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From:   Andrii Nakryiko <andrii.nakryiko@gmail.com>
Date:   Mon, 23 Dec 2019 21:48:14 -0800
Message-ID: <CAEf4BzZQYnSv+0nEkgt1kovXdtqMNv5hMhLdCWkJhUS-Lr3hyQ@mail.gmail.com>
Subject: Re: [PATCH bpf-next v1 07/13] bpf: lsm: Implement attach, detach and execution.
To:     KP Singh <kpsingh@chromium.org>
Cc:     open list <linux-kernel@vger.kernel.org>,
        bpf <bpf@vger.kernel.org>, linux-security-module@vger.kernel.org,
        Alexei Starovoitov <ast@kernel.org>,
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        Kees Cook <keescook@chromium.org>,
        Thomas Garnier <thgarnie@chromium.org>,
        Michael Halcrow <mhalcrow@google.com>,
        Paul Turner <pjt@google.com>,
        Brendan Gregg <brendan.d.gregg@gmail.com>,
        Jann Horn <jannh@google.com>,
        Matthew Garrett <mjg59@google.com>,
        Christian Brauner <christian@brauner.io>,
        =?UTF-8?B?TWlja2HDq2wgU2FsYcO8bg==?= <mic@digikod.net>,
        Florent Revest <revest@chromium.org>,
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        Martin KaFai Lau <kafai@fb.com>,
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        "Serge E. Hallyn" <serge@hallyn.com>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Nicolas Ferre <nicolas.ferre@microchip.com>,
        Stanislav Fomichev <sdf@google.com>,
        Quentin Monnet <quentin.monnet@netronome.com>,
        Andrey Ignatov <rdna@fb.com>, Joe Stringer <joe@wand.net.nz>
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On Fri, Dec 20, 2019 at 7:43 AM KP Singh <kpsingh@chromium.org> wrote:
>
> From: KP Singh <kpsingh@google.com>
>
> A user space program can attach an eBPF program by:
>
>   hook_fd = open("/sys/kernel/security/bpf/bprm_check_security",
>                  O_RDWR|O_CLOEXEC)
>   prog_fd = bpf(BPF_PROG_LOAD, ...)
>   bpf(BPF_PROG_ATTACH, hook_fd, prog_fd)
>
> The following permissions are required to attach a program to a hook:
>
> - CAP_SYS_ADMIN to load eBPF programs
> - CAP_MAC_ADMIN (to update the policy of an LSM)
> - The securityfs file being a valid hook and writable (O_RDWR)
>
> When such an attach call is received, the attachment logic looks up the
> dentry and appends the program to the bpf_prog_array.
>
> The BPF programs are stored in a bpf_prog_array and writes to the array
> are guarded by a mutex. The eBPF programs are executed as a part of the
> LSM hook they are attached to. If any of the eBPF programs return
> an error (-ENOPERM) the action represented by the hook is denied.
>
> Signed-off-by: KP Singh <kpsingh@google.com>
> ---

Acked-by: Andrii Nakryiko <andriin@fb.com>

>  MAINTAINERS             |   1 +
>  include/linux/bpf_lsm.h |  13 ++++
>  kernel/bpf/syscall.c    |   5 +-
>  security/bpf/lsm_fs.c   |  19 +++++-
>  security/bpf/ops.c      | 134 ++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 169 insertions(+), 3 deletions(-)
>

[...]