TOMOYO: Fix lockdep warning.
Currently TOMOYO holds SRCU lock upon open() and releases it upon close()
because list elements stored in the "struct tomoyo_io_buffer" instances are
accessed until close() is called. However, such SRCU usage causes lockdep to
complain about leaving the kernel with SRCU lock held.
This patch solves the warning by holding/releasing SRCU upon each
read()/write(). This patch is doing something similar to calling kfree()
without calling synchronize_srcu(), by selectively deferring kfree() by keeping
track of the "struct tomoyo_io_buffer" instances.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/tomoyo/gc.c b/security/tomoyo/gc.c
index 782e844..1e1a6c8 100644
--- a/security/tomoyo/gc.c
+++ b/security/tomoyo/gc.c
@@ -11,13 +11,123 @@
#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_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;
};
-static LIST_HEAD(tomoyo_gc_queue);
-static DEFINE_MUTEX(tomoyo_gc_mutex);
+/* 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.
@@ -43,10 +153,42 @@
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
+ entry->size = tomoyo_element_size[type];
entry->element = element;
- list_add(&entry->list, &tomoyo_gc_queue);
+ list_add(&entry->list, &tomoyo_gc_list);
list_del_rcu(element);
- return true;
+ 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;
}
/**
@@ -151,6 +293,13 @@
}
}
+/**
+ * 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 =
@@ -360,13 +509,44 @@
mutex_unlock(&tomoyo_policy_lock);
}
-static void tomoyo_kfree_entry(void)
+/**
+ * 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_queue, list) {
+ 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);
@@ -378,6 +558,14 @@
tomoyo_del_manager(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:
@@ -402,7 +590,10 @@
tomoyo_memory_free(element);
list_del(&p->list);
kfree(p);
+ tomoyo_gc_list_len--;
+ result = true;
}
+ return result;
}
/**
@@ -418,25 +609,70 @@
*/
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");
- 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();
+ 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);
}
- mutex_unlock(&tomoyo_gc_mutex);
+ spin_unlock(&tomoyo_io_buffer_list_lock);
}
- do_exit(0);
+ mutex_unlock(&tomoyo_gc_mutex);
+out:
+ /* This acts as do_exit(0). */
+ return 0;
}
-void tomoyo_run_gc(void)
+/**
+ * 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)
{
- struct task_struct *task = kthread_create(tomoyo_gc_thread, NULL,
- "GC for TOMOYO");
- if (!IS_ERR(task))
- wake_up_process(task);
+ 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);
+ }
}