[PATCH] spi: bcm2835: bcm2835_spi_handle_err(): fix NULL pointer deref for non DMA transfers

[Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>]

In case a IRQ based transfer times out the bcm2835_spi_handle_err()
function is called. Since commit 1513ceee70f2 ("spi: bcm2835: Drop
dma_pending flag") the TX and RX DMA transfers are unconditionally
canceled, leading to NULL pointer derefs if ctlr->dma_tx or
ctlr->dma_rx are not set.

Fix the NULL pointer deref by checking that ctlr->dma_tx and
ctlr->dma_rx are valid pointers before accessing them.

Fixes: 1513ceee70f2 ("spi: bcm2835: Drop dma_pending flag")
Cc: Lukas Wunner <lukas@xxxxxxxxx>
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
---
 drivers/spi/spi-bcm2835.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index 775c0bf2f923..0933948d7df3 100644
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -1138,10 +1138,14 @@ static void bcm2835_spi_handle_err(struct spi_controller *ctlr,
 	struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
 
 	/* if an error occurred and we have an active dma, then terminate */
-	dmaengine_terminate_sync(ctlr->dma_tx);
-	bs->tx_dma_active = false;
-	dmaengine_terminate_sync(ctlr->dma_rx);
-	bs->rx_dma_active = false;
+	if (ctlr->dma_tx) {
+		dmaengine_terminate_sync(ctlr->dma_tx);
+		bs->tx_dma_active = false;
+	}
+	if (ctlr->dma_rx) {
+		dmaengine_terminate_sync(ctlr->dma_rx);
+		bs->rx_dma_active = false;
+	}
 	bcm2835_spi_undo_prologue(bs);
 
 	/* and reset */
-- 
2.35.1