[PATCH] iio: adc: xilinx-xadc: free IRQ before cancelling the unmask worker on unbind

The ZYNQ XADC interrupt handler xadc_zynq_interrupt_handler() arms the
zynq_unmask_work delayed work via schedule_delayed_work() every time an
alarm condition is observed, and that worker re-arms itself for as long
as the alarm stays asserted.

In xadc_probe() the IRQ is requested with devm_request_irq() before the
devm_add_action_or_reset() that registers xadc_cancel_delayed_work().
Because devres release runs in LIFO order, on unbind the delayed work is
cancelled before the IRQ is freed. The IRQ is still live at that point,
so a pending alarm can make the handler run once more and re-arm
zynq_unmask_work after it has been cancelled; that instance then runs
after the xadc structure that embeds zynq_unmask_work has been freed, a
use-after-free in xadc_zynq_unmask_worker().

Register the cancel-work devm action before requesting the IRQ so devres
LIFO teardown frees (and synchronizes) the IRQ first, then cancels the
delayed work. After free_irq() the handler can no longer re-arm the
work, and the subsequent cancel_delayed_work_sync() drains any instance
armed just before the IRQ was torn down.

This issue was found by an in-house static analysis tool.

Fixes: 2a9685d1a3b7 ("iio: adc: xilinx: use more devres helpers and remove remove()")
Cc: [email protected]
Assisted-by: Codex:gpt-5.6
Signed-off-by: Fan Wu <[email protected]>
---

 drivers/iio/adc/xilinx-xadc-core.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/xilinx-xadc-core.c b/drivers/iio/adc/xilinx-xadc-core.c
--- a/drivers/iio/adc/xilinx-xadc-core.c
+++ b/drivers/iio/adc/xilinx-xadc-core.c
@@ -1395,13 +1395,16 @@ static int xadc_probe(struct platform_device *pdev)
 	}

 	if (irq > 0) {
-		ret = devm_request_irq(dev, irq, xadc->ops->interrupt_handler,
-				       0, dev_name(dev), indio_dev);
+		/* devm LIFO: register the cancel-work action before the IRQ,
+		 * so unbind frees the IRQ first, then drains the work.
+		 */
+		ret = devm_add_action_or_reset(dev, xadc_cancel_delayed_work,
+					       &xadc->zynq_unmask_work);
 		if (ret)
 			return ret;

-		ret = devm_add_action_or_reset(dev, xadc_cancel_delayed_work,
-					       &xadc->zynq_unmask_work);
+		ret = devm_request_irq(dev, irq, xadc->ops->interrupt_handler,
+				       0, dev_name(dev), indio_dev);
 		if (ret)
 			return ret;
 	}
--
2.43.0