linux-kernel - Re: [2.6.39-rc2, framebuffer] use after free oops

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Message-ID: <BANLkTikF5YL8tJ_f5510yy1Ywm69rOUK2A@mail.gmail.com>
Date:	Fri, 6 May 2011 10:38:58 +0800
From:	Daniel J Blueman <daniel.blueman@...il.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Bruno Prémont <bonbons@...ux-vserver.org>,
	Paul Mundt <lethal@...ux-sh.org>, linux-fbdev@...r.kernel.org,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [2.6.39-rc2, framebuffer] use after free oops

On 20 April 2011 17:56, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> On Wed, 20 Apr 2011 08:05:35 +0200
> Bruno Prémont <bonbons@...ux-vserver.org> wrote:
>
>> On Wed, 20 Apr 2011 13:50:10 Daniel J Blueman <daniel.blueman@...il.com> wrote:
>> > Any ideas on how best to address this issue [0], since it causes
>> > silent corruption, or at best crashes?
>>
>> There is probably no easy short-term fix to this...
>
> The short term fix would be to deliberately leak the buffer. That should
> go into 2.6.39-rc right now with a comment explaining the situation.
> Otherwise who knows what corruption may occur to user data if unlucky.
>
> The other 'cheat' might be to tweak the API so the removal API isn't a
> 'destroy' interface but a 'shut down' and has a matching 'restart' one
> for when the intelfb unloads at which point vga16fb can carry on with the
> original fb_info 8)

It looks like Andy Whitcroft addressed this issue some time ago, but
forgot to send the fix upstream:

http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-natty.git;a=patch;h=c5a742b5f78e161d6a13853a7e3e6e1dfa429e69;hp=26a1443f67eea17d4b78ef75df701782cc8bf35b

Let's hope it can hit -rc7 since it's been in Ubuntu's kernel tree for
considerable time, and fixes a silent corrupter:

http://groups.google.com/group/linux.kernel/browse_thread/thread/fc9083f6f380ed5b/f801112b840785cb?show_docid=f801112b840785cb

Thanks,
  Daniel
-- 
Daniel J Blueman
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