1 files changed, 489 insertions, 188 deletions

diff --git a/security/tomoyo/gc.c b/security/tomoyo/gc.c
index a877e4c..986a6a7 100644
--- a/security/tomoyo/gc.c
+++ b/security/tomoyo/gc.c
@@ -1,59 +1,109 @@
 /*
  * security/tomoyo/gc.c
  *
- * Implementation of the Domain-Based Mandatory Access Control.
- *
- * Copyright (C) 2005-2010  NTT DATA CORPORATION
- *
+ * Copyright (C) 2005-2011  NTT DATA CORPORATION
  */
 
 #include "common.h"
 #include <linux/kthread.h>
 #include <linux/slab.h>
 
-struct tomoyo_gc {
-	struct list_head list;
-	int type;
-	struct list_head *element;
-};
-static LIST_HEAD(tomoyo_gc_queue);
-static DEFINE_MUTEX(tomoyo_gc_mutex);
-
-/* Caller holds tomoyo_policy_lock mutex. */
-static bool tomoyo_add_to_gc(const int type, struct list_head *element)
+/**
+ * tomoyo_memory_free - Free memory for elements.
+ *
+ * @ptr:  Pointer to allocated memory.
+ *
+ * Returns nothing.
+ *
+ * Caller holds tomoyo_policy_lock mutex.
+ */
+static inline void tomoyo_memory_free(void *ptr)
 {
-	struct tomoyo_gc *entry = kzalloc(sizeof(*entry), GFP_ATOMIC);
-	if (!entry)
-		return false;
-	entry->type = type;
-	entry->element = element;
-	list_add(&entry->list, &tomoyo_gc_queue);
-	list_del_rcu(element);
-	return true;
+	tomoyo_memory_used[TOMOYO_MEMORY_POLICY] -= ksize(ptr);
+	kfree(ptr);
 }
 
-static void tomoyo_del_allow_read(struct list_head *element)
-{
-	struct tomoyo_readable_file *ptr =
-		container_of(element, typeof(*ptr), head.list);
-	tomoyo_put_name(ptr->filename);
-}
+/* The list for "struct tomoyo_io_buffer". */
+static LIST_HEAD(tomoyo_io_buffer_list);
+/* Lock for protecting tomoyo_io_buffer_list. */
+static DEFINE_SPINLOCK(tomoyo_io_buffer_list_lock);
 
-static void tomoyo_del_file_pattern(struct list_head *element)
+/**
+ * tomoyo_struct_used_by_io_buffer - Check whether the list element is used by /sys/kernel/security/tomoyo/ users or not.
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns true if @element is used by /sys/kernel/security/tomoyo/ users,
+ * false otherwise.
+ */
+static bool tomoyo_struct_used_by_io_buffer(const struct list_head *element)
 {
-	struct tomoyo_no_pattern *ptr =
-		container_of(element, typeof(*ptr), head.list);
-	tomoyo_put_name(ptr->pattern);
+	struct tomoyo_io_buffer *head;
+	bool in_use = false;
+
+	spin_lock(&tomoyo_io_buffer_list_lock);
+	list_for_each_entry(head, &tomoyo_io_buffer_list, list) {
+		head->users++;
+		spin_unlock(&tomoyo_io_buffer_list_lock);
+		mutex_lock(&head->io_sem);
+		if (head->r.domain == element || head->r.group == element ||
+		    head->r.acl == element || &head->w.domain->list == element)
+			in_use = true;
+		mutex_unlock(&head->io_sem);
+		spin_lock(&tomoyo_io_buffer_list_lock);
+		head->users--;
+		if (in_use)
+			break;
+	}
+	spin_unlock(&tomoyo_io_buffer_list_lock);
+	return in_use;
 }
 
