netdev - Re: [PATCH] Fix caif BUG() with network namespaces

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Message-Id: <20111025.192259.258695838207862829.davem@davemloft.net>
Date:	Tue, 25 Oct 2011 19:22:59 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	dwmw2@...radead.org
Cc:	sjurbren@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH] Fix caif BUG() with network namespaces

From: David Woodhouse <dwmw2@...radead.org>
Date: Tue, 25 Oct 2011 09:25:21 +0200

> The caif code will register its own pernet_operations, and then register
> a netdevice_notifier. Each time the netdevice_notifier is triggered,
> it'll do some stuff... including a lookup of its own pernet stuff with
> net_generic().
> 
> If the net_generic() call ever returns NULL, the caif code will BUG().
> That doesn't seem *so* unreasonable, I suppose — it does seem like it
> should never happen.
> 
> However, it *does* happen. When we clone a network namespace,
> setup_net() runs through all the pernet_operations one at a time. It
> gets to loopback before it gets to caif. And loopback_net_init()
> registers a netdevice... while caif hasn't been initialised. So the caif
> netdevice notifier triggers, and immediately goes BUG().
> 
> We could imagine a complex and overengineered solution to this generic
> class of problems, but this patch takes the simple approach. It just
> makes caif_device_notify() *not* go looking for its pernet data
> structures if the device it's being notified about isn't a caif device
> in the first place.
> 
> Cc: stable@...nel.org
> Signed-off-by: David Woodhouse <David.Woodhouse@...el.com>
> Acked-by: Sjur Brændeland <sjur.brandeland@...ricsson.com>

Applied, thanks.