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

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Date:	Sun, 04 Apr 2010 13:24:16 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Minchan Kim <minchan.kim@...il.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Nick Piggin <npiggin@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	sgunderson@...foot.com
Subject: Re: Ugly rmap NULL ptr deref oopsie on hibernate (was Linux 2.6.34-rc3)

On 04/04/2010 12:12 PM, Minchan Kim wrote:

> While I review the code again due to this BUG, I found some strange
> thing.
>
> In anon_vma_fork, if anon_vma_clone is successful but anon_vma_alloc is
> failed, what happens? Parent VMA's anon_vmas have anon_vma_chain which
> has vma which is destroyed.
> I couldn't find any clean routine to remove this garbage.
> I am missing something?

Good catch.  The parent VMA's anon_vmas will get delinked
eventually, but we need to get rid of the newly allocated
child anon_vmas.  You found a hopefully rare memory leak...

We need a call to unlink_anon_vmas(vma) at the error label
to do that.

> But I think it isn't related to this bug because oops point is not
> vma_address but anon_vma_chain.next.

Agreed, it's probably not it.
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