1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2002,2003 by Andreas Gruenbacher <a.gruenbacher@computer.org>
4  *
5  * Fixes from William Schumacher incorporated on 15 March 2001.
6  *    (Reported by Charles Bertsch, <CBertsch@microtest.com>).
7  */
8 
9 /*
10  *  This file contains generic functions for manipulating
11  *  POSIX 1003.1e draft standard 17 ACLs.
12  */
13 
14 #include <linux/kernel.h>
15 #include <linux/slab.h>
16 #include <linux/atomic.h>
17 #include <linux/fs.h>
18 #include <linux/sched.h>
19 #include <linux/cred.h>
20 #include <linux/posix_acl.h>
21 #include <linux/posix_acl_xattr.h>
22 #include <linux/xattr.h>
23 #include <linux/export.h>
24 #include <linux/user_namespace.h>
25 #include <linux/namei.h>
26 #include <linux/mnt_idmapping.h>
27 
acl_by_type(struct inode * inode,int type)28 static struct posix_acl **acl_by_type(struct inode *inode, int type)
29 {
30 	switch (type) {
31 	case ACL_TYPE_ACCESS:
32 		return &inode->i_acl;
33 	case ACL_TYPE_DEFAULT:
34 		return &inode->i_default_acl;
35 	default:
36 		BUG();
37 	}
38 }
39 
get_cached_acl(struct inode * inode,int type)40 struct posix_acl *get_cached_acl(struct inode *inode, int type)
41 {
42 	struct posix_acl **p = acl_by_type(inode, type);
43 	struct posix_acl *acl;
44 
45 	for (;;) {
46 		rcu_read_lock();
47 		acl = rcu_dereference(*p);
48 		if (!acl || is_uncached_acl(acl) ||
49 		    refcount_inc_not_zero(&acl->a_refcount))
50 			break;
51 		rcu_read_unlock();
52 		cpu_relax();
53 	}
54 	rcu_read_unlock();
55 	return acl;
56 }
57 EXPORT_SYMBOL(get_cached_acl);
58 
get_cached_acl_rcu(struct inode * inode,int type)59 struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
60 {
61 	struct posix_acl *acl = rcu_dereference(*acl_by_type(inode, type));
62 
63 	if (acl == ACL_DONT_CACHE) {
64 		struct posix_acl *ret;
65 
66 		ret = inode->i_op->get_acl(inode, type, LOOKUP_RCU);
67 		if (!IS_ERR(ret))
68 			acl = ret;
69 	}
70 
71 	return acl;
72 }
73 EXPORT_SYMBOL(get_cached_acl_rcu);
74 
set_cached_acl(struct inode * inode,int type,struct posix_acl * acl)75 void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
76 {
77 	struct posix_acl **p = acl_by_type(inode, type);
78 	struct posix_acl *old;
79 
80 	old = xchg(p, posix_acl_dup(acl));
81 	if (!is_uncached_acl(old))
82 		posix_acl_release(old);
83 }
84 EXPORT_SYMBOL(set_cached_acl);
85 
__forget_cached_acl(struct posix_acl ** p)86 static void __forget_cached_acl(struct posix_acl **p)
87 {
88 	struct posix_acl *old;
89 
90 	old = xchg(p, ACL_NOT_CACHED);
91 	if (!is_uncached_acl(old))
92 		posix_acl_release(old);
93 }
94 
forget_cached_acl(struct inode * inode,int type)95 void forget_cached_acl(struct inode *inode, int type)
96 {
97 	__forget_cached_acl(acl_by_type(inode, type));
98 }
99 EXPORT_SYMBOL(forget_cached_acl);
100 
forget_all_cached_acls(struct inode * inode)101 void forget_all_cached_acls(struct inode *inode)
102 {
103 	__forget_cached_acl(&inode->i_acl);
104 	__forget_cached_acl(&inode->i_default_acl);
105 }
106 EXPORT_SYMBOL(forget_all_cached_acls);
107 
get_acl(struct inode * inode,int type)108 struct posix_acl *get_acl(struct inode *inode, int type)
109 {
110 	void *sentinel;
111 	struct posix_acl **p;
112 	struct posix_acl *acl;
113 
114 	/*
115 	 * The sentinel is used to detect when another operation like
116 	 * set_cached_acl() or forget_cached_acl() races with get_acl().
117 	 * It is guaranteed that is_uncached_acl(sentinel) is true.
