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

[Vladimir Zapolskiy]

On 6/11/26 19:07, Maxwell Doose wrote:
> On Wed, Jun 10, 2026 at 7:04 AM Jaeyoung Chung <jjy600901 at 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 at snu.ac.kr>
>> Reported-by: Kyungwook Boo <bookyungwook at gmail.com>
>>
> 
> Thanks for reporting this; I can start working on a fix shortly
> (assuming nobody else is already working on it).
> 

The analysis and the proposed fix are correct, please go ahead, thank you
in advance.

-- 
Best wishes,
Vladimir