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 18:40:38 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Chenbo Feng <chenbofeng.kernel@...il.com>, netdev@...r.kernel.org,
        David Miller <davem@...emloft.net>
CC:     Lorenzo Colitti <lorenzo@...gle.com>,
        Chenbo Feng <fengc@...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 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/