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

[ 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@huawei.com>
Link: https://lore.kernel.org/r/20210907121242.2885564-1-lijinlin3@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 3a4c9a3c1427fc7802c5dee58d131ed6aa638b91..6435dc25be0aab73e78bfbd5d64abd51aad1a66f 100644 (file)
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1584,6 +1584,7 @@ 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);
        kfree(q->td);