From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH 1/2] tuntap: forbid calling TUNSETIFF when detached
Date: Fri, 11 Jan 2013 06:55:47 -0800
Message-ID: <1357916147.27446.3653.camel@edumazet-glaptop>
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Cc: davem@davemloft.net, mst@redhat.com, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, Stefan Hajnoczi <stefanha@redhat.com>
To: Jason Wang <jasowang@redhat.com>
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On Fri, 2013-01-11 at 16:50 +0800, Jason Wang wrote:

>  
> +	if (rcu_dereference_protected(tfile->detached, lockdep_rtnl_is_held()))
> +		return -EINVAL;
> +

Thats an open coded rtnl_dereference()

(please cleanup the whole tun.c file)