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

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