netdev - Re: netdevice notifier and device private data

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Message-ID: <20180608194100.p5jtgook4bp4dkyw@x220t>
Date:   Fri, 8 Jun 2018 15:41:00 -0400
From:   Alexander Aring <aring@...atatu.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org, linux-wpan@...r.kernel.org,
        linux-bluetooth@...r.kernel.org
Subject: Re: netdevice notifier and device private data

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