/*
   * security/tomoyo/gc.c
   *
   * Copyright (C) 2005-2011  NTT DATA CORPORATION
   */
  
  #include "common.h"
  #include <linux/kthread.h>
  #include <linux/slab.h>
  
  /**
   * 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)
  {
  	tomoyo_memory_used[TOMOYO_MEMORY_POLICY] -= ksize(ptr);
  	kfree(ptr);
  }
  
  /* 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);
  
  /**
   * 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_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;
  }
  
  /**
   * 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_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;
  }
  
  /**
   * 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);
  	tomoyo_put_name(ptr->domainname);
  	tomoyo_put_name(ptr->program);
  }
  
  /**
   * 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);
  	tomoyo_put_name(ptr->original_name);
  	tomoyo_put_name(ptr->aggregated_name);
  }
  
  /**
   * 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:
  		{
  			struct tomoyo_path_acl *entry
  				= container_of(acl, typeof(*entry), head);
  			tomoyo_put_name_union(&entry->name);
  		}
  		break;
  	case TOMOYO_TYPE_PATH2_ACL:
  		{
  			struct tomoyo_path2_acl *entry
  				= container_of(acl, typeof(*entry), head);
  			tomoyo_put_name_union(&entry->name1);
  			tomoyo_put_name_union(&entry->name2);
  		}
  		break;
  	case TOMOYO_TYPE_PATH_NUMBER_ACL:
  		{
  			struct tomoyo_path_number_acl *entry
  				= container_of(acl, typeof(*entry), head);
  			tomoyo_put_name_union(&entry->name);
  			tomoyo_put_number_union(&entry->number);
  		}
  		break;
  	case TOMOYO_TYPE_MKDEV_ACL:
  		{
  			struct tomoyo_mkdev_acl *entry
  				= container_of(acl, typeof(*entry), head);
  			tomoyo_put_name_union(&entry->name);
  			tomoyo_put_number_union(&entry->mode);
  			tomoyo_put_number_union(&entry->major);
  			tomoyo_put_number_union(&entry->minor);
  		}
  		break;
  	case TOMOYO_TYPE_MOUNT_ACL:
  		{
  			struct tomoyo_mount_acl *entry
  				= container_of(acl, typeof(*entry), head);
  			tomoyo_put_name_union(&entry->dev_name);
  			tomoyo_put_name_union(&entry->dir_name);
  			tomoyo_put_name_union(&entry->fs_type);
  			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;
  	}
  }
  
  /**
   * 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 this domain is referenced from neither
  	 * "struct tomoyo_io_buffer" nor "struct cred"->security, we can delete
  	 * elements without checking for is_deleted flag.
  	 */
  	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);
  }
  
  /**
   * 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);
  	}
  }
  
  /**
   * 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)
  {
  	/* Nothing to do. */
  }
  
  /**
   * 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);
  }
  
  /**
   * 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), head.list);
  	tomoyo_put_name(group->group_name);
  }
  
  /**
   * 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)
  {
  	/* Nothing to do. */
  }
  
  /**
   * 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;
  	struct tomoyo_acl_head *tmp;
  	list_for_each_entry_safe(member, tmp, member_list, list) {
  		if (!member->is_deleted)
  			continue;
  		member->is_deleted = TOMOYO_GC_IN_PROGRESS;
  		tomoyo_try_to_gc(id, &member->list);
  	}
  }
  
  /**
   * 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;
  	struct tomoyo_acl_info *tmp;
  	list_for_each_entry_safe(acl, tmp, list, list) {
  		if (!acl->is_deleted)
  			continue;
  		acl->is_deleted = TOMOYO_GC_IN_PROGRESS;
  		tomoyo_try_to_gc(TOMOYO_ID_ACL, &acl->list);
  	}
  }
  
  /**
   * tomoyo_collect_entry - Try to kfree() deleted elements.
   *
   * Returns nothing.
   */
  static void tomoyo_collect_entry(void)
  {
  	int i;
  	enum tomoyo_policy_id id;
  	struct tomoyo_policy_namespace *ns;
  	mutex_lock(&tomoyo_policy_lock);
  	{
  		struct tomoyo_domain_info *domain;
  		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;
  			tomoyo_try_to_gc(TOMOYO_ID_DOMAIN, &domain->list);
  		}
  	}
  	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;
  			atomic_set(&ptr->users, TOMOYO_GC_IN_PROGRESS);
  			tomoyo_try_to_gc(TOMOYO_ID_CONDITION, &ptr->list);
  		}
  	}
  	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);
  			}
  		}
  	}
  	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;
  			atomic_set(&ptr->users, TOMOYO_GC_IN_PROGRESS);
  			tomoyo_try_to_gc(TOMOYO_ID_NAME, &ptr->list);
  		}
  	}
  	mutex_unlock(&tomoyo_policy_lock);
  }
  
  /**
   * tomoyo_gc_thread - Garbage collector thread function.
   *
   * @unused: Unused.
   *
   * Returns 0.
   */
  static int tomoyo_gc_thread(void *unused)
  {
  	/* 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;
  
  		spin_lock(&tomoyo_io_buffer_list_lock);
  		list_for_each_entry_safe(head, tmp, &tomoyo_io_buffer_list,
  					 list) {
  			if (head->users)
  				continue;
  			list_del(&head->list);
  			kfree(head->read_buf);
  			kfree(head->write_buf);
  			kfree(head);
  		}
  		spin_unlock(&tomoyo_io_buffer_list_lock);
  	}
  	mutex_unlock(&tomoyo_gc_mutex);
  out:
  	/* This acts as do_exit(0). */
  	return 0;
  }
  
  /**
   * 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)
  {
  	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);
  		}
  	}
  	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);
  	}
  }