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TOMOYO Linux Cross Reference
Linux/security/tomoyo/gc.c

Version: ~ [ linux-5.5-rc7 ] ~ [ linux-5.4.13 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.97 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.166 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.210 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.210 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.81 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
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  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 /* Size of an element. */
 17 static const u8 tomoyo_element_size[TOMOYO_MAX_POLICY] = {
 18         [TOMOYO_ID_GROUP] = sizeof(struct tomoyo_group),
 19         [TOMOYO_ID_PATH_GROUP] = sizeof(struct tomoyo_path_group),
 20         [TOMOYO_ID_NUMBER_GROUP] = sizeof(struct tomoyo_number_group),
 21         [TOMOYO_ID_AGGREGATOR] = sizeof(struct tomoyo_aggregator),
 22         [TOMOYO_ID_TRANSITION_CONTROL] =
 23         sizeof(struct tomoyo_transition_control),
 24         [TOMOYO_ID_MANAGER] = sizeof(struct tomoyo_manager),
 25         /* [TOMOYO_ID_CONDITION] = "struct tomoyo_condition"->size, */
 26         /* [TOMOYO_ID_NAME] = "struct tomoyo_name"->size, */
 27         /* [TOMOYO_ID_ACL] =
 28            tomoyo_acl_size["struct tomoyo_acl_info"->type], */
 29         [TOMOYO_ID_DOMAIN] = sizeof(struct tomoyo_domain_info),
 30 };
 31 
 32 /* Size of a domain ACL element. */
 33 static const u8 tomoyo_acl_size[] = {
 34         [TOMOYO_TYPE_PATH_ACL] = sizeof(struct tomoyo_path_acl),
 35         [TOMOYO_TYPE_PATH2_ACL] = sizeof(struct tomoyo_path2_acl),
 36         [TOMOYO_TYPE_PATH_NUMBER_ACL] = sizeof(struct tomoyo_path_number_acl),
 37         [TOMOYO_TYPE_MKDEV_ACL] = sizeof(struct tomoyo_mkdev_acl),
 38         [TOMOYO_TYPE_MOUNT_ACL] = sizeof(struct tomoyo_mount_acl),
 39 };
 40 
 41 /**
 42  * tomoyo_struct_used_by_io_buffer - Check whether the list element is used by /sys/kernel/security/tomoyo/ users or not.
 43  *
 44  * @element: Pointer to "struct list_head".
 45  *
 46  * Returns true if @element is used by /sys/kernel/security/tomoyo/ users,
 47  * false otherwise.
 48  */
 49 static bool tomoyo_struct_used_by_io_buffer(const struct list_head *element)
 50 {
 51         struct tomoyo_io_buffer *head;
 52         bool in_use = false;
 53 
 54         spin_lock(&tomoyo_io_buffer_list_lock);
 55         list_for_each_entry(head, &tomoyo_io_buffer_list, list) {
 56                 head->users++;
 57                 spin_unlock(&tomoyo_io_buffer_list_lock);
 58                 if (mutex_lock_interruptible(&head->io_sem)) {
 59                         in_use = true;
 60                         goto out;
 61                 }
 62                 if (head->r.domain == element || head->r.group == element ||
 63                     head->r.acl == element || &head->w.domain->list == element)
 64                         in_use = true;
 65                 mutex_unlock(&head->io_sem);
 66 out:
 67                 spin_lock(&tomoyo_io_buffer_list_lock);
 68                 head->users--;
 69                 if (in_use)
 70                         break;
 71         }
 72         spin_unlock(&tomoyo_io_buffer_list_lock);
 73         return in_use;
 74 }
 75 
 76 /**
 77  * tomoyo_name_used_by_io_buffer - Check whether the string is used by /sys/kernel/security/tomoyo/ users or not.
 78  *
 79  * @string: String to check.
 80  * @size:   Memory allocated for @string .
 81  *
 82  * Returns true if @string is used by /sys/kernel/security/tomoyo/ users,
 83  * false otherwise.
