2 * Copyright (C) 2002,2003 by Andreas Gruenbacher <a.gruenbacher@computer.org>
4 * Fixes from William Schumacher incorporated on 15 March 2001.
5 * (Reported by Charles Bertsch, <CBertsch@microtest.com>).
9 * This file contains generic functions for manipulating
10 * POSIX 1003.1e draft standard 17 ACLs.
13 #include <linux/kernel.h>
14 #include <linux/slab.h>
15 #include <linux/atomic.h>
17 #include <linux/sched.h>
18 #include <linux/cred.h>
19 #include <linux/posix_acl.h>
20 #include <linux/posix_acl_xattr.h>
21 #include <linux/xattr.h>
22 #include <linux/export.h>
23 #include <linux/user_namespace.h>
25 static struct posix_acl **acl_by_type(struct inode *inode, int type)
30 case ACL_TYPE_DEFAULT:
31 return &inode->i_default_acl;
37 struct posix_acl *get_cached_acl(struct inode *inode, int type)
39 struct posix_acl **p = acl_by_type(inode, type);
40 struct posix_acl *acl;
44 acl = rcu_dereference(*p);
45 if (!acl || is_uncached_acl(acl) ||
46 atomic_inc_not_zero(&acl->a_refcount))
54 EXPORT_SYMBOL(get_cached_acl);
56 struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
58 return rcu_dereference(*acl_by_type(inode, type));
60 EXPORT_SYMBOL(get_cached_acl_rcu);
62 void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
64 struct posix_acl **p = acl_by_type(inode, type);
65 struct posix_acl *old;
67 old = xchg(p, posix_acl_dup(acl));
68 if (!is_uncached_acl(old))
69 posix_acl_release(old);
71 EXPORT_SYMBOL(set_cached_acl);
73 static void __forget_cached_acl(struct posix_acl **p)
75 struct posix_acl *old;
77 old = xchg(p, ACL_NOT_CACHED);
78 if (!is_uncached_acl(old))
79 posix_acl_release(old);
82 void forget_cached_acl(struct inode *inode, int type)
84 __forget_cached_acl(acl_by_type(inode, type));
86 EXPORT_SYMBOL(forget_cached_acl);
88 void forget_all_cached_acls(struct inode *inode)
90 __forget_cached_acl(&inode->i_acl);
91 __forget_cached_acl(&inode->i_default_acl);
93 EXPORT_SYMBOL(forget_all_cached_acls);
95 struct posix_acl *get_acl(struct inode *inode, int type)
99 struct posix_acl *acl;
102 * The sentinel is used to detect when another operation like
103 * set_cached_acl() or forget_cached_acl() races with get_acl().
104 * It is guaranteed that is_uncached_acl(sentinel) is true.
107 acl = get_cached_acl(inode, type);
108 if (!is_uncached_acl(acl))
111 if (!IS_POSIXACL(inode))
114 sentinel = uncached_acl_sentinel(current);
115 p = acl_by_type(inode, type);
118 * If the ACL isn't being read yet, set our sentinel. Otherwise, the
119 * current value of the ACL will not be ACL_NOT_CACHED and so our own
120 * sentinel will not be set; another task will update the cache. We
121 * could wait for that other task to complete its job, but it's easier
122 * to just call ->get_acl to fetch the ACL ourself. (This is going to
123 * be an unlikely race.)
125 if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED)
129 * Normally, the ACL returned by ->get_acl will be cached.
130 * A filesystem can prevent that by calling
131 * forget_cached_acl(inode, type) in ->get_acl.
133 * If the filesystem doesn't have a get_acl() function at all, we'll
134 * just create the negative cache entry.
136 if (!inode->i_op->get_acl) {
137 set_cached_acl(inode, type, NULL);
140 acl = inode->i_op->get_acl(inode, type);
144 * Remove our sentinel so that we don't block future attempts
147 cmpxchg(p, sentinel, ACL_NOT_CACHED);
152 * Cache the result, but only if our sentinel is still in place.
