[PATCH v9 08/14] iio: afe: rescale: reduce risk of integer overflow

Liam Beguin
2021-11-15T03:45:43Z

Reduce the risk of integer overflow by doing the scale calculation on
a 64-bit integer. Since the rescaling is only performed on *val, reuse
the IIO_VAL_FRACTIONAL_LOG2 case.

Signed-off-by: Liam Beguin <lvb@xiphos.com>
---
drivers/iio/afe/iio-rescale.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 394f8b16b29c..17036130d364 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -27,16 +27,13 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
u32 neg;

switch (scale_type) {
- case IIO_VAL_FRACTIONAL:
- *val *= rescale->numerator;
- *val2 *= rescale->denominator;
- return scale_type;
case IIO_VAL_INT:
*val *= rescale->numerator;
if (rescale->denominator == 1)
return scale_type;
*val2 = rescale->denominator;
return IIO_VAL_FRACTIONAL;
+ case IIO_VAL_FRACTIONAL:
case IIO_VAL_FRACTIONAL_LOG2:
tmp = (s64)*val * 1000000000LL;
tmp = div_s64(tmp, rescale->denominator);
--
2.32.0.452.g940fe202adcb