netdev - Re: [PATCH][NEIGH] Fix race between neigh_parms_release and neightbl_fill

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Date:	Thu, 10 Jan 2008 03:50:32 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	xemul@...nvz.org
Cc:	netdev@...r.kernel.org, devel@...nvz.org
Subject: Re: [PATCH][NEIGH] Fix race between neigh_parms_release and
 neightbl_fill_parms

From: Pavel Emelyanov <xemul@...nvz.org>
Date: Thu, 10 Jan 2008 13:56:53 +0300

> The neightbl_fill_parms() is called under the write-locked
> tbl->lock and accesses the parms->dev. The negh_parm_release()
> calls the dev_put(parms->dev) without this lock. This 
> creates a tiny race window on which the parms contains
> potentially stale dev pointer.
> 
> To fix this race it's enough to move the dev_put() upper
> under the tbl->lock, but note, that the parms are held by
> neighbors and thus can live after the neigh_parms_release()
> is called, so we still can have a parm with bad dev pointer.
> 
> I didn't find where the neigh->parms->dev is accessed, but 
> still think that putting the dev is to be done in a place,
> where the parms are really freed. Am I right with that?
> 
> Signed-off-by: Pavel Emelyanov <xemul@...nvz.org>

It is accessed in lookup_neigh_parms(), neightbl_fill_parms(), and
neightbl_fill_info() (hmmm, that BUG_ON(tbl->parms.dev) is cute).

You fix looks correct, patch applied, thanks!
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