Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 2824bc93 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

[PATCH] fix try_module_get race in elevator_find 



This patch removes try_module_get race in elevator_find.
try_module_get should always be called with the spinlock protecting
what the module init/cleanup routines register/unregister to held. In
the case of elevators, we should be holding elv_list to avoid it going
away between spin_unlock_irq and try_module_get.

Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent b2982649

drivers/block/elevator.c

+14 −10
Original line number Diff line number Diff line
@@ -97,7 +97,6 @@ static struct elevator_type *elevator_find(const char *name) 
	struct elevator_type *e = NULL;

	struct list_head *entry;



	spin_lock_irq(&elv_list_lock);

	list_for_each(entry, &elv_list) {

		struct elevator_type *__e;
@@ -108,7 +107,6 @@ static struct elevator_type *elevator_find(const char *name) 
			break;

		}

	}

	spin_unlock_irq(&elv_list_lock);



	return e;

}
@@ -120,12 +118,15 @@ static void elevator_put(struct elevator_type *e) 


static struct elevator_type *elevator_get(const char *name)

{

	struct elevator_type *e = elevator_find(name);

	struct elevator_type *e;



	if (!e)

		return NULL;

	if (!try_module_get(e->elevator_owner))

		return NULL;

	spin_lock_irq(&elv_list_lock);



	e = elevator_find(name);

	if (e && !try_module_get(e->elevator_owner))

		e = NULL;



	spin_unlock_irq(&elv_list_lock);



	return e;

}
@@ -153,11 +154,15 @@ static char chosen_elevator[16]; 


static void elevator_setup_default(void)

{

	struct elevator_type *e;



	/*

	 * check if default is set and exists

	 */

	if (chosen_elevator[0] && elevator_find(chosen_elevator))

	if (chosen_elevator[0] && (e = elevator_get(chosen_elevator))) {

		elevator_put(e);

		return;

	}



#if defined(CONFIG_IOSCHED_AS)

	strcpy(chosen_elevator, "anticipatory");
@@ -555,10 +560,9 @@ void elv_unregister_queue(struct request_queue *q) 


int elv_register(struct elevator_type *e)

{

	spin_lock_irq(&elv_list_lock);

	if (elevator_find(e->elevator_name))

		BUG();



	spin_lock_irq(&elv_list_lock);

	list_add_tail(&e->list, &elv_list);

	spin_unlock_irq(&elv_list_lock);