serial: sprd: Fix a dereference warning

We should validate if the 'sup' is NULL or not before freeing DMA
memory, to fix below warning.

"drivers/tty/serial/sprd_serial.c:1141 sprd_remove()
 error: we previously assumed 'sup' could be null (see line 1132)"

Fixes: f4487db58eb7 ("serial: sprd: Add DMA mode support")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Lanqing Liu <liuhhome@gmail.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/e2bd92691538e95b04a2c2a728f3292e1617018f.1584325957.git.liuhhome@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
index 9148628..509781e 100644 (file)
--- a/drivers/tty/serial/sprd_serial.c
+++ b/drivers/tty/serial/sprd_serial.c
@@ -1132,14 +1132,13 @@ static int sprd_remove(struct platform_device *dev)
        if (sup) {
                uart_remove_one_port(&sprd_uart_driver, &sup->port);
                sprd_port[sup->port.line] = NULL;
+               sprd_rx_free_buf(sup);
                sprd_ports_num--;
        }
 
        if (!sprd_ports_num)
                uart_unregister_driver(&sprd_uart_driver);
 
-       sprd_rx_free_buf(sup);
-
        return 0;
 }