linux-kernel - Re: [PATCH 2/4] seccomp, bpf: Introduce SECCOMP_LOAD

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Message-ID: <202310101722.B6D6E6CEC@keescook>
Date:   Tue, 10 Oct 2023 17:24:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Hengqi Chen <hengqi.chen@...il.com>
Cc:     linux-kernel@...r.kernel.org, bpf@...r.kernel.org, ast@...nel.org,
        daniel@...earbox.net, andrii@...nel.org, luto@...capital.net,
        wad@...omium.org, alexyonghe@...cent.com
Subject: Re: [PATCH 2/4] seccomp, bpf: Introduce SECCOMP_LOAD_FILTER operation

On Mon, Oct 09, 2023 at 12:40:44PM +0000, Hengqi Chen wrote:
> This patch adds a new operation named SECCOMP_LOAD_FILTER.
> It accepts the same arguments as SECCOMP_SET_MODE_FILTER
> but only performs the loading process. If succeed, return a
> new fd associated with the JITed BPF program (the filter).
> The filter can then be pinned to bpffs using the returned
> fd and reused for different processes. To distinguish the
> filter from other BPF progs, BPF_PROG_TYPE_SECCOMP is added.
> 
> Signed-off-by: Hengqi Chen <hengqi.chen@...il.com>

This part looks okay, I think. I need to spend some more time looking at
the BPF side. I want to make sure it is only possible to build a
BPF_PROG_TYPE_SECCOMP prog by going through seccomp. I want to make sure
we can never side-load some kind of unexpected program into seccomp,
etc. Since BPF_PROG_TYPE_SECCOMP is part of UAPI, is this controllable
through the bpf() syscall?

One thought I had, though, is I wonder if flags are needed to be
included with the fd? I'll ponder this a bit more...

-- 
Kees Cook