netdev - Re: [PATCH net-next v2 1/2] bpf: Allow CGROUP_SKB eBPF program to access sk

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Date:   Tue, 06 Jun 2017 22:27:15 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     David Miller <davem@...emloft.net>, fengc@...gle.com
CC:     chenbofeng.kernel@...il.com, netdev@...r.kernel.org,
        lorenzo@...gle.com, ast@...com
Subject: Re: [PATCH net-next v2 1/2] bpf: Allow CGROUP_SKB eBPF program to
 access sk_buff

On 06/06/2017 10:26 PM, David Miller wrote:
> From: Chenbo Feng <fengc@...gle.com>
> Date: Tue, 6 Jun 2017 13:24:11 -0700
>
>> On Tue, Jun 6, 2017 at 9:40 AM, Daniel Borkmann <daniel@...earbox.net>
>> wrote:
>>
>>> On 06/06/2017 02:04 PM, Daniel Borkmann wrote:
>>>
>>>> On 06/01/2017 03:15 AM, Chenbo Feng wrote:
>>>>
>>>>> From: Chenbo Feng <fengc@...gle.com>
>>>>>
>>>>> This allows cgroup eBPF program to classify packet based on their
>>>>> protocol or other detail information. Currently program need
>>>>> CAP_NET_ADMIN privilege to attach a cgroup eBPF program, and A
>>>>> process with CAP_NET_ADMIN can already see all packets on the system,
>>>>> for example, by creating an iptables rules that causes the packet to
>>>>> be passed to userspace via NFLOG.
>>>>>
>>>>> Signed-off-by: Chenbo Feng <fengc@...gle.com>
>>>>>
>>>>
>>>> Sorry, but I am puzzled what above change log has to do with the
>>>> below diff?! Back then we decided not to add BPF_PROG_TYPE_CGROUP_SKB
>>>> to may_access_skb(), since one can already use bpf_skb_load_bytes()
>>>> helper to access pkt data, which is a much more flexible interface.
>>>> Mind to elaborate why you cannot use bpf_skb_load_bytes() instead?
>>>>
>>>
>>> See my other email [1], this one is also problematic wrt SKF_LL_OFF.
>>>
>>>    [1] http://patchwork.ozlabs.org/patch/771946/
>>
>>
>> Oh sorry I just find out the bpf_skb_load_bytes helper already can achieve
>> the goal. There is no point to add my patch then. Thanks you for pointing
>> it out and fixing it.
>
> If something now needs to be reverted, you need to send that revert to me.

It's sitting here: http://patchwork.ozlabs.org/patch/771946/