Re: iio: adc: KASAN wild-memory-access in complete() on early IRQ

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 10 Jun 2026 20:57:00 +0900
Jaeyoung Chung <jjy600901@snu.ac.kr> wrote:

> Hi,
> 
> lpc32xx_adc_probe() in drivers/iio/adc/lpc32xx_adc.c and
> spear_adc_probe() in drivers/iio/adc/spear_adc.c register their
> interrupt handler with devm_request_irq() before they initialize
> 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 */
> 
> spear_adc_probe() has the same ordering: devm_request_irq() for
> spear_adc_isr() before init_completion(&st->completion).
> 
> Both interrupt handlers, lpc32xx_adc_isr() and spear_adc_isr(), call
> 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.
> 
> Suggested fix: move init_completion(&st->completion) above
> devm_request_irq(), so the completion is valid before the handler can run.
> 
> Reported-by: Sangyun Kim <sangyun.kim@snu.ac.kr>
> Reported-by: Kyungwook Boo <bookyungwook@gmail.com>

Hi I think the report is valid, but I'm curious to whether you ran these
drivers given the hardware is pretty obscure!  If not how did KASAN detect
anything (unless there is a static analysis version I'm not aware of)

Given age of drivers and that this only occurs if a spurious IRQ turns
up I'm not going to rush to fix this.  However, I'd certainly welcome
patches.

Thanks,

Jonathan


> 
> Thanks,
> Jaeyoung Chung