From:   Duoming Zhou <duoming@zju.edu.cn>
To:     linux-media@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, maximlevitsky@gmail.com,
        sean@mess.org, mchehab@kernel.org,
        Duoming Zhou <duoming@zju.edu.cn>
Subject: [PATCH] media: rc: Fix use-after-free bugs caused by ene_tx_irqsim()
Date:   Mon, 23 Jan 2023 09:12:23 +0800
Message-Id: <20230123011223.23804-1-duoming@zju.edu.cn>
Precedence: bulk

When the ene device is detaching, function ene_remove() will
be called. But there is no function to cancel tx_sim_timer
in ene_remove(), the timer handler ene_tx_irqsim() could race
with ene_remove(). As a result, the UAF bugs could happen,
the process is shown below.

    (cleanup routine)          |        (timer routine)
                               | mod_timer(&dev->tx_sim_timer, ..)
ene_remove()                   | (wait a time)
  kfree(dev) //FREE            |
                               | ene_tx_irqsim()
                               |   dev->hw_lock //USE
                               |   ene_tx_sample(dev) //USE

Fix by adding del_timer_sync(&dev->tx_sim_timer) in ene_remove(),
The tx_sim_timer could stop before ene device is deallocated.

This problem is found by static analysis.

Fixes: 9ea53b74df9c ("V4L/DVB: STAGING: remove lirc_ene0100 driver")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
---
 drivers/media/rc/ene_ir.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/media/rc/ene_ir.c b/drivers/media/rc/ene_ir.c
index e09270916fb..716b72a048f 100644
--- a/drivers/media/rc/ene_ir.c
+++ b/drivers/media/rc/ene_ir.c
@@ -1114,6 +1114,7 @@ static void ene_remove(struct pnp_dev *pnp_dev)
 	free_irq(dev->irq, dev);
 	release_region(dev->hw_io, ENE_IO_SIZE);
 	rc_unregister_device(dev->rdev);
+	del_timer_sync(&dev->tx_sim_timer);
 	kfree(dev);
 }
 
-- 
2.17.1