Input: exc3000 - properly stop timer on shutdown

We need to stop the timer on driver unbind or probe failures, otherwise
we get UAF/Oops.

Fixes: 7e577a17f2 ("Input: add I2C attached EETI EXC3000 multi touch driver")
Reported-by: "Stahl, Michael" <mstahl@moba.de>
Link: https://lore.kernel.org/r/Y9dK57BFqtlf8NmN@google.com
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/exc3000.c

@@ -109,6 +109,11 @@ static inline void exc3000_schedule_timer(struct exc3000_data *data)
 	mod_timer(&data->timer, jiffies + msecs_to_jiffies(EXC3000_TIMEOUT_MS));
 }
 
+static void exc3000_shutdown_timer(void *timer)
+{
+	timer_shutdown_sync(timer);
+}
+
 static int exc3000_read_frame(struct exc3000_data *data, u8 *buf)
 {
 	struct i2c_client *client = data->client;
@@ -386,6 +391,11 @@ static int exc3000_probe(struct i2c_client *client)
 	if (error)
 		return error;
 
+	error = devm_add_action_or_reset(&client->dev, exc3000_shutdown_timer,
+					 &data->timer);
+	if (error)
+		return error;
+
 	error = devm_request_threaded_irq(&client->dev, client->irq,
 					  NULL, exc3000_interrupt, IRQF_ONESHOT,
 					  client->name, data);