118 	 */
119 
120 	acl = get_cached_acl(inode, type);
121 	if (!is_uncached_acl(acl))
122 		return acl;
123 
124 	if (!IS_POSIXACL(inode))
125 		return NULL;
126 
127 	sentinel = uncached_acl_sentinel(current);
128 	p = acl_by_type(inode, type);
129 
130 	/*
131 	 * If the ACL isn't being read yet, set our sentinel.  Otherwise, the
132 	 * current value of the ACL will not be ACL_NOT_CACHED and so our own
133 	 * sentinel will not be set; another task will update the cache.  We
134 	 * could wait for that other task to complete its job, but it's easier
135 	 * to just call ->get_acl to fetch the ACL ourself.  (This is going to
136 	 * be an unlikely race.)
137 	 */
138 	cmpxchg(p, ACL_NOT_CACHED, sentinel);
139 
140 	/*
141 	 * Normally, the ACL returned by ->get_acl will be cached.
142 	 * A filesystem can prevent that by calling
143 	 * forget_cached_acl(inode, type) in ->get_acl.
144 	 *
145 	 * If the filesystem doesn't have a get_acl() function at all, we'll
146 	 * just create the negative cache entry.
147 	 */
148 	if (!inode->i_op->get_acl) {
149 		set_cached_acl(inode, type, NULL);
150 		return NULL;
151 	}
152 	acl = inode->i_op->get_acl(inode, type, false);
153 
154 	if (IS_ERR(acl)) {
155 		/*
156 		 * Remove our sentinel so that we don't block future attempts
157 		 * to cache the ACL.
158 		 */
159 		cmpxchg(p, sentinel, ACL_NOT_CACHED);
160 		return acl;
161 	}
162 
163 	/*
164 	 * Cache the result, but only if our sentinel is still in place.
165 	 */
166 	posix_acl_dup(acl);
167 	if (unlikely(cmpxchg(p, sentinel, acl) != sentinel))
168 		posix_acl_release(acl);
169 	return acl;
170 }
171 EXPORT_SYMBOL(get_acl);
172 
173 /*
174  * Init a fresh posix_acl
175  */
176 void
posix_acl_init(struct posix_acl * acl,int count)177 posix_acl_init(struct posix_acl *acl, int count)
178 {
179 	refcount_set(&acl->a_refcount, 1);
180 	acl->a_count = count;
181 }
182 EXPORT_SYMBOL(posix_acl_init);
183 
184 /*
185  * Allocate a new ACL with the specified number of entries.
186  */
187 struct posix_acl *
posix_acl_alloc(int count,gfp_t flags)188 posix_acl_alloc(int count, gfp_t flags)
189 {
190 	const size_t size = sizeof(struct posix_acl) +
191 	                    count * sizeof(struct posix_acl_entry);
192 	struct posix_acl *acl = kmalloc(size, flags);
193 	if (acl)
194 		posix_acl_init(acl, count);
195 	return acl;
196 }
197 EXPORT_SYMBOL(posix_acl_alloc);
198 
199 /*
200  * Clone an ACL.
201  */
202 static struct posix_acl *
posix_acl_clone(const struct posix_acl * acl,gfp_t flags)203 posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
204 {
205 	struct posix_acl *clone = NULL;
206 
207 	if (acl) {
208 		int size = sizeof(struct posix_acl) + acl->a_count *
209 		           sizeof(struct posix_acl_entry);
210 		clone = kmemdup(acl, size, flags);
211 		if (clone)
212 			refcount_set(&clone->a_refcount, 1);
213 	}
214 	return clone;
215 }
216 
217 /*
218  * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
219  */
220 int
posix_acl_valid(struct user_namespace * user_ns,const struct posix_acl * acl)221 posix_acl_valid(struct user_namespace *user_ns, const struct posix_acl *acl)
222 {
223 	const struct posix_acl_entry *pa, *pe;
224 	int state = ACL_USER_OBJ;
225 	int needs_mask = 0;
226 
227 	FOREACH_ACL_ENTRY(pa, acl, pe) {
228 		if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
229 			return -EINVAL;
230 		switch (pa->e_tag) {
231 			case ACL_USER_OBJ:
232 				if (state == ACL_USER_OBJ) {
233 					state = ACL_USER;
234 					break;
235 				}
236 				return -EINVAL;
237 
238 			case ACL_USER:
239 				if (state != ACL_USER)
240 					return -EINVAL;
241 				if (!kuid_has_mapping(user_ns, pa->e_uid))
242 					return -EINVAL;
243 				needs_mask = 1;
244 				break;
245 
246 			case ACL_GROUP_OBJ:
247 				if (state == ACL_USER) {
248 					state = ACL_GROUP;
249 					break;
250 				}
251 				return -EINVAL;
252 
253 			case ACL_GROUP:
254 				if (state != ACL_GROUP)
255 					return -EINVAL;
256 				if (!kgid_has_mapping(user_ns, pa->e_gid))
257 					return -EINVAL;
258 				needs_mask = 1;
259 				break;
260 
261 			case ACL_MASK:
262 				if (state != ACL_GROUP)
263 					return -EINVAL;
264 				state = ACL_OTHER;
265 				break;
266 
267 			case ACL_OTHER:
268 				if (state == ACL_OTHER ||
269 				    (state == ACL_GROUP && !needs_mask)) {
270 					state = 0;
271 					break;
272 				}
273 				return -EINVAL;
274 
275 			default:
276 				return -EINVAL;
277 		}
278 	}
279 	if (state == 0)
280 		return 0;
281 	return -EINVAL;
282 }
283 EXPORT_SYMBOL(posix_acl_valid);
284 
285 /*
286  * Returns 0 if the acl can be exactly represented in the traditional
287  * file mode permission bits, or else 1. Returns -E... on error.
