Re: [PATCH 16/17] hwmon: (gl518sm) Fix overflows seen when writing into limit attributes

[Jean Delvare <jdelvare@suse.de>]

Hi Guenter,

On Sun,  4 Dec 2016 20:55:39 -0800, Guenter Roeck wrote:
> Writes into limit attributes can overflow due to additions and
> multiplications with unchecked parameters.
> 
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
>  drivers/hwmon/gl518sm.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/hwmon/gl518sm.c b/drivers/hwmon/gl518sm.c
> index 0212c8317bca..0a11a550c2a2 100644
> --- a/drivers/hwmon/gl518sm.c
> +++ b/drivers/hwmon/gl518sm.c
> @@ -86,9 +86,8 @@ enum chips { gl518sm_r00, gl518sm_r80 };
>  #define BOOL_FROM_REG(val)	((val) ? 0 : 1)
>  #define BOOL_TO_REG(val)	((val) ? 0 : 1)
>  
> -#define TEMP_TO_REG(val)	clamp_val(((((val) < 0 ? \
> -				(val) - 500 : \
> -				(val) + 500) / 1000) + 119), 0, 255)
> +#define TEMP_TO_REG(val) (DIV_ROUND_CLOSEST(clamp_val(val, -119000, 136000), \
> +					    1000) + 119)
>  #define TEMP_FROM_REG(val)	(((val) - 119) * 1000)
>  
>  static inline u8 FAN_TO_REG(long rpm, int div)
> @@ -101,10 +100,11 @@ static inline u8 FAN_TO_REG(long rpm, int div)
>  }
>  #define FAN_FROM_REG(val, div)	((val) == 0 ? 0 : (480000 / ((val) * (div))))
>  
> -#define IN_TO_REG(val)		clamp_val((((val) + 9) / 19), 0, 255)
> +#define IN_TO_REG(val)	DIV_ROUND_CLOSEST(clamp_val(val, 0, 255 * 19), 19)
>  #define IN_FROM_REG(val)	((val) * 19)
>  
> -#define VDD_TO_REG(val)		clamp_val((((val) * 4 + 47) / 95), 0, 255)
> +#define VDD_TO_REG(val) \
> +	DIV_ROUND_CLOSEST(clamp_val(val, 0, 255 * 95 / 4) * 4, 95)
>  #define VDD_FROM_REG(val)	(((val) * 95 + 2) / 4)
>  
>  #define DIV_FROM_REG(val)	(1 << (val))

Code looks good. Alignment is a bit clumsy though. Also it feels
strange now that you are using DIV_ROUND_CLOSEST for VDD_TO_REG but not
VDD_FROM_REG.

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

-- 
Jean Delvare
SUSE L3 Support