linux-kernel - [PATCH 4.14 26/27] blk-throttle: fix UAF by deleteing timer in blk_throtl

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Date:   Fri, 24 Sep 2021 14:44:20 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Li Jinlin <lijinlin3@...wei.com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.14 26/27] 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 a8cd7b3d9647..fcbbe2e45a2b 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -2414,6 +2414,7 @@ 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);
-- 
2.33.0