From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: David Ahern <dsahern@gmail.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Andrii Nakryiko <andriin@fb.com>, bpf <bpf@vger.kernel.org>,
Networking <netdev@vger.kernel.org>,
Alexei Starovoitov <ast@fb.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrey Ignatov <rdna@fb.com>, Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH v3 bpf-next 0/4] Add support for cgroup bpf_link
Date: Mon, 30 Mar 2020 18:17:53 -0700 [thread overview]
Message-ID: <20200331011753.qxo3pq6ldqm43bo7@ast-mbp> (raw)
In-Reply-To: <58cea4c7-e832-2632-7f69-5502b06310b2@gmail.com>
On Mon, Mar 30, 2020 at 06:57:44PM -0600, David Ahern wrote:
> On 3/30/20 6:32 PM, Alexei Starovoitov wrote:
> >>
> >> This is not a large feature, and there is no reason for CREATE/UPDATE -
> >> a mere 4 patch set - to go in without something as essential as the
> >> QUERY for observability.
> >
> > As I said 'bpftool cgroup' covers it. Observability is not reduced in any way.
>
> You want a feature where a process can prevent another from installing a
> program on a cgroup. How do I learn which process is holding the
> bpf_link reference and preventing me from installing a program? Unless I
> have missed some recent change that is not currently covered by bpftool
> cgroup, and there is no way reading kernel code will tell me.
No. That's not the case at all. You misunderstood the concept.
> That is my point. You are restricting what root can do and people will
> not want to resort to killing random processes trying to find the one
> holding a reference.
Not true either.
bpf_link = old attach with allow_multi (but with extra safety for owner)
The only thing bpf_link protects is the owner of the link from other
processes of nuking that link.
It does _not_ prevent other processes attaching their own cgroup-bpf progs
either via old interface or via bpf_link.
It will be different for xdp where only one prog is allowed per xdp hook.
There it will prevent other xdp progs. And there link_queury and
"human override" will be necessary.
next prev parent reply other threads:[~2020-03-31 1:18 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-30 2:59 [PATCH v3 bpf-next 0/4] Add support for cgroup bpf_link Andrii Nakryiko
2020-03-30 2:59 ` [PATCH v3 bpf-next 1/4] bpf: implement bpf_link-based cgroup BPF program attachment Andrii Nakryiko
2020-03-31 0:05 ` Andrey Ignatov
2020-03-31 0:38 ` Alexei Starovoitov
2020-03-31 1:06 ` Andrii Nakryiko
2020-03-30 2:59 ` [PATCH v3 bpf-next 2/4] bpf: implement bpf_prog replacement for an active bpf_cgroup_link Andrii Nakryiko
2020-03-30 3:00 ` [PATCH v3 bpf-next 3/4] libbpf: add support for bpf_link-based cgroup attachment Andrii Nakryiko
2020-03-30 3:00 ` [PATCH v3 bpf-next 4/4] selftests/bpf: test FD-based " Andrii Nakryiko
2020-03-30 14:49 ` [PATCH v3 bpf-next 0/4] Add support for cgroup bpf_link David Ahern
2020-03-30 20:20 ` Andrii Nakryiko
2020-03-30 20:45 ` David Ahern
2020-03-30 20:50 ` Alexei Starovoitov
2020-03-30 22:50 ` Alexei Starovoitov
2020-03-30 23:43 ` David Ahern
2020-03-31 0:32 ` Alexei Starovoitov
2020-03-31 0:57 ` David Ahern
2020-03-31 1:17 ` Alexei Starovoitov [this message]
2020-04-01 1:42 ` David Ahern
2020-04-01 2:04 ` Alexei Starovoitov
2020-03-31 3:54 ` Andrii Nakryiko
2020-03-31 16:54 ` David Ahern
2020-03-31 17:03 ` Andrii Nakryiko
2020-03-31 17:11 ` Alexei Starovoitov
2020-03-31 21:51 ` Edward Cree
2020-03-31 22:44 ` David Ahern
2020-04-01 0:45 ` Andrii Nakryiko
2020-04-01 0:22 ` Andrii Nakryiko
2020-04-01 14:26 ` Edward Cree
2020-04-01 17:39 ` Andrii Nakryiko
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