7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Fan Wu commit 63069b5917cba2e15b1a78b3f4ff99e45102c56f upstream. The MFC watchdog timer (s5p_mfc_watchdog) is self-rearming: every callback re-arms itself with add_timer() and, on a timeout, schedules watchdog_work. s5p_mfc_remove() tears this down with timer_delete_sync() followed by flush_work(). timer_delete_sync() dequeues the timer and waits for a callback that is already running, but it does not prevent a subsequent re-arm. Because the watchdog callback re-arms via add_timer(), this is the wrong shutdown primitive: once the wait returns nothing guarantees a just-queued re-arm will not fire later, dereferencing dev (clock on/off, deinit_hw, load_firmware, init_hw) after video_unregister_device(), DMA teardown and s5p_mfc_final_pm() have run, a potential use-after-free. Use timer_shutdown_sync(), which puts the timer into a shutdown state so that any add_timer()/mod_timer() from the callback becomes a no-op and no later firing is possible. Switch flush_work() to cancel_work_sync() so any watchdog_work that was already queued before the timer was stopped is cancelled rather than allowed to run to completion against the torn-down device. This issue was found by an in-house static analysis tool. No runtime reproducer is available. Fixes: af9357467810 ("[media] MFC: Add MFC 5.1 V4L2 driver") Cc: stable@vger.kernel.org Cc: Andrzej Hajda Assisted-by: Codex:gpt-5.6 Signed-off-by: Fan Wu Reviewed-by: Marek Szyprowski Signed-off-by: Nicolas Dufresne Signed-off-by: Hans Verkuil Signed-off-by: Greg Kroah-Hartman --- drivers/media/platform/samsung/s5p-mfc/s5p_mfc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/media/platform/samsung/s5p-mfc/s5p_mfc.c +++ b/drivers/media/platform/samsung/s5p-mfc/s5p_mfc.c @@ -1474,8 +1474,8 @@ static void s5p_mfc_remove(struct platfo } mutex_unlock(&dev->mfc_mutex); - timer_delete_sync(&dev->watchdog_timer); - flush_work(&dev->watchdog_work); + timer_shutdown_sync(&dev->watchdog_timer); + cancel_work_sync(&dev->watchdog_work); video_unregister_device(dev->vfd_enc); video_unregister_device(dev->vfd_dec);