Re: [PATCH linux-3.10.y v2 1/3] sit: fix double free of fb_tunnel_dev on exit

Steven Rostedt
2014-01-31T17:19:29Z

Just FYI.

Our full tier tests have completed with no issues due to the sit or
ip6_tunnel modules. These patches appear to have solved our problems.

Nicolas, Thanks again for posting these!

-- Steve

On Fri, 31 Jan 2014 09:24:04 +0100
Nicolas Dichtel <nicolas.dichtel@6wind.com> wrote:

> This problem was fixed upstream by commit 9434266f2c64 ("sit: fix use after free
> of fb_tunnel_dev").
> The upstream patch depends on upstream commit 5e6700b3bf98 ("sit: add support of
> x-netns"), which was not backported into 3.10 branch.
>
> First, explain the problem: when the sit module is unloaded, sit_cleanup() is
> called.
> rmmod sit
> => sit_cleanup()
> => rtnl_link_unregister()
> => __rtnl_kill_links()
> => for_each_netdev(net, dev) {
> if (dev->rtnl_link_ops == ops)
> ops->dellink(dev, &list_kill);
> }
> At this point, the FB device is deleted (and all sit tunnels).
> => unregister_pernet_device()
> => unregister_pernet_operations()
> => ops_exit_list()
> => sit_exit_net()
> => sit_destroy_tunnels()
> In this function, no tunnel is found.
> => unregister_netdevice_queue(sitn->fb_tunnel_dev, &list);
> We delete the FB device a second time here!
>
> Because we cannot simply remove the second deletion (sit_exit_net() must remove
> the FB device when a netns is deleted), we add an rtnl ops which delete all sit
> device excepting the FB device and thus we can keep the explicit deletion in
> sit_exit_net().
>