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

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Date:   Thu, 11 Jul 2019 09:35:48 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Lei YU <mine260309@...il.com>
Cc:     Jean Delvare <jdelvare@...e.com>,
        Eddie James <eajames@...ux.ibm.com>,
        "Gustavo A . R . Silva" <gustavo@...eddedor.com>,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmon (occ): Fix division by zero issue

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@...il.com>
> Reviewed-by: Eddie James <eajames@...ux.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,