f2295c65f1e42eaa0b61c14143bbd8bc33cd1fae
[linux-2.6.git] / security / tomoyo / gc.c
1 /*
2  * security/tomoyo/gc.c
3  *
4  * Copyright (C) 2005-2011  NTT DATA CORPORATION
5  */
6
7 #include "common.h"
8 #include <linux/kthread.h>
9 #include <linux/slab.h>
10
11 /* The list for "struct tomoyo_io_buffer". */
12 static LIST_HEAD(tomoyo_io_buffer_list);
13 /* Lock for protecting tomoyo_io_buffer_list. */
14 static DEFINE_SPINLOCK(tomoyo_io_buffer_list_lock);
15
16 /**
17  * tomoyo_struct_used_by_io_buffer - Check whether the list element is used by /sys/kernel/security/tomoyo/ users or not.
18  *
19  * @element: Pointer to "struct list_head".
20  *
21  * Returns true if @element is used by /sys/kernel/security/tomoyo/ users,
22  * false otherwise.
23  */
24 static bool tomoyo_struct_used_by_io_buffer(const struct list_head *element)
25 {
26         struct tomoyo_io_buffer *head;
27         bool in_use = false;
28
29         spin_lock(&tomoyo_io_buffer_list_lock);
30         list_for_each_entry(head, &tomoyo_io_buffer_list, list) {
31                 head->users++;
32                 spin_unlock(&tomoyo_io_buffer_list_lock);
33                 mutex_lock(&head->io_sem);
34                 if (head->r.domain == element || head->r.group == element ||
35                     head->r.acl == element || &head->w.domain->list == element)
36                         in_use = true;
37                 mutex_unlock(&head->io_sem);
38                 spin_lock(&tomoyo_io_buffer_list_lock);
39                 head->users--;
40                 if (in_use)
41                         break;
42         }
43         spin_unlock(&tomoyo_io_buffer_list_lock);
44         return in_use;
45 }
46
47 /**
48  * tomoyo_name_used_by_io_buffer - Check whether the string is used by /sys/kernel/security/tomoyo/ users or not.
49  *
50  * @string: String to check.
51  *
52  * Returns true if @string is used by /sys/kernel/security/tomoyo/ users,
53  * false otherwise.
54  */
55 static bool tomoyo_name_used_by_io_buffer(const char *string)
56 {
57         struct tomoyo_io_buffer *head;
58         const size_t size = strlen(string) + 1;
59         bool in_use = false;
60
61         spin_lock(&tomoyo_io_buffer_list_lock);
62         list_for_each_entry(head, &tomoyo_io_buffer_list, list) {
63                 int i;
64                 head->users++;
65                 spin_unlock(&tomoyo_io_buffer_list_lock);
66                 mutex_lock(&head->io_sem);
67                 for (i = 0; i < TOMOYO_MAX_IO_READ_QUEUE; i++) {
68                         const char *w = head->r.w[i];
69                         if (w < string || w > string + size)
70                                 continue;
71                         in_use = true;
72                         break;
73                 }
74                 mutex_unlock(&head->io_sem);
75                 spin_lock(&tomoyo_io_buffer_list_lock);
76                 head->users--;
77                 if (in_use)
78                         break;
79         }
80         spin_unlock(&tomoyo_io_buffer_list_lock);
81         return in_use;
82 }
83
84 /**
85  * tomoyo_del_transition_control - Delete members in "struct tomoyo_transition_control".
86  *
87  * @element: Pointer to "struct list_head".
88  *
89  * Returns nothing.
90  */
91 static inline void tomoyo_del_transition_control(struct list_head *element)
92 {
93         struct tomoyo_transition_control *ptr =
94                 container_of(element, typeof(*ptr), head.list);
95         tomoyo_put_name(ptr->domainname);
96         tomoyo_put_name(ptr->program);
97 }
98
99 /**
100  * tomoyo_del_aggregator - Delete members in "struct tomoyo_aggregator".
