/*
 * security/tomoyo/gc.c
 *
 * Implementation of the Domain-Based Mandatory Access Control.
 *
 * Copyright (C) 2005-2010  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)
{
        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;
}

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);
}

static void tomoyo_del_file_pattern(struct list_head *element)
{
        struct tomoyo_no_pattern *ptr =
                container_of(element, typeof(*ptr), head.list);
        tomoyo_put_name(ptr->pattern);
}

static void tomoyo_del_no_rewrite(struct list_head *element)
{
        struct tomoyo_no_rewrite *ptr =
                container_of(element, typeof(*ptr), head.list);
        tomoyo_put_name(ptr->pattern);
}

static 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);
}

static 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);
}

static void tomoyo_del_manager(struct list_head *element)
{
        struct tomoyo_manager *ptr =
                container_of(element, typeof(*ptr), head.list);
        tomoyo_put_name(ptr->manager);
}

static void tomoyo_del_acl(struct list_head *element)
{
        struct tomoyo_acl_info *acl =
                container_of(element, typeof(*acl), list);
        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;
        }
}

static bool 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).
         */
        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;
}


static void tomoyo_del_name(struct list_head *element)
{
        const struct tomoyo_name *ptr =
                container_of(element, typeof(*ptr), list);
}

static 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)
{
        struct tomoyo_group *group =
                container_of(element, typeof(*group), list);
        tomoyo_put_name(group->group_name);
}

static void tomoyo_del_number_group(struct list_head *element)
{
        struct tomoyo_number_group *member =
                container_of(element, typeof(*member), head.list);
}

static bool tomoyo_collect_member(struct list_head *member_list, int id)
{
        struct tomoyo_acl_head *member;
        list_for_each_entry(member, member_list, list) {
                if (!member->is_deleted)
                        continue;
                if (!tomoyo_add_to_gc(id, &member->list))
                        return false;
        }
        return true;
}

static bool tomoyo_collect_acl(struct tomoyo_domain_info *domain)
{
        struct tomoyo_acl_info *acl;
        list_for_each_entry(acl, &domain->acl_info_list, list) {
                if (!acl->is_deleted)
                        continue;
                if (!tomoyo_add_to_gc(TOMOYO_ID_ACL, &acl->list))
                        return false;
        }
        return true;
}

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;
        }
        {
                struct tomoyo_domain_info *domain;
                list_for_each_entry_rcu(domain, &tomoyo_domain_list, list) {
                        if (!tomoyo_collect_acl(domain))
                                goto unlock;
                        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;
                }
        }
        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))
                                continue;
                        if (!tomoyo_add_to_gc(TOMOYO_ID_NAME, &ptr->list))
                                goto unlock;
                }
        }
        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(group, list, list) {
                        if (!tomoyo_collect_member(&group->member_list, id))
                                goto unlock;
                        if (!list_empty(&group->member_list) ||
                            atomic_read(&group->users))
                                continue;
                        if (!tomoyo_add_to_gc(TOMOYO_ID_GROUP, &group->list))
                                goto unlock;
                }
        }
 unlock:
        mutex_unlock(&tomoyo_policy_lock);
}

static void tomoyo_kfree_entry(void)
{
        struct tomoyo_gc *p;
        struct tomoyo_gc *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))
                                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;
                }
                tomoyo_memory_free(element);
                list_del(&p->list);
                kfree(p);
        }
}

static int tomoyo_gc_thread(void *unused)
{
        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();
                }
                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);
}