serial: core: fix potential NULL pointer dereference

The commit 761ed4a94582 ("tty: serial_core: convert uart_close to use
tty_port_close") refactored uart_close() to use tty_port_close().  At the same
time it introduced a potential NULL pointer dereference. Rearrange the code to
avoid kernel crash.

Fixes: 761ed4a94582 ("tty: serial_core: convert uart_close to use tty_port_close")
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 6b7f857fc3b00f325af335df8f334c3cfe5ad1e3..6e4f63627479db8d33547ef18fd1e6e365f5bdb7 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1484,15 +1484,15 @@ static void uart_tty_port_shutdown(struct tty_port *port)
        struct uart_state *state = container_of(port, struct uart_state, port);
        struct uart_port *uport = uart_port_check(state);
 
-       spin_lock_irq(&uport->lock);
        /*
         * At this point, we stop accepting input.  To do this, we
         * disable the receive line status interrupts.
         */
-       WARN(!uport, "detached port still initialized!\n");
+       if (WARN(!uport, "detached port still initialized!\n"))
+               return;
 
+       spin_lock_irq(&uport->lock);
        uport->ops->stop_rx(uport);
-
        spin_unlock_irq(&uport->lock);
 
        uart_port_shutdown(port);