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>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
index fa54d3290659..adf959dcfa5d 100644
--- 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 &&