From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Hao Luo <haoluo@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, KP Singh <kpsingh@kernel.org>,
Shakeel Butt <shakeelb@google.com>,
Joe Burton <jevburton.kernel@gmail.com>,
Tejun Heo <tj@kernel.org>,
joshdon@google.com, sdf@google.com, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH bpf-next v1 7/9] bpf: Lift permission check in __sys_bpf when called from kernel.
Date: Wed, 2 Mar 2022 12:01:55 -0800 [thread overview]
Message-ID: <20220302200155.sid3imy4iqm7k5qf@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <20220225234339.2386398-8-haoluo@google.com>
On Fri, Feb 25, 2022 at 03:43:37PM -0800, Hao Luo wrote:
> After we introduced sleepable tracing programs, we now have an
> interesting problem. There are now three execution paths that can
> reach bpf_sys_bpf:
>
> 1. called from bpf syscall.
> 2. called from kernel context (e.g. kernel modules).
> 3. called from bpf programs.
>
> Ideally, capability check in bpf_sys_bpf is necessary for the first two
> scenarios. But it may not be necessary for the third case.
Well, it's unnecessary for the first two as well.
When called from the kernel lskel it's a pointless check.
The kernel module can do anything regardless.
When called from bpf syscall program it's not quite correct either.
When CAP_BPF was introduced we've designed it to enforce permissions
at prog load time. The prog_run doesn't check permissions.
So syscall progs don't need this secondary permission check.
Please add "case BPF_PROG_TYPE_SYSCALL:" to is_perfmon_prog_type()
and combine it with this patch.
That would be the best. The alternative below is less appealing.
> An alternative of lifting this permission check would be introducing an
> 'unpriv' version of bpf_sys_bpf, which doesn't check the current task's
> capability. If the owner of the tracing prog wants it to be exclusively
> used by root users, they can use the 'priv' version of bpf_sys_bpf; if
> the owner wants it to be usable for non-root users, they can use the
> 'unpriv' version.
...
> - if (sysctl_unprivileged_bpf_disabled && !bpf_capable())
> + if (sysctl_unprivileged_bpf_disabled && !bpf_capable() && !uattr.is_kernel)
This is great idea. If I could think of this I would went with it when prog_syscall
was introduced.
next prev parent reply other threads:[~2022-03-02 20:02 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-25 23:43 [PATCH bpf-next v1 0/9] Extend cgroup interface with bpf Hao Luo
2022-02-25 23:43 ` [PATCH bpf-next v1 1/9] bpf: Add mkdir, rmdir, unlink syscalls for prog_bpf_syscall Hao Luo
2022-02-27 5:18 ` Kumar Kartikeya Dwivedi
2022-02-28 22:10 ` Hao Luo
2022-03-02 19:34 ` Alexei Starovoitov
2022-03-03 18:50 ` Hao Luo
2022-03-04 18:37 ` Hao Luo
2022-03-05 23:47 ` Alexei Starovoitov
2022-03-08 21:08 ` Hao Luo
2022-03-02 20:55 ` Yonghong Song
2022-03-03 18:56 ` Hao Luo
2022-03-03 19:13 ` Yonghong Song
2022-03-03 19:15 ` Hao Luo
2022-03-12 3:46 ` Al Viro
2022-03-14 17:07 ` Hao Luo
2022-03-14 23:10 ` Al Viro
2022-03-15 17:27 ` Hao Luo
2022-03-15 18:59 ` Alexei Starovoitov
2022-03-15 19:03 ` Alexei Starovoitov
2022-03-15 19:00 ` Al Viro
2022-03-15 19:47 ` Hao Luo
2022-02-25 23:43 ` [PATCH bpf-next v1 2/9] bpf: Add BPF_OBJ_PIN and BPF_OBJ_GET in the bpf_sys_bpf helper Hao Luo
2022-02-25 23:43 ` [PATCH bpf-next v1 3/9] selftests/bpf: tests mkdir, rmdir, unlink and pin in syscall Hao Luo
2022-02-25 23:43 ` [PATCH bpf-next v1 4/9] bpf: Introduce sleepable tracepoints Hao Luo
2022-03-02 19:41 ` Alexei Starovoitov
2022-03-03 19:37 ` Hao Luo
2022-03-03 19:59 ` Alexei Starovoitov
2022-03-02 21:23 ` Yonghong Song
2022-03-02 21:30 ` Alexei Starovoitov
2022-03-03 1:08 ` Yonghong Song
2022-03-03 2:29 ` Alexei Starovoitov
2022-03-03 19:43 ` Hao Luo
2022-03-03 20:02 ` Alexei Starovoitov
2022-03-03 20:04 ` Alexei Starovoitov
2022-03-03 22:06 ` Hao Luo
2022-02-25 23:43 ` [PATCH bpf-next v1 5/9] cgroup: Sleepable cgroup tracepoints Hao Luo
2022-02-25 23:43 ` [PATCH bpf-next v1 6/9] libbpf: Add sleepable tp_btf Hao Luo
2022-02-25 23:43 ` [PATCH bpf-next v1 7/9] bpf: Lift permission check in __sys_bpf when called from kernel Hao Luo
2022-03-02 20:01 ` Alexei Starovoitov [this message]
2022-03-03 19:14 ` Hao Luo
2022-02-25 23:43 ` [PATCH bpf-next v1 8/9] bpf: Introduce cgroup iter Hao Luo
2022-02-26 2:32 ` kernel test robot
2022-02-26 2:32 ` kernel test robot
2022-02-26 2:53 ` kernel test robot
2022-03-02 21:59 ` Yonghong Song
2022-03-03 20:02 ` Hao Luo
2022-03-02 22:45 ` Kumar Kartikeya Dwivedi
2022-03-03 2:03 ` Yonghong Song
2022-03-03 3:03 ` Kumar Kartikeya Dwivedi
2022-03-03 4:00 ` Alexei Starovoitov
2022-03-03 7:33 ` Yonghong Song
2022-03-03 8:13 ` Kumar Kartikeya Dwivedi
2022-03-03 21:52 ` Hao Luo
2022-02-25 23:43 ` [PATCH bpf-next v1 9/9] selftests/bpf: Tests using sleepable tracepoints to monitor cgroup events Hao Luo
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