[SCTP]: Add RCU synchronization around sctp_localaddr_list

sctp_localaddr_list is modified dynamically via NETDEV_UP
and NETDEV_DOWN events, but there is not synchronization
between writer (even handler) and readers.  As a result,
the readers can access an entry that has been freed and
crash the sytem.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Sridhar Samdurala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
index fdb287a..7fc369f 100644
--- a/net/sctp/bind_addr.c
+++ b/net/sctp/bind_addr.c
@@ -163,8 +163,10 @@
 		addr->a.v4.sin_port = htons(bp->port);
 
 	addr->use_as_src = use_as_src;
+	addr->valid = 1;
 
 	INIT_LIST_HEAD(&addr->list);
+	INIT_RCU_HEAD(&addr->rcu);
 	list_add_tail(&addr->list, &bp->address_list);
 	SCTP_DBG_OBJCNT_INC(addr);