netdev - Re: [PATCH bpf-next 1/4] xdp: Support specifying expected existing program when attaching XDP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <eba2b6df-e2e8-e756-dead-3f1044a061cd@solarflare.com>
Date:   Mon, 30 Mar 2020 16:25:07 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        David Ahern <dsahern@...il.com>
CC:     Lorenz Bauer <lmb@...udflare.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        "David S. Miller" <davem@...emloft.net>,
        "Jesper Dangaard Brouer" <brouer@...hat.com>,
        Andrey Ignatov <rdna@...com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next 1/4] xdp: Support specifying expected existing
 program when attaching XDP

On 27/03/2020 23:02, Alexei Starovoitov wrote:
> On Fri, Mar 27, 2020 at 10:12:05AM -0600, David Ahern wrote:
>> I had a thought yesterday along similar lines: bpf_link is about
>> ownership and preventing "accidental" deletes.
> The mechanism for "human override" is tbd.
Then that's a question you really need to solve, especially if you're
 going to push bpf_link quite so... forcefully.
Everything that a human operator can do, so can any program with the
 same capabilities/wheel bits.  Especially as the API that the
 operator-tool uses *will* be open and documented.  The Unix Way does
 not allow unscriptable interfaces, and heavily frowns at any kind of
 distinction between 'humans' and 'programs'.
So what will the override look like?  A bpf() syscall with a special
 BPF_F_IM_A_HUMAN_AND_I_KNOW_WHAT_IM_DOING flag?  ptracing the link
 owner, so that you can close() its fd?  Something in between?

In any case, the question is orthogonal to the bpf_link vs. netlink
 issue: the netlink XDP attach could be done with a flag that means
 "don't allow replacement/removal without EXPECTED_FD".  No?

-ed