[PATCH 07/11] comedi: pcm816: Fix sanity check in interrupt handler

[Ian Abbott]

The driver requests an interrupt handler for the device before it is
fully set up.

For safety, the interrupt handler checks the dev->attached flag to
ensure the device is fully set up, but it currently does that after
dereferencing the devpriv->dma pointer which may be NULL if
dev->attached is false.  Move the dereference of the devpriv->dma
pointer after dev->attached has been checked to avoid the possible null
pointer dereference.

Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
---
 drivers/comedi/drivers/pcl816.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/comedi/drivers/pcl816.c b/drivers/comedi/drivers/pcl816.c
index 1fcb2f798c7a5..b0d30cb1cfe9e 100644
--- a/drivers/comedi/drivers/pcl816.c
+++ b/drivers/comedi/drivers/pcl816.c
@@ -242,7 +242,7 @@ static irqreturn_t pcl816_interrupt(int irq, void *d)
 	struct comedi_subdevice *s = dev->read_subdev;
 	struct pcl816_private *devpriv = dev->private;
 	struct comedi_isadma *dma = devpriv->dma;
-	struct comedi_isadma_desc *desc = &dma->desc[dma->cur_dma];
+	struct comedi_isadma_desc *desc;
 	unsigned int nsamples;
 	unsigned int bufptr;
 
@@ -257,6 +257,7 @@ static irqreturn_t pcl816_interrupt(int irq, void *d)
 		return IRQ_HANDLED;
 	}
 
+	desc = &dma->desc[dma->cur_dma];
 	nsamples = comedi_bytes_to_samples(s, desc->size) -
 		   devpriv->ai_poll_ptr;
 	bufptr = devpriv->ai_poll_ptr;
-- 
2.53.0