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Sashiko AI review found 1 potential > issue(s) to consider: > - [High] iio: hid-sensors: divide by zero in convert_to_vtf_format() > for exp < -6 > -- >=20 > commit e56afd4fc65e2d177add5e21d5704d17876c53ec > Author: Srinivas Pandruvada >=20 > iio: hid-sensors: fix fractional part for unit exponents -7 and -8 >=20 > This commit fixes split_micro_fraction() so that HID unit exponents > of -7 and > -8 divide the remainder by 10^(exp - 6) instead of passing a negative > exponent > to int_pow(). >=20 > > diff --git a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c > > b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c > > index 26f8554d18a57..22d33f8c25f14 100644 > > --- a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c > > +++ b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c > > @@ -98,9 +98,14 @@ static void simple_div(int dividend, int > > divisor, int *whole, int *micro_frac) > > =C2=A0static void split_micro_fraction(unsigned int no, int exp, int > > *val1, int *val2) > > =C2=A0{ > > =C2=A0 int divisor =3D int_pow(10, exp); > > + unsigned int rem; > > =C2=A0 > > =C2=A0 *val1 =3D no / divisor; > > - *val2 =3D no % divisor * int_pow(10, 6 - exp); > > + rem =3D no % divisor; > > + if (exp > 6) > > + *val2 =3D rem / (unsigned int)int_pow(10, exp - 6); > > + else > > + *val2 =3D rem * int_pow(10, 6 - exp); > > =C2=A0} >=20 > [Severity: High] > As reported by Sashiko on v1 [1], the commit message notes that > dividing by > 10^(exp - 6) in split_micro_fraction() matches the reverse conversion > in > convert_to_vtf_format(), but does convert_to_vtf_format() also need a > similar > fix for unit exponents -7 and -8? >=20 This patch is a follow up patch [PATCH 11/15] iio: hid-sensors: fix a division by zero posted by Josef Bacik , which did this change.. > In drivers/iio/common/hid-sensors/hid-sensor-attributes.c: >=20 > static u32 convert_to_vtf_format(int size, int exp, int val1, int > val2) > { > ... > exp =3D hid_sensor_convert_exponent(exp); > if (exp < 0) { > divisor =3D int_pow(10, 6 + exp); > value =3D abs(val1) * int_pow(10, -exp); > value +=3D abs(val2) / divisor; > } > ... > } >=20 > When hid_sensor_write_raw_hyst_value() or > hid_sensor_write_raw_hyst_rel_value() calls convert_to_vtf_format() > with a > unit exponent of -7 or -8, 6 + exp is -1 or -2. Because the second > parameter > of int_pow() is unsigned, int_pow(10, 6 + exp) overflows to 0 modulo > 2^64, > causing abs(val2) / divisor to divide by zero in the kernel. >=20 > Should convert_to_vtf_format() multiply abs(val2) by int_pow(10, -6 - > exp) > when exp < -6 instead of dividing? >=20 > [1] > https://lore.kernel.org/r/20261102222309.439895-1-srinivas.pandruvada@lin= ux.intel.com