From: Liam Beguin <lvb@xxxxxxxxxx>
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@xxxxxxxxxx>
---
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 774eb3044edd..4c3cfd4d5181 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -39,7 +39,8 @@ static int rescale_read_raw(struct iio_dev *indio_dev,
int *val, int *val2, long mask)
{
struct rescale *rescale = iio_priv(indio_dev);
- unsigned long long tmp;
+ s64 tmp, tmp2;
+ u32 factor;
int ret;
switch (mask) {
@@ -67,8 +68,16 @@ static int rescale_read_raw(struct iio_dev *indio_dev,
}
switch (ret) {
case IIO_VAL_FRACTIONAL:
- *val *= rescale->numerator;
- *val2 *= rescale->denominator;
+ tmp = (s64)*val * rescale->numerator;
+ tmp2 = (s64)*val2 * rescale->denominator;
+ if (check_mul_overflow(*val, rescale->numerator, (s32 *)&tmp) ||
+ check_mul_overflow(*val2, rescale->denominator, (s32 *)&tmp2)) {
+ factor = gcd(tmp, tmp2);
+ do_div(tmp, factor);
+ do_div(tmp2, factor);
+ }
+ *val = tmp;
+ *val2 = tmp2;
return ret;
case IIO_VAL_INT:
*val *= rescale->numerator;
--
2.30.1.489.g328c10930387
