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
14 static struct posix_acl *__fuse_get_acl(struct fuse_conn *fc,
15 struct mnt_idmap *idmap,
16 struct inode *inode, int type, bool rcu)
17 {
18 int size;
19 const char *name;
20 void *value = NULL;
21 struct posix_acl *acl;
22
23 if (rcu)
24 return ERR_PTR(-ECHILD);
25
26 if (fuse_is_bad(inode))
27 return ERR_PTR(-EIO);
28
29 if (fc->no_getxattr)
30 return NULL;
31
32 if (type == ACL_TYPE_ACCESS)
33 name = XATTR_NAME_POSIX_ACL_ACCESS;
34 else if (type == ACL_TYPE_DEFAULT)
35 name = XATTR_NAME_POSIX_ACL_DEFAULT;
36 else
37 return ERR_PTR(-EOPNOTSUPP);
38
39 value = kmalloc(PAGE_SIZE, GFP_KERNEL);
40 if (!value)
41 return ERR_PTR(-ENOMEM);
42 size = fuse_getxattr(inode, name, value, PAGE_SIZE);
43 if (size > 0)
44 acl = posix_acl_from_xattr(fc->user_ns, value, size);
45 else if ((size == 0) || (size == -ENODATA) ||
46 (size == -EOPNOTSUPP && fc->no_getxattr))
47 acl = NULL;
48 else if (size == -ERANGE)
49 acl = ERR_PTR(-E2BIG);
50 else
51 acl = ERR_PTR(size);
52
53 kfree(value);
54 return acl;
55 }
56
57 static inline bool fuse_no_acl(const struct fuse_conn *fc,
58 const struct inode *inode)
59 {
60 /*
61 * Refuse interacting with POSIX ACLs for daemons that
62 * don't support FUSE_POSIX_ACL and are not mounted on
63 * the host to retain backwards compatibility.
64 */
65 return !fc->posix_acl && (i_user_ns(inode) != &init_user_ns);
66 }
67
68 struct posix_acl *fuse_get_acl(struct mnt_idmap *idmap,
69 struct dentry *dentry, int type)
70 {
71 struct inode *inode = d_inode(dentry);
72 struct fuse_conn *fc = get_fuse_conn(inode);
73
74 if (fuse_no_acl(fc, inode))
75 return ERR_PTR(-EOPNOTSUPP);
76
77 return __fuse_get_acl(fc, idmap, inode, type, false);
78 }
79
80 struct posix_acl *fuse_get_inode_acl(struct inode *inode, int type, bool rcu)
81 {
82 struct fuse_conn *fc = get_fuse_conn(inode);
83
84 /*
85 * FUSE daemons before FUSE_POSIX_ACL was introduced could get and set
86 * POSIX ACLs without them being used for permission checking by the
87 * vfs. Retain that behavior for backwards compatibility as there are
88 * filesystems that do all permission checking for acls in the daemon
89 * and not in the kernel.
90 */
91 if (!fc->posix_acl)
92 return NULL;
93
94 return __fuse_get_acl(fc, &nop_mnt_idmap, inode, type, rcu);
95 }
96
97 int fuse_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
98 struct posix_acl *acl, int type)
99 {
100 struct inode *inode = d_inode(dentry);
101 struct fuse_conn *fc = get_fuse_conn(inode);
102 const char *name;
103 int ret;
104
105 if (fuse_is_bad(inode))
106 return -EIO;
107
108 if (fc->no_setxattr || fuse_no_acl(fc, inode))
109 return -EOPNOTSUPP;
110
111 if (type == ACL_TYPE_ACCESS)
112 name = XATTR_NAME_POSIX_ACL_ACCESS;
113 else if (type == ACL_TYPE_DEFAULT)
114 name = XATTR_NAME_POSIX_ACL_DEFAULT;
115 else
116 return -EINVAL;
117
118 if (acl) {
119 unsigned int extra_flags = 0;
120 /*
121 * Fuse userspace is responsible for updating access
122 * permissions in the inode, if needed. fuse_setxattr
123 * invalidates the inode attributes, which will force
124 * them to be refreshed the next time they are used,
125 * and it also updates i_ctime.
126 */
127 size_t size = posix_acl_xattr_size(acl->a_count);
128 void *value;
129
130 if (size > PAGE_SIZE)
131 return -E2BIG;
132
133 value = kmalloc(size, GFP_KERNEL);
134 if (!value)
135 return -ENOMEM;
136
137 ret = posix_acl_to_xattr(fc->user_ns, acl, value, size);
138 if (ret < 0) {
139 kfree(value);
140 return ret;
141 }
142
143 /*
144 * Fuse daemons without FUSE_POSIX_ACL never changed the passed
145 * through POSIX ACLs. Such daemons don't expect setgid bits to
146 * be stripped.
147 */
148 if (fc->posix_acl &&
149 !in_group_or_capable(&nop_mnt_idmap, inode,
150 i_gid_into_vfsgid(&nop_mnt_idmap, inode)))
151 extra_flags |= FUSE_SETXATTR_ACL_KILL_SGID;
152
153 ret = fuse_setxattr(inode, name, value, size, 0, extra_flags);
154 kfree(value);
155 } else {
156 ret = fuse_removexattr(inode, name);
157 }
158
159 if (fc->posix_acl) {
160 /*
161 * Fuse daemons without FUSE_POSIX_ACL never cached POSIX ACLs
162 * and didn't invalidate attributes. Retain that behavior.
163 */
164 forget_all_cached_acls(inode);
165 fuse_invalidate_attr(inode);
166 }
167
168 return ret;
169 }
170
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