 84  */
 85 static bool tomoyo_name_used_by_io_buffer(const char *string,
 86                                           const size_t size)
 87 {
 88         struct tomoyo_io_buffer *head;
 89         bool in_use = false;
 90 
 91         spin_lock(&tomoyo_io_buffer_list_lock);
 92         list_for_each_entry(head, &tomoyo_io_buffer_list, list) {
 93                 int i;
 94                 head->users++;
 95                 spin_unlock(&tomoyo_io_buffer_list_lock);
 96                 if (mutex_lock_interruptible(&head->io_sem)) {
 97                         in_use = true;
 98                         goto out;
 99                 }
100                 for (i = 0; i < TOMOYO_MAX_IO_READ_QUEUE; i++) {
101                         const char *w = head->r.w[i];
102                         if (w < string || w > string + size)
103                                 continue;
104                         in_use = true;
105                         break;
106                 }
107                 mutex_unlock(&head->io_sem);
108 out:
109                 spin_lock(&tomoyo_io_buffer_list_lock);
110                 head->users--;
111                 if (in_use)
112                         break;
113         }
114         spin_unlock(&tomoyo_io_buffer_list_lock);
115         return in_use;
116 }
117 
118 /* Structure for garbage collection. */
119 struct tomoyo_gc {
120         struct list_head list;
121         enum tomoyo_policy_id type;
122         size_t size;
123         struct list_head *element;
124 };
125 /* List of entries to be deleted. */
126 static LIST_HEAD(tomoyo_gc_list);
127 /* Length of tomoyo_gc_list. */
128 static int tomoyo_gc_list_len;
129 
130 /**
131  * tomoyo_add_to_gc - Add an entry to to be deleted list.
132  *
133  * @type:    One of values in "enum tomoyo_policy_id".
134  * @element: Pointer to "struct list_head".
135  *
136  * Returns true on success, false otherwise.
137  *
138  * Caller holds tomoyo_policy_lock mutex.
139  *
140  * Adding an entry needs kmalloc(). Thus, if we try to add thousands of
141  * entries at once, it will take too long time. Thus, do not add more than 128
142  * entries per a scan. But to be able to handle worst case where all entries
143  * are in-use, we accept one more entry per a scan.
144  *
145  * If we use singly linked list using "struct list_head"->prev (which is
146  * LIST_POISON2), we can avoid kmalloc().
147  */
148 static bool tomoyo_add_to_gc(const int type, struct list_head *element)
149 {
150         struct tomoyo_gc *entry = kzalloc(sizeof(*entry), GFP_ATOMIC);
151         if (!entry)
152                 return false;
153         entry->type = type;
154         if (type == TOMOYO_ID_ACL)
155                 entry->size = tomoyo_acl_size[
156                               container_of(element,
157                                            typeof(struct tomoyo_acl_info),
158                                            list)->type];
159         else if (type == TOMOYO_ID_NAME)
160                 entry->size = strlen(container_of(element,
161                                                   typeof(struct tomoyo_name),
162                                                   head.list)->entry.name) + 1;
163         else if (type == TOMOYO_ID_CONDITION)
164                 entry->size =
165                         container_of(element, typeof(struct tomoyo_condition),
166                                      head.list)->size;
167         else
168                 entry->size = tomoyo_element_size[type];
169         entry->element = element;
170         list_add(&entry->list, &tomoyo_gc_list);
171         list_del_rcu(element);
172         return tomoyo_gc_list_len++ < 128;
173 }
174 
175 /**
176  * tomoyo_element_linked_by_gc - Validate next element of an entry.
177  *
178  * @element: Pointer to an element.
179  * @size:    Size of @element in byte.
180  *
181  * Returns true if @element is linked by other elements in the garbage
182  * collector's queue, false otherwise.
