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Subject: Re: [PATCH] hwmon (occ): Fix potential integer overflow
To:     "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
        Jean Delvare <jdelvare@suse.com>,
        Guenter Roeck <linux@roeck-us.net>
Cc:     linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20190107183431.GA12428@embeddedor>
From:   Eddie James <eajames@linux.vnet.ibm.com>
Date:   Mon, 7 Jan 2019 12:43:31 -0600
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On 01/07/2019 12:34 PM, 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;

Thanks,

Reviewed-by: Eddie James <eajames@linux.ibm.com>

>
> 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@vger.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>   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;