linux-kernel - Re: [PATCH bpf-next v7 4/8] bpf: lsm: Implement attach, detach and execution

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Message-ID: <CAEf4BzaS8xLLrbaWgWbWSEVfc3YBPURQhZxe=zR06B021jH5BA@mail.gmail.com>
Date:   Thu, 26 Mar 2020 12:12:20 -0700
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,
        Brendan Jackman <jackmanb@...gle.com>,
        Florent Revest <revest@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        James Morris <jmorris@...ei.org>,
        Kees Cook <keescook@...omium.org>,
        Paul Turner <pjt@...gle.com>, Jann Horn <jannh@...gle.com>,
        Florent Revest <revest@...omium.org>,
        Brendan Jackman <jackmanb@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH bpf-next v7 4/8] bpf: lsm: Implement attach, detach and execution

On Thu, Mar 26, 2020 at 7:29 AM KP Singh <kpsingh@...omium.org> wrote:
>
> From: KP Singh <kpsingh@...gle.com>
>
> JITed BPF programs are dynamically attached to the LSM hooks
> using BPF trampolines. The trampoline prologue generates code to handle
> conversion of the signature of the hook to the appropriate BPF context.
>
> The allocated trampoline programs are attached to the nop functions
> initialized as LSM hooks.
>
> BPF_PROG_TYPE_LSM programs must have a GPL compatible license and
> and need CAP_SYS_ADMIN (required for loading eBPF programs).
>
> Upon attachment:
>
> * A BPF fexit trampoline is used for LSM hooks with a void return type.
> * A BPF fmod_ret trampoline is used for LSM hooks which return an
>   int. The attached programs can override the return value of the
>   bpf LSM hook to indicate a MAC Policy decision.
>
> Signed-off-by: KP Singh <kpsingh@...gle.com>
> Reviewed-by: Brendan Jackman <jackmanb@...gle.com>
> Reviewed-by: Florent Revest <revest@...gle.com>
> ---

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


>  include/linux/bpf_lsm.h | 11 ++++++++
>  kernel/bpf/bpf_lsm.c    | 28 ++++++++++++++++++++
>  kernel/bpf/btf.c        |  9 ++++++-
>  kernel/bpf/syscall.c    | 57 ++++++++++++++++++++++++++++-------------
>  kernel/bpf/trampoline.c | 17 +++++++++---
>  kernel/bpf/verifier.c   | 19 +++++++++++---
>  6 files changed, 114 insertions(+), 27 deletions(-)
>

[...]

> @@ -2479,6 +2496,10 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
>                 }
>                 buf[sizeof(buf) - 1] = 0;
>                 tp_name = buf;
> +               break;
> +       default:
> +                       err = -EINVAL;
> +                       goto out_put_prog;
>         }

is indentation off here or it's my email client?

[...]