[PATCH] [220/275] hwmon: (sht15) Fix integer overflow in humidity calculation

[Andi Kleen]

2.6.35-longterm review patch.  If anyone has any objections, please let me 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>
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
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(-)

Index: linux-2.6.35.y/drivers/hwmon/sht15.c
===================================================================
--- linux-2.6.35.y.orig/drivers/hwmon/sht15.c	2011-03-29 22:50:29.011516087 -0700
+++ linux-2.6.35.y/drivers/hwmon/sht15.c	2011-03-29 23:03:02.824227904 -0700
@@ -333,11 +333,11 @@
 
 	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;
 }
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/