From: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Date: Thu, 29 Mar 2018 17:03:15 +0300
> the problem is {,un}register_netdevice_notifier() do not take
> pernet_ops_rwsem, and they don't see network namespaces, being
> initialized in setup_net() and cleanup_net(), since at this
> time net is not hashed to net_namespace_list.
>
> This may lead to imbalance, when a notifier is called at time of
> setup_net()/net is alive, but it's not called at time of cleanup_net(),
> for the devices, hashed to the net, and vise versa. See (3/3) for
> the scheme of imbalance.
>
> This patchset fixes the problem by acquiring pernet_ops_rwsem
> at the time of {,un}register_netdevice_notifier() (3/3).
> (1-2/3) are preparations in xfrm and netfilter subsystems.
>
> The problem was introduced a long ago, but backporting won't be easy,
> since every previous kernel version may have changes in netdevice
> notifiers, and they all need review and testing. Otherwise, there
> may be more pernet_operations, which register or unregister
> netdevice notifiers, and that leads to deadlock (which is was fixed
> in 1-2/3). This patchset is for net-next.
I am applying this series and skipping the rwsem revert.
Thanks Kirill.
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