serial: core: Expand port mutex section in uart_poll_init()

Prepare uart_poll_init() to safely dereference uart port; expand the
port mutex section to guarantee uart port remains valid until
uart_poll_init() completes.

Signed-off-by: Peter Hurley <peter@hurleysoftware.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 0c48051db1726477c7ab4c4eb023978e90d13399..53d8486a23d94f70cfdef495738475fa28ee0720 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2230,42 +2230,42 @@ static int uart_poll_init(struct tty_driver *driver, int line, char *options)
 {
        struct uart_driver *drv = driver->driver_state;
        struct uart_state *state = drv->state + line;
+       struct tty_port *tport;
        struct uart_port *port;
        int baud = 9600;
        int bits = 8;
        int parity = 'n';
        int flow = 'n';
-       int ret;
+       int ret = 0;
 
-       if (!state || !state->uart_port)
+       if (!state)
                return -1;
 
+       tport = &state->port;
+       mutex_lock(&tport->mutex);
+
        port = state->uart_port;
-       if (!(port->ops->poll_get_char && port->ops->poll_put_char))
-               return -1;
+       if (!(port->ops->poll_get_char && port->ops->poll_put_char)) {
+               ret = -1;
+               goto out;
+       }
 
        if (port->ops->poll_init) {
-               struct tty_port *tport = &state->port;
-
-               ret = 0;
-               mutex_lock(&tport->mutex);
                /*
                 * We don't set initialized as we only initialized the hw,
                 * e.g. state->xmit is still uninitialized.
                 */
                if (!tty_port_initialized(tport))
                        ret = port->ops->poll_init(port);
-               mutex_unlock(&tport->mutex);
-               if (ret)
-                       return ret;
        }
 
-       if (options) {
+       if (!ret && options) {
                uart_parse_options(options, &baud, &parity, &bits, &flow);
-               return uart_set_options(port, NULL, baud, parity, bits, flow);
+               ret = uart_set_options(port, NULL, baud, parity, bits, flow);
        }
-
-       return 0;
+out:
+       mutex_unlock(&tport->mutex);
+       return ret;
 }
 
 static int uart_poll_get_char(struct tty_driver *driver, int line)