linux-kernel - Re: bpfilter breaks IPT_SO_GET

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Message-ID: <CACT4Y+bdzDe_LhQQh-eLapOg0ZsfXFRm2tjUbiAsgS-ObMvwBg@mail.gmail.com>
Date:   Wed, 19 Sep 2018 10:29:42 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        David Miller <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>,
        NetFilter <netfilter-devel@...r.kernel.org>,
        Fabian Vogt <fvogt@...e.com>, Takashi Iwai <tiwai@...e.de>
Subject: Re: bpfilter breaks IPT_SO_GET_INFO

On Wed, Sep 19, 2018 at 9:18 AM, Michal Kubecek <mkubecek@...e.cz> wrote:
> On Mon, Sep 17, 2018 at 03:36:21PM +0200, Dmitry Vyukov wrote:
>> Hi,
>>
>> I am having some problem with upstream kernel and bpfilter. The
>> manifestation is that IPT_SO_GET_INFO on an ipv4 socket works, then
>> something (that I can't fully localize but can reproduce) happens and
>> then IPT_SO_GET_INFO starts permanently returning 256.
> ...
>> Now the litmus program always fails with:
>>
>> getsockopt(3, SOL_IP, 0x40 /* IP_??? */,
>> "filter\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., [84])
>> = 256
>>
>> I am currently on upstream commit
>> 28619527b8a712590c93d0a9e24b4425b9376a8c, my .config is attached. I
>> don't know what is bpfilter, I see it mentions some umh, if it
>> requires some additional setup I don't it, i.e. I don't install any
>> userspace modules/helpers.
>
> This looks similar to the fallback issue described here:
>
>   https://bugzilla.suse.com/show_bug.cgi?id=1106751#c1
>
> Unfortunately I didn't have time to look into it more closely yet.

+Takashi

But I already have CONFIG_BPFILTER_UMH=y in my config, so it does not
help completely.
Also in my case it is working initially, but breaks after I run the
second program.