[08/35] hwmon: (sht15) Fix integer overflow in humidity calculation

[Greg KH]

2.6.33-longterm review patch.  If anyone has any objections, please let us know.

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

From: Vivien Didelot <vivien.didelot@xxxxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx>
Cc: Jonathan Cameron <jic23@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

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

--- a/drivers/hwmon/sht15.c
+++ b/drivers/hwmon/sht15.c
@@ -332,11 +332,11 @@ 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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