183  */
184 static bool tomoyo_element_linked_by_gc(const u8 *element, const size_t size)
185 {
186         struct tomoyo_gc *p;
187         list_for_each_entry(p, &tomoyo_gc_list, list) {
188                 const u8 *ptr = (const u8 *) p->element->next;
189                 if (ptr < element || element + size < ptr)
190                         continue;
191                 return true;
192         }
193         return false;
194 }
195 
196 /**
197  * tomoyo_del_transition_control - Delete members in "struct tomoyo_transition_control".
198  *
199  * @element: Pointer to "struct list_head".
200  *
201  * Returns nothing.
202  */
203 static void tomoyo_del_transition_control(struct list_head *element)
204 {
205         struct tomoyo_transition_control *ptr =
206                 container_of(element, typeof(*ptr), head.list);
207         tomoyo_put_name(ptr->domainname);
208         tomoyo_put_name(ptr->program);
209 }
210 
211 /**
212  * tomoyo_del_aggregator - Delete members in "struct tomoyo_aggregator".
213  *
214  * @element: Pointer to "struct list_head".
215  *
216  * Returns nothing.
217  */
218 static void tomoyo_del_aggregator(struct list_head *element)
219 {
220         struct tomoyo_aggregator *ptr =
221                 container_of(element, typeof(*ptr), head.list);
222         tomoyo_put_name(ptr->original_name);
223         tomoyo_put_name(ptr->aggregated_name);
224 }
225 
226 /**
227  * tomoyo_del_manager - Delete members in "struct tomoyo_manager".
228  *
229  * @element: Pointer to "struct list_head".
230  *
231  * Returns nothing.
232  */
233 static void tomoyo_del_manager(struct list_head *element)
234 {
235         struct tomoyo_manager *ptr =
236                 container_of(element, typeof(*ptr), head.list);
237         tomoyo_put_name(ptr->manager);
238 }
239 
240 /**
241  * tomoyo_del_acl - Delete members in "struct tomoyo_acl_info".
242  *
243  * @element: Pointer to "struct list_head".
244  *
245  * Returns nothing.
246  */
247 static void tomoyo_del_acl(struct list_head *element)
248 {
249         struct tomoyo_acl_info *acl =
250                 container_of(element, typeof(*acl), list);
251         tomoyo_put_condition(acl->cond);
252         switch (acl->type) {
253         case TOMOYO_TYPE_PATH_ACL:
254                 {
255                         struct tomoyo_path_acl *entry
256                                 = container_of(acl, typeof(*entry), head);
257                         tomoyo_put_name_union(&entry->name);
258                 }
259                 break;
260         case TOMOYO_TYPE_PATH2_ACL:
261                 {
262                         struct tomoyo_path2_acl *entry
263                                 = container_of(acl, typeof(*entry), head);
264                         tomoyo_put_name_union(&entry->name1);
265                         tomoyo_put_name_union(&entry->name2);
266                 }
267                 break;
268         case TOMOYO_TYPE_PATH_NUMBER_ACL:
269                 {
270                         struct tomoyo_path_number_acl *entry
271                                 = container_of(acl, typeof(*entry), head);
272                         tomoyo_put_name_union(&entry->name);
273                         tomoyo_put_number_union(&entry->number);
274                 }
275                 break;
276         case TOMOYO_TYPE_MKDEV_ACL:
277                 {
278                         struct tomoyo_mkdev_acl *entry
279                                 = container_of(acl, typeof(*entry), head);
280                         tomoyo_put_name_union(&entry->name);
281                         tomoyo_put_number_union(&entry->mode);
282                         tomoyo_put_number_union(&entry->major);
283                         tomoyo_put_number_union(&entry->minor);
284                 }
285                 break;
286         case TOMOYO_TYPE_MOUNT_ACL:
287                 {
288                         struct tomoyo_mount_acl *entry
289                                 = container_of(acl, typeof(*entry), head);
290                         tomoyo_put_name_union(&entry->dev_name);
291                         tomoyo_put_name_union(&entry->dir_name);
292                         tomoyo_put_name_union(&entry->fs_type);
293                         tomoyo_put_number_union(&entry->flags);
294                 }
295                 break;
296         }
297 }
298 
299 /**
300  * tomoyo_del_domain - Delete members in "struct tomoyo_domain_info".