101  *
102  * @element: Pointer to "struct list_head".
103  *
104  * Returns nothing.
105  */
106 static inline void tomoyo_del_aggregator(struct list_head *element)
107 {
108         struct tomoyo_aggregator *ptr =
109                 container_of(element, typeof(*ptr), head.list);
110         tomoyo_put_name(ptr->original_name);
111         tomoyo_put_name(ptr->aggregated_name);
112 }
113
114 /**
115  * tomoyo_del_manager - Delete members in "struct tomoyo_manager".
116  *
117  * @element: Pointer to "struct list_head".
118  *
119  * Returns nothing.
120  */
121 static inline void tomoyo_del_manager(struct list_head *element)
122 {
123         struct tomoyo_manager *ptr =
124                 container_of(element, typeof(*ptr), head.list);
125         tomoyo_put_name(ptr->manager);
126 }
127
128 /**
129  * tomoyo_del_acl - Delete members in "struct tomoyo_acl_info".
130  *
131  * @element: Pointer to "struct list_head".
132  *
133  * Returns nothing.
134  */
135 static void tomoyo_del_acl(struct list_head *element)
136 {
137         struct tomoyo_acl_info *acl =
138                 container_of(element, typeof(*acl), list);
139         tomoyo_put_condition(acl->cond);
140         switch (acl->type) {
141         case TOMOYO_TYPE_PATH_ACL:
142                 {
143                         struct tomoyo_path_acl *entry
144                                 = container_of(acl, typeof(*entry), head);
145                         tomoyo_put_name_union(&entry->name);
146                 }
147                 break;
148         case TOMOYO_TYPE_PATH2_ACL:
149                 {
150                         struct tomoyo_path2_acl *entry
151                                 = container_of(acl, typeof(*entry), head);
152                         tomoyo_put_name_union(&entry->name1);
153                         tomoyo_put_name_union(&entry->name2);
154                 }
155                 break;
156         case TOMOYO_TYPE_PATH_NUMBER_ACL:
157                 {
158                         struct tomoyo_path_number_acl *entry
159                                 = container_of(acl, typeof(*entry), head);
160                         tomoyo_put_name_union(&entry->name);
161                         tomoyo_put_number_union(&entry->number);
162                 }
163                 break;
164         case TOMOYO_TYPE_MKDEV_ACL:
165                 {
166                         struct tomoyo_mkdev_acl *entry
167                                 = container_of(acl, typeof(*entry), head);
168                         tomoyo_put_name_union(&entry->name);
169                         tomoyo_put_number_union(&entry->mode);
170                         tomoyo_put_number_union(&entry->major);
171                         tomoyo_put_number_union(&entry->minor);
172                 }
173                 break;
174         case TOMOYO_TYPE_MOUNT_ACL:
175                 {
176                         struct tomoyo_mount_acl *entry
177                                 = container_of(acl, typeof(*entry), head);
178                         tomoyo_put_name_union(&entry->dev_name);
179                         tomoyo_put_name_union(&entry->dir_name);
180                         tomoyo_put_name_union(&entry->fs_type);
181                         tomoyo_put_number_union(&entry->flags);
182                 }
183                 break;
184         case TOMOYO_TYPE_ENV_ACL:
185                 {
186                         struct tomoyo_env_acl *entry =
187                                 container_of(acl, typeof(*entry), head);
188
189                         tomoyo_put_name(entry->env);
190                 }
191                 break;
192         case TOMOYO_TYPE_INET_ACL:
193                 {
194                         struct tomoyo_inet_acl *entry =
195                                 container_of(acl, typeof(*entry), head);
196
197                         tomoyo_put_group(entry->address.group);
198                         tomoyo_put_number_union(&entry->port);
199                 }
200                 break;
201         case TOMOYO_TYPE_UNIX_ACL:
202                 {
203                         struct tomoyo_unix_acl *entry =
204                                 container_of(acl, typeof(*entry), head);
205
206                         tomoyo_put_name_union(&entry->name);
207                 }
208                 break;
209         }
210 }
211
212 /**
213  * tomoyo_del_domain - Delete members in "struct tomoyo_domain_info".
