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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Lorenz Bauer <lmb@cloudflare.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Stanislav Fomichev <sdf@google.com>,
	Jakub Sitnicki <jakub@cloudflare.com>,
	John Fastabend <john.fastabend@gmail.com>,
	kernel-team <kernel-team@cloudflare.com>,
	bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf v2 0/6] Fix attach / detach uapi for sockmap and flow_dissector
Date: Tue, 30 Jun 2020 11:00:11 -0700
Message-ID: <CAADnVQ+VN6nUCQC51nByeKa+uHG=O-GyzeEpWQgJ8OP815RB2A@mail.gmail.com> (raw)
In-Reply-To: <20200629095630.7933-1-lmb@cloudflare.com>

On Mon, Jun 29, 2020 at 2:59 AM Lorenz Bauer <lmb@cloudflare.com> wrote:
>
> Both sockmap and flow_dissector ingnore various arguments passed to
> BPF_PROG_ATTACH and BPF_PROG_DETACH. We can fix the attach case by
> checking that the unused arguments are zero. I considered requiring
> target_fd to be -1 instead of 0, but this leads to a lot of churn
> in selftests. There is also precedent in that bpf_iter already
> expects 0 for a similar field. I think that we can come up with a
> work around for fd 0 should we need to in the future.
>
> The detach case is more problematic: both cgroups and lirc2 verify
> that attach_bpf_fd matches the currently attached program. This
> way you need access to the program fd to be able to remove it.
> Neither sockmap nor flow_dissector do this. flow_dissector even
> has a check for CAP_NET_ADMIN because of this. The patch set
> addresses this by implementing the desired behaviour.
>
> There is a possibility for user space breakage: any callers that
> don't provide the correct fd will fail with ENOENT. For sockmap
> the risk is low: even the selftests assume that sockmap works
> the way I described. For flow_dissector the story is less
> straightforward, and the selftests use a variety of arguments.
>
> I've includes fixes tags for the oldest commits that allow an easy
> backport, however the behaviour dates back to when sockmap and
> flow_dissector were introduced. What is the best way to handle these?
>
> This set is based on top of Jakub's work "bpf, netns: Prepare
> for multi-prog attachment" available at
> https://lore.kernel.org/bpf/87k0zwmhtb.fsf@cloudflare.com/T/

Folks, you should have used 'bpf' in the subject of Jakub's patches.
I've dropped Jakub's set from bpf-next and re-applied to bpf tree.
And applied this set on top.
Thanks!

  parent reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-29  9:56 Lorenz Bauer
2020-06-29  9:56 ` [PATCH bpf v2 1/6] bpf: flow_dissector: check value of unused flags to BPF_PROG_ATTACH Lorenz Bauer
2020-06-29  9:56 ` [PATCH bpf v2 2/6] bpf: flow_dissector: check value of unused flags to BPF_PROG_DETACH Lorenz Bauer
2020-06-29  9:56 ` [PATCH bpf v2 3/6] bpf: sockmap: check value of unused args to BPF_PROG_ATTACH Lorenz Bauer
2020-06-29  9:56 ` [PATCH bpf v2 4/6] bpf: sockmap: require attach_bpf_fd when detaching a program Lorenz Bauer
2020-07-08  1:30   ` Martin KaFai Lau
2020-06-29  9:56 ` [PATCH bpf v2 5/6] selftests: bpf: pass program and target_fd in flow_dissector_reattach Lorenz Bauer
2020-06-29  9:56 ` [PATCH bpf v2 6/6] selftests: bpf: pass program to bpf_prog_detach in flow_dissector Lorenz Bauer
2020-06-30  5:48 ` [PATCH bpf v2 0/6] Fix attach / detach uapi for sockmap and flow_dissector Yonghong Song
2020-06-30  8:39   ` Lorenz Bauer
2020-06-30 15:08     ` Yonghong Song
2020-06-30 15:50       ` Lorenz Bauer
2020-06-30 18:00 ` Alexei Starovoitov [this message]
2020-06-30 18:31   ` Jakub Sitnicki
2020-06-30 18:42     ` Alexei Starovoitov
2020-07-01  7:45       ` Jakub Sitnicki

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