From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Yafang Shao <laoar.shao@gmail.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Song Liu <song@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>, bpf <bpf@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH bpf-next 00/13] bpf: Introduce BPF namespace
Date: Thu, 6 Apr 2023 13:22:26 -0700 [thread overview]
Message-ID: <CAEf4Bza_vM8HE5g+4ANW3NAAt8=+cn7Lw+DSkH42gimqzYxPdw@mail.gmail.com> (raw)
In-Reply-To: <CALOAHbDdtj1Qd0h1jzXKN4R=_webEVW=sqYfhSFXXsYftyvnKw@mail.gmail.com>
On Wed, Apr 5, 2023 at 10:44 PM Yafang Shao <laoar.shao@gmail.com> wrote:
>
> On Thu, Apr 6, 2023 at 12:24 PM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
> >
> > On Wed, Apr 5, 2023 at 8:22 PM Yafang Shao <laoar.shao@gmail.com> wrote:
> > >
> > > On Thu, Apr 6, 2023 at 11:06 AM Alexei Starovoitov
> > > <alexei.starovoitov@gmail.com> wrote:
> > > >
> > > > On Wed, Apr 5, 2023 at 7:55 PM Yafang Shao <laoar.shao@gmail.com> wrote:
> > > > >
> > > > > It seems that I didn't describe the issue clearly.
> > > > > The container doesn't have CAP_SYS_ADMIN, but the CAP_SYS_ADMIN is
> > > > > required to run bpftool, so the bpftool running in the container
> > > > > can't get the ID of bpf objects or convert IDs to FDs.
> > > > > Is there something that I missed ?
> > > >
> > > > Nothing. This is by design. bpftool needs sudo. That's all.
> > > >
> > >
> > > Hmm, what I'm trying to do is make bpftool run without sudo.
> >
> > This is not a task that is worth solving.
> >
>
> Then the container with CAP_BPF enabled can't even iterate its bpf progs ...
I'll leave the BPF namespace discussion aside (I agree that it needs
way more thought).
I am a bit surprised that we require CAP_SYS_ADMIN for GET_NEXT_ID
operations. GET_FD_BY_ID is definitely CAP_SYS_ADMIN, as they allow
you to take over someone else's link and stuff like this. But just
iterating IDs seems like a pretty innocent functionality, so maybe we
should remove CAP_SYS_ADMIN for GET_NEXT_ID?
By itself GET_NEXT_ID is relatively useless without capabilities, but
we've been floating the idea of providing GET_INFO_BY_ID (not by FD)
for a while now, and that seems useful in itself, as it would indeed
help tools like bpftool to get *some* information even without
privileges. Whether those GET_INFO_BY_ID operations should return same
full bpf_{prog,map,link,btf}_info or some trimmed down version of them
would be up to discussion, but I think getting some info without
creating an FD seems useful in itself.
Would it be worth discussing and solving this separately from
namespacing issues?
>
> > > > > Some questions,
> > > > > - What if the process exits after attaching the bpf prog and the prog
> > > > > is not auto-detachable?
> > > > > For example, the reuserport bpf prog is not auto-detachable. After
> > > > > pins the reuserport bpf prog, a task can attach it through the pinned
> > > > > bpf file, but if the task forgets to detach it and the pinned file is
> > > > > removed, then it seems there's no way to figure out which task or
> > > > > cgroup this prog belongs to...
> > > >
> > > > you're saying that there is a bpf prog in the kernel without
> > > > corresponding user space ?
> > >
> > > No, it is corresponding to user space. For example, it may be
> > > corresponding to a socket fd, or a cgroup fd.
> > >
> > > > Meaning no user space process has an FD
> > > > that points to this prog or FD to a map that this prog is using?
> > > > In such a case this is truly kernel bpf prog. It doesn't belong to cgroup.
> > > >
> > >
> > > Even if it is kernel bpf prog, it is created by a process. The user
> > > needs to know which one created it.
> >
> > In some situations it's certainly interesting to know which process
> > loaded a particular program.
> > In many other situations it's irrelevant.
> > For example, the process that loaded a prog could have been moved to a
> > different cgroup.
> > If you want to track the loading you need to install bpf_lsm
> > that monitors prog_load hook and collect that info.
> > It's not the job of the kernel to do it.
> >
>
> Agreed with you that we can add lots of hooks to track every detail of
> the operations.
> But it is not free. More hooks, more overhead.
> If we can change the kernel to make it lightweight, why not...
>
> > > > > - Could you pls. explain in detail how to get comm, pid, or cgroup
> > > > > from a pinned bpffs file?
