From 49b09ae0bf57b4230187d4cdd0a370558e44a6e8 Mon Sep 17 00:00:00 2001 From: Kyle Zeng Date: Thu, 29 Oct 2026 21:22:55 -0700 Subject: [PATCH] mptcp: pm: kernel: use RCU to free endpoint listeners mptcp_pm_nl_create_listen_socket() starts the TCP listener directly instead of going through mptcp_listen(). It consequently misses setting SOCK_RCU_FREE on the parent MPTCP socket. tcp_child_process() can invoke the listener's subflow_data_ready() callback without holding the MPTCP parent lock or a reference to the parent. An authenticated MP_JOIN racing with endpoint teardown can therefore access the parent after its last reference has been dropped. The ADD_ADDR error path can also close an already published listener. Set SOCK_RCU_FREE before __inet_listen_sk() publishes the TCP listener, matching mptcp_listen(). This protects the parent on every subsequent close path, including a failed endpoint addition. Fixes: 1729cf186d8a ("mptcp: create the listening socket for new port") Cc: stable@vger.kernel.org Signed-off-by: Kyle Zeng Reviewed-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20261030042255.74216-1-kylebot@openai.com Signed-off-by: Paolo Abeni --- net/mptcp/pm_kernel.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c index 1a7750813235..f7396628490e 100644 --- a/net/mptcp/pm_kernel.c +++ b/net/mptcp/pm_kernel.c @@ -906,6 +906,7 @@ static int mptcp_pm_nl_create_listen_socket(struct sock *sk, * old status is known (TCP_CLOSE). */ inet_sk_state_store(newsk, TCP_LISTEN); + sock_set_flag(newsk, SOCK_RCU_FREE); lock_sock(ssk); WRITE_ONCE(mptcp_subflow_ctx(ssk)->pm_listener, true); err = __inet_listen_sk(ssk, backlog);