[PATCH v2] hwmon: (adm9240) Fix overflows seen when writing into limit attributes

[PATCH v2] hwmon: (adm9240) Fix overflows seen when writing into limit attributes

[Guenter Roeck]

Module test reports:

in0_min: Suspected overflow: [3320 vs. 0]
in0_max: Suspected overflow: [3320 vs. 0]
in4_min: Suspected overflow: [15938 vs. 0]
in4_max: Suspected overflow: [15938 vs. 0]
temp1_max: Suspected overflow: [127000 vs. 0]
temp1_max_hyst: Suspected overflow: [127000 vs. 0]
aout_output: Suspected overflow: [1250 vs. 0]

Code analysis reveals that the overflows are caused by conversions
from unsigned long to long to int, combined with multiplications on
passed values.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Improved and simplified clamping

 drivers/hwmon/adm9240.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/adm9240.c b/drivers/hwmon/adm9240.c
index 2fe1828bd10b..72bf2489511e 100644
--- a/drivers/hwmon/adm9240.c
+++ b/drivers/hwmon/adm9240.c
@@ -98,13 +98,15 @@ static inline unsigned int IN_FROM_REG(u8 reg, int n)
 
 static inline u8 IN_TO_REG(unsigned long val, int n)
 {
-	return clamp_val(SCALE(val, 192, nom_mv[n]), 0, 255);
+	val = clamp_val(val, 0, nom_mv[n] * 255 / 192);
+	return SCALE(val, 192, nom_mv[n]);
 }
 
 /* temperature range: -40..125, 127 disables temperature alarm */
 static inline s8 TEMP_TO_REG(long val)
 {
-	return clamp_val(SCALE(val, 1, 1000), -40, 127);
+	val = clamp_val(val, -40000, 127000);
+	return SCALE(val, 1, 1000);
 }
 
 /* two fans, each with low fan speed limit */
@@ -122,7 +124,8 @@ static inline unsigned int FAN_FROM_REG(u8 reg, u8 div)
 /* analog out 0..1250mV */
 static inline u8 AOUT_TO_REG(unsigned long val)
 {
-	return clamp_val(SCALE(val, 255, 1250), 0, 255);
+	val = clamp_val(val, 0, 1250);
+	return SCALE(val, 255, 1250);
 }
 
 static inline unsigned int AOUT_FROM_REG(u8 reg)
-- 
2.5.0

Re: [PATCH v2] hwmon: (adm9240) Fix overflows seen when writing into limit attributes

[Jean Delvare]

On Thu,  8 Dec 2016 11:22:29 -0800, Guenter Roeck wrote:
> Module test reports:
> 
> in0_min: Suspected overflow: [3320 vs. 0]
> in0_max: Suspected overflow: [3320 vs. 0]
> in4_min: Suspected overflow: [15938 vs. 0]
> in4_max: Suspected overflow: [15938 vs. 0]
> temp1_max: Suspected overflow: [127000 vs. 0]
> temp1_max_hyst: Suspected overflow: [127000 vs. 0]
> aout_output: Suspected overflow: [1250 vs. 0]
> 
> Code analysis reveals that the overflows are caused by conversions
> from unsigned long to long to int, combined with multiplications on
> passed values.
> 
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> v2: Improved and simplified clamping
> 
>  drivers/hwmon/adm9240.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> (...)

Reviewed-by: Jean Delvare <jdelvare@suse.de>

-- 
Jean Delvare
SUSE L3 Support