swh:1:snp:c2847dfd741eae21606027cf29250d1ebcd63fb4
Tip revision: 322a8b034003c0d46d39af85bf24fee27b902f48 authored by Linus Torvalds on 08 August 2011, 01:23:30 UTC
Linux 3.1-rc1
Linux 3.1-rc1
Tip revision: 322a8b0
gc.c
/*
* security/tomoyo/gc.c
*
* Copyright (C) 2005-2011 NTT DATA CORPORATION
*/
#include "common.h"
#include <linux/kthread.h>
#include <linux/slab.h>
/* 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);
/* Size of an element. */
static const u8 tomoyo_element_size[TOMOYO_MAX_POLICY] = {
[TOMOYO_ID_GROUP] = sizeof(struct tomoyo_group),
[TOMOYO_ID_PATH_GROUP] = sizeof(struct tomoyo_path_group),
[TOMOYO_ID_NUMBER_GROUP] = sizeof(struct tomoyo_number_group),
[TOMOYO_ID_AGGREGATOR] = sizeof(struct tomoyo_aggregator),
[TOMOYO_ID_TRANSITION_CONTROL] =
sizeof(struct tomoyo_transition_control),
[TOMOYO_ID_MANAGER] = sizeof(struct tomoyo_manager),
/* [TOMOYO_ID_CONDITION] = "struct tomoyo_condition"->size, */
/* [TOMOYO_ID_NAME] = "struct tomoyo_name"->size, */
/* [TOMOYO_ID_ACL] =
tomoyo_acl_size["struct tomoyo_acl_info"->type], */
[TOMOYO_ID_DOMAIN] = sizeof(struct tomoyo_domain_info),
};
/* Size of a domain ACL element. */
static const u8 tomoyo_acl_size[] = {
[TOMOYO_TYPE_PATH_ACL] = sizeof(struct tomoyo_path_acl),
[TOMOYO_TYPE_PATH2_ACL] = sizeof(struct tomoyo_path2_acl),
[TOMOYO_TYPE_PATH_NUMBER_ACL] = sizeof(struct tomoyo_path_number_acl),
[TOMOYO_TYPE_MKDEV_ACL] = sizeof(struct tomoyo_mkdev_acl),
[TOMOYO_TYPE_MOUNT_ACL] = sizeof(struct tomoyo_mount_acl),
};
/**
* 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);
if (mutex_lock_interruptible(&head->io_sem)) {
in_use = true;
goto out;
}
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);
out:
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.
* @size: Memory allocated for @string .
*
* 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,
const size_t size)
{
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) {
int i;
head->users++;
spin_unlock(&tomoyo_io_buffer_list_lock);
if (mutex_lock_interruptible(&head->io_sem)) {
in_use = true;
goto out;
}
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);
out:
spin_lock(&tomoyo_io_buffer_list_lock);
head->users--;
if (in_use)
break;
}
spin_unlock(&tomoyo_io_buffer_list_lock);
return in_use;
}
/* Structure for garbage collection. */
struct tomoyo_gc {
struct list_head list;
enum tomoyo_policy_id type;
size_t size;
struct list_head *element;
};
/* List of entries to be deleted. */
static LIST_HEAD(tomoyo_gc_list);
/* Length of tomoyo_gc_list. */
static int tomoyo_gc_list_len;
/**
* tomoyo_add_to_gc - Add an entry to to be deleted list.
*
* @type: One of values in "enum tomoyo_policy_id".
* @element: Pointer to "struct list_head".
*
* Returns true on success, false otherwise.
*
* Caller holds tomoyo_policy_lock mutex.
*
* Adding an entry needs kmalloc(). Thus, if we try to add thousands of
* entries at once, it will take too long time. Thus, do not add more than 128
* entries per a scan. But to be able to handle worst case where all entries
* are in-use, we accept one more entry per a scan.
*
* If we use singly linked list using "struct list_head"->prev (which is
* LIST_POISON2), we can avoid kmalloc().
