Re: [PATCH] iio: inkern: Avoid risky abs() usage in iio_multiply_value()

Andy Shevchenko
2026-03-31T10:08:31Z

On Tue, Mar 31, 2026 at 12:29:22PM +0300, Andy Shevchenko wrote:
> On Tue, Mar 31, 2026 at 10:49:59AM +0200, Romain Gantois wrote:

...

> > - *result = multiplier * abs(val);
> > - *result += div_s64(multiplier * abs(val2), denominator);
> > + *result = multiplier * abs((s64)val);
> > + *result += div_s64(multiplier * abs((s64)val2), denominator);
>
> Right, but here we get val and val2 from either static values from the driver
> (when it is SCALE channel), or when channel has PROCESSED support.
> In the latter one it might theoretically be possible to go till the INT_MIN,
> but practically I don't know how, except for the broken driver code in the
> first place. With that being said, I think it's better to validate somewhere
> the multipliers (when it's SCALE or PROCESSED channel). I also noted that
> for the _PROCESSED some drivers keep a garbage in val2. That probably needs
> to be addressed as well (exempli gratia: bmi270_read_raw() does that).

Actually the data in the val and val2 should be aligned with the returned type,
hence the potential bugs might only come from the untested drivers. Which means
that this patch doesn't improve the situation.