linux-kernel - breaks 2.6.32.21+ (was: [PATCH] percpu: fix a memory leak in pcpu_extend_area

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Date:	Thu, 16 Sep 2010 23:36:03 +0200
From:	Peter Palfrader <peter@...frader.org>
To:	stable@...nel.org
Cc:	Tejun Heo <tj@...nel.org>, Huang Shijie <shijie8@...il.com>,
	akpm@...ux-foundation.org, linux-mm@...ck.org,
	lkml <linux-kernel@...r.kernel.org>, stable@...nel.org
Subject: breaks 2.6.32.21+ (was: [PATCH] percpu: fix a memory leak in
	pcpu_extend_area_map())

Hey,

The patch quoted below seems to have made it into Greg's stable-queue
for 2.6.32.

I tried building a kernel based on 2.6.32.21 plus all the patches
currently in that queue.  The resulting kernel unfortunately didn't
boot for me, neither as a 32 nor as 64 bit x86 kernel.

I have put up a screenshot of a trace at
http://asteria.noreply.org/~weasel/volatile/2010-09-16-SrLl9JHtDTg/trace-64bit.png
since the kernel fortunately also died in kvm - unfortunately only the
last 60 lines are easily available.  If you need more I could try to set
up some serial console thing to catch more.

Bisecting led to this patch and reverting "percpu: fix a memory leak in
pcpu_extend_area_map()" makes the kernel boot for me again.

> From 206c53730b8b1707becca7a868ea8d14ebee24d2 Mon Sep 17 00:00:00 2001
> From: Huang Shijie <shijie8@...il.com>
> Date: Sun, 8 Aug 2010 14:39:07 +0200
> 
> The original code did not free the old map.  This patch fixes it.
> 
> tj: use @old as memcpy source instead of @chunk->map, and indentation
>     and description update
> 
> Signed-off-by: Huang Shijie <shijie8@...il.com>
> Signed-off-by: Tejun Heo <tj@...nel.org>
> ---
> Patch applied to percpu#for-linus w/ some updates.  Thanks a lot for
> catching this.
> 
>  mm/percpu.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/percpu.c b/mm/percpu.c
> index e61dc2c..a1830d8 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -393,7 +393,9 @@ static int pcpu_extend_area_map(struct pcpu_chunk *chunk, int new_alloc)
>  		goto out_unlock;
> 
>  	old_size = chunk->map_alloc * sizeof(chunk->map[0]);
> -	memcpy(new, chunk->map, old_size);
> +	old = chunk->map;
> +
> +	memcpy(new, old, old_size);
> 
>  	chunk->map_alloc = new_alloc;
>  	chunk->map = new;

Cheers,
Peter
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