1 /*
2  * FUSE: Filesystem in Userspace
3  * Copyright (C) 2016 Canonical Ltd. <seth.forshee@canonical.com>
4  *
5  * This program can be distributed under the terms of the GNU GPL.
6  * See the file COPYING.
7  */
8 
9 #include "fuse_i.h"
10 
11 #include <linux/posix_acl.h>
12 #include <linux/posix_acl_xattr.h>
13 
fuse_get_acl(struct inode * inode,int type,bool rcu)14 struct posix_acl *fuse_get_acl(struct inode *inode, int type, bool rcu)
15 {
16 	struct fuse_conn *fc = get_fuse_conn(inode);
17 	int size;
18 	const char *name;
19 	void *value = NULL;
20 	struct posix_acl *acl;
21 
22 	if (rcu)
23 		return ERR_PTR(-ECHILD);
24 
25 	if (fuse_is_bad(inode))
26 		return ERR_PTR(-EIO);
27 
28 	if (!fc->posix_acl || fc->no_getxattr)
29 		return NULL;
30 
31 	if (type == ACL_TYPE_ACCESS)
32 		name = XATTR_NAME_POSIX_ACL_ACCESS;
33 	else if (type == ACL_TYPE_DEFAULT)
34 		name = XATTR_NAME_POSIX_ACL_DEFAULT;
35 	else
36 		return ERR_PTR(-EOPNOTSUPP);
37 
38 	value = kmalloc(PAGE_SIZE, GFP_KERNEL);
39 	if (!value)
40 		return ERR_PTR(-ENOMEM);
41 	size = fuse_getxattr(inode, name, value, PAGE_SIZE);
42 	if (size > 0)
43 		acl = posix_acl_from_xattr(fc->user_ns, value, size);
44 	else if ((size == 0) || (size == -ENODATA) ||
45 		 (size == -EOPNOTSUPP && fc->no_getxattr))
46 		acl = NULL;
47 	else if (size == -ERANGE)
48 		acl = ERR_PTR(-E2BIG);
49 	else
50 		acl = ERR_PTR(size);
51 
52 	kfree(value);
53 	return acl;
54 }
55 
fuse_set_acl(struct user_namespace * mnt_userns,struct inode * inode,struct posix_acl * acl,int type)56 int fuse_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
57 		 struct posix_acl *acl, int type)
58 {
59 	struct fuse_conn *fc = get_fuse_conn(inode);
60 	const char *name;
61 	int ret;
62 
63 	if (fuse_is_bad(inode))
64 		return -EIO;
65 
66 	if (!fc->posix_acl || fc->no_setxattr)
67 		return -EOPNOTSUPP;
68 
69 	if (type == ACL_TYPE_ACCESS)
70 		name = XATTR_NAME_POSIX_ACL_ACCESS;
71 	else if (type == ACL_TYPE_DEFAULT)
72 		name = XATTR_NAME_POSIX_ACL_DEFAULT;
73 	else
74 		return -EINVAL;
75 
76 	if (acl) {
77 		unsigned int extra_flags = 0;
78 		/*
79 		 * Fuse userspace is responsible for updating access
80 		 * permissions in the inode, if needed. fuse_setxattr
81 		 * invalidates the inode attributes, which will force
82 		 * them to be refreshed the next time they are used,
83 		 * and it also updates i_ctime.
84 		 */
85 		size_t size = posix_acl_xattr_size(acl->a_count);
86 		void *value;
87 
88 		if (size > PAGE_SIZE)
89 			return -E2BIG;
90 
91 		value = kmalloc(size, GFP_KERNEL);
92 		if (!value)
93 			return -ENOMEM;
94 
95 		ret = posix_acl_to_xattr(fc->user_ns, acl, value, size);
96 		if (ret < 0) {
97 			kfree(value);
98 			return ret;
99 		}
100 
101 		if (!in_group_p(i_gid_into_mnt(&init_user_ns, inode)) &&
102 		    !capable_wrt_inode_uidgid(&init_user_ns, inode, CAP_FSETID))
103 			extra_flags |= FUSE_SETXATTR_ACL_KILL_SGID;
104 
105 		ret = fuse_setxattr(inode, name, value, size, 0, extra_flags);
106 		kfree(value);
107 	} else {
108 		ret = fuse_removexattr(inode, name);
109 	}
110 	forget_all_cached_acls(inode);
111 	fuse_invalidate_attr(inode);
112 
113 	return ret;
114 }
115