On Mon, Jan 23, 2023 at 09:12:23AM +0800, Duoming Zhou wrote:
> 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@xxxxxxxxxx>
> ---
> 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);
Great catch!
The timer can call ene_tx_sample() which can write to the io ports, so the
ordering still is not quite right. I think the rc_unregister_device() and
del_timer_sync() should be call first in ene_remove().
Sean