288  */
289 int
posix_acl_equiv_mode(const struct posix_acl * acl,umode_t * mode_p)290 posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
291 {
292 	const struct posix_acl_entry *pa, *pe;
293 	umode_t mode = 0;
294 	int not_equiv = 0;
295 
296 	/*
297 	 * A null ACL can always be presented as mode bits.
298 	 */
299 	if (!acl)
300 		return 0;
301 
302 	FOREACH_ACL_ENTRY(pa, acl, pe) {
303 		switch (pa->e_tag) {
304 			case ACL_USER_OBJ:
305 				mode |= (pa->e_perm & S_IRWXO) << 6;
306 				break;
307 			case ACL_GROUP_OBJ:
308 				mode |= (pa->e_perm & S_IRWXO) << 3;
309 				break;
310 			case ACL_OTHER:
311 				mode |= pa->e_perm & S_IRWXO;
312 				break;
313 			case ACL_MASK:
314 				mode = (mode & ~S_IRWXG) |
315 				       ((pa->e_perm & S_IRWXO) << 3);
316 				not_equiv = 1;
317 				break;
318 			case ACL_USER:
319 			case ACL_GROUP:
320 				not_equiv = 1;
321 				break;
322 			default:
323 				return -EINVAL;
324 		}
325 	}
326         if (mode_p)
327                 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
328         return not_equiv;
329 }
330 EXPORT_SYMBOL(posix_acl_equiv_mode);
331 
332 /*
333  * Create an ACL representing the file mode permission bits of an inode.
334  */
335 struct posix_acl *
posix_acl_from_mode(umode_t mode,gfp_t flags)336 posix_acl_from_mode(umode_t mode, gfp_t flags)
337 {
338 	struct posix_acl *acl = posix_acl_alloc(3, flags);
339 	if (!acl)
340 		return ERR_PTR(-ENOMEM);
341 
342 	acl->a_entries[0].e_tag  = ACL_USER_OBJ;
343 	acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
344 
345 	acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;
346 	acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
347 
348 	acl->a_entries[2].e_tag  = ACL_OTHER;
349 	acl->a_entries[2].e_perm = (mode & S_IRWXO);
350 	return acl;
351 }
352 EXPORT_SYMBOL(posix_acl_from_mode);
353 
354 /*
355  * Return 0 if current is granted want access to the inode
356  * by the acl. Returns -E... otherwise.
357  */
358 int
posix_acl_permission(struct user_namespace * mnt_userns,struct inode * inode,const struct posix_acl * acl,int want)359 posix_acl_permission(struct user_namespace *mnt_userns, struct inode *inode,
360 		     const struct posix_acl *acl, int want)
361 {
362 	const struct posix_acl_entry *pa, *pe, *mask_obj;
363 	int found = 0;
364 	kuid_t uid;
365 	kgid_t gid;
366 
367 	want &= MAY_READ | MAY_WRITE | MAY_EXEC;
368 
369 	FOREACH_ACL_ENTRY(pa, acl, pe) {
370                 switch(pa->e_tag) {
371                         case ACL_USER_OBJ:
372 				/* (May have been checked already) */
373 				uid = i_uid_into_mnt(mnt_userns, inode);
374 				if (uid_eq(uid, current_fsuid()))
375                                         goto check_perm;
376                                 break;
377                         case ACL_USER:
378 				uid = mapped_kuid_fs(mnt_userns,
379 						     i_user_ns(inode),
380 						     pa->e_uid);
381 				if (uid_eq(uid, current_fsuid()))
382                                         goto mask;
383 				break;
384                         case ACL_GROUP_OBJ:
385 				gid = i_gid_into_mnt(mnt_userns, inode);
386 				if (in_group_p(gid)) {
387 					found = 1;
388 					if ((pa->e_perm & want) == want)
389 						goto mask;
390                                 }
391 				break;
392                         case ACL_GROUP:
393 				gid = mapped_kgid_fs(mnt_userns,
394 						     i_user_ns(inode),
395 						     pa->e_gid);
396 				if (in_group_p(gid)) {
397 					found = 1;
398 					if ((pa->e_perm & want) == want)
399 						goto mask;
400                                 }
401                                 break;
402                         case ACL_MASK:
403                                 break;
404                         case ACL_OTHER:
405 				if (found)
406 					return -EACCES;
407 				else
408 					goto check_perm;
409 			default:
410 				return -EIO;
411                 }
412         }
413 	return -EIO;
414 
415 mask:
416 	for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
417 		if (mask_obj->e_tag == ACL_MASK) {
418 			if ((pa->e_perm & mask_obj->e_perm & want) == want)
419 				return 0;
420 			return -EACCES;
421 		}
422 	}
423 
424 check_perm:
425 	if ((pa->e_perm & want) == want)
426 		return 0;
427 	return -EACCES;
428 }
429 
430 /*
431  * Modify acl when creating a new inode. The caller must ensure the acl is
432  * only referenced once.
