sctp: Add RCU protection to assoc->transport_addr_list

peer.transport_addr_list is currently only protected by sk_sock
which is inpractical to acquire for procfs dumping purposes.

This patch adds RCU protection allowing for the procfs readers to
enter RCU read-side critical sections.

Modification of the list continues to be serialized via sk_lock.

V2: Use list_del_rcu() in sctp_association_free() to be safe
    Skip transports marked dead when dumping for procfs

Cc: Vlad Yasevich <vyasevich@gmail.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 5 deletions

diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index 310f11eb2206..4e45bb68aef0 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -163,13 +163,11 @@ void sctp_transport_free(struct sctp_transport *transport)
         sctp_transport_put(transport);
 }
 
-/* Destroy the transport data structure.
- * Assumes there are no more users of this structure.
- */
-static void sctp_transport_destroy(struct sctp_transport *transport)
+static void sctp_transport_destroy_rcu(struct rcu_head *head)
 {
-        SCTP_ASSERT(transport->dead, "Transport is not dead", return);
+        struct sctp_transport *transport;
 
+        transport = container_of(head, struct sctp_transport, rcu);
         if (transport->asoc)
                 sctp_association_put(transport->asoc);
 
@@ -180,6 +178,16 @@ static void sctp_transport_destroy(struct sctp_transport *transport)
         SCTP_DBG_OBJCNT_DEC(transport);
 }
 
+/* Destroy the transport data structure.
+ * Assumes there are no more users of this structure.
+ */
+static void sctp_transport_destroy(struct sctp_transport *transport)
+{
+        SCTP_ASSERT(transport->dead, "Transport is not dead", return);
+
+        call_rcu(&transport->rcu, sctp_transport_destroy_rcu);
+}
+
 /* Start T3_rtx timer if it is not already running and update the heartbeat
  * timer.  This routine is called every time a DATA chunk is sent.
  */