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authorVlad Yasevich <vladislav.yasevich@hp.com>2009-01-22 14:53:23 -0800
committerGreg Kroah-Hartman <gregkh@suse.de>2009-02-12 09:50:38 -0800
commit8059205cb1764a590af6cb12108e6b8be465751d (patch)
parente117993af63778e46f68ea7477ff502e90d1c552 (diff)
sctp: Fix another socket race during accept/peeloff
commit ae53b5bd77719fed58086c5be60ce4f22bffe1c6 upstream. 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 <mhocko@suse.cz> Reported-by: Karsten Keil <kkeil@suse.de> Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
1 files changed, 13 insertions, 0 deletions
diff --git a/net/sctp/input.c b/net/sctp/input.c
index bf612d954d41..2e4a8646dbc3 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -249,6 +249,19 @@ int sctp_rcv(struct sk_buff *skb)
+ 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_add_backlog(sk, skb);