diff --git a/drivers/hid/hid-hyperv.c b/drivers/hid/hid-hyperv.c
index 49d4a26895e7..f33485d83d24 100644
--- a/drivers/hid/hid-hyperv.c
+++ b/drivers/hid/hid-hyperv.c
@@ -258,19 +258,17 @@ static void mousevsc_on_receive(struct hv_device *device,
 
 	switch (hid_msg_hdr->type) {
 	case SYNTH_HID_PROTOCOL_RESPONSE:
+		len = struct_size(pipe_msg, data, pipe_msg->size);
+
 		/*
 		 * While it will be impossible for us to protect against
 		 * malicious/buggy hypervisor/host, add a check here to
 		 * ensure we don't corrupt memory.
 		 */
-		if (struct_size(pipe_msg, data, pipe_msg->size)
-			> sizeof(struct mousevsc_prt_msg)) {
-			WARN_ON(1);
+		if (WARN_ON(len > sizeof(struct mousevsc_prt_msg)))
 			break;
-		}
 
-		memcpy(&input_dev->protocol_resp, pipe_msg,
-				struct_size(pipe_msg, data, pipe_msg->size));
+		memcpy(&input_dev->protocol_resp, pipe_msg, len);
 		complete(&input_dev->wait_event);
 		break;