netdev - Re: [PATCH net-next] ixgbevf: fix 'Etherleak' in ixgbevf

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Date:   Tue, 20 Dec 2016 08:36:05 -0800
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Weilong Chen <chenweilong@...wei.com>
Cc:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        intel-wired-lan <intel-wired-lan@...ts.osuosl.org>,
        Netdev <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        wangkefeng.wang@...wei.com
Subject: Re: [PATCH net-next] ixgbevf: fix 'Etherleak' in ixgbevf

The limit of 17 is just based on the hardware.  Specifically the
olinfo field in the Tx descriptor has a minimum length of 17 has a
requirement.  The hardware itself is supposed to be capable of padding
short frames that are supposed to be transmitted.  The drivers are
supposed to pad short frames on receive to get them up to 60 bytes.

When you are seeing this issue are you sending frames from the VF to
one of the local interfaces on the same port or to an external
interface?  Also are you receiving on another linux ixgbevf driver or
are you receiving the packet using a different driver interface such
as DPDK?  I'm just wanting to verify this as it is possible that the
memory leak you are seeing is on the receiver and not on the source if
you are transmitting to a local VF or the PF as the receiver will have
to pad the frame in such a case to get it up to 60 bytes.

- Alex

On Tue, Dec 20, 2016 at 3:50 AM, Weilong Chen <chenweilong@...wei.com> wrote:
> Hi,
>
> Thanks for you reply.
> We test you patch, but the problem is still there, it seems do not work.
>
> I'm not sure why ixgbe use the limit 17. The kenel use ETH_ZLEN (60) with
> out FCS. A lot of drivers such as e1000 use it. Any explaination?
>
> Thanks.
>
>
> On 2016/12/16 0:13, Alexander Duyck wrote:
>>
>> On Thu, Dec 15, 2016 at 3:40 AM, Weilong Chen <chenweilong@...wei.com>
>> wrote:
>>>
>>> Nessus report the vf appears to leak memory in network packets.
>>> Fix this by padding all small packets manually.
>>>
>>> And the CVE-2003-0001.
>>>
>>> https://ofirarkin.files.wordpress.com/2008/11/atstake_etherleak_report.pdf
>>>
>>> Signed-off-by: Weilong Chen <chenweilong@...wei.com>
>>> ---
>>>  drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c | 7 +++++++
>>>  1 file changed, 7 insertions(+)
>>>
>>> diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
>>> b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
>>> index 6d4bef5..137a154 100644
>>> --- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
>>> +++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
>>> @@ -3654,6 +3654,13 @@ static int ixgbevf_xmit_frame(struct sk_buff *skb,
>>> struct net_device *netdev)
>>>                 return NETDEV_TX_OK;
>>>         }
>>>
>>> +       /* On PCI/PCI-X HW, if packet size is less than ETH_ZLEN,
>>> +        * packets may get corrupted during padding by HW.
>>> +        * To WA this issue, pad all small packets manually.
>>> +        */
>>> +       if (eth_skb_pad(skb))
>>> +               return NETDEV_TX_OK;
>>> +
>>
>>
>> So the patch description for this probably isn't correct.  It looks
>> like the problem isn't leaking data it is the fact that the frames
>> aren't being padded to prevent malicious events.  The only issue is
>> the patch is padding by a bit too much.  I would recommend replacing
>> this with the following from ixgbe:
>>
>>         /*
>>          * The minimum packet size for olinfo paylen is 17 so pad the skb
>>          * in order to meet this minimum size requirement.
>>          */
>>         if (skb_put_padto(skb, 17))
>>                 return NETDEV_TX_OK;
>>
>>
>>>         tx_ring = adapter->tx_ring[skb->queue_mapping];
>>>
>>>         /* need: 1 descriptor per page *
>>> PAGE_SIZE/IXGBE_MAX_DATA_PER_TXD,
>>> --
>>> 1.7.12
>>>
>>
>> .
>>
>