433  *
434  * mode_p initially must contain the mode parameter to the open() / creat()
435  * system calls. All permissions that are not granted by the acl are removed.
436  * The permissions in the acl are changed to reflect the mode_p parameter.
437  */
posix_acl_create_masq(struct posix_acl * acl,umode_t * mode_p)438 static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
439 {
440 	struct posix_acl_entry *pa, *pe;
441 	struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
442 	umode_t mode = *mode_p;
443 	int not_equiv = 0;
444 
445 	/* assert(atomic_read(acl->a_refcount) == 1); */
446 
447 	FOREACH_ACL_ENTRY(pa, acl, pe) {
448                 switch(pa->e_tag) {
449                         case ACL_USER_OBJ:
450 				pa->e_perm &= (mode >> 6) | ~S_IRWXO;
451 				mode &= (pa->e_perm << 6) | ~S_IRWXU;
452 				break;
453 
454 			case ACL_USER:
455 			case ACL_GROUP:
456 				not_equiv = 1;
457 				break;
458 
459                         case ACL_GROUP_OBJ:
460 				group_obj = pa;
461                                 break;
462 
463                         case ACL_OTHER:
464 				pa->e_perm &= mode | ~S_IRWXO;
465 				mode &= pa->e_perm | ~S_IRWXO;
466                                 break;
467 
468                         case ACL_MASK:
469 				mask_obj = pa;
470 				not_equiv = 1;
471                                 break;
472 
473 			default:
474 				return -EIO;
475                 }
476         }
477 
478 	if (mask_obj) {
479 		mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
480 		mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
481 	} else {
482 		if (!group_obj)
483 			return -EIO;
484 		group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
485 		mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
486 	}
487 
488 	*mode_p = (*mode_p & ~S_IRWXUGO) | mode;
489         return not_equiv;
490 }
491 
492 /*
493  * Modify the ACL for the chmod syscall.
494  */
__posix_acl_chmod_masq(struct posix_acl * acl,umode_t mode)495 static int __posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)
496 {
497 	struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
498 	struct posix_acl_entry *pa, *pe;
499 
500 	/* assert(atomic_read(acl->a_refcount) == 1); */
501 
502 	FOREACH_ACL_ENTRY(pa, acl, pe) {
503 		switch(pa->e_tag) {
504 			case ACL_USER_OBJ:
505 				pa->e_perm = (mode & S_IRWXU) >> 6;
506 				break;
507 
508 			case ACL_USER:
509 			case ACL_GROUP:
510 				break;
511 
512 			case ACL_GROUP_OBJ:
513 				group_obj = pa;
514 				break;
515 
516 			case ACL_MASK:
517 				mask_obj = pa;
518 				break;
519 
520 			case ACL_OTHER:
521 				pa->e_perm = (mode & S_IRWXO);
522 				break;
523 
524 			default:
525 				return -EIO;
526 		}
527 	}
528 
529 	if (mask_obj) {
530 		mask_obj->e_perm = (mode & S_IRWXG) >> 3;
531 	} else {
532 		if (!group_obj)
533 			return -EIO;
534 		group_obj->e_perm = (mode & S_IRWXG) >> 3;
535 	}
536 
537 	return 0;
538 }
539 
540 int
__posix_acl_create(struct posix_acl ** acl,gfp_t gfp,umode_t * mode_p)541 __posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)
542 {
543 	struct posix_acl *clone = posix_acl_clone(*acl, gfp);
544 	int err = -ENOMEM;
545 	if (clone) {
546 		err = posix_acl_create_masq(clone, mode_p);
547 		if (err < 0) {
548 			posix_acl_release(clone);
549 			clone = NULL;
550 		}
551 	}
552 	posix_acl_release(*acl);
553 	*acl = clone;
554 	return err;
555 }
556 EXPORT_SYMBOL(__posix_acl_create);
557 
558 int
__posix_acl_chmod(struct posix_acl ** acl,gfp_t gfp,umode_t mode)559 __posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
560 {
561 	struct posix_acl *clone = posix_acl_clone(*acl, gfp);
562 	int err = -ENOMEM;
563 	if (clone) {
564 		err = __posix_acl_chmod_masq(clone, mode);
565 		if (err) {
566 			posix_acl_release(clone);
567 			clone = NULL;
568 		}
569 	}
570 	posix_acl_release(*acl);
571 	*acl = clone;
572 	return err;
573 }
574 EXPORT_SYMBOL(__posix_acl_chmod);
575 
576 /**
577  * posix_acl_chmod - chmod a posix acl
578  *
579  * @mnt_userns:	user namespace of the mount @inode was found from
580  * @inode:	inode to check permissions on
581  * @mode:	the new mode of @inode
582  *
583  * If the inode has been found through an idmapped mount the user namespace of
584  * the vfsmount must be passed through @mnt_userns. This function will then
585  * take care to map the inode according to @mnt_userns before checking
586  * permissions. On non-idmapped mounts or if permission checking is to be
587  * performed on the raw inode simply passs init_user_ns.
