From: Song Liu <songliubraving@fb.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
Kernel Team <Kernel-team@fb.com>,
"Lorenz Bauer" <lmb@cloudflare.com>, Jann Horn <jannh@google.com>,
Greg KH <gregkh@linuxfoundation.org>,
Linux API <linux-api@vger.kernel.org>,
LSM List <linux-security-module@vger.kernel.org>
Subject: Re: [PATCH v2 bpf-next 1/4] bpf: unprivileged BPF access via /dev/bpf
Date: Fri, 2 Aug 2019 07:21:33 +0000 [thread overview]
Message-ID: <5A2FCD7E-7F54-41E5-BFAE-BB9494E74F2D@fb.com> (raw)
In-Reply-To: <CALCETrVoZL1YGUxx3kM-d21TWVRKdKw=f2B8aE5wc2zmX1cQ4g@mail.gmail.com>
Hi Andy,
> On Jul 31, 2019, at 12:09 PM, Andy Lutomirski <luto@kernel.org> wrote:
>
> On Wed, Jul 31, 2019 at 1:10 AM Song Liu <songliubraving@fb.com> wrote:
>>
>>
>>
>>> On Jul 30, 2019, at 1:24 PM, Andy Lutomirski <luto@kernel.org> wrote:
>>>
>>> On Mon, Jul 29, 2019 at 10:07 PM Song Liu <songliubraving@fb.com> wrote:
>>>>
>>>> Hi Andy,
>>>>
>>>>> On Jul 27, 2019, at 11:20 AM, Song Liu <songliubraving@fb.com> wrote:
>>>>>
>>>>> Hi Andy,
>>>>>
>>>>>
>>
>> [...]
>>
>>>>>
>>>>
>>>> I would like more comments on this.
>>>>
>>>> Currently, bpf permission is more or less "root or nothing", which we
>>>> would like to change.
>>>>
>>>> The short term goal is to separate bpf from root, in other words, it is
>>>> "all or nothing". Special user space utilities, such as systemd, would
>>>> benefit from this. Once this is implemented, systemd can call sys_bpf()
>>>> when it is not running as root.
>>>
>>> As generally nasty as Linux capabilities are, this sounds like a good
>>> use for CAP_BPF_ADMIN.
>>
>> I actually agree CAP_BPF_ADMIN makes sense. The hard part is to make
>> existing tools (setcap, getcap, etc.) and libraries aware of the new CAP.
>
> It's been done before -- it's not that hard. IMO the main tricky bit
> would be try be somewhat careful about defining exactly what
> CAP_BPF_ADMIN does.
Agreed. I think defining CAP_BPF_ADMIN could be a good topic for the
Plumbers conference.
OTOH, I don't think we have to wait for CAP_BPF_ADMIN to allow daemons
like systemd to do sys_bpf() without root.
>
>>> I don't see why you need to invent a whole new mechanism for this.
>>> The entire cgroup ecosystem outside bpf() does just fine using the
>>> write permission on files in cgroupfs to control access. Why can't
>>> bpf() do the same thing?
>>
>> It is easier to use write permission for BPF_PROG_ATTACH. But it is
>> not easy to do the same for other bpf commands: BPF_PROG_LOAD and
>> BPF_MAP_*. A lot of these commands don't have target concept. Maybe
>> we should have target concept for all these commands. But that is a
>> much bigger project. OTOH, "all or nothing" model allows all these
>> commands at once.
>
> For BPF_PROG_LOAD, I admit I've never understood why permission is
> required at all. I think that CAP_SYS_ADMIN or similar should be
> needed to get is_priv in the verifier, but I think that should mainly
> be useful for tracing, and that requires lots of privilege anyway.
> BPF_MAP_* is probably the trickiest part. One solution would be some
> kind of bpffs, but I'm sure other solutions are possible.
Improving permission management of cgroup_bpf is another good topic to
discuss. However, it is also an overkill for current use case.
Let me get more details about the use case, so that we have a clear
picture about short term and long term goals.
Thanks again for your suggestions.
