1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * fs/nfs_common/nfsacl.c
4 *
5 * Copyright (C) 2002-2003 Andreas Gruenbacher <agruen@suse.de>
6 */
7
8 /*
9 * The Solaris nfsacl protocol represents some ACLs slightly differently
10 * than POSIX 1003.1e draft 17 does (and we do):
11 *
12 * - Minimal ACLs always have an ACL_MASK entry, so they have
13 * four instead of three entries.
14 * - The ACL_MASK entry in such minimal ACLs always has the same
15 * permissions as the ACL_GROUP_OBJ entry. (In extended ACLs
16 * the ACL_MASK and ACL_GROUP_OBJ entries may differ.)
17 * - The identifier fields of the ACL_USER_OBJ and ACL_GROUP_OBJ
18 * entries contain the identifiers of the owner and owning group.
19 * (In POSIX ACLs we always set them to ACL_UNDEFINED_ID).
20 * - ACL entries in the kernel are kept sorted in ascending order
21 * of (e_tag, e_id). Solaris ACLs are unsorted.
22 */
23
24 #include <linux/module.h>
25 #include <linux/fs.h>
26 #include <linux/gfp.h>
27 #include <linux/sunrpc/xdr.h>
28 #include <linux/nfsacl.h>
29 #include <linux/nfs3.h>
30 #include <linux/sort.h>
31
32 MODULE_LICENSE("GPL");
33
34 struct nfsacl_encode_desc {
35 struct xdr_array2_desc desc;
36 unsigned int count;
37 struct posix_acl *acl;
38 int typeflag;
39 kuid_t uid;
40 kgid_t gid;
41 };
42
43 struct nfsacl_simple_acl {
44 struct posix_acl acl;
45 struct posix_acl_entry ace[4];
46 };
47
48 static int
xdr_nfsace_encode(struct xdr_array2_desc * desc,void * elem)49 xdr_nfsace_encode(struct xdr_array2_desc *desc, void *elem)
50 {
51 struct nfsacl_encode_desc *nfsacl_desc =
52 (struct nfsacl_encode_desc *) desc;
53 __be32 *p = elem;
54
55 struct posix_acl_entry *entry =
56 &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
57
58 *p++ = htonl(entry->e_tag | nfsacl_desc->typeflag);
59 switch(entry->e_tag) {
60 case ACL_USER_OBJ:
61 *p++ = htonl(from_kuid(&init_user_ns, nfsacl_desc->uid));
62 break;
63 case ACL_GROUP_OBJ:
64 *p++ = htonl(from_kgid(&init_user_ns, nfsacl_desc->gid));
65 break;
66 case ACL_USER:
67 *p++ = htonl(from_kuid(&init_user_ns, entry->e_uid));
68 break;
69 case ACL_GROUP:
70 *p++ = htonl(from_kgid(&init_user_ns, entry->e_gid));
71 break;
72 default: /* Solaris depends on that! */
73 *p++ = 0;
74 break;
75 }
76 *p++ = htonl(entry->e_perm & S_IRWXO);
77 return 0;
78 }
79
80 /**
81 * nfsacl_encode - Encode an NFSv3 ACL
82 *
83 * @buf: destination xdr_buf to contain XDR encoded ACL
84 * @base: byte offset in xdr_buf where XDR'd ACL begins
85 * @inode: inode of file whose ACL this is
86 * @acl: posix_acl to encode
87 * @encode_entries: whether to encode ACEs as well
88 * @typeflag: ACL type: NFS_ACL_DEFAULT or zero
89 *
90 * Returns size of encoded ACL in bytes or a negative errno value.
