linux-kernel - Re: [PATCH v3 8/9] io_uring/cmd: BPF hook for getsockopt cmd

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Message-ID: <65665aaa-f3c1-123a-c61d-7b128835a1c5@linux.dev>
Date:   Fri, 25 Aug 2023 17:45:54 -0700
From:   Martin KaFai Lau <martin.lau@...ux.dev>
To:     Breno Leitao <leitao@...ian.org>
Cc:     Gabriel Krisman Bertazi <krisman@...e.de>, sdf@...gle.com,
        axboe@...nel.dk, asml.silence@...il.com,
        willemdebruijn.kernel@...il.com, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        io-uring@...r.kernel.org, kuba@...nel.org, pabeni@...hat.com
Subject: Re: [PATCH v3 8/9] io_uring/cmd: BPF hook for getsockopt cmd

On 8/25/23 9:53 AM, Breno Leitao wrote:
> On Mon, Aug 21, 2023 at 01:25:25PM -0700, Martin KaFai Lau wrote:
>> On 8/17/23 12:08 PM, Gabriel Krisman Bertazi wrote:
>>> Shouldn't you call sock->ops->getsockopt for level!=SOL_SOCKET prior to
>>> running the hook?  Before this patch, it would bail out with EOPNOTSUPP,
>>> but now the bpf hook gets called even for level!=SOL_SOCKET, which
>>> doesn't fit __sys_getsockopt. Am I misreading the code?
>> I agree it should not call into bpf if the io_uring cannot support non
>> SOL_SOCKET optnames. Otherwise, the bpf prog will get different optval and
>> optlen when running in _sys_getsockopt vs io_uring getsockopt (e.g. in
>> regular _sys_getsockopt(SOL_TCP), bpf expects the optval returned from
>> tcp_getsockopt).
>>
>> I think __sys_getsockopt can also be refactored similar to __sys_setsockopt
>> in patch 3. Yes, for non SOL_SOCKET it only supports __user *optval and
>> __user *optlen but may be a WARN_ON_ONCE/BUG_ON(sockpt_is_kernel(optval))
>> can be added before calling ops->getsockopt()? Then this details can be
>> hidden away from the io_uring.
> 
> 
> Right, I've spent some time thinking about it, and this could be done.
> This is a draft I have. Is it what you had in mind?

Yes. lgtm. Thanks.