155 if (unlikely(cmpxchg(p, sentinel, acl) != sentinel))
156 posix_acl_release(acl);
159 EXPORT_SYMBOL(get_acl);
162 * Init a fresh posix_acl
165 posix_acl_init(struct posix_acl *acl, int count)
167 atomic_set(&acl->a_refcount, 1);
168 acl->a_count = count;
170 EXPORT_SYMBOL(posix_acl_init);
173 * Allocate a new ACL with the specified number of entries.
176 posix_acl_alloc(int count, gfp_t flags)
178 const size_t size = sizeof(struct posix_acl) +
179 count * sizeof(struct posix_acl_entry);
180 struct posix_acl *acl = kmalloc(size, flags);
182 posix_acl_init(acl, count);
185 EXPORT_SYMBOL(posix_acl_alloc);
190 static struct posix_acl *
191 posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
193 struct posix_acl *clone = NULL;
196 int size = sizeof(struct posix_acl) + acl->a_count *
197 sizeof(struct posix_acl_entry);
198 clone = kmemdup(acl, size, flags);
200 atomic_set(&clone->a_refcount, 1);
206 * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
209 posix_acl_valid(struct user_namespace *user_ns, const struct posix_acl *acl)
211 const struct posix_acl_entry *pa, *pe;
212 int state = ACL_USER_OBJ;
215 FOREACH_ACL_ENTRY(pa, acl, pe) {
216 if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
220 if (state == ACL_USER_OBJ) {
227 if (state != ACL_USER)
229 if (!kuid_has_mapping(user_ns, pa->e_uid))
235 if (state == ACL_USER) {
242 if (state != ACL_GROUP)
244 if (!kgid_has_mapping(user_ns, pa->e_gid))
250 if (state != ACL_GROUP)
256 if (state == ACL_OTHER ||
257 (state == ACL_GROUP && !needs_mask)) {
271 EXPORT_SYMBOL(posix_acl_valid);
274 * Returns 0 if the acl can be exactly represented in the traditional
275 * file mode permission bits, or else 1. Returns -E... on error.
278 posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
280 const struct posix_acl_entry *pa, *pe;
285 * A null ACL can always be presented as mode bits.
290 FOREACH_ACL_ENTRY(pa, acl, pe) {
293 mode |= (pa->e_perm & S_IRWXO) << 6;
296 mode |= (pa->e_perm & S_IRWXO) << 3;
299 mode |= pa->e_perm & S_IRWXO;
302 mode = (mode & ~S_IRWXG) |
303 ((pa->e_perm & S_IRWXO) << 3);
315 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
318 EXPORT_SYMBOL(posix_acl_equiv_mode);
321 * Create an ACL representing the file mode permission bits of an inode.
324 posix_acl_from_mode(umode_t mode, gfp_t flags)
326 struct posix_acl *acl = posix_acl_alloc(3, flags);
328 return ERR_PTR(-ENOMEM);
330 acl->a_entries[0].e_tag = ACL_USER_OBJ;
331 acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
333 acl->a_entries[1].e_tag = ACL_GROUP_OBJ;
334 acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
336 acl->a_entries[2].e_tag = ACL_OTHER;
337 acl->a_entries[2].e_perm = (mode & S_IRWXO);
340 EXPORT_SYMBOL(posix_acl_from_mode);
343 * Return 0 if current is granted want access to the inode
344 * by the acl. Returns -E... otherwise.
