[PATCH] Input: focaltech - fix array out-of-bounds in focaltech_process_rel_packet

[Richard Davies <richard@arachsys.com>]

Make finger2 (and also finger1) unsigned, so that if the finger index in
the packet is 0 then subtracting 1 creates an array index which overflows
above the existing check for FOC_MAX_FINGERS, as the existing comment says
it should, instead of writing to state->fingers[-1].

Fixes: 05be1d079ec0 ("Input: psmouse - support for the FocalTech PS/2 protocol extensions")
Signed-off-by: Richard Davies <richard@arachsys.com>
---
 drivers/input/mouse/focaltech.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/input/mouse/focaltech.c b/drivers/input/mouse/focaltech.c
index 43f9939b7c63..d3ad4af5aa09 100644
--- a/drivers/input/mouse/focaltech.c
+++ b/drivers/input/mouse/focaltech.c
@@ -197,7 +197,7 @@ static void focaltech_process_rel_packet(struct psmouse *psmouse,
 {
 	struct focaltech_data *priv = psmouse->private;
 	struct focaltech_hw_state *state = &priv->state;
-	int finger1, finger2;
+	unsigned int finger1, finger2;
 
 	state->pressed = packet[0] >> 7;
 	finger1 = ((packet[0] >> 4) & 0x7) - 1;
-- 
2.53.0