linux-kernel - Re: [3.3-rc7] sys_poll use after free (hibernate)

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Message-ID: <20120318212443.GA7312@redhat.com>
Date:	Sun, 18 Mar 2012 17:24:44 -0400
From:	Dave Jones <davej@...hat.com>
To:	richard -rw- weinberger <richard.weinberger@...il.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [3.3-rc7] sys_poll use after free (hibernate)

On Sun, Mar 18, 2012 at 08:47:19PM +0100, richard -rw- weinberger wrote:
 > On Tue, Mar 13, 2012 at 1:58 AM, Dave Jones <davej@...hat.com> wrote:
 > > While trying to reproduce the i915 memory corruption problem with hibernate,
 > 
 > If you cannot reproduce the problem you can send me debug/test-patches.
 > I have two machines where I can reproduce the issue within an hour.

At the time I was hoping to bisect it. But it looks like it only happens on
ironlake era graphics and newer, which I don't have.

With that info, I'm not sure it's really bisectable. The bug has probably
been there since day 1 when ironlake support was added.
See the thread 'Subject: Re: inode->i_wb_list corruption.' for some further
thoughts, where it's theorised that the GTT contains stale entries after
when we thaw.  I wouldn't be surprised if no-one had even tried hibernate
(or at least noticed the memory corruption immediately) before that was merged.

My thinking is that some kind of GTT teardown in the ->hibernate routine is
probably what's needed.

	Dave

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