linux-kernel - [PATCH AUTOSEL 4.14 22/31] media: adv7604: fix possible use-after-free in adv76xx

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Message-Id: <20210503164204.2854178-22-sashal@kernel.org>
Date:   Mon,  3 May 2021 12:41:55 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Yang Yingliang <yangyingliang@...wei.com>,
        Hulk Robot <hulkci@...wei.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Sasha Levin <sashal@...nel.org>, linux-media@...r.kernel.org
Subject: [PATCH AUTOSEL 4.14 22/31] media: adv7604: fix possible use-after-free in adv76xx_remove()

From: Yang Yingliang <yangyingliang@...wei.com>

[ Upstream commit fa56f5f1fe31c2050675fa63b84963ebd504a5b3 ]

This driver's remove path calls cancel_delayed_work(). However, that
function does not wait until the work function finishes. This means
that the callback function may still be running after the driver's
remove function has finished, which would result in a use-after-free.

Fix by calling cancel_delayed_work_sync(), which ensures that
the work is properly cancelled, no longer running, and unable
to re-schedule itself.

Reported-by: Hulk Robot <hulkci@...wei.com>
Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/media/i2c/adv7604.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/i2c/adv7604.c b/drivers/media/i2c/adv7604.c
index 26c3ec573a56..3078d47d090a 100644
--- a/drivers/media/i2c/adv7604.c
+++ b/drivers/media/i2c/adv7604.c
@@ -3557,7 +3557,7 @@ static int adv76xx_remove(struct i2c_client *client)
 	io_write(sd, 0x6e, 0);
 	io_write(sd, 0x73, 0);
 
-	cancel_delayed_work(&state->delayed_work_enable_hotplug);
+	cancel_delayed_work_sync(&state->delayed_work_enable_hotplug);
 	v4l2_async_unregister_subdev(sd);
 	media_entity_cleanup(&sd->entity);
 	adv76xx_unregister_clients(to_state(sd));
-- 
2.30.2