[PATCH 5.10 077/105] spi: bcm2835: bcm2835_spi_handle_err(): fix NULL pointer deref for non DMA transfers

[Greg Kroah-Hartman]

From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>

commit 4ceaa684459d414992acbefb4e4c31f2dfc50641 upstream.

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>
Link: https://lore.kernel.org/r/20220719072234.2782764-1-mkl@xxxxxxxxxxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/spi/spi-bcm2835.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -1174,10 +1174,14 @@ static void bcm2835_spi_handle_err(struc
 	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 */