/*
 * 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);
        }
}