diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 64b84291c07e4609f2a0af31588273ea4ee3558e..f92f4d77337487c76929bc58b78e85aa3a184799 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1065,8 +1065,10 @@ static int set_serial_info(struct tty_struct *tty,
 
 	if (!capable(CAP_SYS_ADMIN)) {
 		if (((new_serial.flags & ~ASYNC_USR_MASK) !=
-		     (priv->flags & ~ASYNC_USR_MASK)))
+		     (priv->flags & ~ASYNC_USR_MASK))) {
+			unlock_kernel();
 			return -EPERM;
+		}
 		priv->flags = ((priv->flags & ~ASYNC_USR_MASK) |
 			       (new_serial.flags & ASYNC_USR_MASK));
 		priv->custom_divisor = new_serial.custom_divisor;