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

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Message-ID: <20250903152331.2e31b3cf@kernel.org>
Date: Wed, 3 Sep 2025 15:23:31 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Dmitry Safonov <dima@...sta.com>
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, 3 Sep 2025 18:41:39 +0100 Dmitry Safonov 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.

Hm, maybe I missed something. I did a test allmodconfig build yesterday
and while the md5sig_key rcu was still needed, removing the ao_key
didn't cause issues. But it was just a quick test I didn't even config
kconfig is sane.