91 */
nfsacl_encode(struct xdr_buf * buf,unsigned int base,struct inode * inode,struct posix_acl * acl,int encode_entries,int typeflag)92 int nfsacl_encode(struct xdr_buf *buf, unsigned int base, struct inode *inode,
93 struct posix_acl *acl, int encode_entries, int typeflag)
94 {
95 int entries = (acl && acl->a_count) ? max_t(int, acl->a_count, 4) : 0;
96 struct nfsacl_encode_desc nfsacl_desc = {
97 .desc = {
98 .elem_size = 12,
99 .array_len = encode_entries ? entries : 0,
100 .xcode = xdr_nfsace_encode,
101 },
102 .acl = acl,
103 .typeflag = typeflag,
104 .uid = inode->i_uid,
105 .gid = inode->i_gid,
106 };
107 struct nfsacl_simple_acl aclbuf;
108 int err;
109
110 if (entries > NFS_ACL_MAX_ENTRIES ||
111 xdr_encode_word(buf, base, entries))
112 return -EINVAL;
113 if (encode_entries && acl && acl->a_count == 3) {
114 struct posix_acl *acl2 = &aclbuf.acl;
115
116 /* Avoid the use of posix_acl_alloc(). nfsacl_encode() is
117 * invoked in contexts where a memory allocation failure is
118 * fatal. Fortunately this fake ACL is small enough to
119 * construct on the stack. */
120 posix_acl_init(acl2, 4);
121
122 /* Insert entries in canonical order: other orders seem
123 to confuse Solaris VxFS. */
124 acl2->a_entries[0] = acl->a_entries[0]; /* ACL_USER_OBJ */
125 acl2->a_entries[1] = acl->a_entries[1]; /* ACL_GROUP_OBJ */
126 acl2->a_entries[2] = acl->a_entries[1]; /* ACL_MASK */
127 acl2->a_entries[2].e_tag = ACL_MASK;
128 acl2->a_entries[3] = acl->a_entries[2]; /* ACL_OTHER */
129 nfsacl_desc.acl = acl2;
130 }
131 err = xdr_encode_array2(buf, base + 4, &nfsacl_desc.desc);
132 if (!err)
133 err = 8 + nfsacl_desc.desc.elem_size *
134 nfsacl_desc.desc.array_len;
135 return err;
136 }
137 EXPORT_SYMBOL_GPL(nfsacl_encode);
138
139 struct nfsacl_decode_desc {
140 struct xdr_array2_desc desc;
141 unsigned int count;
142 struct posix_acl *acl;
143 };
144
145 static int
xdr_nfsace_decode(struct xdr_array2_desc * desc,void * elem)146 xdr_nfsace_decode(struct xdr_array2_desc *desc, void *elem)
147 {
148 struct nfsacl_decode_desc *nfsacl_desc =
149 (struct nfsacl_decode_desc *) desc;
150 __be32 *p = elem;
151 struct posix_acl_entry *entry;
152 unsigned int id;
153
154 if (!nfsacl_desc->acl) {
155 if (desc->array_len > NFS_ACL_MAX_ENTRIES)
156 return -EINVAL;
157 nfsacl_desc->acl = posix_acl_alloc(desc->array_len, GFP_KERNEL);
158 if (!nfsacl_desc->acl)
159 return -ENOMEM;
160 nfsacl_desc->count = 0;
161 }
162
163 entry = &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
164 entry->e_tag = ntohl(*p++) & ~NFS_ACL_DEFAULT;
165 id = ntohl(*p++);
166 entry->e_perm = ntohl(*p++);
167
168 switch(entry->e_tag) {
169 case ACL_USER:
170 entry->e_uid = make_kuid(&init_user_ns, id);
171 if (!uid_valid(entry->e_uid))
172 return -EINVAL;
173 break;
174 case ACL_GROUP:
175 entry->e_gid = make_kgid(&init_user_ns, id);
176 if (!gid_valid(entry->e_gid))
177 return -EINVAL;
178 break;
179 case ACL_USER_OBJ:
180 case ACL_GROUP_OBJ:
181 case ACL_OTHER:
182 if (entry->e_perm & ~S_IRWXO)
183 return -EINVAL;
184 break;
185 case ACL_MASK:
186 /* Solaris sometimes sets additional bits in the mask */
187 entry->e_perm &= S_IRWXO;
188 break;
189 default:
190 return -EINVAL;
191 }
192
193 return 0;
194 }
195
196 static int
cmp_acl_entry(const void * x,const void * y)197 cmp_acl_entry(const void *x, const void *y)
198 {
199 const struct posix_acl_entry *a = x, *b = y;
200
201 if (a->e_tag != b->e_tag)
202 return a->e_tag - b->e_tag;
203 else if ((a->e_tag == ACL_USER) && uid_gt(a->e_uid, b->e_uid))
204 return 1;
205 else if ((a->e_tag == ACL_USER) && uid_lt(a->e_uid, b->e_uid))
206 return -1;
207 else if ((a->e_tag == ACL_GROUP) && gid_gt(a->e_gid, b->e_gid))
208 return 1;
209 else if ((a->e_tag == ACL_GROUP) && gid_lt(a->e_gid, b->e_gid))
210 return -1;
211 else
212 return 0;
213 }
214
215 /*
216 * Convert from a Solaris ACL to a POSIX 1003.1e draft 17 ACL.
