kernel-hacking-2024-linux-steffo/security/tomoyo/gc.c

// SPDX-License-Identifier: GPL-2.0
/*
 * security/tomoyo/gc.c
 *
 * Copyright (C) 2005-2011  NTT DATA CORPORATION
 */

#include "common.h"
#include <linux/kthread.h>
#include <linux/slab.h>

/* Lock for GC. */
DEFINE_SRCU(tomoyo_ss);

/**
 * 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 because
	 * (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)
		kthread_run(tomoyo_gc_thread, NULL, "GC for TOMOYO");
}