netdev - Re: [PATCH bpf-next v10 03/11] bpf: per-cgroup lsm flavor

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Message-ID: <20220623224049.4xnxd3kjx4lzpjqu@kafai-mbp>
Date:   Thu, 23 Jun 2022 15:40:49 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org, ast@...nel.org,
        daniel@...earbox.net, andrii@...nel.org
Subject: Re: [PATCH bpf-next v10 03/11] bpf: per-cgroup lsm flavor

On Wed, Jun 22, 2022 at 09:03:38AM -0700, Stanislav Fomichev wrote:
> Allow attaching to lsm hooks in the cgroup context.
> 
> Attaching to per-cgroup LSM works exactly like attaching
> to other per-cgroup hooks. New BPF_LSM_CGROUP is added
> to trigger new mode; the actual lsm hook we attach to is
> signaled via existing attach_btf_id.
> 
> For the hooks that have 'struct socket' or 'struct sock' as its first
> argument, we use the cgroup associated with that socket. For the rest,
> we use 'current' cgroup (this is all on default hierarchy == v2 only).
> Note that for some hooks that work on 'struct sock' we still
> take the cgroup from 'current' because some of them work on the socket
> that hasn't been properly initialized yet.
> 
> Behind the scenes, we allocate a shim program that is attached
> to the trampoline and runs cgroup effective BPF programs array.
> This shim has some rudimentary ref counting and can be shared
> between several programs attaching to the same lsm hook from
> different cgroups.
Reviewed-by: Martin KaFai Lau <kafai@...com>