347 posix_acl_permission(struct inode *inode, const struct posix_acl *acl, int want)
349 const struct posix_acl_entry *pa, *pe, *mask_obj;
352 want &= MAY_READ | MAY_WRITE | MAY_EXEC | MAY_NOT_BLOCK;
354 FOREACH_ACL_ENTRY(pa, acl, pe) {
357 /* (May have been checked already) */
358 if (uid_eq(inode->i_uid, current_fsuid()))
362 if (uid_eq(pa->e_uid, current_fsuid()))
366 if (in_group_p(inode->i_gid)) {
368 if ((pa->e_perm & want) == want)
373 if (in_group_p(pa->e_gid)) {
375 if ((pa->e_perm & want) == want)
393 for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
394 if (mask_obj->e_tag == ACL_MASK) {
395 if ((pa->e_perm & mask_obj->e_perm & want) == want)
402 if ((pa->e_perm & want) == want)
408 * Modify acl when creating a new inode. The caller must ensure the acl is
409 * only referenced once.
411 * mode_p initially must contain the mode parameter to the open() / creat()
412 * system calls. All permissions that are not granted by the acl are removed.
413 * The permissions in the acl are changed to reflect the mode_p parameter.
415 static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
417 struct posix_acl_entry *pa, *pe;
418 struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
419 umode_t mode = *mode_p;
422 /* assert(atomic_read(acl->a_refcount) == 1); */
424 FOREACH_ACL_ENTRY(pa, acl, pe) {
427 pa->e_perm &= (mode >> 6) | ~S_IRWXO;
428 mode &= (pa->e_perm << 6) | ~S_IRWXU;
441 pa->e_perm &= mode | ~S_IRWXO;
442 mode &= pa->e_perm | ~S_IRWXO;
456 mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
457 mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
461 group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
462 mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
465 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
470 * Modify the ACL for the chmod syscall.
472 static int __posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)
474 struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
475 struct posix_acl_entry *pa, *pe;
477 /* assert(atomic_read(acl->a_refcount) == 1); */
479 FOREACH_ACL_ENTRY(pa, acl, pe) {
482 pa->e_perm = (mode & S_IRWXU) >> 6;
498 pa->e_perm = (mode & S_IRWXO);
507 mask_obj->e_perm = (mode & S_IRWXG) >> 3;
511 group_obj->e_perm = (mode & S_IRWXG) >> 3;
518 __posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)
520 struct posix_acl *clone = posix_acl_clone(*acl, gfp);
523 err = posix_acl_create_masq(clone, mode_p);
525 posix_acl_release(clone);
529 posix_acl_release(*acl);
533 EXPORT_SYMBOL(__posix_acl_create);
536 __posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
538 struct posix_acl *clone = posix_acl_clone(*acl, gfp);
541 err = __posix_acl_chmod_masq(clone, mode);
543 posix_acl_release(clone);
547 posix_acl_release(*acl);
551 EXPORT_SYMBOL(__posix_acl_chmod);
554 posix_acl_chmod(struct inode *inode, umode_t mode)
556 struct posix_acl *acl;
559 if (!IS_POSIXACL(inode))
561 if (!inode->i_op->set_acl)
564 acl = get_acl(inode, ACL_TYPE_ACCESS);
565 if (IS_ERR_OR_NULL(acl)) {
566 if (acl == ERR_PTR(-EOPNOTSUPP))
571 ret = __posix_acl_chmod(&acl, GFP_KERNEL, mode);
574 ret = inode->i_op->set_acl(inode, acl, ACL_TYPE_ACCESS);
575 posix_acl_release(acl);
578 EXPORT_SYMBOL(posix_acl_chmod);
581 posix_acl_create(struct inode *dir, umode_t *mode,
582 struct posix_acl **default_acl, struct posix_acl **acl)
585 struct posix_acl *clone;
591 if (S_ISLNK(*mode) || !IS_POSIXACL(dir))
594 p = get_acl(dir, ACL_TYPE_DEFAULT);
595 if (!p || p == ERR_PTR(-EOPNOTSUPP)) {
596 *mode &= ~current_umask();
603 clone = posix_acl_clone(p, GFP_NOFS);
607 ret = posix_acl_create_masq(clone, mode);
609 goto err_release_clone;
612 posix_acl_release(clone);
617 posix_acl_release(p);
624 posix_acl_release(clone);
626 posix_acl_release(p);
629 EXPORT_SYMBOL_GPL(posix_acl_create);
632 * posix_acl_update_mode - update mode in set_acl
634 * Update the file mode when setting an ACL: compute the new file permission
635 * bits based on the ACL. In addition, if the ACL is equivalent to the new
636 * file mode, set *acl to NULL to indicate that no ACL should be set.
