Re: [PATCH] HID: wacom: check input_dev->absinfo in wacom_bpt3_touch_msg

From: Jiri Kosina <jikos@kernel.org>

 
On Mon, 17 May 2021, Yiyuan GUO wrote:

quoted

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