-static void tomoyo_del_no_rewrite(struct list_head *element)
+/**
+ * tomoyo_name_used_by_io_buffer - Check whether the string is used by /sys/kernel/security/tomoyo/ users or not.
+ *
+ * @string: String to check.
+ *
+ * Returns true if @string is used by /sys/kernel/security/tomoyo/ users,
+ * false otherwise.
+ */
+static bool tomoyo_name_used_by_io_buffer(const char *string)
 {
-	struct tomoyo_no_rewrite *ptr =
-		container_of(element, typeof(*ptr), head.list);
-	tomoyo_put_name(ptr->pattern);
+	struct tomoyo_io_buffer *head;
+	const size_t size = strlen(string) + 1;
+	bool in_use = false;
+
+	spin_lock(&tomoyo_io_buffer_list_lock);
+	list_for_each_entry(head, &tomoyo_io_buffer_list, list) {
+		int i;
+		head->users++;
+		spin_unlock(&tomoyo_io_buffer_list_lock);
+		mutex_lock(&head->io_sem);
+		for (i = 0; i < TOMOYO_MAX_IO_READ_QUEUE; i++) {
+			const char *w = head->r.w[i];
+			if (w < string || w > string + size)
+				continue;
+			in_use = true;
+			break;
+		}
+		mutex_unlock(&head->io_sem);
+		spin_lock(&tomoyo_io_buffer_list_lock);
+		head->users--;
+		if (in_use)
+			break;
+	}
+	spin_unlock(&tomoyo_io_buffer_list_lock);
+	return in_use;
 }
 
-static void tomoyo_del_transition_control(struct list_head *element)
+/**
+ * tomoyo_del_transition_control - Delete members in "struct tomoyo_transition_control".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_transition_control(struct list_head *element)
 {
 	struct tomoyo_transition_control *ptr =
 		container_of(element, typeof(*ptr), head.list);
@@ -61,7 +111,14 @@ static void tomoyo_del_transition_control(struct list_head *element)
 	tomoyo_put_name(ptr->program);
 }
 
-static void tomoyo_del_aggregator(struct list_head *element)
+/**
+ * tomoyo_del_aggregator - Delete members in "struct tomoyo_aggregator".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_aggregator(struct list_head *element)
 {
 	struct tomoyo_aggregator *ptr =
 		container_of(element, typeof(*ptr), head.list);
@@ -69,17 +126,32 @@ static void tomoyo_del_aggregator(struct list_head *element)
 	tomoyo_put_name(ptr->aggregated_name);
 }
 
-static void tomoyo_del_manager(struct list_head *element)
+/**
+ * tomoyo_del_manager - Delete members in "struct tomoyo_manager".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_manager(struct list_head *element)
 {
 	struct tomoyo_manager *ptr =
 		container_of(element, typeof(*ptr), head.list);
 	tomoyo_put_name(ptr->manager);
 }
 
+/**
+ * tomoyo_del_acl - Delete members in "struct tomoyo_acl_info".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
 static void tomoyo_del_acl(struct list_head *element)
 {
 	struct tomoyo_acl_info *acl =
 		container_of(element, typeof(*acl), list);
+	tomoyo_put_condition(acl->cond);
 	switch (acl->type) {
 	case TOMOYO_TYPE_PATH_ACL:
 		{
@@ -124,231 +196,460 @@ static void tomoyo_del_acl(struct list_head *element)
 			tomoyo_put_number_union(&entry->flags);
 		}
 		break;
+	case TOMOYO_TYPE_ENV_ACL:
+		{
+			struct tomoyo_env_acl *entry =
+				container_of(acl, typeof(*entry), head);
+
+			tomoyo_put_name(entry->env);
+		}
+		break;
+	case TOMOYO_TYPE_INET_ACL:
+		{
+			struct tomoyo_inet_acl *entry =
+				container_of(acl, typeof(*entry), head);
+
+			tomoyo_put_group(entry->address.group);
+			tomoyo_put_number_union(&entry->port);
+		}
+		break;
+	case TOMOYO_TYPE_UNIX_ACL:
+		{
+			struct tomoyo_unix_acl *entry =
+				container_of(acl, typeof(*entry), head);
+
+			tomoyo_put_name_union(&entry->name);
+		}
+		break;
+	case TOMOYO_TYPE_MANUAL_TASK_ACL:
+		{
+			struct tomoyo_task_acl *entry =
+				container_of(acl, typeof(*entry), head);
+			tomoyo_put_name(entry->domainname);
+		}
+		break;
 	}
 }
 