214  *
215  * @element: Pointer to "struct list_head".
216  *
217  * Returns nothing.
218  */
219 static inline void tomoyo_del_domain(struct list_head *element)
220 {
221         struct tomoyo_domain_info *domain =
222                 container_of(element, typeof(*domain), list);
223         struct tomoyo_acl_info *acl;
224         struct tomoyo_acl_info *tmp;
225         /*
226          * Since this domain is referenced from neither
227          * "struct tomoyo_io_buffer" nor "struct cred"->security, we can delete
228          * elements without checking for is_deleted flag.
229          */
230         list_for_each_entry_safe(acl, tmp, &domain->acl_info_list, list) {
231                 tomoyo_del_acl(&acl->list);
232                 tomoyo_memory_free(acl);
233         }
234         tomoyo_put_name(domain->domainname);
235 }
236
237 /**
238  * tomoyo_del_condition - Delete members in "struct tomoyo_condition".
239  *
240  * @element: Pointer to "struct list_head".
241  *
242  * Returns nothing.
243  */
244 void tomoyo_del_condition(struct list_head *element)
245 {
246         struct tomoyo_condition *cond = container_of(element, typeof(*cond),
247                                                      head.list);
248         const u16 condc = cond->condc;
249         const u16 numbers_count = cond->numbers_count;
250         const u16 names_count = cond->names_count;
251         const u16 argc = cond->argc;
252         const u16 envc = cond->envc;
253         unsigned int i;
254         const struct tomoyo_condition_element *condp
255                 = (const struct tomoyo_condition_element *) (cond + 1);
256         struct tomoyo_number_union *numbers_p
257                 = (struct tomoyo_number_union *) (condp + condc);
258         struct tomoyo_name_union *names_p
259                 = (struct tomoyo_name_union *) (numbers_p + numbers_count);
260         const struct tomoyo_argv *argv
261                 = (const struct tomoyo_argv *) (names_p + names_count);
262         const struct tomoyo_envp *envp
263                 = (const struct tomoyo_envp *) (argv + argc);
264         for (i = 0; i < numbers_count; i++)
265                 tomoyo_put_number_union(numbers_p++);
266         for (i = 0; i < names_count; i++)
267                 tomoyo_put_name_union(names_p++);
268         for (i = 0; i < argc; argv++, i++)
269                 tomoyo_put_name(argv->value);
270         for (i = 0; i < envc; envp++, i++) {
271                 tomoyo_put_name(envp->name);
272                 tomoyo_put_name(envp->value);
273         }
274 }
275
276 /**
277  * tomoyo_del_name - Delete members in "struct tomoyo_name".
278  *
279  * @element: Pointer to "struct list_head".
280  *
281  * Returns nothing.
282  */
283 static inline void tomoyo_del_name(struct list_head *element)
284 {
285         /* Nothing to do. */
286 }
287
288 /**
289  * tomoyo_del_path_group - Delete members in "struct tomoyo_path_group".
290  *
291  * @element: Pointer to "struct list_head".
292  *
293  * Returns nothing.
294  */
295 static inline void tomoyo_del_path_group(struct list_head *element)
296 {
297         struct tomoyo_path_group *member =
298                 container_of(element, typeof(*member), head.list);
299         tomoyo_put_name(member->member_name);
300 }
301
302 /**
303  * tomoyo_del_group - Delete "struct tomoyo_group".
304  *
305  * @element: Pointer to "struct list_head".
306  *
307  * Returns nothing.
308  */
309 static inline void tomoyo_del_group(struct list_head *element)
310 {
311         struct tomoyo_group *group =
312                 container_of(element, typeof(*group), head.list);
313         tomoyo_put_name(group->group_name);
314 }
315
316 /**
317  * tomoyo_del_address_group - Delete members in "struct tomoyo_address_group".
318  *
319  * @element: Pointer to "struct list_head".
