gc.c

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/*
 * security/tomoyo/gc.c
 *
 * Copyright (C) 2005-2011  NTT DATA CORPORATION
 */

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

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);

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;
}

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;
}

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);
}

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);
}

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);
}

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;
    }
}

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);
}

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 inline void tomoyo_del_name(struct list_head *element)
{
    /* Nothing to do. */
}

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 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);
}

static inline void tomoyo_del_address_group(struct list_head *element)
{
    /* Nothing to do. */
}

static inline void tomoyo_del_number_group(struct list_head *element)
{
    /* Nothing to do. */
}

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);
}

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);
    }
}

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);
    }
}

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);
}

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;
}

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);
    }
}