-static bool tomoyo_del_domain(struct list_head *element)
+/**
+ * tomoyo_del_domain - Delete members in "struct tomoyo_domain_info".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ *
+ * Caller holds tomoyo_policy_lock mutex.
+ */
+static inline void tomoyo_del_domain(struct list_head *element)
 {
 	struct tomoyo_domain_info *domain =
 		container_of(element, typeof(*domain), list);
 	struct tomoyo_acl_info *acl;
 	struct tomoyo_acl_info *tmp;
 	/*
-	 * Since we don't protect whole execve() operation using SRCU,
-	 * we need to recheck domain->users at this point.
-	 *
-	 * (1) Reader starts SRCU section upon execve().
-	 * (2) Reader traverses tomoyo_domain_list and finds this domain.
-	 * (3) Writer marks this domain as deleted.
-	 * (4) Garbage collector removes this domain from tomoyo_domain_list
-	 *     because this domain is marked as deleted and used by nobody.
-	 * (5) Reader saves reference to this domain into
-	 *     "struct linux_binprm"->cred->security .
-	 * (6) Reader finishes SRCU section, although execve() operation has
-	 *     not finished yet.
-	 * (7) Garbage collector waits for SRCU synchronization.
-	 * (8) Garbage collector kfree() this domain because this domain is
-	 *     used by nobody.
-	 * (9) Reader finishes execve() operation and restores this domain from
-	 *     "struct linux_binprm"->cred->security.
-	 *
-	 * By updating domain->users at (5), we can solve this race problem
-	 * by rechecking domain->users at (8).
+	 * Since this domain is referenced from neither
+	 * "struct tomoyo_io_buffer" nor "struct cred"->security, we can delete
+	 * elements without checking for is_deleted flag.
 	 */
-	if (atomic_read(&domain->users))
-		return false;
 	list_for_each_entry_safe(acl, tmp, &domain->acl_info_list, list) {
 		tomoyo_del_acl(&acl->list);
 		tomoyo_memory_free(acl);
 	}
 	tomoyo_put_name(domain->domainname);
-	return true;
 }
 
+/**
+ * tomoyo_del_condition - Delete members in "struct tomoyo_condition".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+void tomoyo_del_condition(struct list_head *element)
+{
+	struct tomoyo_condition *cond = container_of(element, typeof(*cond),
+						     head.list);
+	const u16 condc = cond->condc;
+	const u16 numbers_count = cond->numbers_count;
+	const u16 names_count = cond->names_count;
+	const u16 argc = cond->argc;
+	const u16 envc = cond->envc;
+	unsigned int i;
+	const struct tomoyo_condition_element *condp
+		= (const struct tomoyo_condition_element *) (cond + 1);
+	struct tomoyo_number_union *numbers_p
+		= (struct tomoyo_number_union *) (condp + condc);
+	struct tomoyo_name_union *names_p
+		= (struct tomoyo_name_union *) (numbers_p + numbers_count);
+	const struct tomoyo_argv *argv
+		= (const struct tomoyo_argv *) (names_p + names_count);
+	const struct tomoyo_envp *envp
+		= (const struct tomoyo_envp *) (argv + argc);
+	for (i = 0; i < numbers_count; i++)
+		tomoyo_put_number_union(numbers_p++);
+	for (i = 0; i < names_count; i++)
+		tomoyo_put_name_union(names_p++);
+	for (i = 0; i < argc; argv++, i++)
+		tomoyo_put_name(argv->value);
+	for (i = 0; i < envc; envp++, i++) {
+		tomoyo_put_name(envp->name);
+		tomoyo_put_name(envp->value);
+	}
+}
 
-static void tomoyo_del_name(struct list_head *element)
+/**
+ * tomoyo_del_name - Delete members in "struct tomoyo_name".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_name(struct list_head *element)
 {
-	const struct tomoyo_name *ptr =
-		container_of(element, typeof(*ptr), list);
+	/* Nothing to do. */
 }
 
-static void tomoyo_del_path_group(struct list_head *element)
+/**
+ * tomoyo_del_path_group - Delete members in "struct tomoyo_path_group".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_path_group(struct list_head *element)
 {
 	struct tomoyo_path_group *member =
 		container_of(element, typeof(*member), head.list);
 	tomoyo_put_name(member->member_name);
 }
 