320  *
321  * Returns nothing.
322  */
323 static inline void tomoyo_del_address_group(struct list_head *element)
324 {
325         /* Nothing to do. */
326 }
327
328 /**
329  * tomoyo_del_number_group - Delete members in "struct tomoyo_number_group".
330  *
331  * @element: Pointer to "struct list_head".
332  *
333  * Returns nothing.
334  */
335 static inline void tomoyo_del_number_group(struct list_head *element)
336 {
337         /* Nothing to do. */
338 }
339
340 /**
341  * tomoyo_try_to_gc - Try to kfree() an entry.
342  *
343  * @type:    One of values in "enum tomoyo_policy_id".
344  * @element: Pointer to "struct list_head".
345  *
346  * Returns nothing.
347  *
348  * Caller holds tomoyo_policy_lock mutex.
349  */
350 static void tomoyo_try_to_gc(const enum tomoyo_policy_id type,
351                              struct list_head *element)
352 {
353         /*
354          * __list_del_entry() guarantees that the list element became no longer
355          * reachable from the list which the element was originally on (e.g.
356          * tomoyo_domain_list). Also, synchronize_srcu() guarantees that the
357          * list element became no longer referenced by syscall users.
358          */
359         __list_del_entry(element);
360         mutex_unlock(&tomoyo_policy_lock);
361         synchronize_srcu(&tomoyo_ss);
362         /*
363          * However, there are two users which may still be using the list
364          * element. We need to defer until both users forget this element.
365          *
366          * Don't kfree() until "struct tomoyo_io_buffer"->r.{domain,group,acl}
367          * and "struct tomoyo_io_buffer"->w.domain forget this element.
368          */
369         if (tomoyo_struct_used_by_io_buffer(element))
370                 goto reinject;
371         switch (type) {
372         case TOMOYO_ID_TRANSITION_CONTROL:
373                 tomoyo_del_transition_control(element);
374                 break;
375         case TOMOYO_ID_MANAGER:
376                 tomoyo_del_manager(element);
377                 break;
378         case TOMOYO_ID_AGGREGATOR:
379                 tomoyo_del_aggregator(element);
380                 break;
381         case TOMOYO_ID_GROUP:
382                 tomoyo_del_group(element);
383                 break;
384         case TOMOYO_ID_PATH_GROUP:
385                 tomoyo_del_path_group(element);
386                 break;
387         case TOMOYO_ID_ADDRESS_GROUP:
388                 tomoyo_del_address_group(element);
389                 break;
390         case TOMOYO_ID_NUMBER_GROUP:
391                 tomoyo_del_number_group(element);
392                 break;
393         case TOMOYO_ID_CONDITION:
394                 tomoyo_del_condition(element);
395                 break;
396         case TOMOYO_ID_NAME:
397                 /*
398                  * Don't kfree() until all "struct tomoyo_io_buffer"->r.w[]
399                  * forget this element.
400                  */
401                 if (tomoyo_name_used_by_io_buffer
402                     (container_of(element, typeof(struct tomoyo_name),
403                                   head.list)->entry.name))
404                         goto reinject;
405                 tomoyo_del_name(element);
406                 break;
407         case TOMOYO_ID_ACL:
408                 tomoyo_del_acl(element);
409                 break;
410         case TOMOYO_ID_DOMAIN:
411                 /*
412                  * Don't kfree() until all "struct cred"->security forget this
413                  * element.
414                  */
415                 if (atomic_read(&container_of
416                                 (element, typeof(struct tomoyo_domain_info),
417                                  list)->users))
418                         goto reinject;
419                 tomoyo_del_domain(element);
420                 break;
421         case TOMOYO_MAX_POLICY:
422                 break;
423         }
424         mutex_lock(&tomoyo_policy_lock);
425         tomoyo_memory_free(element);
426         return;
427 reinject:
428         /*
429          * We can safely reinject this element here bacause
430          * (1) Appending list elements and removing list elements are protected
431          *     by tomoyo_policy_lock mutex.