588  */
589 int
posix_acl_chmod(struct user_namespace * mnt_userns,struct inode * inode,umode_t mode)590  posix_acl_chmod(struct user_namespace *mnt_userns, struct inode *inode,
591 		    umode_t mode)
592 {
593 	struct posix_acl *acl;
594 	int ret = 0;
595 
596 	if (!IS_POSIXACL(inode))
597 		return 0;
598 	if (!inode->i_op->set_acl)
599 		return -EOPNOTSUPP;
600 
601 	acl = get_acl(inode, ACL_TYPE_ACCESS);
602 	if (IS_ERR_OR_NULL(acl)) {
603 		if (acl == ERR_PTR(-EOPNOTSUPP))
604 			return 0;
605 		return PTR_ERR(acl);
606 	}
607 
608 	ret = __posix_acl_chmod(&acl, GFP_KERNEL, mode);
609 	if (ret)
610 		return ret;
611 	ret = inode->i_op->set_acl(mnt_userns, inode, acl, ACL_TYPE_ACCESS);
612 	posix_acl_release(acl);
613 	return ret;
614 }
615 EXPORT_SYMBOL(posix_acl_chmod);
616 
617 int
posix_acl_create(struct inode * dir,umode_t * mode,struct posix_acl ** default_acl,struct posix_acl ** acl)618 posix_acl_create(struct inode *dir, umode_t *mode,
619 		struct posix_acl **default_acl, struct posix_acl **acl)
620 {
621 	struct posix_acl *p;
622 	struct posix_acl *clone;
623 	int ret;
624 
625 	*acl = NULL;
626 	*default_acl = NULL;
627 
628 	if (S_ISLNK(*mode) || !IS_POSIXACL(dir))
629 		return 0;
630 
631 	p = get_acl(dir, ACL_TYPE_DEFAULT);
632 	if (!p || p == ERR_PTR(-EOPNOTSUPP)) {
633 		*mode &= ~current_umask();
634 		return 0;
635 	}
636 	if (IS_ERR(p))
637 		return PTR_ERR(p);
638 
639 	ret = -ENOMEM;
640 	clone = posix_acl_clone(p, GFP_NOFS);
641 	if (!clone)
642 		goto err_release;
643 
644 	ret = posix_acl_create_masq(clone, mode);
645 	if (ret < 0)
646 		goto err_release_clone;
647 
648 	if (ret == 0)
649 		posix_acl_release(clone);
650 	else
651 		*acl = clone;
652 
653 	if (!S_ISDIR(*mode))
654 		posix_acl_release(p);
655 	else
656 		*default_acl = p;
657 
658 	return 0;
659 
660 err_release_clone:
661 	posix_acl_release(clone);
662 err_release:
663 	posix_acl_release(p);
664 	return ret;
665 }
666 EXPORT_SYMBOL_GPL(posix_acl_create);
667 
668 /**
669  * posix_acl_update_mode  -  update mode in set_acl
670  * @mnt_userns:	user namespace of the mount @inode was found from
671  * @inode:	target inode
672  * @mode_p:	mode (pointer) for update
673  * @acl:	acl pointer
674  *
675  * Update the file mode when setting an ACL: compute the new file permission
676  * bits based on the ACL.  In addition, if the ACL is equivalent to the new
677  * file mode, set *@acl to NULL to indicate that no ACL should be set.