-static void tomoyo_del_group(struct list_head *element)
+/**
+ * tomoyo_del_group - Delete "struct tomoyo_group".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_group(struct list_head *element)
 {
 	struct tomoyo_group *group =
-		container_of(element, typeof(*group), list);
+		container_of(element, typeof(*group), head.list);
 	tomoyo_put_name(group->group_name);
 }
 
-static void tomoyo_del_number_group(struct list_head *element)
+/**
+ * tomoyo_del_address_group - Delete members in "struct tomoyo_address_group".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_address_group(struct list_head *element)
 {
-	struct tomoyo_number_group *member =
-		container_of(element, typeof(*member), head.list);
+	/* Nothing to do. */
 }
 
-static bool tomoyo_collect_member(struct list_head *member_list, int id)
+/**
+ * tomoyo_del_number_group - Delete members in "struct tomoyo_number_group".
+ *
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static inline void tomoyo_del_number_group(struct list_head *element)
+{
+	/* Nothing to do. */
+}
+
+/**
+ * tomoyo_try_to_gc - Try to kfree() an entry.
+ *
+ * @type:    One of values in "enum tomoyo_policy_id".
+ * @element: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ *
+ * Caller holds tomoyo_policy_lock mutex.
+ */
+static void tomoyo_try_to_gc(const enum tomoyo_policy_id type,
+			     struct list_head *element)
+{
+	/*
+	 * __list_del_entry() guarantees that the list element became no longer
+	 * reachable from the list which the element was originally on (e.g.
+	 * tomoyo_domain_list). Also, synchronize_srcu() guarantees that the
+	 * list element became no longer referenced by syscall users.
+	 */
+	__list_del_entry(element);
+	mutex_unlock(&tomoyo_policy_lock);
+	synchronize_srcu(&tomoyo_ss);
+	/*
+	 * However, there are two users which may still be using the list
+	 * element. We need to defer until both users forget this element.
+	 *
+	 * Don't kfree() until "struct tomoyo_io_buffer"->r.{domain,group,acl}
+	 * and "struct tomoyo_io_buffer"->w.domain forget this element.
+	 */
+	if (tomoyo_struct_used_by_io_buffer(element))
+		goto reinject;
+	switch (type) {
+	case TOMOYO_ID_TRANSITION_CONTROL:
+		tomoyo_del_transition_control(element);
+		break;
+	case TOMOYO_ID_MANAGER:
+		tomoyo_del_manager(element);
+		break;
+	case TOMOYO_ID_AGGREGATOR:
+		tomoyo_del_aggregator(element);
+		break;
+	case TOMOYO_ID_GROUP:
+		tomoyo_del_group(element);
+		break;
+	case TOMOYO_ID_PATH_GROUP:
+		tomoyo_del_path_group(element);
+		break;
+	case TOMOYO_ID_ADDRESS_GROUP:
+		tomoyo_del_address_group(element);
+		break;
+	case TOMOYO_ID_NUMBER_GROUP:
+		tomoyo_del_number_group(element);
+		break;
+	case TOMOYO_ID_CONDITION:
+		tomoyo_del_condition(element);
+		break;
+	case TOMOYO_ID_NAME:
+		/*
+		 * Don't kfree() until all "struct tomoyo_io_buffer"->r.w[]
+		 * forget this element.
+		 */
+		if (tomoyo_name_used_by_io_buffer
+		    (container_of(element, typeof(struct tomoyo_name),
+				  head.list)->entry.name))
+			goto reinject;
+		tomoyo_del_name(element);
+		break;
+	case TOMOYO_ID_ACL:
+		tomoyo_del_acl(element);
+		break;
+	case TOMOYO_ID_DOMAIN:
+		/*
+		 * Don't kfree() until all "struct cred"->security forget this
+		 * element.
+		 */
+		if (atomic_read(&container_of
+				(element, typeof(struct tomoyo_domain_info),
+				 list)->users))
+			goto reinject;
+		break;
+	case TOMOYO_MAX_POLICY:
+		break;
+	}
+	mutex_lock(&tomoyo_policy_lock);
+	if (type == TOMOYO_ID_DOMAIN)
+		tomoyo_del_domain(element);
+	tomoyo_memory_free(element);
+	return;
+reinject:
+	/*
+	 * We can safely reinject this element here bacause
+	 * (1) Appending list elements and removing list elements are protected
+	 *     by tomoyo_policy_lock mutex.
+	 * (2) Only this function removes list elements and this function is
+	 *     exclusively executed by tomoyo_gc_mutex mutex.
+	 * are true.
+	 */
+	mutex_lock(&tomoyo_policy_lock);
+	list_add_rcu(element, element->prev);
+}
+
+/**
+ * tomoyo_collect_member - Delete elements with "struct tomoyo_acl_head".
+ *
+ * @id:          One of values in "enum tomoyo_policy_id".
+ * @member_list: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static void tomoyo_collect_member(const enum tomoyo_policy_id id,
+				  struct list_head *member_list)
 {
 	struct tomoyo_acl_head *member;
-	list_for_each_entry(member, member_list, list) {
+	struct tomoyo_acl_head *tmp;
+	list_for_each_entry_safe(member, tmp, member_list, list) {
 		if (!member->is_deleted)
 			continue;
-		if (!tomoyo_add_to_gc(id, &member->list))
-			return false;
+		member->is_deleted = TOMOYO_GC_IN_PROGRESS;
+		tomoyo_try_to_gc(id, &member->list);
 	}
-        return true;
 }
 
