[PATCH 02/11] comedi: das6402: Add sanity check to interrupt handler

[Ian Abbott]

The driver requests an interrupt handler for the device, after setting
device registers to disable interrupt generation.  The interrupt handler
should not be called prematurely unless the user-configured I/O port
base address and/or IRQ number are incorrect or the hardware is bad.

For safety, check the dev->attached flag in the interrupt handler to
ensure the device has been fully set up, avoiding a possible null
pointer dereference of dev->read_subdev.

Reported-by: Jaeyoung Chung <jjy600901@xxxxxxxxx>
Link: https://lore.kernel.org/lkml/20260610115912.780131-1-jjy600901@xxxxxxxxx/
Reported-by: Sangyun Kim <sangyun.kim@xxxxxxxxx>
Reported-by: Kyungwook Boo <bookyungwook@xxxxxxxxx>
Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
---
 drivers/comedi/drivers/das6402.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/comedi/drivers/das6402.c b/drivers/comedi/drivers/das6402.c
index 516a5d5a28404..384e9ba8d5df6 100644
--- a/drivers/comedi/drivers/das6402.c
+++ b/drivers/comedi/drivers/das6402.c
@@ -173,10 +173,16 @@ static irqreturn_t das6402_interrupt(int irq, void *d)
 {
 	struct comedi_device *dev = d;
 	struct comedi_subdevice *s = dev->read_subdev;
-	struct comedi_async *async = s->async;
-	struct comedi_cmd *cmd = &async->cmd;
+	struct comedi_async *async;
+	struct comedi_cmd *cmd;
 	unsigned int status;
 
+	if (!dev->attached)
+		return IRQ_NONE;
+
+	async = s->async;
+	cmd = &async->cmd;
+
 	status = inb(dev->iobase + DAS6402_STATUS_REG);
 	if ((status & DAS6402_STATUS_INT) == 0)
 		return IRQ_NONE;
-- 
2.53.0