678  *
679  * As with chmod, clear the setgid bit if the caller is not in the owning group
680  * or capable of CAP_FSETID (see inode_change_ok).
681  *
682  * If the inode has been found through an idmapped mount the user namespace of
683  * the vfsmount must be passed through @mnt_userns. This function will then
684  * take care to map the inode according to @mnt_userns before checking
685  * permissions. On non-idmapped mounts or if permission checking is to be
686  * performed on the raw inode simply passs init_user_ns.
687  *
688  * Called from set_acl inode operations.
689  */
posix_acl_update_mode(struct user_namespace * mnt_userns,struct inode * inode,umode_t * mode_p,struct posix_acl ** acl)690 int posix_acl_update_mode(struct user_namespace *mnt_userns,
691 			  struct inode *inode, umode_t *mode_p,
692 			  struct posix_acl **acl)
693 {
694 	umode_t mode = inode->i_mode;
695 	int error;
696 
697 	error = posix_acl_equiv_mode(*acl, &mode);
698 	if (error < 0)
699 		return error;
700 	if (error == 0)
701 		*acl = NULL;
702 	if (!in_group_p(i_gid_into_mnt(mnt_userns, inode)) &&
703 	    !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID))
704 		mode &= ~S_ISGID;
705 	*mode_p = mode;
706 	return 0;
707 }
708 EXPORT_SYMBOL(posix_acl_update_mode);
709 
710 /*
711  * Fix up the uids and gids in posix acl extended attributes in place.
712  */
posix_acl_fix_xattr_userns(struct user_namespace * to,struct user_namespace * from,struct user_namespace * mnt_userns,void * value,size_t size,bool from_user)713 static void posix_acl_fix_xattr_userns(
714 	struct user_namespace *to, struct user_namespace *from,
715 	struct user_namespace *mnt_userns,
716 	void *value, size_t size, bool from_user)
717 {
718 	struct posix_acl_xattr_header *header = value;
719 	struct posix_acl_xattr_entry *entry = (void *)(header + 1), *end;
720 	int count;
721 	kuid_t uid;
722 	kgid_t gid;
723 
724 	if (!value)
725 		return;
726 	if (size < sizeof(struct posix_acl_xattr_header))
727 		return;
728 	if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
729 		return;
730 
731 	count = posix_acl_xattr_count(size);
732 	if (count < 0)
733 		return;
734 	if (count == 0)
735 		return;
736 
737 	for (end = entry + count; entry != end; entry++) {
738 		switch(le16_to_cpu(entry->e_tag)) {
739 		case ACL_USER:
740 			uid = make_kuid(from, le32_to_cpu(entry->e_id));
741 			if (from_user)
742 				uid = mapped_kuid_user(mnt_userns, &init_user_ns, uid);
743 			else
744 				uid = mapped_kuid_fs(mnt_userns, &init_user_ns, uid);
745 			entry->e_id = cpu_to_le32(from_kuid(to, uid));
746 			break;
747 		case ACL_GROUP:
748 			gid = make_kgid(from, le32_to_cpu(entry->e_id));
749 			if (from_user)
750 				gid = mapped_kgid_user(mnt_userns, &init_user_ns, gid);
751 			else
752 				gid = mapped_kgid_fs(mnt_userns, &init_user_ns, gid);
753 			entry->e_id = cpu_to_le32(from_kgid(to, gid));
754 			break;
755 		default:
756 			break;
757 		}
758 	}
759 }
760 
posix_acl_fix_xattr_from_user(struct user_namespace * mnt_userns,struct inode * inode,void * value,size_t size)761 void posix_acl_fix_xattr_from_user(struct user_namespace *mnt_userns,
762 				   struct inode *inode,
763 				   void *value, size_t size)
764 {
765 	struct user_namespace *user_ns = current_user_ns();
766 
767 	/* Leave ids untouched on non-idmapped mounts. */
768 	if (no_idmapping(mnt_userns, i_user_ns(inode)))
769 		mnt_userns = &init_user_ns;
770 	if ((user_ns == &init_user_ns) && (mnt_userns == &init_user_ns))
771 		return;
772 	posix_acl_fix_xattr_userns(&init_user_ns, user_ns, mnt_userns, value,
773 				   size, true);
774 }
775 
posix_acl_fix_xattr_to_user(struct user_namespace * mnt_userns,struct inode * inode,void * value,size_t size)776 void posix_acl_fix_xattr_to_user(struct user_namespace *mnt_userns,
777 				 struct inode *inode,
778 				 void *value, size_t size)
779 {
780 	struct user_namespace *user_ns = current_user_ns();
781 
782 	/* Leave ids untouched on non-idmapped mounts. */
783 	if (no_idmapping(mnt_userns, i_user_ns(inode)))
784 		mnt_userns = &init_user_ns;
785 	if ((user_ns == &init_user_ns) && (mnt_userns == &init_user_ns))
786 		return;
787 	posix_acl_fix_xattr_userns(user_ns, &init_user_ns, mnt_userns, value,
788 				   size, false);
789 }
790 
791 /*
792  * Convert from extended attribute to in-memory representation.
