From: Liam Beguin <liambeguin@gmail.com>
To: liambeguin@gmail.com, peda@axentia.se, jic23@kernel.org,
lars@metafoo.de, pmeerw@pmeerw.net
Cc: linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org,
devicetree@vger.kernel.org, robh+dt@kernel.org
Subject: [PATCH v4 04/10] iio: afe: rescale: reduce risk of integer overflow
Date: Tue, 6 Jul 2021 12:09:36 -0400 [thread overview]
Message-ID: <20210706160942.3181474-5-liambeguin@gmail.com> (raw)
In-Reply-To: <20210706160942.3181474-1-liambeguin@gmail.com>
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 | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 774eb3044edd..ba3bdcc69b16 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 +68,13 @@ 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);
+ do_div(tmp, factor);
+ *val = tmp;
+ do_div(tmp2, factor);
+ *val2 = tmp2;
return ret;
case IIO_VAL_INT:
*val *= rescale->numerator;
--
2.30.1.489.g328c10930387
next prev parent reply other threads:[~2021-07-06 16:10 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-06 16:09 [PATCH v4 00/10] iio: afe: add temperature rescaling support Liam Beguin
2021-07-06 16:09 ` [PATCH v4 01/10] iio: inkern: apply consumer scale on IIO_VAL_INT cases Liam Beguin
2021-07-06 16:09 ` [PATCH v4 02/10] iio: inkern: apply consumer scale when no channel scale is available Liam Beguin
2021-07-06 16:09 ` [PATCH v4 03/10] iio: inkern: make a best effort on offset calculation Liam Beguin
2021-07-06 16:09 ` Liam Beguin [this message]
2021-07-09 16:24 ` [PATCH v4 04/10] iio: afe: rescale: reduce risk of integer overflow Peter Rosin
2021-07-09 19:22 ` Liam Beguin
2021-07-06 16:09 ` [PATCH v4 05/10] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support Liam Beguin
2021-07-09 16:29 ` Peter Rosin
2021-07-09 19:30 ` Liam Beguin
2021-07-10 8:14 ` Peter Rosin
2021-07-10 17:45 ` Liam Beguin
2021-07-06 16:09 ` [PATCH v4 06/10] iio: afe: rescale: add offset support Liam Beguin
2021-07-06 16:09 ` [PATCH v4 07/10] iio: afe: rescale: add RTD temperature sensor support Liam Beguin
2021-07-06 16:09 ` [PATCH v4 08/10] iio: afe: rescale: add temperature transducers Liam Beguin
2021-07-06 16:09 ` [PATCH v4 09/10] dt-bindings: iio: afe: add bindings for temperature-sense-rtd Liam Beguin
2021-07-12 16:08 ` Rob Herring
2021-07-06 16:09 ` [PATCH v4 10/10] dt-bindings: iio: afe: add bindings for temperature transducers Liam Beguin
2021-07-12 16:11 ` Rob Herring
2021-07-13 4:20 ` Liam Beguin
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