# Re: \[PATCH\] HID: wacom: check input\_dev-\>absinfo in wacom\_bpt3\_touch\_msg

- From: Gerecke, Jason \<Jason.Gerecke@wacom.com\>
- Date: 2021-05-28 14:19:41 
- List: linux-input
- Page: https://ratatoskr.run/linux-input/2021/05/8933089
- Thread: https://ratatoskr.run/linux-input/2021/05/8933010/t.md

```text
From: Jiri Kosina <jikos@kernel.org>
>  
> On Mon, 17 May 2021, Yiyuan GUO wrote:
> 
> > The function wacom_bpt3_touch_msg calls input_abs_get_res(input,
> > ABS_MT_POSITION_X) to obtain x_res, which may equal to 0 if
> > input->absinfo is NULL. Since x_res is used as a divisor, this
> > may lead to divide by zero problem.
> >
> > Signed-off-by: Yiyuan GUO <redacted>
> > ---
> >  drivers/hid/wacom_wac.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
> > index 81d7d12bc..a5a6fb8bc 100644
> > --- a/drivers/hid/wacom_wac.c
> > +++ b/drivers/hid/wacom_wac.c
> > @@ -2892,7 +2892,7 @@ static void wacom_bpt3_touch_msg(struct wacom_wac *wacom, unsigned char *data)
> >       bool touch = data[1] & 0x80;
> >       int slot = input_mt_get_slot_by_key(input, data[0]);
> >
> > -     if (slot < 0)
> > +     if (slot < 0 || !input->absinfo)
> >               return;
> >
> >       touch = touch && report_touch_events(wacom);
> 
> CCing Wacom driver maintainers in order to get their ack.
> 
> --
> Jiri Kosina
> SUSE Labs

A NULL input->absinfo is very much an unexpected condition. We've either failed somewhere during setup or things have gone off the rails afterwards. Silently limping along like this is a bad idea. I'd really like to see an error message logged and the device removed if possible.

Jason Gerecke
```