linux-kernel - [PATCH v8 08/14] iio: afe: rescale: reduce risk of integer overflow

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Message-Id: <20210820191714.69898-9-liambeguin@gmail.com>
Date:   Fri, 20 Aug 2021 15:17:08 -0400
From:   Liam Beguin <liambeguin@...il.com>
To:     liambeguin@...il.com, peda@...ntia.se, jic23@...nel.org,
        lars@...afoo.de
Cc:     linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        devicetree@...r.kernel.org, robh+dt@...nel.org
Subject: [PATCH v8 08/14] iio: afe: rescale: reduce risk of integer overflow

From: Liam Beguin <lvb@...hos.com>

Reduce the risk of integer overflow by doing the scale calculation on
a 64-bit integer. Since the rescaling is only performed on *val, reuse
the IIO_VAL_FRACTIONAL_LOG2 case.

Signed-off-by: Liam Beguin <lvb@...hos.com>
---
 drivers/iio/afe/iio-rescale.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 809e966f7058..c408c4057c08 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -27,16 +27,13 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
 	u32 neg;
 
 	switch (scale_type) {
-	case IIO_VAL_FRACTIONAL:
-		*val *= rescale->numerator;
-		*val2 *= rescale->denominator;
-		return scale_type;
 	case IIO_VAL_INT:
 		*val *= rescale->numerator;
 		if (rescale->denominator == 1)
 			return scale_type;
 		*val2 = rescale->denominator;
 		return IIO_VAL_FRACTIONAL;
+	case IIO_VAL_FRACTIONAL:
 	case IIO_VAL_FRACTIONAL_LOG2:
 		tmp = (s64)*val * 1000000000LL;
 		tmp = div_s64(tmp, rescale->denominator);
-- 
2.32.0.452.g940fe202adcb