[PATCH] media: au0828: fix use-after-free in bulk_timeout timer on disconnect

start_urb_transfer() arms dev->bulk_timeout, whose callback
au0828_bulk_timeout() queues dev->restart_streaming; that work in turn
calls start_urb_transfer() and re-arms the timer.

au0828_dvb_unregister() cancels restart_streaming on disconnect but does
not sync bulk_timeout. au0828_usb_release() then frees dev with kfree(),
so a timer still armed or pending at that point can fire after the free
and dereference dev through timer_container_of().

Sync the timer with timer_shutdown_sync() before cancel_work_sync().  The
timer callback queues the work, so the timer must be stopped first; the
shutdown variant is needed because the work re-arms the timer through
start_urb_transfer().  The dvb->frontend == NULL early return guards the
register-failure path where the timer was never set up.

This bug was found by static analysis.

Fixes: 53460c53b761 ("[media] au0828: Add timer to restart TS stream if no data arrives on bulk endpoint")
Cc: [email protected]
Assisted-by: Codex:gpt-5.6
Signed-off-by: Fan Wu <[email protected]>
---
 drivers/media/usb/au0828/au0828-dvb.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/media/usb/au0828/au0828-dvb.c b/drivers/media/usb/au0828/au0828-dvb.c
index 31123e6f9fc3..4c13aeae8b79 100644
--- a/drivers/media/usb/au0828/au0828-dvb.c
+++ b/drivers/media/usb/au0828/au0828-dvb.c
@@ -537,6 +537,7 @@ void au0828_dvb_unregister(struct au0828_dev *dev)
 	if (dvb->frontend == NULL)
 		return;
 
+	timer_shutdown_sync(&dev->bulk_timeout);
 	cancel_work_sync(&dev->restart_streaming);
 
 	dvb_net_release(&dvb->net);
-- 
2.34.1