638 * As with chmod, clear the setgit bit if the caller is not in the owning group
639 * or capable of CAP_FSETID (see inode_change_ok).
641 * Called from set_acl inode operations.
643 int posix_acl_update_mode(struct inode *inode, umode_t *mode_p,
644 struct posix_acl **acl)
646 umode_t mode = inode->i_mode;
649 error = posix_acl_equiv_mode(*acl, &mode);
654 if (!in_group_p(inode->i_gid) &&
655 !capable_wrt_inode_uidgid(inode, CAP_FSETID))
660 EXPORT_SYMBOL(posix_acl_update_mode);
663 * Fix up the uids and gids in posix acl extended attributes in place.
665 static void posix_acl_fix_xattr_userns(
666 struct user_namespace *to, struct user_namespace *from,
667 void *value, size_t size)
669 struct posix_acl_xattr_header *header = value;
670 struct posix_acl_xattr_entry *entry = (void *)(header + 1), *end;
677 if (size < sizeof(struct posix_acl_xattr_header))
679 if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
682 count = posix_acl_xattr_count(size);
688 for (end = entry + count; entry != end; entry++) {
689 switch(le16_to_cpu(entry->e_tag)) {
691 uid = make_kuid(from, le32_to_cpu(entry->e_id));
692 entry->e_id = cpu_to_le32(from_kuid(to, uid));
695 gid = make_kgid(from, le32_to_cpu(entry->e_id));
696 entry->e_id = cpu_to_le32(from_kgid(to, gid));
704 void posix_acl_fix_xattr_from_user(void *value, size_t size)
706 struct user_namespace *user_ns = current_user_ns();
707 if (user_ns == &init_user_ns)
709 posix_acl_fix_xattr_userns(&init_user_ns, user_ns, value, size);
712 void posix_acl_fix_xattr_to_user(void *value, size_t size)
714 struct user_namespace *user_ns = current_user_ns();
715 if (user_ns == &init_user_ns)
717 posix_acl_fix_xattr_userns(user_ns, &init_user_ns, value, size);
721 * Convert from extended attribute to in-memory representation.
724 posix_acl_from_xattr(struct user_namespace *user_ns,
725 const void *value, size_t size)
727 const struct posix_acl_xattr_header *header = value;
728 const struct posix_acl_xattr_entry *entry = (const void *)(header + 1), *end;
730 struct posix_acl *acl;
731 struct posix_acl_entry *acl_e;
735 if (size < sizeof(struct posix_acl_xattr_header))
736 return ERR_PTR(-EINVAL);
737 if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
738 return ERR_PTR(-EOPNOTSUPP);
740 count = posix_acl_xattr_count(size);
742 return ERR_PTR(-EINVAL);
746 acl = posix_acl_alloc(count, GFP_NOFS);
748 return ERR_PTR(-ENOMEM);
749 acl_e = acl->a_entries;
751 for (end = entry + count; entry != end; acl_e++, entry++) {
752 acl_e->e_tag = le16_to_cpu(entry->e_tag);
753 acl_e->e_perm = le16_to_cpu(entry->e_perm);
755 switch(acl_e->e_tag) {
765 le32_to_cpu(entry->e_id));
766 if (!uid_valid(acl_e->e_uid))
772 le32_to_cpu(entry->e_id));
773 if (!gid_valid(acl_e->e_gid))
784 posix_acl_release(acl);
785 return ERR_PTR(-EINVAL);
787 EXPORT_SYMBOL (posix_acl_from_xattr);
790 * Convert from in-memory to extended attribute representation.
