linux-kernel - [PATCH] blk-throttle: fix UAF by deleteing timer in blk_throtl

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Date:   Tue, 7 Sep 2021 20:12:42 +0800
From:   Li Jinlin <lijinlin3@...wei.com>
To:     <tj@...nel.org>, <axboe@...nel.dk>
CC:     <cgroups@...r.kernel.org>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linfeilong@...wei.com>,
        <louhongxiang@...wei.com>
Subject: [PATCH] blk-throttle: fix UAF by deleteing timer in blk_throtl_exit()

From: Li Jinlin <lijinlin3@...wei.com>

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@...wei.com>
---
 block/blk-throttle.c | 1 +
 1 file changed, 1 insertion(+)

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]);
-- 
2.27.0