> > > >
> > > > pinned bpf prog and no user space holds FD to it?
> > > > It's not part of any cgroup. Nothing to print.
> > >
> > > As I explained above, even if it holds nothing, the user needs to know
> > > the information from it. For example, if it is expected, which one
> > > created it?
> >
> > See the answer above. The kernel has enough hooks already to provide
> > this information to user space. No kernel changes necessary.
>
>
>
> --
> Regards
> Yafang
next prev parent reply other threads:[~2023-04-06 20:23 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-26 9:21 [RFC PATCH bpf-next 00/13] bpf: Introduce BPF namespace Yafang Shao
2023-03-26 9:21 ` [RFC PATCH bpf-next 01/13] fork: New clone3 flag for " Yafang Shao
2023-03-26 9:21 ` [RFC PATCH bpf-next 02/13] proc_ns: Extend the field type in struct proc_ns_operations to long Yafang Shao
2023-03-26 9:21 ` [RFC PATCH bpf-next 03/13] bpf: Implement bpf namespace Yafang Shao
2023-03-26 9:21 ` [RFC PATCH bpf-next 04/13] bpf: No need to check if id is 0 Yafang Shao
2023-03-26 9:22 ` [RFC PATCH bpf-next 05/13] bpf: Make bpf objects id have the same alloc and free pattern Yafang Shao
2023-03-26 9:22 ` [RFC PATCH bpf-next 06/13] bpf: Helpers to alloc and free object id in bpf namespace Yafang Shao
2023-03-26 9:22 ` [RFC PATCH bpf-next 07/13] bpf: Add bpf helper to get bpf object id Yafang Shao
2023-03-26 9:22 ` [RFC PATCH bpf-next 08/13] bpf: Alloc and free bpf_map id in bpf namespace Yafang Shao
2023-03-26 10:50 ` Toke Høiland-Jørgensen
2023-03-27 2:44 ` Yafang Shao
2023-03-26 9:22 ` [RFC PATCH bpf-next 09/13] bpf: Alloc and free bpf_prog " Yafang Shao
2023-03-26 9:22 ` [RFC PATCH bpf-next 10/13] bpf: Alloc and free bpf_link " Yafang Shao
2023-03-26 9:22 ` [RFC PATCH bpf-next 11/13] bpf: Allow iterating bpf objects with CAP_BPF " Yafang Shao
2023-03-26 9:22 ` [RFC PATCH bpf-next 12/13] bpf: Use bpf_idr_lock array instead Yafang Shao
2023-03-26 9:22 ` [RFC PATCH bpf-next 13/13] selftests/bpf: Add selftest for bpf namespace Yafang Shao
2023-03-26 10:49 ` [RFC PATCH bpf-next 00/13] bpf: Introduce BPF namespace Toke Høiland-Jørgensen
2023-03-27 3:07 ` Yafang Shao
2023-03-27 20:51 ` Toke Høiland-Jørgensen
2023-03-28 3:48 ` Yafang Shao
2023-03-27 17:28 ` Stanislav Fomichev
2023-03-28 3:42 ` Yafang Shao
2023-03-28 17:15 ` Stanislav Fomichev
2023-03-29 3:02 ` Yafang Shao
2023-03-29 20:50 ` Stanislav Fomichev
2023-03-30 2:40 ` Yafang Shao
2023-03-27 19:03 ` Song Liu
2023-03-28 3:47 ` Yafang Shao
2023-04-02 23:37 ` Alexei Starovoitov
2023-04-03 3:05 ` Yafang Shao
2023-04-03 22:50 ` Alexei Starovoitov
2023-04-04 2:59 ` Yafang Shao
2023-04-06 2:06 ` Alexei Starovoitov
2023-04-06 2:54 ` Yafang Shao
2023-04-06 3:05 ` Alexei Starovoitov
2023-04-06 3:22 ` Yafang Shao
2023-04-06 4:24 ` Alexei Starovoitov
2023-04-06 5:43 ` Yafang Shao
2023-04-06 20:22 ` Andrii Nakryiko [this message]
2023-04-07 1:43 ` Alexei Starovoitov
2023-04-07 4:33 ` Yafang Shao
2023-04-07 15:32 ` Alexei Starovoitov
2023-04-07 15:59 ` Andrii Nakryiko
2023-04-07 16:05 ` Alexei Starovoitov
2023-04-07 16:21 ` Yafang Shao
2023-04-07 16:31 ` Alexei Starovoitov
2023-04-07 16:35 ` Yafang Shao
2023-03-31 5:52 ` Hao Luo
2023-04-01 16:32 ` Yafang Shao
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