staging: rtl8712: add error handler in r8712_usbctrl_vendorreq()

When 'status' returned from usb_control_msg() is not equal to 'len',
that usb_control_msg() is on partial failure, r8712_usbctrl_vendorreq()
will treat partial reads as success.
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Wang Cheng <wanngchenng@gmail.com>
Link: https://lore.kernel.org/r/e33ea53d36c422fbe7eabec5bd9eecb0ebce1bc5.1652618244.git.wanngchenng@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8712/usb_ops_linux.c

@@ -495,14 +495,21 @@ int r8712_usbctrl_vendorreq(struct intf_priv *pintfpriv, u8 request, u16 value,
 	}
 	status = usb_control_msg(udev, pipe, request, reqtype, value, index,
 				 pIo_buf, len, 500);
-	if (status > 0) {  /* Success this control transfer. */
-		if (requesttype == 0x01) {
-			/* For Control read transfer, we have to copy the read
-			 * data from pIo_buf to pdata.
-			 */
-			memcpy(pdata, pIo_buf,  status);
-		}
+	if (status < 0)
+		goto free;
+	if (status != len) {
+		status = -EREMOTEIO;
+		goto free;
+	}
+	/* Success this control transfer. */
+	if (requesttype == 0x01) {
+		/* For Control read transfer, we have to copy the read
+		 * data from pIo_buf to pdata.
+		 */
+		memcpy(pdata, pIo_buf, status);
 	}
+
+free:
 	kfree(palloc_buf);
 	return status;
 }