Re: [PATCH 3/3] net: Don't leak packets when a netns is going down

[David Miller <davem@davemloft.net>]

From: ebiederm@xmission.com (Eric W. Biederman)
Date: Wed, 05 Nov 2008 15:27:34 -0800

> 
> 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 <ebiederm@xmission.com>

Applied.