Date:   Tue, 20 Dec 2016 18:20:16 -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

I find it curious that only the last 4 bytes have data in them.  I'm
wondering if the NIC/driver in the Windows/Nessus system is
interpreting the 4 byte CRC on the end of the frame as padding instead
of stripping it.

Is there any chance you could capture the entire frame instead of just
the padding?  Maybe you could run something like wireshark without
enabling promiscuous mode on the VF and capture the frames it is
trying to send and receive.  What I want to verify is what the actual
amount of padding is that is needed to get to 60 bytes and where the
CRC should start.

- Alex

On Tue, Dec 20, 2016 at 5:40 PM, Weilong Chen <chenweilong@...wei.com> wrote:
> Thanks for you explanation, it's very professional.
>
> My test is like this:
> The Nessus is deployed on a windows server, the peer is a X86_64 linux host
> which run several VMs on it. The nic is Intel 82599 and SRIOV is enabled.
> VFs are passthroughed to the VMs. No DPDK.
>
> The Nessus server send small ICMP echo request packets to the VM, and
> then check the reply, and report the error:
>
> "11197 - Multiple Ethernet Driver Frame Padding Information Disclosure
> (Etherleak)"
>
> "Padding observed in one frame :
>
> 0x00: 00 00 00 00 00 00 00 00 00 00 00 00 00 57 37 28 .............W7(
> 0x10: 76 v
>
> Padding observed in another frame :
>
> 0x00: 00 00 00 00 00 00 00 00 00 00 00 00 00 D3 4D 75 ..............Mu
> 0x10: 28 ("
>
> I only have Nessus's windows version, so can't test on linux. Maybe the
> windows server does not pad small packets to 60 bytes on the receive path.
>
>
> On 2016/12/21 0:36, Alexander Duyck wrote:
>>
>> 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
>>>>>
>>>>
>>>> .
>>>>
>>>
>>
>> .
>>
>

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