattr(struct user_namespace *user_ns,
723                      const void *value, size_t size)
724 {
725         posix_acl_xattr_header *header = (posix_acl_xattr_header *)value;
726         posix_acl_xattr_entry *entry = (posix_acl_xattr_entry *)(header+1), *end;
727         int count;
728         struct posix_acl *acl;
729         struct posix_acl_entry *acl_e;
730 
731         if (!value)
732                 return NULL;
733         if (size < sizeof(posix_acl_xattr_header))
734                  return ERR_PTR(-EINVAL);
735         if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
736                 return ERR_PTR(-EOPNOTSUPP);
737 
738         count = posix_acl_xattr_count(size);
739         if (count < 0)
740                 return ERR_PTR(-EINVAL);
741         if (count == 0)
742                 return NULL;
743         
744         acl = posix_acl_alloc(count, GFP_NOFS);
745         if (!acl)
746                 return ERR_PTR(-ENOMEM);
747         acl_e = acl->a_entries;
748         
749         for (end = entry + count; entry != end; acl_e++, entry++) {
750                 acl_e->e_tag  = le16_to_cpu(entry->e_tag);
751                 acl_e->e_perm = le16_to_cpu(entry->e_perm);
752 
753                 switch(acl_e->e_tag) {
754                         case ACL_USER_OBJ:
755                         case ACL_GROUP_OBJ:
756                         case ACL_MASK:
757                         case ACL_OTHER:
758                                 break;
759 
760                         case ACL_USER:
761                                 acl_e->e_uid =
762                                         make_kuid(user_ns,
763                                                   le32_to_cpu(entry->e_id));
764                                 if (!uid_valid(acl_e->e_uid))
765                                         goto fail;
766                                 break;
767                         case ACL_GROUP:
768                                 acl_e->e_gid =
769                                         make_kgid(user_ns,
770                                                   le32_to_cpu(entry->e_id));
771                                 if (!gid_valid(acl_e->e_gid))
772                                         goto fail;
773                                 break;
774 
775                         default:
776                                 goto fail;
777                 }
778         }
779         return acl;
780 
781 fail:
782         posix_acl_release(acl);
783         return ERR_PTR(-EINVAL);
784 }
785 EXPORT_SYMBOL (posix_acl_from_xattr);
786 
787 /*
788  * Convert from in-memory to extended attribute representation.
789  */
790 int
791 posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
792                    void *buffer, size_t size)
793 {
794         posix_acl_xattr_header *ext_acl = (posix_acl_xattr_header *)buffer;
795         posix_acl_xattr_entry *ext_entry;
796         int real_size, n;
797 
798         real_size = posix_acl_xattr_size(acl->a_count);
799         if (!buffer)
800                 return real_size;
801         if (real_size > size)
802                 return -ERANGE;
803 
804         ext_entry = ext_acl->a_entries;
805         ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
806 
807         for (n=0; n < acl->a_count; n++, ext_entry++) {
808                 const struct posix_acl_entry *acl_e = &acl->a_entries[n];
809                 ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
810                 ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
811                 switch(acl_e->e_tag) {
812                 case ACL_USER:
813                         ext_entry->e_id =
814                                 cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
815                         break;
816                 case ACL_GROUP:
817                         ext_entry->e_id =
818                                 cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
819                         break;
820                 default:
821                         ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
822                         break;
823                 }
824         }
825         return real_size;
826 }
827 EXPORT_SYMBOL (posix_acl_to_xattr);
828 
829 static int
830 posix_acl_xattr_get(const struct xattr_handler *handler,
831                     struct dentry *unused, struct inode *inode,
832                     const char *name, void *value, size_t size)
833 {
834         struct posix_acl *acl;
835         int error;
836 
837         if (!IS_POSIXACL(inode))
838                 return -EOPNOTSUPP;
839         if (S_ISLNK(inode->i_mode))
840                 return -EOPNOTSUPP;
841 
842         acl = get_acl(inode, handler->flags);
843         if (IS_ERR(acl))
844                 return PTR_ERR(acl);
845         if (acl == NULL)
846                 return -ENODATA;
847 
848         error = posix_acl_to_xattr(&init_user_ns, acl, value, size);
849         posix_acl_release(acl);
850 
851         return error;
852 }
853 
854 int
855 set_posix_acl(struct inode *inode, int type, struct posix_acl *acl)
856 {
857         if (!IS_POSIXACL(inode))
858                 return -EOPNOTSUPP;
859         if (!inode->i_op->set_acl)
860                 return -EOPNOTSUPP;
861 
862         if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
863                 return acl ? -EACCES : 0;
864         if (!inode_owner_or_capable(inode))
865                 return -EPERM;
866 
867         if (acl) {
868                 int ret = posix_acl_valid(inode->i_sb->s_user_ns, acl);
869                 if (ret)
870                         return ret;
871         }
872         return inode->i_op->set_acl(inode, acl, type);
873 }
874 EXPORT_SYMBOL(set_posix_acl);
875 
876 static int
877 posix_acl_xattr_set(const struct xattr_handler *handler,
878                     struct dentry *unused, struct inode *inode,
879                     const char *name, const void *value,
880                     size_t size, int flags)
881 {
882         struct posix_acl *acl = NULL;
883         int ret;
884 
885         if (value) {
886                 acl = posix_acl_from_xattr(&init_user_ns, value, size);
887                 if (IS_ERR(acl))
888                         return PTR_ERR(acl);
889         }
890         ret = set_posix_acl(inode, handler->flags, acl);
891         posix_acl_release(acl);
892         return ret;
893 }
894 
895 static bool
896 posix_acl_xattr_list(struct dentry *dentry)
897 {
898         return IS_POSIXACL(d_backing_inode(dentry));
899 }
900 
901 const struct xattr_handler posix_acl_access_xattr_handler = {
902         .name = XATTR_NAME_POSIX_ACL_ACCESS,
903         .flags = ACL_TYPE_ACCESS,
904         .list = posix_acl_xattr_list,
905         .get = posix_acl_xattr_get,
906         .set = posix_acl_xattr_set,
907 };
908 EXPORT_SYMBOL_GPL(posix_acl_access_xattr_handler);
909 
910 const struct xattr_handler posix_acl_default_xattr_handler = {
911         .name = XATTR_NAME_POSIX_ACL_DEFAULT,
912         .flags = ACL_TYPE_DEFAULT,
913         .list = posix_acl_xattr_list,
914         .get = posix_acl_xattr_get,
915         .set = posix_acl_xattr_set,
916 };
917 EXPORT_SYMBOL_GPL(posix_acl_default_xattr_handler);
918 
919 int simple_set_acl(struct inode *inode, struct posix_acl *acl, int type)
920 {
921         int error;
922 
923         if (type == ACL_TYPE_ACCESS) {
924                 error = posix_acl_equiv_mode(acl, &inode->i_mode);
925                 if (error < 0)
926                         return 0;
927                 if (error == 0)
928                         acl = NULL;
929         }
930 
931         inode->i_ctime = CURRENT_TIME;
932         set_cached_acl(inode, type, acl);
933         return 0;
934 }
935 
936 int simple_acl_create(struct inode *dir, struct inode *inode)
937 {
938         struct posix_acl *default_acl, *acl;
939         int error;
940 
941         error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
942         if (error)
943                 return error;
944 
945         set_cached_acl(inode, ACL_TYPE_DEFAULT, default_acl);
946         set_cached_acl(inode, ACL_TYPE_ACCESS, acl);
947 
948         if (default_acl)
949                 posix_acl_release(default_acl);
950         if (acl)
951                 posix_acl_release(acl);
952         return 0;
953 }
954 

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