From 42c556fef92361bbc58be22f91b1c49db0963c34 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Wed, 29 Apr 2020 20:43:20 +0200 Subject: 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 Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- net/mptcp/protocol.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) (limited to 'net/mptcp') diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index b22a63ba2348..6e0188f5d3f3 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -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) -- cgit v1.2.3