Messages in this thread Patch in this message | | | From | Liam Beguin <> | Subject | [PATCH v3 04/10] iio: afe: rescale: reduce risk of integer overflow | Date | Wed, 30 Jun 2021 21:00:28 -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.
Signed-off-by: Liam Beguin <lvb@xiphos.com> --- drivers/iio/afe/iio-rescale.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c index 774eb3044edd..98bcb5d418d6 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 +68,11 @@ 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; + factor = gcd(tmp, tmp2); + *val = tmp / factor; + *val2 = tmp2 / factor; return ret; case IIO_VAL_INT: *val *= rescale->numerator; -- 2.30.1.489.g328c10930387
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