sctp: listen on the sock only when it's state is listening or closed

[ Upstream commit 34b2789f1d9bf8dcca9b5cb553d076ca2cd898ee ]

Now sctp doesn't check sock's state before listening on it. It could
even cause changing a sock with any state to become a listening sock
when doing sctp_listen.

This patch is to fix it by checking sock's state in sctp_listen, so
that it will listen on the sock with right state.

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 673442025bfd..14346dccc4fe 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -6861,6 +6861,9 @@ int sctp_inet_listen(struct socket *sock, int backlog)
         if (sock->state != SS_UNCONNECTED)
                 goto out;
 
+        if (!sctp_sstate(sk, LISTENING) && !sctp_sstate(sk, CLOSED))
+                goto out;
+
         /* If backlog is zero, disable listening. */
         if (!backlog) {
                 if (sctp_sstate(sk, CLOSED))