[PATCH] hwmon (occ): Fix division by zero issue

[PATCH] hwmon (occ): Fix division by zero issue

[Lei YU]

The code in occ_get_powr_avg() invokes div64_u64() without checking the
divisor. In case the divisor is zero, kernel gets an "Division by zero
in kernel" error.

Check the divisor and make it return 0 if the divisor is 0.

Signed-off-by: Lei YU <mine260309@gmail.com>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
---
 drivers/hwmon/occ/common.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
index 13a6290..f02aa40 100644
--- a/drivers/hwmon/occ/common.c
+++ b/drivers/hwmon/occ/common.c
@@ -402,8 +402,10 @@ static ssize_t occ_show_power_1(struct device *dev,
 
 static u64 occ_get_powr_avg(u64 *accum, u32 *samples)
 {
-	return div64_u64(get_unaligned_be64(accum) * 1000000ULL,
-			 get_unaligned_be32(samples));
+	u64 divisor = get_unaligned_be32(samples);
+
+	return (divisor == 0) ? 0 :
+		div64_u64(get_unaligned_be64(accum) * 1000000ULL, divisor);
 }
 
 static ssize_t occ_show_power_2(struct device *dev,
-- 
2.7.4

Re: [PATCH] hwmon (occ): Fix division by zero issue

[Guenter Roeck]

On Thu, Jul 11, 2019 at 10:44:48AM +0800, Lei YU wrote:
> The code in occ_get_powr_avg() invokes div64_u64() without checking the
> divisor. In case the divisor is zero, kernel gets an "Division by zero
> in kernel" error.
> 
> Check the divisor and make it return 0 if the divisor is 0.
> 
> Signed-off-by: Lei YU <mine260309@gmail.com>
> Reviewed-by: Eddie James <eajames@linux.ibm.com>

Applied.

Thanks,
Guenter

> ---
>  drivers/hwmon/occ/common.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
> index 13a6290..f02aa40 100644
> --- a/drivers/hwmon/occ/common.c
> +++ b/drivers/hwmon/occ/common.c
> @@ -402,8 +402,10 @@ static ssize_t occ_show_power_1(struct device *dev,
>  
>  static u64 occ_get_powr_avg(u64 *accum, u32 *samples)
>  {
> -	return div64_u64(get_unaligned_be64(accum) * 1000000ULL,
> -			 get_unaligned_be32(samples));
> +	u64 divisor = get_unaligned_be32(samples);
> +
> +	return (divisor == 0) ? 0 :
> +		div64_u64(get_unaligned_be64(accum) * 1000000ULL, divisor);
>  }
>  
>  static ssize_t occ_show_power_2(struct device *dev,