xref: /openbmc/linux/fs/posix_acl.c (revision 4f205687)
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(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 (!uid_valid(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 (!gid_valid(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  * Fix up the uids and gids in posix acl extended attributes in place.
631  */
632 static void posix_acl_fix_xattr_userns(
633 	struct user_namespace *to, struct user_namespace *from,
634 	void *value, size_t size)
635 {
636 	posix_acl_xattr_header *header = (posix_acl_xattr_header *)value;
637 	posix_acl_xattr_entry *entry = (posix_acl_xattr_entry *)(header+1), *end;
638 	int count;
639 	kuid_t uid;
640 	kgid_t gid;
641 
642 	if (!value)
643 		return;
644 	if (size < sizeof(posix_acl_xattr_header))
645 		return;
646 	if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
647 		return;
648 
649 	count = posix_acl_xattr_count(size);
650 	if (count < 0)
651 		return;
652 	if (count == 0)
653 		return;
654 
655 	for (end = entry + count; entry != end; entry++) {
656 		switch(le16_to_cpu(entry->e_tag)) {
657 		case ACL_USER:
658 			uid = make_kuid(from, le32_to_cpu(entry->e_id));
659 			entry->e_id = cpu_to_le32(from_kuid(to, uid));
660 			break;
661 		case ACL_GROUP:
662 			gid = make_kgid(from, le32_to_cpu(entry->e_id));
663 			entry->e_id = cpu_to_le32(from_kgid(to, gid));
664 			break;
665 		default:
666 			break;
667 		}
668 	}
669 }
670 
671 void posix_acl_fix_xattr_from_user(void *value, size_t size)
672 {
673 	struct user_namespace *user_ns = current_user_ns();
674 	if (user_ns == &init_user_ns)
675 		return;
676 	posix_acl_fix_xattr_userns(&init_user_ns, user_ns, value, size);
677 }
678 
679 void posix_acl_fix_xattr_to_user(void *value, size_t size)
680 {
681 	struct user_namespace *user_ns = current_user_ns();
682 	if (user_ns == &init_user_ns)
683 		return;
684 	posix_acl_fix_xattr_userns(user_ns, &init_user_ns, value, size);
685 }
686 
687 /*
688  * Convert from extended attribute to in-memory representation.
689  */
690 struct posix_acl *
691 posix_acl_from_xattr(struct user_namespace *user_ns,
692 		     const void *value, size_t size)
693 {
694 	posix_acl_xattr_header *header = (posix_acl_xattr_header *)value;
695 	posix_acl_xattr_entry *entry = (posix_acl_xattr_entry *)(header+1), *end;
696 	int count;
697 	struct posix_acl *acl;
698 	struct posix_acl_entry *acl_e;
699 
700 	if (!value)
701 		return NULL;
702 	if (size < sizeof(posix_acl_xattr_header))
703 		 return ERR_PTR(-EINVAL);
704 	if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
705 		return ERR_PTR(-EOPNOTSUPP);
706 
707 	count = posix_acl_xattr_count(size);
708 	if (count < 0)
709 		return ERR_PTR(-EINVAL);
710 	if (count == 0)
711 		return NULL;
712 
713 	acl = posix_acl_alloc(count, GFP_NOFS);
714 	if (!acl)
715 		return ERR_PTR(-ENOMEM);
716 	acl_e = acl->a_entries;
717 
718 	for (end = entry + count; entry != end; acl_e++, entry++) {
719 		acl_e->e_tag  = le16_to_cpu(entry->e_tag);
720 		acl_e->e_perm = le16_to_cpu(entry->e_perm);
721 
722 		switch(acl_e->e_tag) {
723 			case ACL_USER_OBJ:
724 			case ACL_GROUP_OBJ:
725 			case ACL_MASK:
726 			case ACL_OTHER:
727 				break;
728 
729 			case ACL_USER:
730 				acl_e->e_uid =
731 					make_kuid(user_ns,
732 						  le32_to_cpu(entry->e_id));
733 				if (!uid_valid(acl_e->e_uid))
734 					goto fail;
735 				break;
736 			case ACL_GROUP:
737 				acl_e->e_gid =
738 					make_kgid(user_ns,
739 						  le32_to_cpu(entry->e_id));
740 				if (!gid_valid(acl_e->e_gid))
741 					goto fail;
742 				break;
743 
744 			default:
745 				goto fail;
746 		}
747 	}
748 	return acl;
749 
750 fail:
751 	posix_acl_release(acl);
752 	return ERR_PTR(-EINVAL);
753 }
754 EXPORT_SYMBOL (posix_acl_from_xattr);
755 
756 /*
757  * Convert from in-memory to extended attribute representation.
