linux-kernel - [PATCH AUTOSEL 4.19 4/4] blk-throttle: fix UAF by deleteing timer in blk_throtl

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Message-Id: <20210917023457.816816-4-sashal@kernel.org>
Date:   Thu, 16 Sep 2021 22:34:57 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Li Jinlin <lijinlin3@...wei.com>, Jens Axboe <axboe@...nel.dk>,
        Sasha Levin <sashal@...nel.org>, tj@...nel.org,
        cgroups@...r.kernel.org, linux-block@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 4/4] blk-throttle: fix UAF by deleteing timer in blk_throtl_exit()

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

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

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index caee658609d7..853b1770df36 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -2437,6 +2437,7 @@ 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]);
-- 
2.30.2