linux-kernel - Re: [PATCH] hwmon (occ): Fix potential integer overflow

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Date:   Mon, 7 Jan 2019 11:32:27 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Eddie James <eajames@...ux.vnet.ibm.com>,
        Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmon (occ): Fix potential integer overflow

On Mon, Jan 07, 2019 at 12:34:31PM -0600, Gustavo A. R. Silva wrote:
> Cast get_unaligned_be32(...) to u64 in order to give the compiler
> complete information about the proper arithmetic to use and avoid
> a potential integer overflow.
> 
> Notice that such function call is used in contexts that expect
> expressions of type u64 (64 bits, unsigned); and the following
> expressions are currently being evaluated using 32-bit
> arithmetic:
> 
> val = get_unaligned_be32(&power->update_tag) *
>                         occ->powr_sample_time_us;
> 
> val = get_unaligned_be32(&power->vdn.update_tag) *
>                         occ->powr_sample_time_us;
> 
> Addresses-Coverity-ID: 1442357 ("Unintentional integer overflow")
> Addresses-Coverity-ID: 1442476 ("Unintentional integer overflow")
> Addresses-Coverity-ID: 1442508 ("Unintentional integer overflow")
> Fixes: ff692d80b2e2 ("hwmon (occ): Add sensor types and versions")
> Cc: stable@...r.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

Applied.

Thanks,
Guenter

> ---
>  drivers/hwmon/occ/common.c | 24 ++++++++++++------------
>  1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
> index 423903f87955..391118c8aae8 100644
> --- a/drivers/hwmon/occ/common.c
> +++ b/drivers/hwmon/occ/common.c
> @@ -380,8 +380,8 @@ static ssize_t occ_show_power_1(struct device *dev,
>  		val *= 1000000ULL;
>  		break;
>  	case 2:
> -		val = get_unaligned_be32(&power->update_tag) *
> -			occ->powr_sample_time_us;
> +		val = (u64)get_unaligned_be32(&power->update_tag) *
> +			   occ->powr_sample_time_us;
>  		break;
>  	case 3:
>  		val = get_unaligned_be16(&power->value) * 1000000ULL;
> @@ -425,8 +425,8 @@ static ssize_t occ_show_power_2(struct device *dev,
>  				       &power->update_tag);
>  		break;
>  	case 2:
> -		val = get_unaligned_be32(&power->update_tag) *
> -			occ->powr_sample_time_us;
> +		val = (u64)get_unaligned_be32(&power->update_tag) *
> +			   occ->powr_sample_time_us;
>  		break;
>  	case 3:
>  		val = get_unaligned_be16(&power->value) * 1000000ULL;
> @@ -463,8 +463,8 @@ static ssize_t occ_show_power_a0(struct device *dev,
>  				       &power->system.update_tag);
>  		break;
>  	case 2:
> -		val = get_unaligned_be32(&power->system.update_tag) *
> -			occ->powr_sample_time_us;
> +		val = (u64)get_unaligned_be32(&power->system.update_tag) *
> +			   occ->powr_sample_time_us;
>  		break;
>  	case 3:
>  		val = get_unaligned_be16(&power->system.value) * 1000000ULL;
> @@ -477,8 +477,8 @@ static ssize_t occ_show_power_a0(struct device *dev,
>  				       &power->proc.update_tag);
>  		break;
>  	case 6:
> -		val = get_unaligned_be32(&power->proc.update_tag) *
> -			occ->powr_sample_time_us;
> +		val = (u64)get_unaligned_be32(&power->proc.update_tag) *
> +			   occ->powr_sample_time_us;
>  		break;
>  	case 7:
>  		val = get_unaligned_be16(&power->proc.value) * 1000000ULL;
> @@ -491,8 +491,8 @@ static ssize_t occ_show_power_a0(struct device *dev,
>  				       &power->vdd.update_tag);
>  		break;
>  	case 10:
> -		val = get_unaligned_be32(&power->vdd.update_tag) *
> -			occ->powr_sample_time_us;
> +		val = (u64)get_unaligned_be32(&power->vdd.update_tag) *
> +			   occ->powr_sample_time_us;
>  		break;
>  	case 11:
>  		val = get_unaligned_be16(&power->vdd.value) * 1000000ULL;
> @@ -505,8 +505,8 @@ static ssize_t occ_show_power_a0(struct device *dev,
>  				       &power->vdn.update_tag);
>  		break;
>  	case 14:
> -		val = get_unaligned_be32(&power->vdn.update_tag) *
> -			occ->powr_sample_time_us;
> +		val = (u64)get_unaligned_be32(&power->vdn.update_tag) *
> +			   occ->powr_sample_time_us;
>  		break;
>  	case 15:
>  		val = get_unaligned_be16(&power->vdn.value) * 1000000ULL;