Hello,
On Mon, 23 Jan 2023 15:13:40 +0000 Sean Young wrote:
> 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.
Thank your for your time and suggestions, I understand it.
Best regards,
Duoming Zhou