*/
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;
if (type == TOMOYO_ID_ACL)
entry->size = tomoyo_acl_size[
container_of(element,
typeof(struct tomoyo_acl_info),
list)->type];
else if (type == TOMOYO_ID_NAME)
entry->size = strlen(container_of(element,
typeof(struct tomoyo_name),
head.list)->entry.name) + 1;
else if (type == TOMOYO_ID_CONDITION)
entry->size =
container_of(element, typeof(struct tomoyo_condition),
head.list)->size;
else
entry->size = tomoyo_element_size[type];
entry->element = element;
list_add(&entry->list, &tomoyo_gc_list);
list_del_rcu(element);
return tomoyo_gc_list_len++ < 128;
}
/**
* tomoyo_element_linked_by_gc - Validate next element of an entry.
*
* @element: Pointer to an element.
* @size: Size of @element in byte.
*
* Returns true if @element is linked by other elements in the garbage
* collector's queue, false otherwise.
*/
static bool tomoyo_element_linked_by_gc(const u8 *element, const size_t size)
{
struct tomoyo_gc *p;
list_for_each_entry(p, &tomoyo_gc_list, list) {
const u8 *ptr = (const u8 *) p->element->next;
if (ptr < element || element + size < ptr)
continue;
return true;
}
return false;
}
/**
* tomoyo_del_transition_control - Delete members in "struct tomoyo_transition_control".
*
* @element: Pointer to "struct list_head".
*
* Returns nothing.
*/
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);
}
/**
* tomoyo_del_aggregator - Delete members in "struct tomoyo_aggregator".
*
* @element: Pointer to "struct list_head".
*
* Returns nothing.
*/
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);
}
/**
* tomoyo_del_manager - Delete members in "struct tomoyo_manager".
*
* @element: Pointer to "struct list_head".
*
* Returns nothing.
*/
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);
}
/**
* 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;
}
}
/**
* tomoyo_del_domain - Delete members in "struct tomoyo_domain_info".
*
* @element: Pointer to "struct list_head".
*
* Returns true if deleted, false otherwise.
*/
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;
}
/**
* 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 void tomoyo_del_name(struct list_head *element)
{
const struct tomoyo_name *ptr =
container_of(element, typeof(*ptr), head.list);
}
/**
* tomoyo_del_path_group - Delete members in "struct tomoyo_path_group".
*
* @element: Pointer to "struct list_head".
*
* Returns nothing.
*/
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);
}
/**
* tomoyo_del_group - Delete "struct tomoyo_group".
*
* @element: Pointer to "struct list_head".
*
* Returns nothing.
*/
static 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_number_group - Delete members in "struct tomoyo_number_group".
*
* @element: Pointer to "struct list_head".
*
* Returns nothing.
*/
static void tomoyo_del_number_group(struct list_head *element)
{
struct tomoyo_number_group *member =
container_of(element, typeof(*member), head.list);
}
/**
* 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 true if some elements are deleted, false otherwise.
*/
static bool tomoyo_collect_member(const enum tomoyo_policy_id id,
struct list_head *member_list)
{
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;
}
/**
* tomoyo_collect_acl - Delete elements in "struct tomoyo_domain_info".
*
* @list: Pointer to "struct list_head".
*
* Returns true if some elements are deleted, false otherwise.
*/
static bool tomoyo_collect_acl(struct list_head *list)
{
struct tomoyo_acl_info *acl;
list_for_each_entry(acl, list, list) {
if (!acl->is_deleted)
continue;
if (!tomoyo_add_to_gc(TOMOYO_ID_ACL, &acl->list))
return false;
}
return true;
}
/**
* tomoyo_collect_entry - Scan lists for deleted elements.
*
* Returns nothing.
