media: streamzap: fix race between device disconnection and urb callback

[ Upstream commit f656cfbc7a293a039d6a0c7100e1c846845148c1 ]

Syzkaller has reported a general protection fault at function
ir_raw_event_store_with_filter(). This crash is caused by a NULL pointer
dereference of dev->raw pointer, even though it is checked for NULL in
the same function, which means there is a race condition. It occurs due
to the incorrect order of actions in the streamzap_disconnect() function:
rc_unregister_device() is called before usb_kill_urb(). The dev->raw
pointer is freed and set to NULL in rc_unregister_device(), and only
after that usb_kill_urb() waits for in-progress requests to finish.

If rc_unregister_device() is called while streamzap_callback() handler is
not finished, this can lead to accessing freed resources. Thus
rc_unregister_device() should be called after usb_kill_urb().

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 8e9e60640067 ("V4L/DVB: staging/lirc: port lirc_streamzap to ir-core")
Cc: stable@vger.kernel.org
Reported-by: syzbot+34008406ee9a31b13c73@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=34008406ee9a31b13c73
Signed-off-by: Murad Masimov <m.masimov@mt-integration.ru>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/media/rc/streamzap.c b/drivers/media/rc/streamzap.c
index cd994e27362eb114158cc8ec7c5ba5d203aa7c7c..c0a48f991d9d22605b6604bbd40d88e41c5cca82 100644 (file)
--- a/drivers/media/rc/streamzap.c
+++ b/drivers/media/rc/streamzap.c
@@ -433,8 +433,8 @@ static void streamzap_disconnect(struct usb_interface *interface)
        if (!sz)
                return;
 
-       rc_unregister_device(sz->rdev);
        usb_kill_urb(sz->urb_in);
+       rc_unregister_device(sz->rdev);
        usb_free_urb(sz->urb_in);
        usb_free_coherent(usbdev, sz->buf_in_len, sz->buf_in, sz->dma_in);