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 v7 07/13] iio: afe: rescale: reduce risk of integer overflow
Date: Sun, 1 Aug 2021 15:39:54 -0400 [thread overview]
Message-ID: <20210801194000.3646303-8-liambeguin@gmail.com> (raw)
In-Reply-To: <20210801194000.3646303-1-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 623744da269a..abd7ad73d1ce 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -21,15 +21,24 @@
int rescale_process_scale(struct rescale *rescale, int scale_type,
int *val, int *val2)
{
- unsigned long long tmp;
+ s64 tmp, tmp2;
+ u32 factor;
u32 mult;
u32 rem;
u32 neg;
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(abs(tmp), abs(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:[~2021-08-01 19:40 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-01 19:39 [PATCH v7 00/13] iio: afe: add temperature rescaling support Liam Beguin
2021-08-01 19:39 ` [PATCH v7 01/13] iio: inkern: apply consumer scale on IIO_VAL_INT cases Liam Beguin
2021-08-01 19:39 ` [PATCH v7 02/13] iio: inkern: apply consumer scale when no channel scale is available Liam Beguin
2021-08-01 19:39 ` [PATCH v7 03/13] iio: inkern: make a best effort on offset calculation Liam Beguin
2021-08-01 19:39 ` [PATCH v7 04/13] iio: afe: rescale: expose scale processing function Liam Beguin
2021-08-01 19:39 ` [PATCH v7 05/13] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support Liam Beguin
2021-08-01 19:39 ` [PATCH v7 06/13] iio: afe: rescale: add offset support Liam Beguin
2021-08-01 19:39 ` Liam Beguin [this message]
2021-08-01 19:39 ` [PATCH v7 08/13] iio: afe: rescale: fix precision on fractional log scale Liam Beguin
2021-08-02 9:17 ` Peter Rosin
2021-08-15 22:14 ` Liam Beguin
2021-08-01 19:39 ` [PATCH v7 09/13] iio: test: add basic tests for the iio-rescale driver Liam Beguin
2021-08-01 19:39 ` [PATCH v7 10/13] iio: afe: rescale: add RTD temperature sensor support Liam Beguin
2021-08-01 19:39 ` [PATCH v7 11/13] iio: afe: rescale: add temperature transducers Liam Beguin
2021-08-01 19:39 ` [PATCH v7 12/13] dt-bindings: iio: afe: add bindings for temperature-sense-rtd Liam Beguin
2021-08-01 19:40 ` [PATCH v7 13/13] dt-bindings: iio: afe: add bindings for temperature transducers Liam Beguin
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