tty: atmel_serial: fix a potential NULL pointer dereference

commit c85be041065c0be8bc48eda4c45e0319caf1d0e5 upstream.

In case dmaengine_prep_dma_cyclic fails, the fix returns a proper
error code to avoid NULL pointer dereference.

Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Fixes: 34df42f59a60 ("serial: at91: add rx dma support")
Acked-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index bc1c68c926bd361b019834795dd22c2ef2267cc4..d8676716467b15f533904bc894eca074d1c7b093 100644 (file)
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -1045,6 +1045,10 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
                                sg_dma_len(&atmel_port->sg_rx)/2,
                                DMA_DEV_TO_MEM,
                                DMA_PREP_INTERRUPT);
+       if (!desc) {
+               dev_err(port->dev, "Preparing DMA cyclic failed\n");
+               goto chan_err;
+       }
        desc->callback = atmel_complete_rx_dma;
        desc->callback_param = port;
        atmel_port->desc_rx = desc;