serial_core: Get a reference for port->tty in uart_remove_one_port()

Suggested-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@linux-m68k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/serial_core.c

@@ -2645,6 +2645,7 @@ int uart_remove_one_port(struct uart_driver *drv, struct uart_port *uport)
 {
 	struct uart_state *state = drv->state + uport->line;
 	struct tty_port *port = &state->port;
+	struct tty_struct *tty;
 	int ret = 0;
 
 	BUG_ON(in_interrupt());
@@ -2673,8 +2674,11 @@ int uart_remove_one_port(struct uart_driver *drv, struct uart_port *uport)
 	 */
 	tty_unregister_device(drv->tty_driver, uport->line);
 
-	if (port->tty)
+	tty = tty_port_tty_get(port);
+	if (tty) {
 		tty_vhangup(port->tty);
+		tty_kref_put(tty);
+	}
 
 	/*
 	 * If the port is used as a console, unregister it