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From:   Alexander Lobakin <alexandr.lobakin@intel.com>
To:     Maxim Korotkov <korotkov.maxim.s@gmail.com>
Cc:     Alexander Lobakin <alexandr.lobakin@intel.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Guangbin Huang <huangguangbin2@huawei.com>,
        Andrew Lunn <andrew@lunn.ch>,
        "Keller, Jacob E" <jacob.e.keller@intel.com>,
        Tom Rix <trix@redhat.com>, Marco Bonelli <marco@mebeim.net>,
        Edward Cree <ecree@solarflare.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, lvc-project@linuxtesting.org
Subject: Re: [PATCH v2] ethtool: avoiding integer overflow in ethtool_phys_id()
Date:   Tue, 22 Nov 2022 13:14:00 +0100
Message-Id: <20221122121400.420417-1-alexandr.lobakin@intel.com>
In-Reply-To: <20221122065423.19458-1-korotkov.maxim.s@gmail.com>
References: <20221122065423.19458-1-korotkov.maxim.s@gmail.com>
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From: Maxim Korotkov <korotkov.maxim.s@gmail.com>
Date: Tue, 22 Nov 2022 09:54:23 +0300

> The value of an arithmetic expression "n * id.data" is subject
> to possible overflow due to a failure to cast operands to a larger data
> type before performing arithmetic. Used macro for multiplication instead
> operator for avoiding overflow.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Maxim Korotkov <korotkov.maxim.s@gmail.com>
> ---
>  net/ethtool/ioctl.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
> index 6a7308de192d..f845e8be4d7c 100644
> --- a/net/ethtool/ioctl.c
> +++ b/net/ethtool/ioctl.c
> @@ -2007,7 +2007,8 @@ static int ethtool_phys_id(struct net_device *dev, void __user *useraddr)
>  	} else {
>  		/* Driver expects to be called at twice the frequency in rc */
>  		int n = rc * 2, interval = HZ / n;
> -		u64 count = n * id.data, i = 0;
> +		u64 count = mul_u32_u32(n,id.data);

                                         ^^

Meh, you forgot to put a space after the comma :s

Other than that (please add it to a v3):

Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>

> +		u64 i = 0;
>  
>  		do {
>  			rtnl_lock();
> -- 
> 2.17.1

Thanks,
Olek