From: Paolo Abeni pabeni@redhat.com
[ Upstream commit 0226436acf2495cde4b93e7400e5a87305c26054 ]
Since the blamed commit, closing the first subflow resets the first subflow socket state to SS_UNCONNECTED.
The current mptcp listen implementation relies only on such state to prevent touching not-fully-disconnected sockets.
Incoming mptcp fastclose (or paired endpoint removal) unconditionally closes the first subflow.
All the above allows an incoming fastclose followed by a listen() call to successfully race with a blocking recvmsg(), potentially causing the latter to hit a divide by zero bug in cleanup_rbuf/__tcp_select_window().
Address the issue explicitly checking the msk socket state in mptcp_listen(). An alternative solution would be moving the first subflow socket state update into mptcp_disconnect(), but in the long term the first subflow socket should be removed: better avoid relaying on it for internal consistency check.
Fixes: b29fcfb54cd7 ("mptcp: full disconnect implementation") Cc: stable@vger.kernel.org Reported-by: Christoph Paasch cpaasch@apple.com Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/414 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 Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/mptcp/protocol.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 208da9a9909c2..37ff6766fd526 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -3753,6 +3753,11 @@ static int mptcp_listen(struct socket *sock, int backlog) pr_debug("msk=%p", msk);
lock_sock(sk); + + err = -EINVAL; + if (sock->state != SS_UNCONNECTED || sock->type != SOCK_STREAM) + goto unlock; + ssock = __mptcp_nmpc_socket(msk); if (!ssock) { err = -EINVAL;