HID: wacom: fix an Oops caused by wacom_wac_finger_count_touches

We assumed all touch interfaces report touch data. But, Bamboo
and Intuos non-touch devices report express keys on touch
interface. We need to check touch_max before counting touches.

Reported-by: Tasos Sahanidis <tasos@tasossah.com>
Signed-off-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
index fa54d329065945bade5b9048df9cb5a98c0bf7f2..adf959dcfa5df9da7bca7414e2d4ac74a35e1457 100644 (file)
--- a/drivers/hid/wacom_wac.c
+++ b/drivers/hid/wacom_wac.c
@@ -1072,6 +1072,9 @@ static int wacom_wac_finger_count_touches(struct wacom_wac *wacom)
        int count = 0;
        int i;
 
+       if (!touch_max)
+               return 0;
+
        /* non-HID_GENERIC single touch input doesn't call this routine */
        if ((touch_max == 1) && (wacom->features.type == HID_GENERIC))
                return wacom->hid_data.tipswitch &&