Song
next prev parent reply other threads:[~2019-08-02 7:22 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190627201923.2589391-1-songliubraving@fb.com>
[not found] ` <20190627201923.2589391-2-songliubraving@fb.com>
[not found] ` <21894f45-70d8-dfca-8c02-044f776c5e05@kernel.org>
[not found] ` <3C595328-3ABE-4421-9772-8D41094A4F57@fb.com>
[not found] ` <CALCETrWBnH4Q43POU8cQ7YMjb9LioK28FDEQf7aHZbdf1eBZWg@mail.gmail.com>
[not found] ` <0DE7F23E-9CD2-4F03-82B5-835506B59056@fb.com>
[not found] ` <CALCETrWBWbNFJvsTCeUchu3BZJ3SH3dvtXLUB2EhnPrzFfsLNA@mail.gmail.com>
[not found] ` <201907021115.DCD56BBABB@keescook>
[not found] ` <CALCETrXTta26CTtEDnzvtd03-WOGdXcnsAogP8JjLkcj4-mHvg@mail.gmail.com>
[not found] ` <4A7A225A-6C23-4C0F-9A95-7C6C56B281ED@fb.com>
[not found] ` <CALCETrX2bMnwC6_t4b_G-hzJSfMPrkK4YKs5ebcecv2LJ0rt3w@mail.gmail.com>
[not found] ` <514D5453-0AEE-420F-AEB6-3F4F58C62E7E@fb.com>
[not found] ` <1DE886F3-3982-45DE-B545-67AD6A4871AB@amacapital.net>
[not found] ` <7F51F8B8-CF4C-4D82-AAE1-F0F28951DB7F@fb.com>
[not found] ` <77354A95-4107-41A7-8936-D144F01C3CA4@fb.com>
[not found] ` <369476A8-4CE1-43DA-9239-06437C0384C7@fb.com>
2019-07-30 20:24 ` [PATCH v2 bpf-next 1/4] bpf: unprivileged BPF access via /dev/bpf Andy Lutomirski
2019-07-31 8:10 ` Song Liu
2019-07-31 19:09 ` Andy Lutomirski
2019-08-02 7:21 ` Song Liu [this message]
2019-08-04 22:16 ` Andy Lutomirski
2019-08-05 0:08 ` Andy Lutomirski
2019-08-05 5:47 ` Andy Lutomirski
2019-08-05 7:36 ` Song Liu
2019-08-05 17:23 ` Andy Lutomirski
2019-08-05 19:21 ` Alexei Starovoitov
2019-08-05 21:25 ` Andy Lutomirski
2019-08-05 22:21 ` Andy Lutomirski
2019-08-06 1:11 ` Alexei Starovoitov
2019-08-07 5:24 ` Andy Lutomirski
2019-08-07 9:03 ` Lorenz Bauer
2019-08-07 13:52 ` Andy Lutomirski
2019-08-13 21:58 ` Alexei Starovoitov
2019-08-13 22:26 ` Daniel Colascione
2019-08-13 23:24 ` Andy Lutomirski
2019-08-13 23:06 ` Andy Lutomirski
2019-08-14 0:57 ` Alexei Starovoitov
2019-08-14 17:51 ` Andy Lutomirski
2019-08-14 22:05 ` Alexei Starovoitov
2019-08-14 22:30 ` Andy Lutomirski
2019-08-14 23:33 ` Alexei Starovoitov
2019-08-14 23:59 ` Andy Lutomirski
2019-08-15 0:36 ` Alexei Starovoitov
2019-08-15 11:24 ` Jordan Glover
2019-08-15 17:28 ` Alexei Starovoitov
2019-08-15 18:36 ` Andy Lutomirski
2019-08-15 23:08 ` Alexei Starovoitov
2019-08-16 9:34 ` Jordan Glover
2019-08-16 9:59 ` Thomas Gleixner
2019-08-16 11:33 ` Jordan Glover
2019-08-16 19:52 ` Alexei Starovoitov
2019-08-16 20:28 ` Thomas Gleixner
2019-08-17 15:02 ` Alexei Starovoitov
2019-08-17 15:44 ` Andy Lutomirski
2019-08-19 9:15 ` Thomas Gleixner
2019-08-19 17:27 ` Alexei Starovoitov
2019-08-19 17:38 ` Andy Lutomirski
2019-08-15 18:43 ` Jordan Glover
2019-08-15 19:46 ` Kees Cook
2019-08-15 23:46 ` Alexei Starovoitov
2019-08-16 0:54 ` Andy Lutomirski
2019-08-16 5:56 ` Song Liu
2019-08-16 21:45 ` Alexei Starovoitov
2019-08-16 22:22 ` Christian Brauner
2019-08-17 15:08 ` Alexei Starovoitov
2019-08-17 15:16 ` Christian Brauner
2019-08-17 15:36 ` Alexei Starovoitov
2019-08-17 15:42 ` Christian Brauner
2019-08-22 14:17 ` Daniel Borkmann
2019-08-22 15:16 ` Andy Lutomirski
2019-08-22 15:17 ` RFC: very rough draft of a bpf permission model Andy Lutomirski
2019-08-22 23:26 ` Alexei Starovoitov
2019-08-23 23:09 ` Andy Lutomirski
2019-08-26 22:36 ` Alexei Starovoitov
2019-08-27 0:05 ` Andy Lutomirski
2019-08-27 0:34 ` Alexei Starovoitov
2019-08-22 22:48 ` [PATCH v2 bpf-next 1/4] bpf: unprivileged BPF access via /dev/bpf Alexei Starovoitov
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