[PATCH 3.16.y-ckt 079/170] macvlan: fix a race on port dismantle and possible skb leaks

[Luis Henriques]

3.16.7-ckt1 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet at google.com>

commit fe0ca7328d03d36aafecebb3af650e1bb2841c20 upstream.

We need to cancel the work queue after rcu grace period,
otherwise it can be rescheduled by incoming packets.

We need to purge queue if some skbs are still in it.

We can use __skb_queue_head_init() variant in
macvlan_process_broadcast()

Signed-off-by: Eric Dumazet <edumazet at google.com>
Fixes: 412ca1550cbec ("macvlan: Move broadcasts into a work queue")
Cc: Herbert Xu <herbert at gondor.apana.org.au>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/net/macvlan.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index f3008e3cf118..d4404e4cad41 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -201,7 +201,7 @@ static void macvlan_process_broadcast(struct work_struct *w)
 	struct sk_buff *skb;
 	struct sk_buff_head list;
 
-	skb_queue_head_init(&list);
+	__skb_queue_head_init(&list);
 
 	spin_lock_bh(&port->bc_queue.lock);
 	skb_queue_splice_tail_init(&port->bc_queue, &list);
@@ -935,9 +935,15 @@ static void macvlan_port_destroy(struct net_device *dev)
 {
 	struct macvlan_port *port = macvlan_port_get_rtnl(dev);
 
-	cancel_work_sync(&port->bc_work);
 	dev->priv_flags &= ~IFF_MACVLAN_PORT;
 	netdev_rx_handler_unregister(dev);
+
+	/* After this point, no packet can schedule bc_work anymore,
+	 * but we need to cancel it and purge left skbs if any.
+	 */
+	cancel_work_sync(&port->bc_work);
+	__skb_queue_purge(&port->bc_queue);
+
 	kfree_rcu(port, rcu);
 }
 
-- 
2.1.0