On Mon, Jan 23, 2023 at 10:21:23PM +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.
>
> What's more, the timer can call ene_tx_sample() which can write
> to the io ports. So we should put rc_unregister_device() and
> del_timer_sync(&dev->tx_sim_timer) before release_region() in
> ene_remove().
>
> Fixes: 9ea53b74df9c ("V4L/DVB: STAGING: remove lirc_ene0100 driver")
> Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
> ---
> Changes in v2:
> - Move rc_unregister_device() and del_timer_sync() before release_region().
>
> drivers/media/rc/ene_ir.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/rc/ene_ir.c b/drivers/media/rc/ene_ir.c
> index e09270916fb..2864360af9e 100644
> --- a/drivers/media/rc/ene_ir.c
> +++ b/drivers/media/rc/ene_ir.c
> @@ -1112,8 +1112,9 @@ static void ene_remove(struct pnp_dev *pnp_dev)
> spin_unlock_irqrestore(&dev->hw_lock, flags);
>
> 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);
> + release_region(dev->hw_io, ENE_IO_SIZE);
> kfree(dev);
> }
I'm sorry, I think there might be a problem there: the irq is freed before
the rc device is unregistered.
The rx receiver is disabled with ene_rx_disable() before rc_unregister_device()
is called, which means it can be enabled again if a process opens /dev/lirc0
between ene_rx_disable() and rc_unregister_device().
ene_remove() should call rc_unregister_device() and del_timer_sync() before
anything else.
Sean