793  */
794 struct posix_acl *
posix_acl_from_xattr(struct user_namespace * user_ns,const void * value,size_t size)795 posix_acl_from_xattr(struct user_namespace *user_ns,
796 		     const void *value, size_t size)
797 {
798 	const struct posix_acl_xattr_header *header = value;
799 	const struct posix_acl_xattr_entry *entry = (const void *)(header + 1), *end;
800 	int count;
801 	struct posix_acl *acl;
802 	struct posix_acl_entry *acl_e;
803 
804 	if (!value)
805 		return NULL;
806 	if (size < sizeof(struct posix_acl_xattr_header))
807 		 return ERR_PTR(-EINVAL);
808 	if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
809 		return ERR_PTR(-EOPNOTSUPP);
810 
811 	count = posix_acl_xattr_count(size);
812 	if (count < 0)
813 		return ERR_PTR(-EINVAL);
814 	if (count == 0)
815 		return NULL;
816 
817 	acl = posix_acl_alloc(count, GFP_NOFS);
818 	if (!acl)
819 		return ERR_PTR(-ENOMEM);
820 	acl_e = acl->a_entries;
821 
822 	for (end = entry + count; entry != end; acl_e++, entry++) {
823 		acl_e->e_tag  = le16_to_cpu(entry->e_tag);
824 		acl_e->e_perm = le16_to_cpu(entry->e_perm);
825 
826 		switch(acl_e->e_tag) {
827 			case ACL_USER_OBJ:
828 			case ACL_GROUP_OBJ:
829 			case ACL_MASK:
830 			case ACL_OTHER:
831 				break;
832 
833 			case ACL_USER:
834 				acl_e->e_uid =
835 					make_kuid(user_ns,
836 						  le32_to_cpu(entry->e_id));
837 				if (!uid_valid(acl_e->e_uid))
838 					goto fail;
839 				break;
840 			case ACL_GROUP:
841 				acl_e->e_gid =
842 					make_kgid(user_ns,
843 						  le32_to_cpu(entry->e_id));
844 				if (!gid_valid(acl_e->e_gid))
845 					goto fail;
846 				break;
847 
848 			default:
849 				goto fail;
850 		}
851 	}
852 	return acl;
853 
854 fail:
855 	posix_acl_release(acl);
856 	return ERR_PTR(-EINVAL);
857 }
858 EXPORT_SYMBOL (posix_acl_from_xattr);
859 
860 /*
861  * Convert from in-memory to extended attribute representation.
862  */
863 int
posix_acl_to_xattr(struct user_namespace * user_ns,const struct posix_acl * acl,void * buffer,size_t size)864 posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
865 		   void *buffer, size_t size)
866 {
867 	struct posix_acl_xattr_header *ext_acl = buffer;
868 	struct posix_acl_xattr_entry *ext_entry;
869 	int real_size, n;
870 
871 	real_size = posix_acl_xattr_size(acl->a_count);
872 	if (!buffer)
873 		return real_size;
874 	if (real_size > size)
875 		return -ERANGE;
876 
877 	ext_entry = (void *)(ext_acl + 1);
878 	ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
879 
880 	for (n=0; n < acl->a_count; n++, ext_entry++) {
881 		const struct posix_acl_entry *acl_e = &acl->a_entries[n];
882 		ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
883 		ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
884 		switch(acl_e->e_tag) {
885 		case ACL_USER:
886 			ext_entry->e_id =
887 				cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
888 			break;
889 		case ACL_GROUP:
890 			ext_entry->e_id =
891 				cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
892 			break;
893 		default:
894 			ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
895 			break;
896 		}
897 	}
898 	return real_size;
899 }
900 EXPORT_SYMBOL (posix_acl_to_xattr);
901 
902 static int
posix_acl_xattr_get(const struct xattr_handler * handler,struct dentry * unused,struct inode * inode,const char * name,void * value,size_t size)903 posix_acl_xattr_get(const struct xattr_handler *handler,
904 		    struct dentry *unused, struct inode *inode,
905 		    const char *name, void *value, size_t size)
906 {
907 	struct posix_acl *acl;
908 	int error;
909 
910 	if (!IS_POSIXACL(inode))
911 		return -EOPNOTSUPP;
912 	if (S_ISLNK(inode->i_mode))
913 		return -EOPNOTSUPP;
