netdev - Re: [PATCH] pppoe: fix race at init time

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Message-ID: <20090728184834.GD4678@lenovo>
Date:	Tue, 28 Jul 2009 22:48:34 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Igor M Podlesny <for.poige+bugzilla.kernel.org@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	netdev@...r.kernel.org
Subject: Re: [PATCH] pppoe: fix race at init time

[Eric Dumazet - Tue, Jul 28, 2009 at 07:46:37PM +0200]
... 
| So Igor still has a panic... lets try a third patch then :)
| 
| [PATCH] pppoe: fix race at init time
| 
| I believe we have a race in ppoe_init() :
| 
| As soon as dev_add_pack(&pppoes_ptype); and/or dev_add_pack(&pppoed_ptype); 
| are called, we can receive packets while nets not yet fully ready
| (ie : pppoe_init_net() not yet called)
| 
| This means we should be prepared to get a NULL pointer
| from net_generic(net, pppoe_net_id) call.
| 
| We miss this NULL check in get_item() and possibly crash if this nets 
| has no struct pppoe_net attached yet. Other subroutines
| are safe.

Hmm. It seems the problem is not in pppoe_init_net since it's
called *before* dev_add_pack via register_pernet_gen_device
(which is protected by a global net mutex). Or I miss something?

(sorry guys I have quite a limited internet connection this week)

	-- Cyrill
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