diff --git a/drivers/usb/serial/option.c b/drivers/usb/serial/option.c
index 7275f4e7f569..fd8f96294199 100644
--- a/drivers/usb/serial/option.c
+++ b/drivers/usb/serial/option.c
@@ -2688,12 +2688,26 @@ static void option_instat_callback(struct urb *urb)
 			dev_dbg(dev, "%s: NULL req_pkt\n", __func__);
 			return;
 		}
+
+		if (urb->actual_length < sizeof(*req_pkt)) {
+			dev_err(dev, "%s: short packet: %u bytes\n", __func__,
+				urb->actual_length);
+			return;
+		}
+
 		if ((req_pkt->bRequestType == 0xA1) &&
 				(req_pkt->bRequest == 0x20)) {
+			unsigned char signals;
 			int old_dcd_state;
-			unsigned char signals = *((unsigned char *)
-					urb->transfer_buffer +
-					sizeof(struct usb_ctrlrequest));
+
+			if (urb->actual_length < sizeof(*req_pkt) + 1) {
+				dev_err(dev, "%s: short interrupt transfer: %u bytes\n",
+					__func__, urb->actual_length);
+				return;
+			}
+
+			signals = *((unsigned char *)urb->transfer_buffer +
+					sizeof(*req_pkt));
 
 			dev_dbg(dev, "%s: signal x%x\n", __func__, signals);