432          * (2) Only this function removes list elements and this function is
433          *     exclusively executed by tomoyo_gc_mutex mutex.
434          * are true.
435          */
436         mutex_lock(&tomoyo_policy_lock);
437         list_add_rcu(element, element->prev);
438 }
439
440 /**
441  * tomoyo_collect_member - Delete elements with "struct tomoyo_acl_head".
442  *
443  * @id:          One of values in "enum tomoyo_policy_id".
444  * @member_list: Pointer to "struct list_head".
445  *
446  * Returns nothing.
447  */
448 static void tomoyo_collect_member(const enum tomoyo_policy_id id,
449                                   struct list_head *member_list)
450 {
451         struct tomoyo_acl_head *member;
452         struct tomoyo_acl_head *tmp;
453         list_for_each_entry_safe(member, tmp, member_list, list) {
454                 if (!member->is_deleted)
455                         continue;
456                 member->is_deleted = TOMOYO_GC_IN_PROGRESS;
457                 tomoyo_try_to_gc(id, &member->list);
458         }
459 }
460
461 /**
462  * tomoyo_collect_acl - Delete elements in "struct tomoyo_domain_info".
463  *
464  * @list: Pointer to "struct list_head".
465  *
466  * Returns nothing.
467  */
468 static void tomoyo_collect_acl(struct list_head *list)
469 {
470         struct tomoyo_acl_info *acl;
471         struct tomoyo_acl_info *tmp;
472         list_for_each_entry_safe(acl, tmp, list, list) {
473                 if (!acl->is_deleted)
474                         continue;
475                 acl->is_deleted = TOMOYO_GC_IN_PROGRESS;
476                 tomoyo_try_to_gc(TOMOYO_ID_ACL, &acl->list);
477         }
478 }
479
480 /**
481  * tomoyo_collect_entry - Try to kfree() deleted elements.
482  *
483  * Returns nothing.
484  */
485 static void tomoyo_collect_entry(void)
486 {
487         int i;
488         enum tomoyo_policy_id id;
489         struct tomoyo_policy_namespace *ns;
490         mutex_lock(&tomoyo_policy_lock);
491         {
492                 struct tomoyo_domain_info *domain;
493                 struct tomoyo_domain_info *tmp;
494                 list_for_each_entry_safe(domain, tmp, &tomoyo_domain_list,
495                                          list) {
496                         tomoyo_collect_acl(&domain->acl_info_list);
497                         if (!domain->is_deleted || atomic_read(&domain->users))
498                                 continue;
499                         tomoyo_try_to_gc(TOMOYO_ID_DOMAIN, &domain->list);
500                 }
501         }
502         list_for_each_entry(ns, &tomoyo_namespace_list, namespace_list) {
503                 for (id = 0; id < TOMOYO_MAX_POLICY; id++)
504                         tomoyo_collect_member(id, &ns->policy_list[id]);
505                 for (i = 0; i < TOMOYO_MAX_ACL_GROUPS; i++)
506                         tomoyo_collect_acl(&ns->acl_group[i]);
507         }
508         {
509                 struct tomoyo_shared_acl_head *ptr;
510                 struct tomoyo_shared_acl_head *tmp;
511                 list_for_each_entry_safe(ptr, tmp, &tomoyo_condition_list,
512                                          list) {
513                         if (atomic_read(&ptr->users) > 0)
514                                 continue;
515                         atomic_set(&ptr->users, TOMOYO_GC_IN_PROGRESS);
516                         tomoyo_try_to_gc(TOMOYO_ID_CONDITION, &ptr->list);
517                 }
518         }
519         list_for_each_entry(ns, &tomoyo_namespace_list, namespace_list) {
520                 for (i = 0; i < TOMOYO_MAX_GROUP; i++) {
521                         struct list_head *list = &ns->group_list[i];
522                         struct tomoyo_group *group;
523                         struct tomoyo_group *tmp;
524                         switch (i) {
525                         case 0:
526                                 id = TOMOYO_ID_PATH_GROUP;
527                                 break;
528                         case 1:
529                                 id = TOMOYO_ID_NUMBER_GROUP;
530                                 break;
