linux-kernel - Re: [PATCH bpf-next v8 4/8] bpf: lsm: Implement attach, detach and execution

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Message-ID: <alpine.LRH.2.21.2003281207420.30073@namei.org>
Date:   Sat, 28 Mar 2020 12:08:15 +1100 (AEDT)
From:   James Morris <jmorris@...ei.org>
To:     KP Singh <kpsingh@...omium.org>
cc:     linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Andrii Nakryiko <andriin@...com>,
        Brendan Jackman <jackmanb@...gle.com>,
        Florent Revest <revest@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        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 v8 4/8] bpf: lsm: Implement attach, detach and
 execution

On Fri, 27 Mar 2020, KP Singh 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>
> Acked-by: Andrii Nakryiko <andriin@...com>
> Reviewed-by: Brendan Jackman <jackmanb@...gle.com>
> Reviewed-by: Florent Revest <revest@...gle.com>


Acked-by: James Morris <jamorris@...ux.microsoft.com>


-- 
James Morris
<jmorris@...ei.org>