netdev - Re: [PATCH] net: Fix NETDEV_CHANGE notifier usage causing spurious arp flush

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Date:	Mon, 07 Jul 2014 21:20:34 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	loicp@...gle.com
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	timo.teras@....fi, jiri@...nulli.us
Subject: Re: [PATCH] net: Fix NETDEV_CHANGE notifier usage causing spurious
 arp flush

From: Loic Prylli <loicp@...gle.com>
Date: Tue,  1 Jul 2014 21:39:43 -0700

> A bug was introduced in NETDEV_CHANGE notifier sequence causing the
> arp table to be sometimes spuriously cleared (including manual arp
> entries marked permanent), upon network link carrier changes.
> 
> The changed argument for the notifier was applied only to a single
> caller of NETDEV_CHANGE, missing among others netdev_state_change().
> So upon net_carrier events induced by the network, which are
> triggering a call to netdev_state_change(), arp_netdev_event() would
> decide whether to clear or not arp cache based on random/junk stack
> values (a kind of read buffer overflow).
> 
> Fixes: be9efd365328 ("net: pass changed flags along with NETDEV_CHANGE event")
> Fixes: 6c8b4e3ff81b ("arp: flush arp cache on IFF_NOARP change")
> Signed-off-by: Loic Prylli <loicp@...gle.com>

Applied, thanks.

We should probably make plain call_netdevice_notifiers() BUG if it is
invoked for NETDEV_CHANGE.
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