From ae53b5bd77719fed58086c5be60ce4f22bffe1c6 Mon Sep 17 00:00:00 2001 From: Vlad Yasevich Date: Thu, 22 Jan 2009 14:53:23 -0800 Subject: [PATCH] sctp: Fix another socket race during accept/peeloff There is a race between sctp_rcv() and sctp_accept() where we have moved the association from the listening socket to the accepted socket, but sctp_rcv() processing cached the old socket and continues to use it. The easy solution is to check for the socket mismatch once we've grabed the socket lock. If we hit a mis-match, that means that were are currently holding the lock on the listening socket, but the association is refrencing a newly accepted socket. We need to drop the lock on the old socket and grab the lock on the new one. A more proper solution might be to create accepted sockets when the new association is established, similar to TCP. That would eliminate the race for 1-to-1 style sockets, but it would still existing for 1-to-many sockets where a user wished to peeloff an association. For now, we'll live with this easy solution as it addresses the problem. Reported-by: Michal Hocko Reported-by: Karsten Keil Signed-off-by: Vlad Yasevich Signed-off-by: David S. Miller --- net/sctp/input.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/net/sctp/input.c b/net/sctp/input.c index bf612d954d4..2e4a8646dbc 100644 --- a/net/sctp/input.c +++ b/net/sctp/input.c @@ -249,6 +249,19 @@ int sctp_rcv(struct sk_buff *skb) */ sctp_bh_lock_sock(sk); + if (sk != rcvr->sk) { + /* Our cached sk is different from the rcvr->sk. This is + * because migrate()/accept() may have moved the association + * to a new socket and released all the sockets. So now we + * are holding a lock on the old socket while the user may + * be doing something with the new socket. Switch our veiw + * of the current sk. + */ + sctp_bh_unlock_sock(sk); + sk = rcvr->sk; + sctp_bh_lock_sock(sk); + } + if (sock_owned_by_user(sk)) { SCTP_INC_STATS_BH(SCTP_MIB_IN_PKT_BACKLOG); sctp_add_backlog(sk, skb); -- 2.20.1