Hello,
On Mon, 23 Jan 2023 09:10:01, Sean Young wrote:
> 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().
Thank you for your time and suggestions! I will put rc_unregister_device() and
del_timer_sync() before release_region() in order that the tx_sim_timer could
finish before io ports are released.
Best regards,
Duoming Zhou
