macvlan: fix a race on port dismantle and possible skb leaks

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@google.com>
Fixes: 412ca1550cbec ("macvlan: Move broadcasts into a work queue")
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 29b3bb410781c2530a41ae689b8a91d51e1de3ef..bfb0b6ec8c56e26d67fa94814fe460af34c95fed 100644 (file)
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -272,7 +272,7 @@ 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);
@@ -1082,9 +1082,15 @@ 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);
 }