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mptcp: pm: kernel: use RCU to free endpoint listeners

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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: 1729cf186d ("mptcp: create the listening socket for new port")
Cc: stable@vger.kernel.org
Signed-off-by: Kyle Zeng <kylebot@openai.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20261030042255.74216-1-kylebot@openai.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Kyle Zeng 2026-10-29 21:22:55 -07:00 committed by Paolo Abeni
parent 57889a8f6d
commit 49b09ae0bf
1 changed files with 1 additions and 0 deletions
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net/mptcp/pm_kernel.c
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@ -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);