linux-kernel - Re: [PATCH bpf-next v1 07/13] bpf: lsm: Implement attach, detach and execution.

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Date:   Mon, 23 Dec 2019 21:48:14 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     KP Singh <kpsingh@...omium.org>
Cc:     open list <linux-kernel@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, linux-security-module@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        James Morris <jmorris@...ei.org>,
        Kees Cook <keescook@...omium.org>,
        Thomas Garnier <thgarnie@...omium.org>,
        Michael Halcrow <mhalcrow@...gle.com>,
        Paul Turner <pjt@...gle.com>,
        Brendan Gregg <brendan.d.gregg@...il.com>,
        Jann Horn <jannh@...gle.com>,
        Matthew Garrett <mjg59@...gle.com>,
        Christian Brauner <christian@...uner.io>,
        Mickaël Salaün <mic@...ikod.net>,
        Florent Revest <revest@...omium.org>,
        Brendan Jackman <jackmanb@...omium.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Stanislav Fomichev <sdf@...gle.com>,
        Quentin Monnet <quentin.monnet@...ronome.com>,
        Andrey Ignatov <rdna@...com>, Joe Stringer <joe@...d.net.nz>
Subject: Re: [PATCH bpf-next v1 07/13] bpf: lsm: Implement attach, detach and execution.

On Fri, Dec 20, 2019 at 7:43 AM KP Singh <kpsingh@...omium.org> wrote:
>
> From: KP Singh <kpsingh@...gle.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@...gle.com>
> ---

Acked-by: Andrii Nakryiko <andriin@...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(-)
>

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