1 /*
2 * linux/fs/posix_acl.c
3 *
4 * Copyright (C) 2002 by Andreas Gruenbacher <a.gruenbacher@computer.org>
5 *
6 * Fixes from William Schumacher incorporated on 15 March 2001.
7 * (Reported by Charles Bertsch, <CBertsch@microtest.com>).
8 */
9
10 /*
11 * This file contains generic functions for manipulating
12 * POSIX 1003.1e draft standard 17 ACLs.
13 */
14
15 #include <linux/kernel.h>
16 #include <linux/slab.h>
17 #include <asm/atomic.h>
18 #include <linux/fs.h>
19 #include <linux/sched.h>
20 #include <linux/posix_acl.h>
21 #include <linux/module.h>
22
23 #include <linux/errno.h>
24
25 EXPORT_SYMBOL(posix_acl_alloc);
26 EXPORT_SYMBOL(posix_acl_clone);
27 EXPORT_SYMBOL(posix_acl_valid);
28 EXPORT_SYMBOL(posix_acl_equiv_mode);
29 EXPORT_SYMBOL(posix_acl_from_mode);
30 EXPORT_SYMBOL(posix_acl_create_masq);
31 EXPORT_SYMBOL(posix_acl_chmod_masq);
32 EXPORT_SYMBOL(posix_acl_permission);
33
34 /*
35 * Allocate a new ACL with the specified number of entries.
36 */
37 struct posix_acl *
38 posix_acl_alloc(int count, gfp_t flags)
39 {
40 const size_t size = sizeof(struct posix_acl) +
41 count * sizeof(struct posix_acl_entry);
42 struct posix_acl *acl = kmalloc(size, flags);
43 if (acl) {
44 atomic_set(&acl->a_refcount, 1);
45 acl->a_count = count;
46 }
47 return acl;
48 }
49
50 /*
51 * Clone an ACL.
52 */
53 struct posix_acl *
54 posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
55 {
56 struct posix_acl *clone = NULL;
57
58 if (acl) {
59 int size = sizeof(struct posix_acl) + acl->a_count *
60 sizeof(struct posix_acl_entry);
61 clone = kmemdup(acl, size, flags);
62 if (clone)
63 atomic_set(&clone->a_refcount, 1);
64 }
65 return clone;
66 }
67
68 /*
69 * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
70 */
71 int
72 posix_acl_valid(const struct posix_acl *acl)
73 {
74 const struct posix_acl_entry *pa, *pe;
75 int state = ACL_USER_OBJ;
76 unsigned int id = 0; /* keep gcc happy */
77 int needs_mask = 0;
78
79 FOREACH_ACL_ENTRY(pa, acl, pe) {
80 if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
81 return -EINVAL;
82 switch (pa->e_tag) {
83 case ACL_USER_OBJ:
84 if (state == ACL_USER_OBJ) {
85 id = 0;
86 state = ACL_USER;
87 break;
88 }
89 return -EINVAL;
90
91 case ACL_USER:
92 if (state != ACL_USER)
93 return -EINVAL;
94 if (pa->e_id == ACL_UNDEFINED_ID ||
95 pa->e_id < id)
96 return -EINVAL;
97 id = pa->e_id + 1;
98 needs_mask = 1;
99 break;
100
101 case ACL_GROUP_OBJ:
102 if (state == ACL_USER) {
103 id = 0;
104 state = ACL_GROUP;
105 break;
106 }
107 return -EINVAL;
108
109 case ACL_GROUP:
110 if (state != ACL_GROUP)
111 return -EINVAL;
112 if (pa->e_id == ACL_UNDEFINED_ID ||
113 pa->e_id < id)
114 return -EINVAL;
115 id = pa->e_id + 1;
116 needs_mask = 1;
117 break;
118
119 case ACL_MASK:
120 if (state != ACL_GROUP)
121 return -EINVAL;
122 state = ACL_OTHER;
123 break;
124
125 case ACL_OTHER:
126 if (state == ACL_OTHER ||
127 (state == ACL_GROUP && !needs_mask)) {
128 state = 0;
129 break;
130 }
131 return -EINVAL;
132
133 default:
134 return -EINVAL;
135 }
136 }
137 if (state == 0)
138 return 0;
139 return -EINVAL;
140 }
141
142 /*
143 * Returns 0 if the acl can be exactly represented in the traditional
144 * file mode permission bits, or else 1. Returns -E... on error.
145 */
146 int
147 posix_acl_equiv_mode(const struct posix_acl *acl, mode_t *mode_p)
148 {
149 const struct posix_acl_entry *pa, *pe;
150 mode_t mode = 0;
151 int not_equiv = 0;
152
153 FOREACH_ACL_ENTRY(pa, acl, pe) {
154 switch (pa->e_tag) {
155 case ACL_USER_OBJ:
156 mode |= (pa->e_perm & S_IRWXO) << 6;
157 break;
158 case ACL_GROUP_OBJ:
159 mode |= (pa->e_perm & S_IRWXO) << 3;
160 break;
161 case ACL_OTHER:
162 mode |= pa->e_perm & S_IRWXO;
163 break;
164 case ACL_MASK:
165 mode = (mode & ~S_IRWXG) |
166 ((pa->e_perm & S_IRWXO) << 3);
167 not_equiv = 1;
168 break;
169 case ACL_USER:
170 case ACL_GROUP:
171 not_equiv = 1;
172 break;
173 default:
174 return -EINVAL;
175 }
176 }
177 if (mode_p)
178 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
179 return not_equiv;
180 }
181
182 /*
183 * Create an ACL representing the file mode permission bits of an inode.
