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1 | /* |
2 | * security/tomoyo/gc.c |
3 | * |
4 | * Implementation of the Domain-Based Mandatory Access Control. |
5 | * |
6 | * Copyright (C) 2005-2010 NTT DATA CORPORATION |
7 | * |
8 | */ |
9 | |
10 | #include "common.h" |
11 | #include <linux/kthread.h> |
12 | #include <linux/slab.h> |
13 | |
14 | struct tomoyo_gc { |
15 | struct list_head list; |
16 | int type; |
17 | struct list_head *element; |
18 | }; |
19 | static LIST_HEAD(tomoyo_gc_queue); |
20 | static DEFINE_MUTEX(tomoyo_gc_mutex); |
21 | |
22 | /* Caller holds tomoyo_policy_lock mutex. */ |
23 | static bool tomoyo_add_to_gc(const int type, struct list_head *element) |
24 | { |
25 | struct tomoyo_gc *entry = kzalloc(sizeof(*entry), GFP_ATOMIC); |
26 | if (!entry) |
27 | return false; |
28 | entry->type = type; |
29 | entry->element = element; |
30 | list_add(&entry->list, &tomoyo_gc_queue); |
31 | list_del_rcu(element); |
32 | return true; |
33 | } |
34 | |
35 | static void tomoyo_del_allow_read(struct list_head *element) |
36 | { |
37 | struct tomoyo_readable_file *ptr = |
38 | container_of(element, typeof(*ptr), head.list); |
39 | tomoyo_put_name(ptr->filename); |
40 | } |
41 | |
42 | static void tomoyo_del_file_pattern(struct list_head *element) |
43 | { |
44 | struct tomoyo_no_pattern *ptr = |
45 | container_of(element, typeof(*ptr), head.list); |
46 | tomoyo_put_name(ptr->pattern); |
47 | } |
48 | |
49 | static void tomoyo_del_no_rewrite(struct list_head *element) |
50 | { |
51 | struct tomoyo_no_rewrite *ptr = |
52 | container_of(element, typeof(*ptr), head.list); |
53 | tomoyo_put_name(ptr->pattern); |
54 | } |
55 | |
56 | static void tomoyo_del_transition_control(struct list_head *element) |
57 | { |
58 | struct tomoyo_transition_control *ptr = |
59 | container_of(element, typeof(*ptr), head.list); |
60 | tomoyo_put_name(ptr->domainname); |
61 | tomoyo_put_name(ptr->program); |
62 | } |
63 | |
64 | static void tomoyo_del_aggregator(struct list_head *element) |
65 | { |
66 | struct tomoyo_aggregator *ptr = |
67 | container_of(element, typeof(*ptr), head.list); |
68 | tomoyo_put_name(ptr->original_name); |
69 | tomoyo_put_name(ptr->aggregated_name); |
70 | } |
71 | |
72 | static void tomoyo_del_manager(struct list_head *element) |
73 | { |
74 | struct tomoyo_manager *ptr = |
75 | container_of(element, typeof(*ptr), head.list); |
76 | tomoyo_put_name(ptr->manager); |
77 | } |
78 | |
79 | static void tomoyo_del_acl(struct list_head *element) |
80 | { |
81 | struct tomoyo_acl_info *acl = |
82 | container_of(element, typeof(*acl), list); |
83 | switch (acl->type) { |
84 | case TOMOYO_TYPE_PATH_ACL: |
85 | { |
86 | struct tomoyo_path_acl *entry |
87 | = container_of(acl, typeof(*entry), head); |
88 | tomoyo_put_name_union(&entry->name); |
89 | } |
90 | break; |
91 | case TOMOYO_TYPE_PATH2_ACL: |
92 | { |
93 | struct tomoyo_path2_acl *entry |
94 | = container_of(acl, typeof(*entry), head); |
95 | tomoyo_put_name_union(&entry->name1); |
96 | tomoyo_put_name_union(&entry->name2); |
97 | } |
98 | break; |
99 | case TOMOYO_TYPE_PATH_NUMBER_ACL: |
100 | { |
101 | struct tomoyo_path_number_acl *entry |
102 | = container_of(acl, typeof(*entry), head); |
103 | tomoyo_put_name_union(&entry->name); |
104 | tomoyo_put_number_union(&entry->number); |
105 | } |
106 | break; |
107 | case TOMOYO_TYPE_MKDEV_ACL: |
108 | { |
109 | struct tomoyo_mkdev_acl *entry |
110 | = container_of(acl, typeof(*entry), head); |
111 | tomoyo_put_name_union(&entry->name); |
112 | tomoyo_put_number_union(&entry->mode); |
113 | tomoyo_put_number_union(&entry->major); |
114 | tomoyo_put_number_union(&entry->minor); |
115 | } |
116 | break; |
117 | case TOMOYO_TYPE_MOUNT_ACL: |
118 | { |
119 | struct tomoyo_mount_acl *entry |
120 | = container_of(acl, typeof(*entry), head); |
