netdev - Re: [PATCH] netfilter: xt_bpf: Fix XT_BPF_MODE_FD_PINNED mode of 'xt_bpf_info

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Date:   Mon, 09 Oct 2017 14:01:34 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Pablo Neira Ayuso <pablo@...filter.org>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>
CC:     Shmulik Ladkani <shmulik@...f.io>,
        netfilter-devel <netfilter-devel@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Network Development <netdev@...r.kernel.org>,
        Rafael Buchbinder <rafi@....ms>,
        Shmulik Ladkani <shmulik.ladkani@...il.com>
Subject: Re: [PATCH] netfilter: xt_bpf: Fix XT_BPF_MODE_FD_PINNED mode of
 'xt_bpf_info_v1'

Hi Shmulik,

On 10/09/2017 01:57 PM, Pablo Neira Ayuso wrote:
> On Mon, Oct 09, 2017 at 01:18:23PM +0200, Pablo Neira Ayuso wrote:
>> On Fri, Oct 06, 2017 at 01:40:13PM -0400, Willem de Bruijn wrote:
>>> On Fri, Oct 6, 2017 at 12:02 PM, Shmulik Ladkani <shmulik@...f.io> wrote:
>>>> From: Shmulik Ladkani <shmulik.ladkani@...il.com>
>>>>
>>>> Commit 2c16d6033264 ("netfilter: xt_bpf: support ebpf") introduced
>>>> support for attaching an eBPF object by an fd, with the
>>>> 'bpf_mt_check_v1' ABI expecting the '.fd' to be specified upon each
>>>> IPT_SO_SET_REPLACE call.
>>>>
>>>> However this breaks subsequent iptables calls:
>>>>
>>>>   # iptables -A INPUT -m bpf --object-pinned /sys/fs/bpf/xxx -j ACCEPT
>>>>   # iptables -A INPUT -s 5.6.7.8 -j ACCEPT
>>>>   iptables: Invalid argument. Run `dmesg' for more information.
>> [...]
>>>>
>>>> References: [1] https://marc.info/?l=netfilter-devel&m=150564724607440&w=2
>>>>              [2] https://marc.info/?l=netfilter-devel&m=150575727129880&w=2
>>>>
>>>> Cc: Pablo Neira Ayuso <pablo@...filter.org>
>>>> Cc: Willem de Bruijn <willemb@...gle.com>
>>>> Reported-by: Rafael Buchbinder <rafi@....ms>
>>>> Signed-off-by: Shmulik Ladkani <shmulik.ladkani@...il.com>
>>>
>>> Acked-by: Willem de Bruijn <willemb@...gle.com>
>>
>> Applied, thanks.
>
> Hm, I have to keep this back. Compilation breaks here.
>
> net/netfilter/xt_bpf.c: In function ‘__bpf_mt_check_path’:
> net/netfilter/xt_bpf.c:59:2: error: implicit declaration of function
> ‘bpf_obj_get_user’ [-Werror=implicit-function-declaration]
>    fd = bpf_obj_get_user(path);
>    ^

Yeah, probably best to just add a dummy bpf_obj_get_user()
returning an error when CONFIG_BPF_SYSCALL is disabled.