2019-07-11 02:47:09

by Lei YU

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

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 <[email protected]>
Reviewed-by: Eddie James <[email protected]>
---
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

2019-07-11 16:42:38

by Guenter Roeck

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 <[email protected]>
> Reviewed-by: Eddie James <[email protected]>

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,