linux-kernel - Re: [PATCH linux-3.10.y v2 1/3] sit: fix double free of fb_tunnel

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Date:	Fri, 31 Jan 2014 12:19:29 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	stable@...r.kernel.org, williams@...hat.com, lclaudio@...g.org,
	jkacur@...hat.com, willemb@...gle.com
Subject: Re: [PATCH linux-3.10.y v2 1/3] sit: fix double free of
 fb_tunnel_dev on exit

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@...nd.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().
> 
--
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