netdev - Re: [PATCH net v2] ppp: fix device unregistration upon netns deletion

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Date:	Mon, 17 Aug 2015 12:22:45 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	g.nault@...halink.fr
Cc:	netdev@...r.kernel.org, paulus@...ba.org
Subject: Re: [PATCH net v2] ppp: fix device unregistration upon netns
 deletion

From: Guillaume Nault <g.nault@...halink.fr>
Date: Fri, 14 Aug 2015 10:42:56 +0200

> PPP devices may get automatically unregistered when their network
> namespace is getting removed. This happens if the ppp control plane
> daemon (e.g. pppd) exits while it is the last user of this namespace.
> 
> This leads to several races:
> 
>   * ppp_exit_net() may destroy the per namespace idr (pn->units_idr)
>     before all file descriptors were released. Successive ppp_release()
>     calls may then cleanup PPP devices with ppp_shutdown_interface() and
>     try to use the already destroyed idr.
> 
>   * Automatic device unregistration may also happen before the
>     ppp_release() call for that device gets executed. Once called on
>     the file owning the device, ppp_release() will then clean it up and
>     try to unregister it a second time.
> 
> To fix these issues, operations defined in ppp_shutdown_interface() are
> moved to the PPP device's ndo_uninit() callback. This allows PPP
> devices to be properly cleaned up by unregister_netdev() and friends.
> So checking for ppp->owner is now an accurate test to decide if a PPP
> device should be unregistered.
> 
> Setting ppp->owner is done in ppp_create_interface(), before device
> registration, in order to avoid unprotected modification of this field.
> 
> Finally, ppp_exit_net() now starts by unregistering all remaining PPP
> devices to ensure that none will get unregistered after the call to
> idr_destroy().
> 
> Signed-off-by: Guillaume Nault <g.nault@...halink.fr>
> ---
> v2: remove unnecessary curly braces in idr_for_each_entry()

Applied, thank you.
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