184 */
185 struct posix_acl *
186 posix_acl_from_mode(mode_t mode, gfp_t flags)
187 {
188 struct posix_acl *acl = posix_acl_alloc(3, flags);
189 if (!acl)
190 return ERR_PTR(-ENOMEM);
191
192 acl->a_entries[0].e_tag = ACL_USER_OBJ;
193 acl->a_entries[0].e_id = ACL_UNDEFINED_ID;
194 acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
195
196 acl->a_entries[1].e_tag = ACL_GROUP_OBJ;
197 acl->a_entries[1].e_id = ACL_UNDEFINED_ID;
198 acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
199
200 acl->a_entries[2].e_tag = ACL_OTHER;
201 acl->a_entries[2].e_id = ACL_UNDEFINED_ID;
202 acl->a_entries[2].e_perm = (mode & S_IRWXO);
203 return acl;
204 }
205
206 /*
207 * Return 0 if current is granted want access to the inode
208 * by the acl. Returns -E... otherwise.
209 */
210 int
211 posix_acl_permission(struct inode *inode, const struct posix_acl *acl, int want)
212 {
213 const struct posix_acl_entry *pa, *pe, *mask_obj;
214 int found = 0;
215
216 FOREACH_ACL_ENTRY(pa, acl, pe) {
217 switch(pa->e_tag) {
218 case ACL_USER_OBJ:
219 /* (May have been checked already) */
220 if (inode->i_uid == current->fsuid)
221 goto check_perm;
222 break;
223 case ACL_USER:
224 if (pa->e_id == current->fsuid)
225 goto mask;
226 break;
227 case ACL_GROUP_OBJ:
228 if (in_group_p(inode->i_gid)) {
229 found = 1;
230 if ((pa->e_perm & want) == want)
231 goto mask;
232 }
233 break;
234 case ACL_GROUP:
235 if (in_group_p(pa->e_id)) {
236 found = 1;
237 if ((pa->e_perm & want) == want)
238 goto mask;
239 }
240 break;
241 case ACL_MASK:
242 break;
243 case ACL_OTHER:
244 if (found)
245 return -EACCES;
246 else
247 goto check_perm;
248 default:
249 return -EIO;
250 }
251 }
252 return -EIO;
253
254 mask:
255 for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
256 if (mask_obj->e_tag == ACL_MASK) {
257 if ((pa->e_perm & mask_obj->e_perm & want) == want)
258 return 0;
259 return -EACCES;
260 }
261 }
262
263 check_perm:
264 if ((pa->e_perm & want) == want)
265 return 0;
266 return -EACCES;
267 }
268
269 /*
270 * Modify acl when creating a new inode. The caller must ensure the acl is
271 * only referenced once.
272 *
273 * mode_p initially must contain the mode parameter to the open() / creat()
274 * system calls. All permissions that are not granted by the acl are removed.
275 * The permissions in the acl are changed to reflect the mode_p parameter.
276 */
277 int
278 posix_acl_create_masq(struct posix_acl *acl, mode_t *mode_p)
279 {
280 struct posix_acl_entry *pa, *pe;
281 struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
282 mode_t mode = *mode_p;
283 int not_equiv = 0;
284
285 /* assert(atomic_read(acl->a_refcount) == 1); */
286
287 FOREACH_ACL_ENTRY(pa, acl, pe) {
288 switch(pa->e_tag) {
289 case ACL_USER_OBJ:
290 pa->e_perm &= (mode >> 6) | ~S_IRWXO;
291 mode &= (pa->e_perm << 6) | ~S_IRWXU;
292 break;
293
294 case ACL_USER:
295 case ACL_GROUP:
296 not_equiv = 1;
297 break;
298
299 case ACL_GROUP_OBJ:
300 group_obj = pa;
301 break;
302
303 case ACL_OTHER:
304 pa->e_perm &= mode | ~S_IRWXO;
305 mode &= pa->e_perm | ~S_IRWXO;
306 break;
307
308 case ACL_MASK:
309 mask_obj = pa;
310 not_equiv = 1;
311 break;
312
313 default:
314 return -EIO;
315 }
316 }
317
318 if (mask_obj) {
319 mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
320 mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
321 } else {
322 if (!group_obj)
323 return -EIO;
324 group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
325 mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
326 }
327
328 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
329 return not_equiv;
330 }
331
332 /*
333 * Modify the ACL for the chmod syscall.
334 */
335 int
336 posix_acl_chmod_masq(struct posix_acl *acl, mode_t mode)
337 {
338 struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
339 struct posix_acl_entry *pa, *pe;
340
341 /* assert(atomic_read(acl->a_refcount) == 1); */
342
343 FOREACH_ACL_ENTRY(pa, acl, pe) {
344 switch(pa->e_tag) {
345 case ACL_USER_OBJ:
346 pa->e_perm = (mode & S_IRWXU) >> 6;
347 break;
348
349 case ACL_USER:
350 case ACL_GROUP:
351 break;
352
353 case ACL_GROUP_OBJ:
354 group_obj = pa;
355 break;
356
357 case ACL_MASK:
358 mask_obj = pa;
359 break;
360
361 case ACL_OTHER:
362 pa->e_perm = (mode & S_IRWXO);
363 break;
364
365 default:
366 return -EIO;
367 }
368 }
369
370 if (mask_obj) {
371 mask_obj->e_perm = (mode & S_IRWXG) >> 3;
372 } else {
373 if (!group_obj)
374 return -EIO;
375 group_obj->e_perm = (mode & S_IRWXG) >> 3;
376 }
377
378 return 0;
379 }
380
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