[PATCH 09/11] comedi: pcmmio: 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/pcmmio.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/comedi/drivers/pcmmio.c b/drivers/comedi/drivers/pcmmio.c
index d38202c8a12b8..f42b7343b4e45 100644
--- a/drivers/comedi/drivers/pcmmio.c
+++ b/drivers/comedi/drivers/pcmmio.c
@@ -362,6 +362,9 @@ static irqreturn_t interrupt_pcmmio(int irq, void *d)
 	unsigned int triggered;
 	unsigned char int_pend;
 
+	if (!dev->attached)
+		return IRQ_NONE;
+
 	/* are there any interrupts pending */
 	int_pend = inb(dev->iobase + PCMMIO_INT_PENDING_REG) & 0x07;
 	if (!int_pend)
-- 
2.53.0