[PATCH 5.6 03/10] serial: sprd: Fix a dereference warning

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Lanqing Liu <liuhhome@gmail.com>

commit efc176929a3505a30c3993ddd393b40893649bd2 upstream.

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>

---
 drivers/tty/serial/sprd_serial.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/tty/serial/sprd_serial.c
+++ b/drivers/tty/serial/sprd_serial.c
@@ -1132,14 +1132,13 @@ static int sprd_remove(struct platform_d
 	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;
 }