Re: [stable] breaks 2.6.32.21+ (was: [PATCH] percpu: fix a memory leak in pcpu_extend_area_map())

[Greg KH <greg@kroah.com>]

On Thu, Sep 16, 2010 at 11:36:03PM +0200, Peter Palfrader wrote:
> 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.

Odd, someone just reported the same problem for .35-stable as well.

Tejun, what's going on here?

thanks,

greg k-h

> 
> > From 206c53730b8b1707becca7a868ea8d14ebee24d2 Mon Sep 17 00:00:00 2001
> > From: Huang Shijie <shijie8@gmail.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@gmail.com>
> > Signed-off-by: Tejun Heo <tj@kernel.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
> -- 
>                            |  .''`.  ** Debian GNU/Linux **
>       Peter Palfrader      | : :' :      The  universal
>  http://www.palfrader.org/ | `. `'      Operating System
>                            |   `-    http://www.debian.org/
> 
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