netdev - Re: [PATCH 2/6] tcp: copy write-data from listen socket to accept child socket

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Message-ID: <CANn89iLNEnF1YYwOmPsuQn6n-O9N9yVxnZ_djEGxaZ11i4AsVA@mail.gmail.com>
Date: Fri, 16 May 2025 10:51:28 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Jeremy Harris <jgh@...m.org>
Cc: netdev@...r.kernel.org, linux-api@...r.kernel.org, ncardwell@...gle.com
Subject: Re: [PATCH 2/6] tcp: copy write-data from listen socket to accept
 child socket

On Fri, May 16, 2025 at 8:56 AM Jeremy Harris <jgh@...m.org> wrote:
>
> Set the request_sock flag for fastopen earlier, making it available
> to the af_ops SYN-handler function.
>
> In that function copy data from the listen socket write queue into an
> sk_buff, allocating if needed and adding to the write queue of the
> newly-created child socket.
> Set sequence number values depending on the fastopen status.

I do not see any locking. I think you should run a local KASAN/syzbot
instance and you will be shocked.

Honestly we need to be convinced of why adding code in sendmsg() fast
path is worth this.