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comedi: dt2811: Fix sanity check in interrupt handler

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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, the interrupt handler checks the dev->attached flag to
ensure the device is fully set up, but it currently does that after
dereferencing dev->read_subdev, 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@mev.co.uk>
Link: https://patch.msgid.link/20260618102949.26607-4-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott
2026-06-18 11:09:10 +01:00
committed by Greg Kroah-Hartman
parent e90d0550c5
commit 8dda638257
1 changed files with 5 additions and 2 deletions
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7
drivers/comedi/drivers/dt2811.c
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@@ -193,13 +193,16 @@ static irqreturn_t dt2811_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 + DT2811_ADCSR_REG);
if (status & DT2811_ADCSR_ADERROR) {