Re: [PATCH 2/2] iio: adc: spear: Initialize completion before requesting IRQ

[Vladimir Zapolskiy]

On 6/13/26 03:58, Maxwell Doose wrote:
> In the report from Jaeyoung Chung:
>
> "spear_adc_probe() in drivers/iio/adc/spear_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 spear_adc_probe():
>
>      iodev = devm_iio_device_alloc(&pdev->dev, sizeof(*st)); /* st kzalloc-zeroed */
>      ...
>      retval = devm_request_irq(&pdev->dev, irq, spear_adc_isr, 0,
>                                LPC32XXAD_NAME, st);           /* register handler */
>      ...
>      init_completion(&st->completion);                       /* initialize completion */
>
> spear_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: b586e5d9eee0 ("staging:iio:adc:spear rename device specific state structure to _state")
> Reported-by: Sangyun Kim <sangyun.kim@xxxxxxxxx>
> Reported-by: Kyungwook Boo <bookyungwook@xxxxxxxxx>
> Reported-by: Jaeyoung Chung <jjy600901@xxxxxxxxx>
> Closes: https://lore.kernel.org/linux-iio/20260610115700.774689-1-jjy600901@xxxxxxxxx/
> Signed-off-by: Maxwell Doose <m32285159@xxxxxxxxx>
> ---
>   drivers/iio/adc/spear_adc.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/iio/adc/spear_adc.c b/drivers/iio/adc/spear_adc.c
> index 4be722406bb5..ab02a14682ed 100644
> --- a/drivers/iio/adc/spear_adc.c
> +++ b/drivers/iio/adc/spear_adc.c
> @@ -283,6 +283,7 @@ static int spear_adc_probe(struct platform_device *pdev)
>   	st = iio_priv(indio_dev);
>   	st->dev = dev;
>   
> +	init_completion(&st->completion);
>   	mutex_init(&st->lock);
>   
>   	/*
> @@ -329,8 +330,6 @@ static int spear_adc_probe(struct platform_device *pdev)
>   
>   	spear_adc_configure(st);
>   
> -	init_completion(&st->completion);
> -
>   	indio_dev->name = SPEAR_ADC_MOD_NAME;
>   	indio_dev->info = &spear_adc_info;
>   	indio_dev->modes = INDIO_DIRECT_MODE;

Reviewed-by: Vladimir Zapolskiy <vz@xxxxxxxxxx>

--
Best wishes,
Vladimir