[media] lirc: validate transmission ir data

The lirc interface allows 255 u32 spaces and pulses, which are usec. If
the driver can handle this (e.g. winbond-cir) you can produce hours of
meaningless IR data and there is no method of interrupting it.
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/rc/ir-lirc-codec.c

@@ -140,11 +140,20 @@ static ssize_t ir_lirc_transmit_ir(struct file *file, const char __user *buf,
 		goto out;
 	}
 
+	for (i = 0; i < count; i++) {
+		if (txbuf[i] > IR_MAX_DURATION / 1000 - duration || !txbuf[i]) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		duration += txbuf[i];
+	}
+
 	ret = dev->tx_ir(dev, txbuf, count);
 	if (ret < 0)
 		goto out;
 
-	for (i = 0; i < ret; i++)
+	for (duration = i = 0; i < ret; i++)
 		duration += txbuf[i];
 
 	ret *= sizeof(unsigned int);