[PATCH 1/2] iio: adc: lpc32xx: Initialize completion before requesting IRQ

[Maxwell Doose]

In the report from Jaeyoung Chung:

"lpc32xx_adc_probe() in drivers/iio/adc/lpc32xx_adc.c registers its
interrupt handler with devm_request_irq() before it initializes
st->completion with init_completion(). If an interrupt arrives after
devm_request_irq() and before init_completion(), the handler calls
complete() on an uninitialized completion, causing a kernel panic.

The probe path, in lpc32xx_adc_probe():

    iodev = devm_iio_device_alloc(&pdev->dev, sizeof(*st)); /* st kzalloc-zeroed */
    ...
    retval = devm_request_irq(&pdev->dev, irq, lpc32xx_adc_isr, 0,
                              LPC32XXAD_NAME, st);           /* register handler */
    ...
    init_completion(&st->completion);                       /* initialize completion */

lpc32xx_adc_isr() calls complete():

    complete(&st->completion);

If the device raises an interrupt before init_completion() runs,
complete() acquires the uninitialized wait.lock and walks the zeroed
task_list in swake_up_locked(). The zeroed task_list makes list_empty()
return false, so swake_up_locked() dereferences a NULL list entry,
triggering a KASAN wild-memory-access."

Fix the chance of a spurious IRQ causing an uninitialized pointer
dereference by moving init_completion() above devm_request_irq().

Fixes: 7901b2a1453e ("staging:iio:adc:lpc32xx rename local state structure to _state")
Reported-by: Sangyun Kim <sangyun.kim at snu.ac.kr>
Reported-by: Kyungwook Boo <bookyungwook at gmail.com>
Reported-by: Jaeyoung Chung <jjy600901 at snu.ac.kr>
Closes: https://lore.kernel.org/linux-iio/20260610115700.774689-1-jjy600901@snu.ac.kr/
Signed-off-by: Maxwell Doose <m32285159 at gmail.com>
---
 drivers/iio/adc/lpc32xx_adc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/lpc32xx_adc.c b/drivers/iio/adc/lpc32xx_adc.c
index 43a7bc8158b5..db3a602327ff 100644
--- a/drivers/iio/adc/lpc32xx_adc.c
+++ b/drivers/iio/adc/lpc32xx_adc.c
@@ -179,6 +179,8 @@ static int lpc32xx_adc_probe(struct platform_device *pdev)
 	if (irq < 0)
 		return irq;
 
+	init_completion(&st->completion);
+
 	retval = devm_request_irq(&pdev->dev, irq, lpc32xx_adc_isr, 0,
 				  LPC32XXAD_NAME, st);
 	if (retval < 0) {
@@ -197,8 +199,6 @@ static int lpc32xx_adc_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, iodev);
 
-	init_completion(&st->completion);
-
 	iodev->name = LPC32XXAD_NAME;
 	iodev->info = &lpc32xx_adc_iio_info;
 	iodev->modes = INDIO_DIRECT_MODE;
-- 
2.54.0