*/
static void tomoyo_collect_entry(void)
{
int i;
enum tomoyo_policy_id id;
struct tomoyo_policy_namespace *ns;
int idx;
if (mutex_lock_interruptible(&tomoyo_policy_lock))
return;
idx = tomoyo_read_lock();
{
struct tomoyo_domain_info *domain;
list_for_each_entry_rcu(domain, &tomoyo_domain_list, list) {
if (!tomoyo_collect_acl(&domain->acl_info_list))
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;
}
}
list_for_each_entry_rcu(ns, &tomoyo_namespace_list, namespace_list) {
for (id = 0; id < TOMOYO_MAX_POLICY; id++)
if (!tomoyo_collect_member(id, &ns->policy_list[id]))
goto unlock;
for (i = 0; i < TOMOYO_MAX_ACL_GROUPS; i++)
if (!tomoyo_collect_acl(&ns->acl_group[i]))
goto unlock;
for (i = 0; i < TOMOYO_MAX_GROUP; i++) {
struct list_head *list = &ns->group_list[i];
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, head.list) {
if (!tomoyo_collect_member
(id, &group->member_list))
goto unlock;
if (!list_empty(&group->member_list) ||
atomic_read(&group->head.users))
continue;
if (!tomoyo_add_to_gc(TOMOYO_ID_GROUP,
&group->head.list))
goto unlock;
}
}
}
id = TOMOYO_ID_CONDITION;
for (i = 0; i < TOMOYO_MAX_HASH + 1; i++) {
struct list_head *list = !i ?
&tomoyo_condition_list : &tomoyo_name_list[i - 1];
struct tomoyo_shared_acl_head *ptr;
list_for_each_entry(ptr, list, list) {
if (atomic_read(&ptr->users))
continue;
if (!tomoyo_add_to_gc(id, &ptr->list))
goto unlock;
}
id = TOMOYO_ID_NAME;
}
unlock:
tomoyo_read_unlock(idx);
mutex_unlock(&tomoyo_policy_lock);
}
/**
* tomoyo_kfree_entry - Delete entries in tomoyo_gc_list.
*
* Returns true if some entries were kfree()d, false otherwise.
*/
static bool tomoyo_kfree_entry(void)
{
struct tomoyo_gc *p;
struct tomoyo_gc *tmp;
bool result = false;
list_for_each_entry_safe(p, tmp, &tomoyo_gc_list, list) {
struct list_head *element = p->element;
/*
* list_del_rcu() in tomoyo_add_to_gc() 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() in tomoyo_gc_thread() guarantees
* that the list element became no longer referenced by syscall
* users.
*
* However, there are three users which may still be using the
* list element. We need to defer until all of these users
* forget the list element.
*
* Firstly, defer until "struct tomoyo_io_buffer"->r.{domain,
* group,acl} and "struct tomoyo_io_buffer"->w.domain forget
* the list element.
*/
if (tomoyo_struct_used_by_io_buffer(element))
continue;
/*
* Secondly, defer until all other elements in the
* tomoyo_gc_list list forget the list element.
*/
if (tomoyo_element_linked_by_gc((const u8 *) element, p->size))
continue;
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_MANAGER:
tomoyo_del_manager(element);
break;
case TOMOYO_ID_CONDITION:
tomoyo_del_condition(element);
break;
case TOMOYO_ID_NAME:
/*
* Thirdly, defer until all "struct tomoyo_io_buffer"
* ->r.w[] forget the list element.
*/
if (tomoyo_name_used_by_io_buffer(
container_of(element, typeof(struct tomoyo_name),
head.list)->entry.name, p->size))
continue;
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;
case TOMOYO_MAX_POLICY:
break;
}
tomoyo_memory_free(element);
list_del(&p->list);
kfree(p);
tomoyo_gc_list_len--;
result = true;
}
return result;
}
/**
* tomoyo_gc_thread - Garbage collector thread function.
*
* @unused: Unused.
*
* In case OOM-killer choose this thread for termination, we create this thread
* as a short live thread whenever /sys/kernel/security/tomoyo/ interface was
* close()d.
*
* 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;
daemonize("GC for TOMOYO");
do {
tomoyo_collect_entry();
if (list_empty(&tomoyo_gc_list))
break;
synchronize_srcu(&tomoyo_ss);
} while (tomoyo_kfree_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);
}
}