4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kangjie Lu <kjlu@xxxxxxx> 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@xxxxxxx> Fixes: 34df42f59a60 ("serial: at91: add rx dma support") Acked-by: Richard Genoud <richard.genoud@xxxxxxxxx> Cc: stable <stable@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/tty/serial/atmel_serial.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -1167,6 +1167,10 @@ static int atmel_prepare_rx_dma(struct u 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;