linux-kernel - Re: [PATCH] rmap: fix anon_vma

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Date:	Tue, 6 Apr 2010 00:48:35 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Rik van Riel <riel@...hat.com>,
	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: [PATCH] rmap: fix anon_vma_fork() memory leak

On Tue, Apr 6, 2010 at 12:37 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
>
> On Sun, 4 Apr 2010, Rik van Riel wrote:
>>
>> Fix a memory leak in anon_vma_fork(), where we fail to tear down the
>> anon_vmas attached to the new VMA in case setting up the new anon_vma
>> fails.
>>
>> Reported-by: Minchan Kim <minchan.kim@...il.com>
>> Signed-off-by: Rik van Riel <riel@...hat.com>
>> Reviewed-by: Minchan Kim <minchan.kim@...il.com>
>> ---
>>
>> diff --git a/mm/rmap.c b/mm/rmap.c
>> index fcd593c..fb7ce99 100644
>> --- a/mm/rmap.c
>> +++ b/mm/rmap.c
>> @@ -231,6 +231,7 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
>>
>>   out_error_free_anon_vma:
>>       anon_vma_free(anon_vma);
>> +     unlink_anon_vmas(vma);
>>   out_error:
>>       return -ENOMEM;
>>  }
>
> This looks _very_ wrong to me.
>
> Shouldn't the unlink_anon_vmas() be in the "out_error" case? IOW, we
> should do it even if the "anon_vma_alloc()" failed, nbot just if the
> "anon_vma_chain_alloc()" failed?
>
> No?
>
> What am I missing?

Indeed. You're right.
I should have been reviewed more carefully.



-- 
Kind regards,
Minchan Kim
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