netdev - Re: [Patch net] net: check dead netns for peernet2id

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Date:   Thu, 17 Nov 2016 11:20:44 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     xiyou.wangcong@...il.com
Cc:     netdev@...r.kernel.org, avagin@...il.com, nicolas.dichtel@...nd.com
Subject: Re: [Patch net] net: check dead netns for peernet2id_alloc()

From: Cong Wang <xiyou.wangcong@...il.com>
Date: Wed, 16 Nov 2016 10:27:02 -0800

> Andrei reports we still allocate netns ID from idr after we destroy
> it in cleanup_net().
> 
> cleanup_net():
>   ...
>   idr_destroy(&net->netns_ids);
>   ...
>   list_for_each_entry_reverse(ops, &pernet_list, list)
>     ops_exit_list(ops, &net_exit_list);
>       -> rollback_registered_many()
>         -> rtmsg_ifinfo_build_skb()
>          -> rtnl_fill_ifinfo()
>            -> peernet2id_alloc()
> 
> After that point we should not even access net->netns_ids, we
> should check the death of the current netns as early as we can in
> peernet2id_alloc().
> 
> For net-next we can consider to avoid sending rtmsg totally,
> it is a good optimization for netns teardown path.
> 
> Fixes: 0c7aecd4bde4 ("netns: add rtnl cmd to add and get peer netns ids")
> Reported-by: Andrei Vagin <avagin@...il.com>
> Cc: Nicolas Dichtel <nicolas.dichtel@...nd.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>

Applied and queued up for -stable, thanks.