netdev - Re: [PATCH v2 bpf-next 1/4] bpf: unprivileged BPF access via /dev/bpf

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Message-Id: <FEA301AD-01E9-4B1D-A7F8-AA1DBF4FDE66@amacapital.net>
Date:   Mon, 5 Aug 2019 15:21:09 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Song Liu <songliubraving@...com>,
        Kees Cook <keescook@...omium.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>,
        Lorenz Bauer <lmb@...udflare.com>,
        Jann Horn <jannh@...gle.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Linux API <linux-api@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v2 bpf-next 1/4] bpf: unprivileged BPF access via /dev/bpf



> On Aug 5, 2019, at 2:25 PM, Andy Lutomirski <luto@...nel.org> wrote:
> 
> On Mon, Aug 5, 2019 at 12:21 PM Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:


> 
>> What we need is to drop privileges sooner in daemons like systemd.
> 
> This is doable right now: systemd could fork off a subprocess and
> delegate its cgroup operations to it.  It would be maybe a couple
> hundred lines of code.  As an added benefit, that subprocess could
> verify that the bpf operations in question are reasonable.
> Alternatively, if there was a CAP_BPF_ADMIN, systemd could retain that
> capability and flip it on and off as needed.

I tried to look at the code and I couldn’t find it. Does systemd drop privileges at all?  Can you point me at the code you’re thinking of