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