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Date: Fri, 26 Jul 2024 19:34:03 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Dmitry Safonov via B4 Relay <devnull+0x7f454c46.gmail.com@kernel.org>
Cc: 0x7f454c46@gmail.com, Eric Dumazet <edumazet@google.com>, "David S.
 Miller" <davem@davemloft.net>, David Ahern <dsahern@kernel.org>, Paolo
 Abeni <pabeni@redhat.com>, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org, stable@kernel.org
Subject: Re: [PATCH net] net/tcp: Disable TCP-AO static key after RCU grace
 period
Message-ID: <20240726193403.1b15a2af@kernel.org>
In-Reply-To: <20240725-tcp-ao-static-branch-rcu-v1-1-021d009beebf@gmail.com>
References: <20240725-tcp-ao-static-branch-rcu-v1-1-021d009beebf@gmail.com>
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On Thu, 25 Jul 2024 06:00:02 +0100 Dmitry Safonov via B4 Relay wrote:
> @@ -290,9 +298,7 @@ void tcp_ao_destroy_sock(struct sock *sk, bool twsk)
>  			atomic_sub(tcp_ao_sizeof_key(key), &sk->sk_omem_alloc);
>  		call_rcu(&key->rcu, tcp_ao_key_free_rcu);
>  	}
> -
> -	kfree_rcu(ao, rcu);
> -	static_branch_slow_dec_deferred(&tcp_ao_needed);
> +	call_rcu(&ao->rcu, tcp_ao_info_free_rcu);

Maybe free the keys inside tcp_ao_info_free_rcu, too?
IIUC you're saying that new sock is still looking at this ao under RCU
protection - messing with the key list feels a tiny bit odd since the
object is technically "live" until the end of the RCU grace period.