serial: serial_core: Perform NULL checks for release/request_port ops

Doing the following UART bind/unbind sequence on a i.mx platform causes
a kernel crash due to NULL pointer dereference:

echo  21f4000.serial > /sys/bus/platform/drivers/imx-uart/bind
echo  21f4000.serial > /sys/bus/platform/drivers/imx-uart/unbind

Fix this problem by adding NULL checks prior to calling release/request_port
ops.

Reported-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Tested-by: Fugang Duan <fugang.duan@nxp.com>
Acked-by: Fugang Duan <fugang.duan@nxp.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 a333c59..9fc1533 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -887,7 +887,7 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port,
                /*
                 * Free and release old regions
                 */
-               if (old_type != PORT_UNKNOWN)
+               if (old_type != PORT_UNKNOWN && uport->ops->release_port)
                        uport->ops->release_port(uport);
 
                uport->iobase = new_port;
@@ -900,7 +900,7 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port,
                /*
                 * Claim and map the new regions
                 */
-               if (uport->type != PORT_UNKNOWN) {
+               if (uport->type != PORT_UNKNOWN && uport->ops->request_port) {
                        retval = uport->ops->request_port(uport);
                } else {
                        /* Always success - Jean II */
@@ -1125,7 +1125,7 @@ static int uart_do_autoconfig(struct tty_struct *tty,struct uart_state *state)
                 * If we already have a port type configured,
                 * we must release its resources.
                 */
-               if (uport->type != PORT_UNKNOWN)
+               if (uport->type != PORT_UNKNOWN && uport->ops->release_port)
                        uport->ops->release_port(uport);
 
                flags = UART_CONFIG_TYPE;
@@ -2897,7 +2897,7 @@ int uart_remove_one_port(struct uart_driver *drv, struct uart_port *uport)
        /*
         * Free the port IO and memory resources, if any.
         */
-       if (uport->type != PORT_UNKNOWN)
+       if (uport->type != PORT_UNKNOWN && uport->ops->release_port)
                uport->ops->release_port(uport);
        kfree(uport->tty_groups);