301  *
302  * @element: Pointer to "struct list_head".
303  *
304  * Returns true if deleted, false otherwise.
305  */
306 static bool tomoyo_del_domain(struct list_head *element)
307 {
308         struct tomoyo_domain_info *domain =
309                 container_of(element, typeof(*domain), list);
310         struct tomoyo_acl_info *acl;
311         struct tomoyo_acl_info *tmp;
312         /*
313          * Since we don't protect whole execve() operation using SRCU,
314          * we need to recheck domain->users at this point.
315          *
316          * (1) Reader starts SRCU section upon execve().
317          * (2) Reader traverses tomoyo_domain_list and finds this domain.
318          * (3) Writer marks this domain as deleted.
319          * (4) Garbage collector removes this domain from tomoyo_domain_list
320          *     because this domain is marked as deleted and used by nobody.
321          * (5) Reader saves reference to this domain into
322          *     "struct linux_binprm"->cred->security .
323          * (6) Reader finishes SRCU section, although execve() operation has
324          *     not finished yet.
325          * (7) Garbage collector waits for SRCU synchronization.
326          * (8) Garbage collector kfree() this domain because this domain is
327          *     used by nobody.
328          * (9) Reader finishes execve() operation and restores this domain from
329          *     "struct linux_binprm"->cred->security.
330          *
331          * By updating domain->users at (5), we can solve this race problem
332          * by rechecking domain->users at (8).
333          */
334         if (atomic_read(&domain->users))
335                 return false;
336         list_for_each_entry_safe(acl, tmp, &domain->acl_info_list, list) {
337                 tomoyo_del_acl(&acl->list);
338                 tomoyo_memory_free(acl);
339         }
340         tomoyo_put_name(domain->domainname);
341         return true;
342 }
343 
344 /**
345  * tomoyo_del_condition - Delete members in "struct tomoyo_condition".
346  *
347  * @element: Pointer to "struct list_head".
348  *
349  * Returns nothing.
350  */
351 void tomoyo_del_condition(struct list_head *element)
352 {
353         struct tomoyo_condition *cond = container_of(element, typeof(*cond),
354                                                      head.list);
355         const u16 condc = cond->condc;
356         const u16 numbers_count = cond->numbers_count;
357         const u16 names_count = cond->names_count;
358         const u16 argc = cond->argc;
359         const u16 envc = cond->envc;
360         unsigned int i;
361         const struct tomoyo_condition_element *condp
362                 = (const struct tomoyo_condition_element *) (cond + 1);
363         struct tomoyo_number_union *numbers_p
364                 = (struct tomoyo_number_union *) (condp + condc);
365         struct tomoyo_name_union *names_p
366                 = (struct tomoyo_name_union *) (numbers_p + numbers_count);
367         const struct tomoyo_argv *argv
368                 = (const struct tomoyo_argv *) (names_p + names_count);
369         const struct tomoyo_envp *envp
370                 = (const struct tomoyo_envp *) (argv + argc);
371         for (i = 0; i < numbers_count; i++)
372                 tomoyo_put_number_union(numbers_p++);
373         for (i = 0; i < names_count; i++)
374                 tomoyo_put_name_union(names_p++);
375         for (i = 0; i < argc; argv++, i++)
376                 tomoyo_put_name(argv->value);
377         for (i = 0; i < envc; envp++, i++) {
378                 tomoyo_put_name(envp->name);
379                 tomoyo_put_name(envp->value);
380         }
381 }
382 
383 /**
384  * tomoyo_del_name - Delete members in "struct tomoyo_name".
385  *
386  * @element: Pointer to "struct list_head".
387  *
388  * Returns nothing.
389  */
390 static void tomoyo_del_name(struct list_head *element)
391 {
392         const struct tomoyo_name *ptr =
393                 container_of(element, typeof(*ptr), head.list);
394 }
395 
396 /**
397  * tomoyo_del_path_group - Delete members in "struct tomoyo_path_group".