217 */
218 static int
posix_acl_from_nfsacl(struct posix_acl * acl)219 posix_acl_from_nfsacl(struct posix_acl *acl)
220 {
221 struct posix_acl_entry *pa, *pe,
222 *group_obj = NULL, *mask = NULL;
223
224 if (!acl)
225 return 0;
226
227 sort(acl->a_entries, acl->a_count, sizeof(struct posix_acl_entry),
228 cmp_acl_entry, NULL);
229
230 /* Find the ACL_GROUP_OBJ and ACL_MASK entries. */
231 FOREACH_ACL_ENTRY(pa, acl, pe) {
232 switch(pa->e_tag) {
233 case ACL_USER_OBJ:
234 break;
235 case ACL_GROUP_OBJ:
236 group_obj = pa;
237 break;
238 case ACL_MASK:
239 mask = pa;
240 fallthrough;
241 case ACL_OTHER:
242 break;
243 }
244 }
245 if (acl->a_count == 4 && group_obj && mask &&
246 mask->e_perm == group_obj->e_perm) {
247 /* remove bogus ACL_MASK entry */
248 memmove(mask, mask+1, (3 - (mask - acl->a_entries)) *
249 sizeof(struct posix_acl_entry));
250 acl->a_count = 3;
251 }
252 return 0;
253 }
254
255 /**
256 * nfsacl_decode - Decode an NFSv3 ACL
257 *
258 * @buf: xdr_buf containing XDR'd ACL data to decode
259 * @base: byte offset in xdr_buf where XDR'd ACL begins
260 * @aclcnt: count of ACEs in decoded posix_acl
261 * @pacl: buffer in which to place decoded posix_acl
262 *
263 * Returns the length of the decoded ACL in bytes, or a negative errno value.
264 */
nfsacl_decode(struct xdr_buf * buf,unsigned int base,unsigned int * aclcnt,struct posix_acl ** pacl)265 int nfsacl_decode(struct xdr_buf *buf, unsigned int base, unsigned int *aclcnt,
266 struct posix_acl **pacl)
267 {
268 struct nfsacl_decode_desc nfsacl_desc = {
269 .desc = {
270 .elem_size = 12,
271 .xcode = pacl ? xdr_nfsace_decode : NULL,
272 },
273 };
274 u32 entries;
275 int err;
276
277 if (xdr_decode_word(buf, base, &entries) ||
278 entries > NFS_ACL_MAX_ENTRIES)
279 return -EINVAL;
280 nfsacl_desc.desc.array_maxlen = entries;
281 err = xdr_decode_array2(buf, base + 4, &nfsacl_desc.desc);
282 if (err)
283 return err;
284 if (pacl) {
285 if (entries != nfsacl_desc.desc.array_len ||
286 posix_acl_from_nfsacl(nfsacl_desc.acl) != 0) {
287 posix_acl_release(nfsacl_desc.acl);
288 return -EINVAL;
289 }
290 *pacl = nfsacl_desc.acl;
291 }
292 if (aclcnt)
293 *aclcnt = entries;
294 return 8 + nfsacl_desc.desc.elem_size *
295 nfsacl_desc.desc.array_len;
296 }
297 EXPORT_SYMBOL_GPL(nfsacl_decode);
298