netdev - Re: [PATCH net-next 0/3] Close race between {un, }register_netdevice_notifier and pernet

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Message-ID: <8c9717e3-3388-9f88-7de6-ce7b201aff77@virtuozzo.com>
Date:   Fri, 30 Mar 2018 18:01:24 +0300
From:   Kirill Tkhai <ktkhai@...tuozzo.com>
To:     David Miller <davem@...emloft.net>
Cc:     steffen.klassert@...unet.com, herbert@...dor.apana.org.au,
        pablo@...filter.org, kadlec@...ckhole.kfki.hu, fw@...len.de,
        daniel@...earbox.net, jakub.kicinski@...ronome.com, ast@...nel.org,
        brouer@...hat.com, linux@...musvillemoes.dk,
        john.fastabend@...il.com, dsahern@...il.com,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org
Subject: Re: [PATCH net-next 0/3] Close race between {un,
 }register_netdevice_notifier and pernet_operations

On 30.03.2018 18:00, David Miller wrote:
> From: Kirill Tkhai <ktkhai@...tuozzo.com>
> 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.

Thanks, David.

I'll send the fixing patch soon today.

Kirill