914 
915 	acl = get_acl(inode, handler->flags);
916 	if (IS_ERR(acl))
917 		return PTR_ERR(acl);
918 	if (acl == NULL)
919 		return -ENODATA;
920 
921 	error = posix_acl_to_xattr(&init_user_ns, acl, value, size);
922 	posix_acl_release(acl);
923 
924 	return error;
925 }
926 
927 int
set_posix_acl(struct user_namespace * mnt_userns,struct inode * inode,int type,struct posix_acl * acl)928 set_posix_acl(struct user_namespace *mnt_userns, struct inode *inode,
929 	      int type, struct posix_acl *acl)
930 {
931 	if (!IS_POSIXACL(inode))
932 		return -EOPNOTSUPP;
933 	if (!inode->i_op->set_acl)
934 		return -EOPNOTSUPP;
935 
936 	if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
937 		return acl ? -EACCES : 0;
938 	if (!inode_owner_or_capable(mnt_userns, inode))
939 		return -EPERM;
940 
941 	if (acl) {
942 		int ret = posix_acl_valid(inode->i_sb->s_user_ns, acl);
943 		if (ret)
944 			return ret;
945 	}
946 	return inode->i_op->set_acl(mnt_userns, inode, acl, type);
947 }
948 EXPORT_SYMBOL(set_posix_acl);
949 
950 static int
posix_acl_xattr_set(const struct xattr_handler * handler,struct user_namespace * mnt_userns,struct dentry * unused,struct inode * inode,const char * name,const void * value,size_t size,int flags)951 posix_acl_xattr_set(const struct xattr_handler *handler,
952 			   struct user_namespace *mnt_userns,
953 			   struct dentry *unused, struct inode *inode,
954 			   const char *name, const void *value, size_t size,
955 			   int flags)
956 {
957 	struct posix_acl *acl = NULL;
958 	int ret;
959 
960 	if (value) {
961 		acl = posix_acl_from_xattr(&init_user_ns, value, size);
962 		if (IS_ERR(acl))
963 			return PTR_ERR(acl);
964 	}
965 	ret = set_posix_acl(mnt_userns, inode, handler->flags, acl);
966 	posix_acl_release(acl);
967 	return ret;
968 }
969 
970 static bool
posix_acl_xattr_list(struct dentry * dentry)971 posix_acl_xattr_list(struct dentry *dentry)
972 {
973 	return IS_POSIXACL(d_backing_inode(dentry));
974 }
975 
976 const struct xattr_handler posix_acl_access_xattr_handler = {
977 	.name = XATTR_NAME_POSIX_ACL_ACCESS,
978 	.flags = ACL_TYPE_ACCESS,
979 	.list = posix_acl_xattr_list,
980 	.get = posix_acl_xattr_get,
981 	.set = posix_acl_xattr_set,
982 };
983 EXPORT_SYMBOL_GPL(posix_acl_access_xattr_handler);
984 
985 const struct xattr_handler posix_acl_default_xattr_handler = {
986 	.name = XATTR_NAME_POSIX_ACL_DEFAULT,
987 	.flags = ACL_TYPE_DEFAULT,
988 	.list = posix_acl_xattr_list,
989 	.get = posix_acl_xattr_get,
990 	.set = posix_acl_xattr_set,
991 };
992 EXPORT_SYMBOL_GPL(posix_acl_default_xattr_handler);
993 
simple_set_acl(struct user_namespace * mnt_userns,struct inode * inode,struct posix_acl * acl,int type)994 int simple_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
995 		   struct posix_acl *acl, int type)
996 {
997 	int error;
998 
999 	if (type == ACL_TYPE_ACCESS) {
1000 		error = posix_acl_update_mode(mnt_userns, inode,
1001 				&inode->i_mode, &acl);
1002 		if (error)
1003 			return error;
1004 	}
1005 
1006 	inode->i_ctime = current_time(inode);
1007 	set_cached_acl(inode, type, acl);
1008 	return 0;
1009 }
1010 
simple_acl_create(struct inode * dir,struct inode * inode)1011 int simple_acl_create(struct inode *dir, struct inode *inode)
1012 {
1013 	struct posix_acl *default_acl, *acl;
1014 	int error;
1015 
1016 	error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
1017 	if (error)
1018 		return error;
1019 
1020 	set_cached_acl(inode, ACL_TYPE_DEFAULT, default_acl);
1021 	set_cached_acl(inode, ACL_TYPE_ACCESS, acl);
1022 
1023 	if (default_acl)
1024 		posix_acl_release(default_acl);
1025 	if (acl)
1026 		posix_acl_release(acl);
1027 	return 0;
1028 }
1029