398  *
399  * @element: Pointer to "struct list_head".
400  *
401  * Returns nothing.
402  */
403 static void tomoyo_del_path_group(struct list_head *element)
404 {
405         struct tomoyo_path_group *member =
406                 container_of(element, typeof(*member), head.list);
407         tomoyo_put_name(member->member_name);
408 }
409 
410 /**
411  * tomoyo_del_group - Delete "struct tomoyo_group".
412  *
413  * @element: Pointer to "struct list_head".
414  *
415  * Returns nothing.
416  */
417 static void tomoyo_del_group(struct list_head *element)
418 {
419         struct tomoyo_group *group =
420                 container_of(element, typeof(*group), head.list);
421         tomoyo_put_name(group->group_name);
422 }
423 
424 /**
425  * tomoyo_del_number_group - Delete members in "struct tomoyo_number_group".
426  *
427  * @element: Pointer to "struct list_head".
428  *
429  * Returns nothing.
430  */
431 static void tomoyo_del_number_group(struct list_head *element)
432 {
433         struct tomoyo_number_group *member =
434                 container_of(element, typeof(*member), head.list);
435 }
436 
437 /**
438  * tomoyo_collect_member - Delete elements with "struct tomoyo_acl_head".
439  *
440  * @id:          One of values in "enum tomoyo_policy_id".
441  * @member_list: Pointer to "struct list_head".
442  *
443  * Returns true if some elements are deleted, false otherwise.
444  */
445 static bool tomoyo_collect_member(const enum tomoyo_policy_id id,
446                                   struct list_head *member_list)
447 {
448         struct tomoyo_acl_head *member;
449         list_for_each_entry(member, member_list, list) {
450                 if (!member->is_deleted)
451                         continue;
452                 if (!tomoyo_add_to_gc(id, &member->list))
453                         return false;
454         }
455         return true;
456 }
457 
458 /**
459  * tomoyo_collect_acl - Delete elements in "struct tomoyo_domain_info".
460  *
461  * @list: Pointer to "struct list_head".
462  *
463  * Returns true if some elements are deleted, false otherwise.
464  */
465 static bool tomoyo_collect_acl(struct list_head *list)
466 {
467         struct tomoyo_acl_info *acl;
468         list_for_each_entry(acl, list, list) {
469                 if (!acl->is_deleted)
470                         continue;
471                 if (!tomoyo_add_to_gc(TOMOYO_ID_ACL, &acl->list))
472                         return false;
473         }
474         return true;
475 }
476 
477 /**
478  * tomoyo_collect_entry - Scan lists for deleted elements.
479  *
480  * Returns nothing.
481  */
482 static void tomoyo_collect_entry(void)
483 {
484         int i;
485         enum tomoyo_policy_id id;
486         struct tomoyo_policy_namespace *ns;
487         int idx;
488         if (mutex_lock_interruptible(&tomoyo_policy_lock))
489                 return;
490         idx = tomoyo_read_lock();
491         {
492                 struct tomoyo_domain_info *domain;
493                 list_for_each_entry_rcu(domain, &tomoyo_domain_list, list) {
494                         if (!tomoyo_collect_acl(&domain->acl_info_list))
495                                 goto unlock;
496                         if (!domain->is_deleted || atomic_read(&domain->users))
497                                 continue;
498                         /*
499                          * Nobody is referring this domain. But somebody may
500                          * refer this domain after successful execve().
501                          * We recheck domain->users after SRCU synchronization.
