From 0a36b345ab99d6b3c96999e7e3b79bd243cf9bf7 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Wed, 5 Nov 2008 16:00:24 -0800 Subject: [PATCH] net: Don't leak packets when a netns is going down I have been tracking for a while a case where when the network namespace exits the cleanup gets stck in an endless precessess of: unregister_netdevice: waiting for lo to become free. Usage count = 3 unregister_netdevice: waiting for lo to become free. Usage count = 3 unregister_netdevice: waiting for lo to become free. Usage count = 3 unregister_netdevice: waiting for lo to become free. Usage count = 3 unregister_netdevice: waiting for lo to become free. Usage count = 3 unregister_netdevice: waiting for lo to become free. Usage count = 3 unregister_netdevice: waiting for lo to become free. Usage count = 3 It turns out that if you listen on a multicast address an unsubscribe packet is sent when the network device goes down. If you shutdown the network namespace without carefully cleaning up this can trigger the unsubscribe packet to be sent over the loopback interface while the network namespace is going down. All of which is fine except when we drop the packet and forget to free it leaking the skb and the dst entry attached to. As it turns out the dst entry hold a reference to the idev which holds the dev and keeps everything from being cleaned up. Yuck! By fixing my earlier thinko and add the needed kfree_skb and everything cleans up beautifully. Signed-off-by: Eric W. Biederman Signed-off-by: David S. Miller --- net/core/dev.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/core/dev.c b/net/core/dev.c index 811507c..a0c60607 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2253,8 +2253,10 @@ int netif_receive_skb(struct sk_buff *skb) rcu_read_lock(); /* Don't receive packets in an exiting network namespace */ - if (!net_alive(dev_net(skb->dev))) + if (!net_alive(dev_net(skb->dev))) { + kfree_skb(skb); goto out; + } #ifdef CONFIG_NET_CLS_ACT if (skb->tc_verd & TC_NCLS) { -- 1.8.1