Re: [PATCH v5] iio: adc: ad4030: fix invalid oversampling_ratio validation

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 6 Sep 2026 19:11:12 +0100
Jonathan Cameron <jic23@kernel.org> wrote:

> On Thu,  3 Sep 2026 12:43:09 +0100
> Salah Triki <salah.triki@gmail.com> wrote:
> 
> > In ad4030_set_avg_frame_len(), the logarithm is calculated before input
> > validation. Passing zero or negative values leads to an undefined result
> > from ilog2().
> > 
> > Validate that the input is strictly positive prior to computing its
> > logarithm.
> > 
> > Fixes: 949abd1ca5a4 ("iio: adc: ad4030: add averaging support")
> > Assisted-by: Claude:claude-sonnet-5
> > Signed-off-by: Salah Triki <salah.triki@gmail.com>  
> 
> Given it is an Analog Devices part and Nuno is usually quick to reply
> I'm going to wait for a tag from them before picking this up.

Nuno had looked at v4 and I don't think raised any particular
problems so I've applied this one to the fixes-togreg branch of iio.git
and marked it for stable.

Thanks
Jonathan

> 
> Thanks
> 
> Jonathan
> 
> > ---
> > Changes in v5:
> >   - Split validation into two distinct checks with explanatory comments
> >   (per Andy Shevchenko and Nuno Sá).
> >   - Used 'avg_val < 1' to explicitly reject invalid values for ilog2()
> >   (per Andy Shevchenko and Nuno Sá).
> >   - Tightened commit log description.
> > 
> > Changes in v4:
> >   - Reordered local variables to enforce strict reversed Christmas tree layout
> >   (per Andy Shevchenko).
> >   - Rephrased commit log in plain English without C-specific terms
> >   (per Andy Shevchenko).
> >   - Converted AI assistance note into a formal Assisted-by tag
> >   (per Andy Shevchenko).
> > 
> > Changes in v3:
> >   - Dropped the !is_power_of_2() check to preserve standard IIO attribute
> >    rounding behavior, per feedback from David Lechner and Jonathan Cameron.
> > 
> > Changes in v2:
> >   - Added note stating the issue was identified with assistance from
> >   Claude AI and verified manually.
> >   - Removed initialization of avg_log2 at declaration.
> > 
> >  drivers/iio/adc/ad4030.c | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/ad4030.c b/drivers/iio/adc/ad4030.c
> > index 9c5f19321e3b..f1499b4792b5 100644
> > --- a/drivers/iio/adc/ad4030.c
> > +++ b/drivers/iio/adc/ad4030.c
> > @@ -746,14 +746,21 @@ static int ad4030_set_chan_calibbias(struct iio_dev *indio_dev,
> >  static int ad4030_set_avg_frame_len(struct iio_dev *dev, int avg_val)
> >  {
> >  	struct ad4030_state *st = iio_priv(dev);
> > -	unsigned int avg_log2 = ilog2(avg_val);
> >  	unsigned int last_avg_idx = ARRAY_SIZE(ad4030_average_modes) - 1;
> > +	unsigned int avg_log2;
> >  	int freq_hz;
> >  	int ret;
> >  
> > -	if (avg_val < 0 || avg_val > ad4030_average_modes[last_avg_idx])
> > +	/* Reject unsupported modes */
> > +	if (avg_val > ad4030_average_modes[last_avg_idx])
> > +		return -EINVAL;
> > +
> > +	/* Avoid invalid values for logarithm since it's undefined */
> > +	if (avg_val < 1)
> >  		return -EINVAL;
> >  
> > +	avg_log2 = ilog2(avg_val);
> > +
> >  	if (st->offload_trigger) {
> >  		/*
> >  		 * The sample averaging and sampling frequency configurations  
> 
>