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[net,4/6] mptcp: be careful on subflow status propagation on errors

Message ID 20230207-upstream-net-20230207-various-fix-6-2-v1-4-2031b495c7cc@tessares.net (mailing list archive)
State Accepted
Commit 1249db44a102d9d3541ed7798d4b01ffdcf03524
Headers show
Series mptcp: fixes for v6.2 | expand

Commit Message

Matthieu Baerts Feb. 7, 2023, 1:04 p.m. UTC
From: Paolo Abeni <pabeni@redhat.com>

Currently the subflow error report callback unconditionally
propagates the fallback subflow status to the owning msk.

If the msk is already orphaned, the above prevents the code
from correctly tracking the msk moving to the TCP_CLOSE state
and doing the appropriate cleanup.

All the above causes increasing memory usage over time and
sporadic self-tests failures.

There is a great deal of infrastructure trying to propagate
correctly the fallback subflow status to the owning mptcp socket,
e.g. via mptcp_subflow_eof() and subflow_sched_work_if_closed():
in the error propagation path we need only to cope with unorphaned

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/339
Fixes: 15cc10453398 ("mptcp: deliver ssk errors to msk")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
 net/mptcp/subflow.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)
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diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index a3e5026bee5b..32904c76c6a1 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1399,6 +1399,7 @@  void __mptcp_error_report(struct sock *sk)
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 		int err = sock_error(ssk);
+		int ssk_state;
 		if (!err)
@@ -1409,7 +1410,14 @@  void __mptcp_error_report(struct sock *sk)
 		if (sk->sk_state != TCP_SYN_SENT && !__mptcp_check_fallback(msk))
-		inet_sk_state_store(sk, inet_sk_state_load(ssk));
+		/* We need to propagate only transition to CLOSE state.
+		 * Orphaned socket will see such state change via
+		 * subflow_sched_work_if_closed() and that path will properly
+		 * destroy the msk as needed.
+		 */
+		ssk_state = inet_sk_state_load(ssk);
+		if (ssk_state == TCP_CLOSE && !sock_flag(sk, SOCK_DEAD))
+			inet_sk_state_store(sk, ssk_state);
 		sk->sk_err = -err;
 		/* This barrier is coupled with smp_rmb() in mptcp_poll() */