From 98f4b42d6cc98802e6cb1ca5572487a1fc4f21ef Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Wed, 3 Mar 2021 08:33:18 +0000 Subject: [PATCH] mptcp: reset 'first' and ack_hint on subflow close Just like with last_snd, we have to NULL 'first' on subflow close. ack_hint isn't strictly required (its never dereferenced), but better to clear this explicitly as well instead of making it an exception. msk->first is dereferenced unconditionally at accept time, but at that point the ssk is not on the conn_list yet -- this means worker can't see it when iterating the conn_list. Reported-by: Paolo Abeni Reviewed-by: Matthieu Baerts Signed-off-by: Florian Westphal --- net/mptcp/protocol.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 410f44a74eef7..db2fadbd4f98e 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2162,6 +2162,12 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, if (ssk == msk->last_snd) msk->last_snd = NULL; + if (ssk == msk->ack_hint) + msk->ack_hint = NULL; + + if (ssk == msk->first) + msk->first = NULL; + if (msk->subflow && ssk == msk->subflow->sk) mptcp_dispose_initial_subflow(msk); } @@ -3293,6 +3299,9 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock, /* PM/worker can now acquire the first subflow socket * lock without racing with listener queue cleanup, * we can notify it, if needed. + * + * Even if remote has reset the initial subflow by now + * the refcnt is still at least one. */ subflow = mptcp_subflow_ctx(msk->first); list_add(&subflow->node, &msk->conn_list);