-static bool tomoyo_collect_acl(struct tomoyo_domain_info *domain)
+/**
+ * tomoyo_collect_acl - Delete elements in "struct tomoyo_domain_info".
+ *
+ * @list: Pointer to "struct list_head".
+ *
+ * Returns nothing.
+ */
+static void tomoyo_collect_acl(struct list_head *list)
 {
 	struct tomoyo_acl_info *acl;
-	list_for_each_entry(acl, &domain->acl_info_list, list) {
+	struct tomoyo_acl_info *tmp;
+	list_for_each_entry_safe(acl, tmp, list, list) {
 		if (!acl->is_deleted)
 			continue;
-		if (!tomoyo_add_to_gc(TOMOYO_ID_ACL, &acl->list))
-			return false;
+		acl->is_deleted = TOMOYO_GC_IN_PROGRESS;
+		tomoyo_try_to_gc(TOMOYO_ID_ACL, &acl->list);
 	}
-	return true;
 }
 
+/**
+ * tomoyo_collect_entry - Try to kfree() deleted elements.
+ *
+ * Returns nothing.
+ */
 static void tomoyo_collect_entry(void)
 {
 	int i;
-	if (mutex_lock_interruptible(&tomoyo_policy_lock))
-		return;
-	for (i = 0; i < TOMOYO_MAX_POLICY; i++) {
-		if (!tomoyo_collect_member(&tomoyo_policy_list[i], i))
-			goto unlock;
-	}
+	enum tomoyo_policy_id id;
+	struct tomoyo_policy_namespace *ns;
+	mutex_lock(&tomoyo_policy_lock);
 	{
 		struct tomoyo_domain_info *domain;
-		list_for_each_entry_rcu(domain, &tomoyo_domain_list, list) {
-			if (!tomoyo_collect_acl(domain))
-				goto unlock;
+		struct tomoyo_domain_info *tmp;
+		list_for_each_entry_safe(domain, tmp, &tomoyo_domain_list,
+					 list) {
+			tomoyo_collect_acl(&domain->acl_info_list);
 			if (!domain->is_deleted || atomic_read(&domain->users))
 				continue;
-			/*
-			 * Nobody is referring this domain. But somebody may
-			 * refer this domain after successful execve().
-			 * We recheck domain->users after SRCU synchronization.
-			 */
-			if (!tomoyo_add_to_gc(TOMOYO_ID_DOMAIN, &domain->list))
-				goto unlock;
+			tomoyo_try_to_gc(TOMOYO_ID_DOMAIN, &domain->list);
 		}
 	}
-	for (i = 0; i < TOMOYO_MAX_HASH; i++) {
-		struct tomoyo_name *ptr;
-		list_for_each_entry_rcu(ptr, &tomoyo_name_list[i], list) {
-			if (atomic_read(&ptr->users))
+	list_for_each_entry(ns, &tomoyo_namespace_list, namespace_list) {
+		for (id = 0; id < TOMOYO_MAX_POLICY; id++)
+			tomoyo_collect_member(id, &ns->policy_list[id]);
+		for (i = 0; i < TOMOYO_MAX_ACL_GROUPS; i++)
+			tomoyo_collect_acl(&ns->acl_group[i]);
+	}
+	{
+		struct tomoyo_shared_acl_head *ptr;
+		struct tomoyo_shared_acl_head *tmp;
+		list_for_each_entry_safe(ptr, tmp, &tomoyo_condition_list,
+					 list) {
+			if (atomic_read(&ptr->users) > 0)
