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Date: Fri, 8 Jun 2018 15:41:00 -0400
From: Alexander Aring <aring@mojatatu.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: netdev@vger.kernel.org, linux-wpan@vger.kernel.org,
        linux-bluetooth@vger.kernel.org
Subject: Re: netdevice notifier and device private data
Message-ID: <20180608194100.p5jtgook4bp4dkyw@x220t>
References: <20180608173455.vrnfvv7dlu4oxwqf@x220t>
 <20180608111457.0a9b4cae@xeon-e3>
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Hi Stephen,

On Fri, Jun 08, 2018 at 11:14:57AM -0700, Stephen Hemminger wrote:
...
> 
> notifiers are always called with RTNL mutex held
> and dev->type should not change unless RTNL is held.

thanks for you answer. I am not talking about any race between notifiers
vs dev->type change.

I am talking that dev->type was already changed and a upcoming notifier ends
in undefined behaviour when it derefences dev->priv. I have some notifier
which maps a cast from dev->type to a specific structure at dev->priv. This
structure is not there in tap/tun devices if they changed to "my" dev->type
and the notifier occurs.

- Alex