502                          */
503                         if (!tomoyo_add_to_gc(TOMOYO_ID_DOMAIN, &domain->list))
504                                 goto unlock;
505                 }
506         }
507         list_for_each_entry_rcu(ns, &tomoyo_namespace_list, namespace_list) {
508                 for (id = 0; id < TOMOYO_MAX_POLICY; id++)
509                         if (!tomoyo_collect_member(id, &ns->policy_list[id]))
510                                 goto unlock;
511                 for (i = 0; i < TOMOYO_MAX_ACL_GROUPS; i++)
512                         if (!tomoyo_collect_acl(&ns->acl_group[i]))
513                                 goto unlock;
514                 for (i = 0; i < TOMOYO_MAX_GROUP; i++) {
515                         struct list_head *list = &ns->group_list[i];
516                         struct tomoyo_group *group;
517                         switch (i) {
518                         case 0:
519                                 id = TOMOYO_ID_PATH_GROUP;
520                                 break;
521                         default:
522                                 id = TOMOYO_ID_NUMBER_GROUP;
523                                 break;
524                         }
525                         list_for_each_entry(group, list, head.list) {
526                                 if (!tomoyo_collect_member
527                                     (id, &group->member_list))
528                                         goto unlock;
529                                 if (!list_empty(&group->member_list) ||
530                                     atomic_read(&group->head.users))
531                                         continue;
532                                 if (!tomoyo_add_to_gc(TOMOYO_ID_GROUP,
533                                                       &group->head.list))
534                                         goto unlock;
535                         }
536                 }
537         }
538         id = TOMOYO_ID_CONDITION;
539         for (i = 0; i < TOMOYO_MAX_HASH + 1; i++) {
540                 struct list_head *list = !i ?
541                         &tomoyo_condition_list : &tomoyo_name_list[i - 1];
542                 struct tomoyo_shared_acl_head *ptr;
543                 list_for_each_entry(ptr, list, list) {
544                         if (atomic_read(&ptr->users))
545                                 continue;
546                         if (!tomoyo_add_to_gc(id, &ptr->list))
547                                 goto unlock;
548                 }
549                 id = TOMOYO_ID_NAME;
550         }
551 unlock:
552         tomoyo_read_unlock(idx);
553         mutex_unlock(&tomoyo_policy_lock);
554 }
555 
556 /**
557  * tomoyo_kfree_entry - Delete entries in tomoyo_gc_list.
558  *
559  * Returns true if some entries were kfree()d, false otherwise.
560  */
561 static bool tomoyo_kfree_entry(void)
562 {
563         struct tomoyo_gc *p;
564         struct tomoyo_gc *tmp;
565         bool result = false;
566 
567         list_for_each_entry_safe(p, tmp, &tomoyo_gc_list, list) {
568                 struct list_head *element = p->element;
569 
570                 /*
571                  * list_del_rcu() in tomoyo_add_to_gc() guarantees that the
572                  * list element became no longer reachable from the list which
573                  * the element was originally on (e.g. tomoyo_domain_list).
574                  * Also, synchronize_srcu() in tomoyo_gc_thread() guarantees
575                  * that the list element became no longer referenced by syscall
576                  * users.
577                  *
578                  * However, there are three users which may still be using the
579                  * list element. We need to defer until all of these users
580                  * forget the list element.
581                  *
582                  * Firstly, defer until "struct tomoyo_io_buffer"->r.{domain,
583                  * group,acl} and "struct tomoyo_io_buffer"->w.domain forget
584                  * the list element.
585                  */
586                 if (tomoyo_struct_used_by_io_buffer(element))
587                         continue;
588                 /*
589                  * Secondly, defer until all other elements in the
590                  * tomoyo_gc_list list forget the list element.
591                  */
592                 if (tomoyo_element_linked_by_gc((const u8 *) element, p->size))
593                         continue;
594                 switch (p->type) {
595                 case TOMOYO_ID_TRANSITION_CONTROL:
596                         tomoyo_del_transition_control(element);
597                         break;
598                 case TOMOYO_ID_AGGREGATOR:
599                         tomoyo_del_aggregator(element);
600                         break;
601                 case TOMOYO_ID_MANAGER:
602                         tomoyo_del_manager(element);
603                         break;
604                 case TOMOYO_ID_CONDITION:
605                         tomoyo_del_condition(element);
606                         break;
607                 case TOMOYO_ID_NAME:
608                         /*
609                          * Thirdly, defer until all "struct tomoyo_io_buffer"
610                          * ->r.w[] forget the list element.
