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Date:   Fri, 17 Jul 2020 07:52:45 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Alexei Starovoitov <ast@kernel.org>
Cc:     "David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org,
        bpf@vger.kernel.org
Subject: how is the bpfilter sockopt processing supposed to work
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Hi Alexei,

I've just been auditing the sockopt code, and bpfilter looks really
odd.  Both getsockopts and setsockopt eventually end up
in__bpfilter_process_sockopt, which then passes record to the
userspace helper containing the address of the optval buffer.
Which depending on bpf-cgroup might be in user or kernel space.
But even if it is in userspace it would be in a different process
than the bpfiler helper.  What makes all this work?