[PATCH 29/35] staging: comedi: das1800: fix NULL pointer dereference in das1800_ai_setup_dma()

[H Hartley Sweeten]

DMA is optional with this driver. If it was not enabled the devpriv->dma
pointer will be NULL. It's probably harmless here because the 'desc' pointer
will not be used if DMA is disabled. But, fix the possible NULL pointer
dereference.

Signed-off-by: H Hartley Sweeten <hsweeten at visionengravers.com>
Cc: Ian Abbott <abbotti at mev.co.uk>
Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 drivers/staging/comedi/drivers/das1800.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/comedi/drivers/das1800.c b/drivers/staging/comedi/drivers/das1800.c
index d8f4e3f..ceecfb2 100644
--- a/drivers/staging/comedi/drivers/das1800.c
+++ b/drivers/staging/comedi/drivers/das1800.c
@@ -783,13 +783,14 @@ static void das1800_ai_setup_dma(struct comedi_device *dev,
 {
 	struct das1800_private *devpriv = dev->private;
 	struct comedi_isadma *dma = devpriv->dma;
-	struct comedi_isadma_desc *desc = &dma->desc[0];
+	struct comedi_isadma_desc *desc;
 	unsigned int bytes;
 
 	if ((devpriv->irq_dma_bits & DMA_ENABLED) == 0)
 		return;
 
 	dma->cur_dma = 0;
+	desc = &dma->desc[0];
 
 	/* determine a dma transfer size to fill buffer in 0.3 sec */
 	bytes = das1800_ai_transfer_size(dev, s, desc->maxsize, 300000000);
-- 
2.6.3