611                          */
612                         if (tomoyo_name_used_by_io_buffer(
613                             container_of(element, typeof(struct tomoyo_name),
614                                          head.list)->entry.name, p->size))
615                                 continue;
616                         tomoyo_del_name(element);
617                         break;
618                 case TOMOYO_ID_ACL:
619                         tomoyo_del_acl(element);
620                         break;
621                 case TOMOYO_ID_DOMAIN:
622                         if (!tomoyo_del_domain(element))
623                                 continue;
624                         break;
625                 case TOMOYO_ID_PATH_GROUP:
626                         tomoyo_del_path_group(element);
627                         break;
628                 case TOMOYO_ID_GROUP:
629                         tomoyo_del_group(element);
630                         break;
631                 case TOMOYO_ID_NUMBER_GROUP:
632                         tomoyo_del_number_group(element);
633                         break;
634                 case TOMOYO_MAX_POLICY:
635                         break;
636                 }
637                 tomoyo_memory_free(element);
638                 list_del(&p->list);
639                 kfree(p);
640                 tomoyo_gc_list_len--;
641                 result = true;
642         }
643         return result;
644 }
645 
646 /**
647  * tomoyo_gc_thread - Garbage collector thread function.
648  *
649  * @unused: Unused.
650  *
651  * In case OOM-killer choose this thread for termination, we create this thread
652  * as a short live thread whenever /sys/kernel/security/tomoyo/ interface was
653  * close()d.
654  *
655  * Returns 0.
656  */
657 static int tomoyo_gc_thread(void *unused)
658 {
659         /* Garbage collector thread is exclusive. */
660         static DEFINE_MUTEX(tomoyo_gc_mutex);
661         if (!mutex_trylock(&tomoyo_gc_mutex))
662                 goto out;
663         daemonize("GC for TOMOYO");
664         do {
665                 tomoyo_collect_entry();
666                 if (list_empty(&tomoyo_gc_list))
667                         break;
668                 synchronize_srcu(&tomoyo_ss);
669         } while (tomoyo_kfree_entry());
670         {
671                 struct tomoyo_io_buffer *head;
672                 struct tomoyo_io_buffer *tmp;
673 
674                 spin_lock(&tomoyo_io_buffer_list_lock);
675                 list_for_each_entry_safe(head, tmp, &tomoyo_io_buffer_list,
676                                          list) {
677                         if (head->users)
678                                 continue;
679                         list_del(&head->list);
680                         kfree(head->read_buf);
681                         kfree(head->write_buf);
682                         kfree(head);
683                 }
684                 spin_unlock(&tomoyo_io_buffer_list_lock);
685         }
686         mutex_unlock(&tomoyo_gc_mutex);
687 out:
688         /* This acts as do_exit(0). */
689         return 0;
690 }
691 
692 /**
693  * tomoyo_notify_gc - Register/unregister /sys/kernel/security/tomoyo/ users.
694  *
695  * @head:        Pointer to "struct tomoyo_io_buffer".
696  * @is_register: True if register, false if unregister.
697  *
698  * Returns nothing.
699  */
700 void tomoyo_notify_gc(struct tomoyo_io_buffer *head, const bool is_register)
701 {
702         bool is_write = false;
703 
704         spin_lock(&tomoyo_io_buffer_list_lock);
705         if (is_register) {
706                 head->users = 1;
707                 list_add(&head->list, &tomoyo_io_buffer_list);
708         } else {
709                 is_write = head->write_buf != NULL;
710                 if (!--head->users) {
711                         list_del(&head->list);
712                         kfree(head->read_buf);
713                         kfree(head->write_buf);
714                         kfree(head);
715                 }
716         }
717         spin_unlock(&tomoyo_io_buffer_list_lock);
718         if (is_write) {
719                 struct task_struct *task = kthread_create(tomoyo_gc_thread,
720                                                           NULL,
721                                                           "GC for TOMOYO");
722                 if (!IS_ERR(task))
723                         wake_up_process(task);
724         }
725 }
726 

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