531                         default:
532                                 id = TOMOYO_ID_ADDRESS_GROUP;
533                                 break;
534                         }
535                         list_for_each_entry_safe(group, tmp, list, head.list) {
536                                 tomoyo_collect_member(id, &group->member_list);
537                                 if (!list_empty(&group->member_list) ||
538                                     atomic_read(&group->head.users) > 0)
539                                         continue;
540                                 atomic_set(&group->head.users,
541                                            TOMOYO_GC_IN_PROGRESS);
542                                 tomoyo_try_to_gc(TOMOYO_ID_GROUP,
543                                                  &group->head.list);
544                         }
545                 }
546         }
547         for (i = 0; i < TOMOYO_MAX_HASH; i++) {
548                 struct list_head *list = &tomoyo_name_list[i];
549                 struct tomoyo_shared_acl_head *ptr;
550                 struct tomoyo_shared_acl_head *tmp;
551                 list_for_each_entry_safe(ptr, tmp, list, list) {
552                         if (atomic_read(&ptr->users) > 0)
553                                 continue;
554                         atomic_set(&ptr->users, TOMOYO_GC_IN_PROGRESS);
555                         tomoyo_try_to_gc(TOMOYO_ID_NAME, &ptr->list);
556                 }
557         }
558         mutex_unlock(&tomoyo_policy_lock);
559 }
560
561 /**
562  * tomoyo_gc_thread - Garbage collector thread function.
563  *
564  * @unused: Unused.
565  *
566  * Returns 0.
567  */
568 static int tomoyo_gc_thread(void *unused)
569 {
570         /* Garbage collector thread is exclusive. */
571         static DEFINE_MUTEX(tomoyo_gc_mutex);
572         if (!mutex_trylock(&tomoyo_gc_mutex))
573                 goto out;
574         tomoyo_collect_entry();
575         {
576                 struct tomoyo_io_buffer *head;
577                 struct tomoyo_io_buffer *tmp;
578
579                 spin_lock(&tomoyo_io_buffer_list_lock);
580                 list_for_each_entry_safe(head, tmp, &tomoyo_io_buffer_list,
581                                          list) {
582                         if (head->users)
583                                 continue;
584                         list_del(&head->list);
585                         kfree(head->read_buf);
586                         kfree(head->write_buf);
587                         kfree(head);
588                 }
589                 spin_unlock(&tomoyo_io_buffer_list_lock);
590         }
591         mutex_unlock(&tomoyo_gc_mutex);
592 out:
593         /* This acts as do_exit(0). */
594         return 0;
595 }
596
597 /**
598  * tomoyo_notify_gc - Register/unregister /sys/kernel/security/tomoyo/ users.
599  *
600  * @head:        Pointer to "struct tomoyo_io_buffer".
601  * @is_register: True if register, false if unregister.
602  *
603  * Returns nothing.
604  */
605 void tomoyo_notify_gc(struct tomoyo_io_buffer *head, const bool is_register)
606 {
607         bool is_write = false;
608
609         spin_lock(&tomoyo_io_buffer_list_lock);
610         if (is_register) {
611                 head->users = 1;
612                 list_add(&head->list, &tomoyo_io_buffer_list);
613         } else {
614                 is_write = head->write_buf != NULL;
615                 if (!--head->users) {
616                         list_del(&head->list);
617                         kfree(head->read_buf);
618                         kfree(head->write_buf);
619                         kfree(head);
620                 }
621         }
622         spin_unlock(&tomoyo_io_buffer_list_lock);
623         if (is_write) {
624                 struct task_struct *task = kthread_create(tomoyo_gc_thread,
625                                                           NULL,
626                                                           "GC for TOMOYO");
627                 if (!IS_ERR(task))
628                         wake_up_process(task);
629         }
630 }