linux-kernel - Re: Ugly rmap NULL ptr deref oopsie on hibernate (was Linux 2.6.34-rc3)

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Message-ID: <1270572866.1711.10.camel@barrios-desktop>
Date:	Wed, 07 Apr 2010 01:54:26 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Borislav Petkov <bp@...en8.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Nick Piggin <npiggin@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>
Subject: Re: Ugly rmap NULL ptr deref oopsie on hibernate (was Linux
 2.6.34-rc3)

On Tue, 2010-04-06 at 09:32 -0700, Linus Torvalds wrote:
> 
> On Wed, 7 Apr 2010, Minchan Kim wrote:
> > > 
> > > I don't think so. That isn't the racy case. We're working with a 
> > > anon_vma_chain, so the anonvma is all there.
> > 
> > But the anon_vma is using for another anon_vma. 
> 
> No, that can only happen if somebody has done "anon_vma_free()" on it. And 
> nobody does that if the anonvma still has a non-empty'&anon_vma->head'.
> 
> So as long as the anon_vma has a anon_vma_chain entry associated with it 
> (or a ksm refcount, but that's a separate issue), it's not going to be 
> re-allocated for any other use, because it's not going to be free'd.
> 	

> 		Linus

That's what I am missing.
Thanks, Linus. 

I will think over the problem. :)

-- 
Kind regards,
Minchan Kim


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