793 posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
794 void *buffer, size_t size)
796 struct posix_acl_xattr_header *ext_acl = buffer;
797 struct posix_acl_xattr_entry *ext_entry;
800 real_size = posix_acl_xattr_size(acl->a_count);
803 if (real_size > size)
806 ext_entry = (void *)(ext_acl + 1);
807 ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
809 for (n=0; n < acl->a_count; n++, ext_entry++) {
810 const struct posix_acl_entry *acl_e = &acl->a_entries[n];
811 ext_entry->e_tag = cpu_to_le16(acl_e->e_tag);
812 ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
813 switch(acl_e->e_tag) {
816 cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
820 cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
823 ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
829 EXPORT_SYMBOL (posix_acl_to_xattr);
832 posix_acl_xattr_get(const struct xattr_handler *handler,
833 struct dentry *unused, struct inode *inode,
834 const char *name, void *value, size_t size)
836 struct posix_acl *acl;
839 if (!IS_POSIXACL(inode))
841 if (S_ISLNK(inode->i_mode))
844 acl = get_acl(inode, handler->flags);
850 error = posix_acl_to_xattr(&init_user_ns, acl, value, size);
851 posix_acl_release(acl);
857 set_posix_acl(struct inode *inode, int type, struct posix_acl *acl)
859 if (!IS_POSIXACL(inode))
861 if (!inode->i_op->set_acl)
864 if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
865 return acl ? -EACCES : 0;
866 if (!inode_owner_or_capable(inode))
870 int ret = posix_acl_valid(inode->i_sb->s_user_ns, acl);
874 return inode->i_op->set_acl(inode, acl, type);
876 EXPORT_SYMBOL(set_posix_acl);
879 posix_acl_xattr_set(const struct xattr_handler *handler,
880 struct dentry *unused, struct inode *inode,
881 const char *name, const void *value,
882 size_t size, int flags)
884 struct posix_acl *acl = NULL;
888 acl = posix_acl_from_xattr(&init_user_ns, value, size);
892 ret = set_posix_acl(inode, handler->flags, acl);
893 posix_acl_release(acl);
898 posix_acl_xattr_list(struct dentry *dentry)
900 return IS_POSIXACL(d_backing_inode(dentry));
903 const struct xattr_handler posix_acl_access_xattr_handler = {
904 .name = XATTR_NAME_POSIX_ACL_ACCESS,
905 .flags = ACL_TYPE_ACCESS,
906 .list = posix_acl_xattr_list,
907 .get = posix_acl_xattr_get,
908 .set = posix_acl_xattr_set,
910 EXPORT_SYMBOL_GPL(posix_acl_access_xattr_handler);
912 const struct xattr_handler posix_acl_default_xattr_handler = {
913 .name = XATTR_NAME_POSIX_ACL_DEFAULT,
914 .flags = ACL_TYPE_DEFAULT,
915 .list = posix_acl_xattr_list,
916 .get = posix_acl_xattr_get,
917 .set = posix_acl_xattr_set,
919 EXPORT_SYMBOL_GPL(posix_acl_default_xattr_handler);
921 int simple_set_acl(struct inode *inode, struct posix_acl *acl, int type)
925 if (type == ACL_TYPE_ACCESS) {
926 error = posix_acl_update_mode(inode,
927 &inode->i_mode, &acl);
932 inode->i_ctime = current_time(inode);
933 set_cached_acl(inode, type, acl);
937 int simple_acl_create(struct inode *dir, struct inode *inode)
939 struct posix_acl *default_acl, *acl;
942 error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
946 set_cached_acl(inode, ACL_TYPE_DEFAULT, default_acl);
947 set_cached_acl(inode, ACL_TYPE_ACCESS, acl);
950 posix_acl_release(default_acl);
952 posix_acl_release(acl);