netdev - Re: [PATCH 5/6] net: add and use helpers when adjusting gso

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Date:   Thu, 1 Mar 2018 01:47:19 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Daniel Axtens <dja@...ens.net>, David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, alexei.starovoitov@...il.com
Subject: Re: [PATCH 5/6] net: add and use helpers when adjusting gso_size

On 03/01/2018 01:17 AM, Daniel Axtens wrote:
[...]
>>> It means that a user loaded eBPF program can trigger logs full of
>>> warnings merely by using this eBPF helper and generating GSO'd SCTP
>>> traffic.
>>>
>>> Daniel and Alexei, this is a serious problem.  The eBPF helpers
>>> mentioned here cannot handle SCTP GSO packets properly, and in fact
>>> corrupt them if they adjust the gso_size.
>>>
>>> SCTP GSO packets use the GSO_BY_FRAGS scheme and cannot be treated
>>> the same way we treat normal GSO packets.
>>
>> Thanks for Cc, I would have missed it. This patch in combination with
>> patch 6/6 seems okay since we reject it in these cases, which is fine
>> (although it could be a warn_once), but patch 6/6 is definitely buggy
>> in that we leave the skb in a half edited state when leaving the helper.
>> Daniel, want me to fix this up from bpf side and route 5/6 and actual
>> fix via bpf tree? Otherwise please respin with fixed 6/6.
> 
> I'm happy for you to take these two via the bpf tree with whatever
> fixes/changes are appropriate - I'm no eBPF expert so my fix was a 'best
> guess' only. Let me know if you would like anything respun on my end.

Ok, sounds good. In that case you would need to only resend the first
4 patches of your series targeted at -net (I presume?). For the others
no further action required from your side, I'll take care of them
tomorrow then.

Thanks,
Daniel