[PATCH 08/11] comedi: pcm818: 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 dev->read_dev pointer which may be NULL if
dev->attached is false.  Move the check to avoid the possible null
pointer dereference.

Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
---
 drivers/comedi/drivers/pcl818.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/comedi/drivers/pcl818.c b/drivers/comedi/drivers/pcl818.c
index aa775a024fc7f..89f32c493caac 100644
--- a/drivers/comedi/drivers/pcl818.c
+++ b/drivers/comedi/drivers/pcl818.c
@@ -534,13 +534,14 @@ static irqreturn_t pcl818_interrupt(int irq, void *d)
 	struct comedi_device *dev = d;
 	struct pcl818_private *devpriv = dev->private;
 	struct comedi_subdevice *s = dev->read_subdev;
-	struct comedi_cmd *cmd = &s->async->cmd;
+	struct comedi_cmd *cmd;
 
 	if (!dev->attached || !devpriv->ai_cmd_running) {
 		pcl818_ai_clear_eoc(dev);
 		return IRQ_HANDLED;
 	}
 
+	cmd = &s->async->cmd;
 	if (devpriv->ai_cmd_canceled) {
 		/*
 		 * The cleanup from ai_cancel() has been delayed
-- 
2.53.0