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 v6 08/13] iio: afe: rescale: reduce risk of integer overflow
Date: Tue, 20 Jul 2021 23:06:08 -0400 [thread overview]
Message-ID: <20210721030613.3105327-9-liambeguin@gmail.com> (raw)
In-Reply-To: <20210721030613.3105327-1-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 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
next prev parent reply other threads:[~2021-07-21 3:12 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-21 3:06 [PATCH v6 00/13] iio: afe: add temperature rescaling support Liam Beguin
2021-07-21 3:06 ` [PATCH v6 01/13] iio: inkern: apply consumer scale on IIO_VAL_INT cases Liam Beguin
2021-07-21 3:06 ` [PATCH v6 02/13] iio: inkern: apply consumer scale when no channel scale is available Liam Beguin
2021-07-21 3:06 ` [PATCH v6 03/13] iio: inkern: make a best effort on offset calculation Liam Beguin
2021-07-21 3:06 ` [PATCH v6 04/13] iio: afe: rescale: expose scale processing function Liam Beguin
2021-07-21 3:06 ` [PATCH v6 05/13] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support Liam Beguin
2021-07-23 21:16 ` Peter Rosin
2021-07-28 0:21 ` Liam Beguin
2021-07-28 7:19 ` Peter Rosin
2021-07-29 15:56 ` Liam Beguin
2021-07-30 6:49 ` Peter Rosin
2021-07-30 7:01 ` Peter Rosin
2021-07-30 20:01 ` Liam Beguin
2021-07-30 19:57 ` Liam Beguin
2021-07-31 17:47 ` Jonathan Cameron
2021-07-21 3:06 ` [PATCH v6 06/13] iio: afe: rescale: add offset support Liam Beguin
2021-07-21 3:06 ` [PATCH v6 07/13] iio: test: add basic tests for the iio-rescale driver Liam Beguin
2021-07-24 8:40 ` kernel test robot
2021-07-21 3:06 ` Liam Beguin [this message]
2021-07-23 21:17 ` [PATCH v6 08/13] iio: afe: rescale: reduce risk of integer overflow Peter Rosin
2021-07-28 0:07 ` Liam Beguin
2021-07-28 7:47 ` Peter Rosin
2021-07-29 16:02 ` Liam Beguin
2021-07-21 3:06 ` [PATCH v6 09/13] iio: afe: rescale: fix precision on fractional log scale Liam Beguin
2021-07-23 21:20 ` Peter Rosin
2021-07-28 0:26 ` Liam Beguin
2021-07-28 7:58 ` Peter Rosin
2021-07-29 16:19 ` Liam Beguin
2021-07-21 3:06 ` [PATCH v6 10/13] iio: afe: rescale: add RTD temperature sensor support Liam Beguin
2021-07-21 3:06 ` [PATCH v6 11/13] iio: afe: rescale: add temperature transducers Liam Beguin
2021-07-21 3:06 ` [PATCH v6 12/13] dt-bindings: iio: afe: add bindings for temperature-sense-rtd Liam Beguin
2021-07-21 3:06 ` [PATCH v6 13/13] dt-bindings: iio: afe: add bindings for temperature transducers Liam Beguin
2021-07-23 22:59 ` Rob Herring
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