 				continue;
-			if (!tomoyo_add_to_gc(TOMOYO_ID_NAME, &ptr->list))
-				goto unlock;
+			atomic_set(&ptr->users, TOMOYO_GC_IN_PROGRESS);
+			tomoyo_try_to_gc(TOMOYO_ID_CONDITION, &ptr->list);
 		}
 	}
-	for (i = 0; i < TOMOYO_MAX_GROUP; i++) {
-		struct list_head *list = &tomoyo_group_list[i];
-		int id;
-		struct tomoyo_group *group;
-		switch (i) {
-		case 0:
-			id = TOMOYO_ID_PATH_GROUP;
-			break;
-		default:
-			id = TOMOYO_ID_NUMBER_GROUP;
-			break;
+	list_for_each_entry(ns, &tomoyo_namespace_list, namespace_list) {
+		for (i = 0; i < TOMOYO_MAX_GROUP; i++) {
+			struct list_head *list = &ns->group_list[i];
+			struct tomoyo_group *group;
+			struct tomoyo_group *tmp;
+			switch (i) {
+			case 0:
+				id = TOMOYO_ID_PATH_GROUP;
+				break;
+			case 1:
+				id = TOMOYO_ID_NUMBER_GROUP;
+				break;
+			default:
+				id = TOMOYO_ID_ADDRESS_GROUP;
+				break;
+			}
+			list_for_each_entry_safe(group, tmp, list, head.list) {
+				tomoyo_collect_member(id, &group->member_list);
+				if (!list_empty(&group->member_list) ||
+				    atomic_read(&group->head.users) > 0)
+					continue;
+				atomic_set(&group->head.users,
+					   TOMOYO_GC_IN_PROGRESS);
+				tomoyo_try_to_gc(TOMOYO_ID_GROUP,
+						 &group->head.list);
+			}
 		}
-		list_for_each_entry(group, list, list) {
-			if (!tomoyo_collect_member(&group->member_list, id))
-				goto unlock;
-			if (!list_empty(&group->member_list) ||
-			    atomic_read(&group->users))
+	}
+	for (i = 0; i < TOMOYO_MAX_HASH; i++) {
+		struct list_head *list = &tomoyo_name_list[i];
+		struct tomoyo_shared_acl_head *ptr;
+		struct tomoyo_shared_acl_head *tmp;
+		list_for_each_entry_safe(ptr, tmp, list, list) {
+			if (atomic_read(&ptr->users) > 0)
 				continue;
-			if (!tomoyo_add_to_gc(TOMOYO_ID_GROUP, &group->list))
-				goto unlock;
+			atomic_set(&ptr->users, TOMOYO_GC_IN_PROGRESS);
+			tomoyo_try_to_gc(TOMOYO_ID_NAME, &ptr->list);
 		}
 	}
- unlock:
 	mutex_unlock(&tomoyo_policy_lock);
 }
 
-static void tomoyo_kfree_entry(void)
+/**
+ * tomoyo_gc_thread - Garbage collector thread function.
+ *
+ * @unused: Unused.
+ *
+ * Returns 0.
+ */
+static int tomoyo_gc_thread(void *unused)
 {
-	struct tomoyo_gc *p;
-	struct tomoyo_gc *tmp;
+	/* Garbage collector thread is exclusive. */
+	static DEFINE_MUTEX(tomoyo_gc_mutex);
+	if (!mutex_trylock(&tomoyo_gc_mutex))
+		goto out;
+	tomoyo_collect_entry();
+	{
+		struct tomoyo_io_buffer *head;
+		struct tomoyo_io_buffer *tmp;
 
