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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Jiayuan Chen , Kuniyuki Iwashima , Willem de Bruijn , bpf@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH bpf-next 2/2] bpf, sockmap: Use sock_hold() instead of refcount_inc_not_zero() in lookup In-Reply-To: <20260813-sockmap-lookup-get-ref-v1-2-31f5d55f44ac@rbox.co> (Michal Luczaj's message of "Thu, 13 Aug 2026 14:42:00 +0200") References: <20260813-sockmap-lookup-get-ref-v1-0-31f5d55f44ac@rbox.co> <20260813-sockmap-lookup-get-ref-v1-2-31f5d55f44ac@rbox.co> User-Agent: mu4e 1.14.1; emacs 30.2 Date: Fri, 14 Aug 2026 12:42:37 +0200 Message-ID: <877blt0yqq.fsf@cloudflare.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Thu, Aug 13, 2026 at 02:42 PM +02, Michal Luczaj wrote: > psock's hold on the looked up socket isn't dropped until sk_psock_drop() -> > queue_rcu_work() -> sk_psock_destroy() runs, which happens only after the > entry is unlinked and an RCU grace period elapses. Since the lookup runs > under RCU, a non-NULL result guarantees sk_refcnt >= 1: > refcount_inc_not_zero() can never fail here. Use sock_hold() instead. > > Reviewed-by: Emil Tsalapatis > Signed-off-by: Michal Luczaj > --- Reviewed-by: Jakub Sitnicki