758  */
759 int
760 posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
761 		   void *buffer, size_t size)
762 {
763 	posix_acl_xattr_header *ext_acl = (posix_acl_xattr_header *)buffer;
764 	posix_acl_xattr_entry *ext_entry;
765 	int real_size, n;
766 
767 	real_size = posix_acl_xattr_size(acl->a_count);
768 	if (!buffer)
769 		return real_size;
770 	if (real_size > size)
771 		return -ERANGE;
772 
773 	ext_entry = ext_acl->a_entries;
774 	ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
775 
776 	for (n=0; n < acl->a_count; n++, ext_entry++) {
777 		const struct posix_acl_entry *acl_e = &acl->a_entries[n];
778 		ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
779 		ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
780 		switch(acl_e->e_tag) {
781 		case ACL_USER:
782 			ext_entry->e_id =
783 				cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
784 			break;
785 		case ACL_GROUP:
786 			ext_entry->e_id =
787 				cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
788 			break;
789 		default:
790 			ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
791 			break;
792 		}
793 	}
794 	return real_size;
795 }
796 EXPORT_SYMBOL (posix_acl_to_xattr);
797 
798 static int
799 posix_acl_xattr_get(const struct xattr_handler *handler,
800 		    struct dentry *unused, struct inode *inode,
801 		    const char *name, void *value, size_t size)
802 {
803 	struct posix_acl *acl;
804 	int error;
805 
806 	if (!IS_POSIXACL(inode))
807 		return -EOPNOTSUPP;
808 	if (S_ISLNK(inode->i_mode))
809 		return -EOPNOTSUPP;
810 
811 	acl = get_acl(inode, handler->flags);
812 	if (IS_ERR(acl))
813 		return PTR_ERR(acl);
814 	if (acl == NULL)
815 		return -ENODATA;
816 
817 	error = posix_acl_to_xattr(&init_user_ns, acl, value, size);
818 	posix_acl_release(acl);
819 
820 	return error;
821 }
822 
823 int
824 set_posix_acl(struct inode *inode, int type, struct posix_acl *acl)
825 {
826 	if (!IS_POSIXACL(inode))
827 		return -EOPNOTSUPP;
828 	if (!inode->i_op->set_acl)
829 		return -EOPNOTSUPP;
830 
831 	if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
832 		return acl ? -EACCES : 0;
833 	if (!inode_owner_or_capable(inode))
834 		return -EPERM;
835 
836 	if (acl) {
837 		int ret = posix_acl_valid(acl);
838 		if (ret)
839 			return ret;
840 	}
841 	return inode->i_op->set_acl(inode, acl, type);
842 }
843 EXPORT_SYMBOL(set_posix_acl);
844 
845 static int
846 posix_acl_xattr_set(const struct xattr_handler *handler,
847 		    struct dentry *unused, struct inode *inode,
848 		    const char *name, const void *value,
849 		    size_t size, int flags)
850 {
851 	struct posix_acl *acl = NULL;
852 	int ret;
853 
854 	if (value) {
855 		acl = posix_acl_from_xattr(&init_user_ns, value, size);
856 		if (IS_ERR(acl))
857 			return PTR_ERR(acl);
858 	}
859 	ret = set_posix_acl(inode, handler->flags, acl);
860 	posix_acl_release(acl);
861 	return ret;
862 }
863 
864 static bool
865 posix_acl_xattr_list(struct dentry *dentry)
866 {
867 	return IS_POSIXACL(d_backing_inode(dentry));
868 }
869 
870 const struct xattr_handler posix_acl_access_xattr_handler = {
871 	.name = XATTR_NAME_POSIX_ACL_ACCESS,
872 	.flags = ACL_TYPE_ACCESS,
873 	.list = posix_acl_xattr_list,
874 	.get = posix_acl_xattr_get,
875 	.set = posix_acl_xattr_set,
876 };
877 EXPORT_SYMBOL_GPL(posix_acl_access_xattr_handler);
878 
879 const struct xattr_handler posix_acl_default_xattr_handler = {
880 	.name = XATTR_NAME_POSIX_ACL_DEFAULT,
881 	.flags = ACL_TYPE_DEFAULT,
882 	.list = posix_acl_xattr_list,
883 	.get = posix_acl_xattr_get,
884 	.set = posix_acl_xattr_set,
885 };
886 EXPORT_SYMBOL_GPL(posix_acl_default_xattr_handler);
887 
888 int simple_set_acl(struct inode *inode, struct posix_acl *acl, int type)
889 {
890 	int error;
891 
892 	if (type == ACL_TYPE_ACCESS) {
893 		error = posix_acl_equiv_mode(acl, &inode->i_mode);
894 		if (error < 0)
895 			return 0;
896 		if (error == 0)
897 			acl = NULL;
898 	}
899 
900 	inode->i_ctime = CURRENT_TIME;
901 	set_cached_acl(inode, type, acl);
902 	return 0;
903 }
904 
905 int simple_acl_create(struct inode *dir, struct inode *inode)
906 {
907 	struct posix_acl *default_acl, *acl;
908 	int error;
909 
910 	error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
911 	if (error)
912 		return error;
913 
914 	set_cached_acl(inode, ACL_TYPE_DEFAULT, default_acl);
915 	set_cached_acl(inode, ACL_TYPE_ACCESS, acl);
916 
917 	if (default_acl)
918 		posix_acl_release(default_acl);
919 	if (acl)
920 		posix_acl_release(acl);
921 	return 0;
922 }
923