-	list_for_each_entry_safe(p, tmp, &tomoyo_gc_queue, list) {
-		struct list_head *element = p->element;
-		switch (p->type) {
-		case TOMOYO_ID_TRANSITION_CONTROL:
-			tomoyo_del_transition_control(element);
-			break;
-		case TOMOYO_ID_AGGREGATOR:
-			tomoyo_del_aggregator(element);
-			break;
-		case TOMOYO_ID_GLOBALLY_READABLE:
-			tomoyo_del_allow_read(element);
-			break;
-		case TOMOYO_ID_PATTERN:
-			tomoyo_del_file_pattern(element);
-			break;
-		case TOMOYO_ID_NO_REWRITE:
-			tomoyo_del_no_rewrite(element);
-			break;
-		case TOMOYO_ID_MANAGER:
-			tomoyo_del_manager(element);
-			break;
-		case TOMOYO_ID_NAME:
-			tomoyo_del_name(element);
-			break;
-		case TOMOYO_ID_ACL:
-			tomoyo_del_acl(element);
-			break;
-		case TOMOYO_ID_DOMAIN:
-			if (!tomoyo_del_domain(element))
+		spin_lock(&tomoyo_io_buffer_list_lock);
+		list_for_each_entry_safe(head, tmp, &tomoyo_io_buffer_list,
+					 list) {
+			if (head->users)
 				continue;
-			break;
-		case TOMOYO_ID_PATH_GROUP:
-			tomoyo_del_path_group(element);
-			break;
-		case TOMOYO_ID_GROUP:
-			tomoyo_del_group(element);
-			break;
-		case TOMOYO_ID_NUMBER_GROUP:
-			tomoyo_del_number_group(element);
-			break;
+			list_del(&head->list);
+			kfree(head->read_buf);
+			kfree(head->write_buf);
+			kfree(head);
 		}
-		tomoyo_memory_free(element);
-		list_del(&p->list);
-		kfree(p);
+		spin_unlock(&tomoyo_io_buffer_list_lock);
 	}
+	mutex_unlock(&tomoyo_gc_mutex);
+out:
+	/* This acts as do_exit(0). */
+	return 0;
 }
 
-static int tomoyo_gc_thread(void *unused)
+/**
+ * tomoyo_notify_gc - Register/unregister /sys/kernel/security/tomoyo/ users.
+ *
+ * @head:        Pointer to "struct tomoyo_io_buffer".
+ * @is_register: True if register, false if unregister.
+ *
+ * Returns nothing.
+ */
+void tomoyo_notify_gc(struct tomoyo_io_buffer *head, const bool is_register)
 {
-	daemonize("GC for TOMOYO");
-	if (mutex_trylock(&tomoyo_gc_mutex)) {
-		int i;
-		for (i = 0; i < 10; i++) {
-			tomoyo_collect_entry();
-			if (list_empty(&tomoyo_gc_queue))
-				break;
-			synchronize_srcu(&tomoyo_ss);
-			tomoyo_kfree_entry();
+	bool is_write = false;
+
+	spin_lock(&tomoyo_io_buffer_list_lock);
+	if (is_register) {
+		head->users = 1;
+		list_add(&head->list, &tomoyo_io_buffer_list);
+	} else {
+		is_write = head->write_buf != NULL;
+		if (!--head->users) {
+			list_del(&head->list);
+			kfree(head->read_buf);
+			kfree(head->write_buf);
+			kfree(head);
 		}
-		mutex_unlock(&tomoyo_gc_mutex);
 	}
-	do_exit(0);
-}
-
-void tomoyo_run_gc(void)
-{
-	struct task_struct *task = kthread_create(tomoyo_gc_thread, NULL,
-						  "GC for TOMOYO");
-	if (!IS_ERR(task))
-		wake_up_process(task);
+	spin_unlock(&tomoyo_io_buffer_list_lock);
+	if (is_write) {
+		struct task_struct *task = kthread_create(tomoyo_gc_thread,
+							  NULL,
+							  "GC for TOMOYO");
+		if (!IS_ERR(task))
+			wake_up_process(task);
+	}
 }