blk-throttle: fix UAF by deleteing timer in blk_throtl_exit()

Commit Message

Li Jinlin Sept. 7, 2021, 12:12 p.m. UTC

From: Li Jinlin <[e-mail]>

The pending timer has been set up in blk_throtl_init(). However, the
timer is not deleted in blk_throtl_exit(). This means that the timer
handler may still be running after freeing the timer, which would
result in a use-after-free.

Fix by calling del_timer_sync() to delete the timer in blk_throtl_exit().

Signed-off-by: Li Jinlin <[e-mail]>
---
 block/blk-throttle.c | 1 +
 1 file changed, 1 insertion(+)

Comments

Jens Axboe Sept. 7, 2021, 2:37 p.m. UTC | #1

On 9/7/21 6:12 AM, Li Jinlin wrote:
> From: Li Jinlin <[e-mail]>
> 
> The pending timer has been set up in blk_throtl_init(). However, the
> timer is not deleted in blk_throtl_exit(). This means that the timer
> handler may still be running after freeing the timer, which would
> result in a use-after-free.
> 
> Fix by calling del_timer_sync() to delete the timer in blk_throtl_exit().

Applied, thanks.

Patch

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 55c49015e533..dbe49e181a88 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -2458,6 +2458,7 @@  int blk_throtl_init(struct request_queue *q)
 void blk_throtl_exit(struct request_queue *q)
 {
 	BUG_ON(!q->td);
+	del_timer_sync(&q->td->service_queue.pending_timer);
 	throtl_shutdown_wq(q);
 	blkcg_deactivate_policy(q, &blkcg_policy_throtl);
 	free_percpu(q->td->latency_buckets[READ]);