linux-kernel - Re: [PATCH net-next v3 2/2] tcp: Free TCP-AO/TCP-MD5 info/keys without RCU

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Message-ID: <CAGrbwDRHOaiBcMecGrE=bdRG6m0aHyk_VBtpN6-g-B92NF=hTA@mail.gmail.com>
Date: Wed, 3 Sep 2025 18:41:39 +0100
From: Dmitry Safonov <dima@...sta.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Dmitry Safonov via B4 Relay <devnull+dima.arista.com@...nel.org>, Eric Dumazet <edumazet@...gle.com>, 
	Neal Cardwell <ncardwell@...gle.com>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	"David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, Bob Gilligan <gilligan@...sta.com>, 
	Salam Noureddine <noureddine@...sta.com>, Dmitry Safonov <0x7f454c46@...il.com>, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 2/2] tcp: Free TCP-AO/TCP-MD5 info/keys
 without RCU

On Wed, Sep 3, 2025 at 12:09 AM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Sat, 30 Aug 2025 05:31:47 +0100 Dmitry Safonov via B4 Relay wrote:
> > Now that the destruction of info/keys is delayed until the socket
> > destructor, it's safe to use kfree() without an RCU callback.
> > As either socket was yet in TCP_CLOSE state or the socket refcounter is
> > zero and no one can discover it anymore, it's safe to release memory
> > straight away.
> > Similar thing was possible for twsk already.
>
> After this patch the rcu members of struct tcp_ao* seem to no longer
> be used?

Right. I'll remove tcp_ao_info::rcu in v4.
For tcp_ao_key it's needed for the regular key rotation, as well as
for tcp_md5sig_key.

Thanks,
             Dmitry