media: cedrus: fix use after free bug in cedrus_remove due to race condition

In cedrus_probe, dev->watchdog_work is bound with cedrus_watchdog function.
In cedrus_device_run, it will started by schedule_delayed_work. If there is
an unfinished work in cedrus_remove, there may be a race condition and
trigger UAF bug.

CPU0                  CPU1

                    |cedrus_watchdog
cedrus_remove       |
  v4l2_m2m_release  |
  kfree(m2m_dev)    |
                    |
                    | v4l2_m2m_get_curr_priv
                    |   m2m_dev //use

Fix it by canceling the worker in cedrus_remove.

Fixes: 7c38a551bda1 ("media: cedrus: Add watchdog for job completion")
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.c b/drivers/staging/media/sunxi/cedrus/cedrus.c
index a43d5ff667163d79ef04fa1441daa55be328bc43..a50a4d0a8f715afcb49a23337233a86a828c91fe 100644 (file)
--- a/drivers/staging/media/sunxi/cedrus/cedrus.c
+++ b/drivers/staging/media/sunxi/cedrus/cedrus.c
@@ -547,6 +547,7 @@ static int cedrus_remove(struct platform_device *pdev)
 {
        struct cedrus_dev *dev = platform_get_drvdata(pdev);
 
+       cancel_delayed_work_sync(&dev->watchdog_work);
        if (media_devnode_is_registered(dev->mdev.devnode)) {
                media_device_unregister(&dev->mdev);
                v4l2_m2m_unregister_media_controller(dev->m2m_dev);