Commit 42c556fe authored Apr 29, 2020 by Florian Westphal Committed by David S. Miller Apr 29, 2020

mptcp: replace mptcp_disconnect with a stub

Paolo points out that mptcp_disconnect is bogus:
"lock_sock(sk);
looks suspicious (lock should be already held by the caller)
And call to: tcp_disconnect(sk, flags); too, sk is not a tcp
socket".

->disconnect() gets called from e.g. inet_stream_connect when
one tries to disassociate a connected socket again (to re-connect
without closing the socket first).
MPTCP however uses mptcp_stream_connect, not inet_stream_connect,
for the mptcp-socket connect call.

inet_stream_connect only gets called indirectly, for the tcp socket,
so any ->disconnect() calls end up calling tcp_disconnect for that
tcp subflow sk.

This also explains why syzkaller has not yet reported a problem
here.  So for now replace this with a stub that doesn't do anything.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/14


Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 98123074

net/mptcp/protocol.c

+6 −5

Original line number	Diff line number	Diff line
		@@ -1316,11 +1316,12 @@ static void mptcp_copy_inaddrs(struct sock msk, const struct sock ssk)

		static int mptcp_disconnect(struct sock *sk, int flags)
		{
		lock_sock(sk);
		__mptcp_clear_xmit(sk);
		release_sock(sk);
		mptcp_cancel_work(sk);
		return tcp_disconnect(sk, flags);
		/* Should never be called.
		* inet_stream_connect() calls ->disconnect, but that
		* refers to the subflow socket, not the mptcp one.
		*/
		WARN_ON_ONCE(1);
		return 0;
		}

		#if IS_ENABLED(CONFIG_MPTCP_IPV6)

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