[PATCH 5.14 093/100] blk-throttle: fix UAF by deleteing timer in blk_throtl_exit()

From: Greg Kroah-Hartman
Date: Fri Sep 24 2021 - 09:05:01 EST

From: Li Jinlin <lijinlin3@xxxxxxxxxx>

[ Upstream commit 884f0e84f1e3195b801319c8ec3d5774e9bf2710 ]

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 <lijinlin3@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210907121242.2885564-1-lijinlin3@xxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
block/blk-throttle.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 55c49015e533..7c4e7993ba97 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)
+ del_timer_sync(&q->td->service_queue.pending_timer);
blkcg_deactivate_policy(q, &blkcg_policy_throtl);