linux-kernel - [87/87] hwmon: (sht15) Fix integer overflow in humidity calculation

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Date:	Mon, 21 Mar 2011 16:07:26 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
	Jean Delvare <khali@...ux-fr.org>,
	Jonathan Cameron <jic23@....ac.uk>
Subject: [87/87] hwmon: (sht15) Fix integer overflow in humidity calculation

2.6.37-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Vivien Didelot <vivien.didelot@...oirfairelinux.com>

commit ccd32e735de7a941906e093f8dca924bb05c5794 upstream.

An integer overflow occurs in the calculation of RHlinear when the
relative humidity is greater than around 30%. The consequence is a subtle
(but noticeable) error in the resulting humidity measurement.

Signed-off-by: Vivien Didelot <vivien.didelot@...oirfairelinux.com>
Signed-off-by: Jean Delvare <khali@...ux-fr.org>
Cc: Jonathan Cameron <jic23@....ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/hwmon/sht15.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/hwmon/sht15.c
+++ b/drivers/hwmon/sht15.c
@@ -333,11 +333,11 @@ static inline int sht15_calc_humid(struc
 
 	const int c1 = -4;
 	const int c2 = 40500; /* x 10 ^ -6 */
-	const int c3 = -2800; /* x10 ^ -9 */
+	const int c3 = -28; /* x 10 ^ -7 */
 
 	RHlinear = c1*1000
 		+ c2 * data->val_humid/1000
-		+ (data->val_humid * data->val_humid * c3)/1000000;
+		+ (data->val_humid * data->val_humid * c3) / 10000;
 	return (temp - 25000) * (10000 + 80 * data->val_humid)
 		/ 1000000 + RHlinear;
 }


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