Re: [PATCH] iio: adc: ad4030: fix invalid oversampling_ratio validation

[Joshua Crofts <joshua.crofts1@gmail.com>]

On Sat, 22 Aug 2026 03:19:35 +0100
Salah Triki <salah.triki@gmail.com> wrote:

> ad4030_set_avg_frame_len() computes avg_log2 = ilog2(avg_val) before
> validating avg_val, and the subsequent range check only rejects
> negative values or values above the maximum supported OSR. It does
> not reject avg_val == 0, nor values that are not exact powers of 2.
> 
> - avg_val == 0 passes the check (0 is not < 0 and not > max), so
>   ilog2(0) is called with an undefined/garbage result.
> 
> - Non-power-of-2 values (e.g. avg_val == 3) also pass the check and
>   silently get rounded down by ilog2() to the nearest lower power of
>   2, so userspace can write a value to the oversampling_ratio sysfs
>   attribute that does not match what actually gets programmed into
>   hardware, without any error being reported.
> 
> Only powers of 2 in [1, 65536] are valid OSR values, as listed in
> ad4030_average_modes[]. Validate avg_val fully before computing its
> log2, using is_power_of_2() and requiring avg_val > 0.
> 
> Fixes: 949abd1ca5a4 ("iio: adc: ad4030: add averaging support")
> Signed-off-by: Salah Triki <salah.triki@gmail.com>
> ---
>  drivers/iio/adc/ad4030.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/adc/ad4030.c b/drivers/iio/adc/ad4030.c
> index 9c5f19321e3b..93d9f143cc91 100644
> --- a/drivers/iio/adc/ad4030.c
> +++ b/drivers/iio/adc/ad4030.c
> @@ -751,9 +751,11 @@ static int ad4030_set_avg_frame_len(struct iio_dev *dev, int avg_val)
>  	int freq_hz;
>  	int ret;
>  
> -	if (avg_val < 0 || avg_val > ad4030_average_modes[last_avg_idx])
> +	if (avg_val <= 0 || avg_val > ad4030_average_modes[last_avg_idx] || !is_power_of_2(avg_val))
>  		return -EINVAL;
>  
> +	avg_log2 = ilog2(avg_val);
> +
>  	if (st->offload_trigger) {
>  		/*
>  		 * The sample averaging and sampling frequency configurations

This seems correct. How was this found? By reading the code or some tool/LLM?

-- 
Kind regards,
Joshua Crofts