121 | tomoyo_put_name_union(&entry->dev_name); |
122 | tomoyo_put_name_union(&entry->dir_name); |
123 | tomoyo_put_name_union(&entry->fs_type); |
124 | tomoyo_put_number_union(&entry->flags); |
125 | } |
126 | break; |
127 | } |
128 | } |
129 | |
130 | static bool tomoyo_del_domain(struct list_head *element) |
131 | { |
132 | struct tomoyo_domain_info *domain = |
133 | container_of(element, typeof(*domain), list); |
134 | struct tomoyo_acl_info *acl; |
135 | struct tomoyo_acl_info *tmp; |
136 | /* |
137 | * Since we don't protect whole execve() operation using SRCU, |
138 | * we need to recheck domain->users at this point. |
139 | * |
140 | * (1) Reader starts SRCU section upon execve(). |
141 | * (2) Reader traverses tomoyo_domain_list and finds this domain. |
142 | * (3) Writer marks this domain as deleted. |
143 | * (4) Garbage collector removes this domain from tomoyo_domain_list |
144 | * because this domain is marked as deleted and used by nobody. |
145 | * (5) Reader saves reference to this domain into |
146 | * "struct linux_binprm"->cred->security . |
147 | * (6) Reader finishes SRCU section, although execve() operation has |
148 | * not finished yet. |
149 | * (7) Garbage collector waits for SRCU synchronization. |
150 | * (8) Garbage collector kfree() this domain because this domain is |
151 | * used by nobody. |
152 | * (9) Reader finishes execve() operation and restores this domain from |
153 | * "struct linux_binprm"->cred->security. |
154 | * |
155 | * By updating domain->users at (5), we can solve this race problem |
156 | * by rechecking domain->users at (8). |
157 | */ |
158 | if (atomic_read(&domain->users)) |
159 | return false; |
160 | list_for_each_entry_safe(acl, tmp, &domain->acl_info_list, list) { |
161 | tomoyo_del_acl(&acl->list); |
162 | tomoyo_memory_free(acl); |
163 | } |
164 | tomoyo_put_name(domain->domainname); |
165 | return true; |
166 | } |
167 | |
168 | |
169 | static void tomoyo_del_name(struct list_head *element) |
170 | { |
171 | const struct tomoyo_name *ptr = |
172 | container_of(element, typeof(*ptr), list); |
173 | } |
174 | |
175 | static void tomoyo_del_path_group(struct list_head *element) |
176 | { |
177 | struct tomoyo_path_group *member = |
178 | container_of(element, typeof(*member), head.list); |
179 | tomoyo_put_name(member->member_name); |
180 | } |
181 | |
182 | static void tomoyo_del_group(struct list_head *element) |
183 | { |
184 | struct tomoyo_group *group = |
185 | container_of(element, typeof(*group), list); |
186 | tomoyo_put_name(group->group_name); |
187 | } |
188 | |
189 | static void tomoyo_del_number_group(struct list_head *element) |
190 | { |
191 | struct tomoyo_number_group *member = |
192 | container_of(element, typeof(*member), head.list); |
193 | } |
194 | |
195 | static bool tomoyo_collect_member(struct list_head *member_list, int id) |
196 | { |
197 | struct tomoyo_acl_head *member; |
198 | list_for_each_entry(member, member_list, list) { |
199 | if (!member->is_deleted) |
200 | continue; |
201 | if (!tomoyo_add_to_gc(id, &member->list)) |
202 | return false; |
203 | } |
204 | return true; |
205 | } |
206 | |
207 | static bool tomoyo_collect_acl(struct tomoyo_domain_info *domain) |
208 | { |
209 | struct tomoyo_acl_info *acl; |
210 | list_for_each_entry(acl, &domain->acl_info_list, list) { |
211 | if (!acl->is_deleted) |
212 | continue; |
213 | if (!tomoyo_add_to_gc(TOMOYO_ID_ACL, &acl->list)) |
214 | return false; |
215 | } |
216 | return true; |
217 | } |
218 | |
219 | static void tomoyo_collect_entry(void) |
220 | { |
221 | int i; |
222 | if (mutex_lock_interruptible(&tomoyo_policy_lock)) |
223 | return; |
224 | for (i = 0; i < TOMOYO_MAX_POLICY; i++) { |
225 | if (!tomoyo_collect_member(&tomoyo_policy_list[i], i)) |
226 | goto unlock; |
