netdev - Re: [PATCH bpf-next 02/14] bpf: net: Avoid sock_setsockopt() taking sk lock when called from bpf

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Message-ID: <20220728172004.6mpkycl52sszuudc@kafai-mbp.dhcp.thefacebook.com>
Date:   Thu, 28 Jul 2022 10:20:04 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Stanislav Fomichev <sdf@...gle.com>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, kernel-team@...com,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH bpf-next 02/14] bpf: net: Avoid sock_setsockopt() taking
 sk lock when called from bpf

On Thu, Jul 28, 2022 at 09:56:29AM -0700, Jakub Kicinski wrote:
> On Thu, 28 Jul 2022 09:31:04 -0700 Martin KaFai Lau wrote:
> > If I understand the concern correctly, it may not be straight forward to
> > grip the reason behind the testings at in_bpf() [ the in_task() and
> > the current->bpf_ctx test ] ?  Yes, it is a valid point.
> > 
> > The optval.is_bpf bit can be directly traced back to the bpf_setsockopt
> > helper and should be easier to reason about.
> 
> I think we're saying the opposite thing. in_bpf() the context checking
> function is fine. There is a clear parallel to in_task() and combined
> with the capability check it should be pretty obvious what the code
> is intending to achieve.
> 
> sockptr_t::in_bpf which randomly implies that the lock is already held
> will be hard to understand for anyone not intimately familiar with the
> BPF code. Naming that bit is_locked seems much clearer.
> 
> Which is what I believe Stan was proposing.
Yeah, I think I read the 'vote against @in_bpf' in the other way. :)

Sure. I will do s/is_bpf/is_locked/ and do the in_bpf() context
checking before ns_capable().