Re: [PATCH 11/15] iio: hid-sensors: fix a division by zero

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 02 Nov 2026 09:33:34 -0800
srinivas pandruvada <srinivas.pandruvada@linux.intel.com> wrote:

> On Sun, 2026-11-01 at 02:17 +0000, Jonathan Cameron wrote:
> > On Tue, 27 Oct 2026 17:19:15 +0100
> > Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> >   
> > > From: Josef Bacik <josef@toxicpanda.com>
> > > 
> > > convert_to_vtf_format() divides the micro part of a value by
> > > 10^(6 + exp).  The unit exponent of a HID field is a nibble and
> > > goes
> > > down to -8.  For -7 and -8 the argument of int_pow() is negative,
> > > which
> > > the unsigned parameter turns into a huge power of ten: 0 modulo
> > > 2^64.
> > > The division by it is a divide error.  The exponent comes from the
> > > report
> > > descriptor of the sensor hub, the value from a write to the
> > > hysteresis
> > > attribute of the IIO device.
> > > 
> > > Multiply by 10^(-exp - 6) in these two cases.
> > > 
> > > Fixes: 73c6768b710a ("iio: hid-sensors: Common attribute and
> > > trigger")
> > > Cc: stable <stable@kernel.org>
> > > Cc: David Lechner <dlechner@baylibre.com>
> > > Cc: "Nuno Sá" <nuno.sa@analog.com>
> > > Cc: Andy Shevchenko <andy@kernel.org>
> > > Cc: Sanjay Chitroda <sanjayembeddedse@gmail.com>
> > > Cc: Shi Hao <i.shihao.999@gmail.com>
> > > Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>  
> > +CC Jiri, and Srinivas given they are co-maintainers of this driver.
> > 
> >   
> Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Applied.
> 
> 
> 
> > > ---
> > >  drivers/iio/common/hid-sensors/hid-sensor-attributes.c | 5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
> > > b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
> > > index 9e7c26e37880..3b0985d500ae 100644
> > > --- a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
> > > +++ b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
> > > @@ -140,7 +140,10 @@ static u32 convert_to_vtf_format(int size, int
> > > exp, int val1, int val2)
> > >  	if (val1 < 0 || val2 < 0)
> > >  		sign = -1;
> > >  	exp = hid_sensor_convert_exponent(exp);
> > > -	if (exp < 0) {
> > > +	if (exp < -6) {
> > > +		value = abs(val1) * int_pow(10, -exp);
> > > +		value += abs(val2) * int_pow(10, -exp - 6);
> > > +	} else if (exp < 0) {
> > >  		divisor = int_pow(10, 6 + exp);
> > >  		value = abs(val1) * int_pow(10, -exp);
> > >  		value += abs(val2) / divisor;
> > >