227 | } |
228 | { |
229 | struct tomoyo_domain_info *domain; |
230 | list_for_each_entry_rcu(domain, &tomoyo_domain_list, list) { |
231 | if (!tomoyo_collect_acl(domain)) |
232 | goto unlock; |
233 | if (!domain->is_deleted || atomic_read(&domain->users)) |
234 | continue; |
235 | /* |
236 | * Nobody is referring this domain. But somebody may |
237 | * refer this domain after successful execve(). |
238 | * We recheck domain->users after SRCU synchronization. |
239 | */ |
240 | if (!tomoyo_add_to_gc(TOMOYO_ID_DOMAIN, &domain->list)) |
241 | goto unlock; |
242 | } |
243 | } |
244 | for (i = 0; i < TOMOYO_MAX_HASH; i++) { |
245 | struct tomoyo_name *ptr; |
246 | list_for_each_entry_rcu(ptr, &tomoyo_name_list[i], list) { |
247 | if (atomic_read(&ptr->users)) |
248 | continue; |
249 | if (!tomoyo_add_to_gc(TOMOYO_ID_NAME, &ptr->list)) |
250 | goto unlock; |
251 | } |
252 | } |
253 | for (i = 0; i < TOMOYO_MAX_GROUP; i++) { |
254 | struct list_head *list = &tomoyo_group_list[i]; |
255 | int id; |
256 | struct tomoyo_group *group; |
257 | switch (i) { |
258 | case 0: |
259 | id = TOMOYO_ID_PATH_GROUP; |
260 | break; |
261 | default: |
262 | id = TOMOYO_ID_NUMBER_GROUP; |
263 | break; |
264 | } |
265 | list_for_each_entry(group, list, list) { |
266 | if (!tomoyo_collect_member(&group->member_list, id)) |
267 | goto unlock; |
268 | if (!list_empty(&group->member_list) || |
269 | atomic_read(&group->users)) |
270 | continue; |
271 | if (!tomoyo_add_to_gc(TOMOYO_ID_GROUP, &group->list)) |
272 | goto unlock; |
273 | } |
274 | } |
275 | unlock: |
276 | mutex_unlock(&tomoyo_policy_lock); |
277 | } |
278 | |
279 | static void tomoyo_kfree_entry(void) |
280 | { |
281 | struct tomoyo_gc *p; |
282 | struct tomoyo_gc *tmp; |
283 | |
284 | list_for_each_entry_safe(p, tmp, &tomoyo_gc_queue, list) { |
285 | struct list_head *element = p->element; |
286 | switch (p->type) { |
287 | case TOMOYO_ID_TRANSITION_CONTROL: |
288 | tomoyo_del_transition_control(element); |
289 | break; |
290 | case TOMOYO_ID_AGGREGATOR: |
291 | tomoyo_del_aggregator(element); |
292 | break; |
293 | case TOMOYO_ID_GLOBALLY_READABLE: |
294 | tomoyo_del_allow_read(element); |
295 | break; |
296 | case TOMOYO_ID_PATTERN: |
297 | tomoyo_del_file_pattern(element); |
298 | break; |
299 | case TOMOYO_ID_NO_REWRITE: |
300 | tomoyo_del_no_rewrite(element); |
301 | break; |
302 | case TOMOYO_ID_MANAGER: |
303 | tomoyo_del_manager(element); |
304 | break; |
305 | case TOMOYO_ID_NAME: |
306 | tomoyo_del_name(element); |
307 | break; |
308 | case TOMOYO_ID_ACL: |
309 | tomoyo_del_acl(element); |
310 | break; |
311 | case TOMOYO_ID_DOMAIN: |
312 | if (!tomoyo_del_domain(element)) |
313 | continue; |
314 | break; |
315 | case TOMOYO_ID_PATH_GROUP: |
316 | tomoyo_del_path_group(element); |
317 | break; |
318 | case TOMOYO_ID_GROUP: |
319 | tomoyo_del_group(element); |
320 | break; |
321 | case TOMOYO_ID_NUMBER_GROUP: |
322 | tomoyo_del_number_group(element); |
323 | break; |
324 | } |
325 | tomoyo_memory_free(element); |
326 | list_del(&p->list); |
327 | kfree(p); |
328 | } |
329 | } |
330 | |
331 | static int tomoyo_gc_thread(void *unused) |
332 | { |
333 | daemonize("GC for TOMOYO"); |
334 | if (mutex_trylock(&tomoyo_gc_mutex)) { |
335 | int i; |
336 | for (i = 0; i < 10; i++) { |
337 | tomoyo_collect_entry(); |
338 | if (list_empty(&tomoyo_gc_queue)) |
339 | break; |
340 | synchronize_srcu(&tomoyo_ss); |
341 | tomoyo_kfree_entry(); |
342 | } |
343 | mutex_unlock(&tomoyo_gc_mutex); |
344 | } |
345 | do_exit(0); |
346 | } |
347 | |
348 | void tomoyo_run_gc(void) |
349 | { |
350 | struct task_struct *task = kthread_create(tomoyo_gc_thread, NULL, |
351 | "GC for TOMOYO"); |
352 | if (!IS_ERR(task)) |
353 | wake_up_process(task); |
354 | } |
355 |
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