Messages in this thread Patch in this message | | | From | Liam Beguin <> | Subject | [PATCH v6 08/13] iio: afe: rescale: reduce risk of integer overflow | Date | Tue, 20 Jul 2021 23:06:08 -0400 |
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From: Liam Beguin <lvb@xiphos.com>
Reduce the risk of integer overflow by doing the scale calculation with 64bit integers and looking for a Greatest Common Divider for both parts of the fractional value when required.
Signed-off-by: Liam Beguin <lvb@xiphos.com> --- drivers/iio/afe/iio-rescale.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c index 6f6a711ae3ae..35fa3b4e53e0 100644 --- a/drivers/iio/afe/iio-rescale.c +++ b/drivers/iio/afe/iio-rescale.c @@ -21,12 +21,21 @@ int rescale_process_scale(struct rescale *rescale, int scale_type, int *val, int *val2) { - unsigned long long tmp; + s64 tmp, tmp2; + u32 factor; switch (scale_type) { case IIO_VAL_FRACTIONAL: - *val *= rescale->numerator; - *val2 *= rescale->denominator; + if (check_mul_overflow(*val, rescale->numerator, (s32 *)&tmp) || + check_mul_overflow(*val2, rescale->denominator, (s32 *)&tmp2)) { + tmp = (s64)*val * rescale->numerator; + tmp2 = (s64)*val2 * rescale->denominator; + factor = gcd(tmp, tmp2); + tmp = div_s64(tmp, factor); + tmp2 = div_s64(tmp2, factor); + } + *val = tmp; + *val2 = tmp2; return scale_type; case IIO_VAL_INT: *val *= rescale->numerator; -- 2.30.1.489.g328c10930387
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