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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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