linux-kernel - Re: [PATCH] numa, mem-hotplug: Fix stack overflow in numa when seting kernel nodes to unhotpluggable.

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Message-ID: <alpine.DEB.2.02.1401271631090.17114@chino.kir.corp.google.com>
Date:	Mon, 27 Jan 2014 16:32:56 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Tang Chen <tangchen@...fujitsu.com>
cc:	davej@...hat.com, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, akpm@...ux-foundation.org,
	zhangyanfei@...fujitsu.com, guz.fnst@...fujitsu.com,
	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] numa, mem-hotplug: Fix stack overflow in numa when seting
 kernel nodes to unhotpluggable.

On Wed, 22 Jan 2014, David Rientjes wrote:

> >  arch/x86/mm/numa.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> > index 81b2750..ebefeb7 100644
> > --- a/arch/x86/mm/numa.c
> > +++ b/arch/x86/mm/numa.c
> > @@ -562,10 +562,10 @@ static void __init numa_init_array(void)
> >  	}
> >  }
> >  
> > +static nodemask_t numa_kernel_nodes __initdata;
> >  static void __init numa_clear_kernel_node_hotplug(void)
> >  {
> >  	int i, nid;
> > -	nodemask_t numa_kernel_nodes;
> >  	unsigned long start, end;
> >  	struct memblock_type *type = &memblock.reserved;
> >  
> 
> Isn't this also a bugfix since you never initialize numa_kernel_nodes when 
> it's allocated on the stack with NODE_MASK_NONE?
> 

This hasn't been answered and the patch still isn't in linux-kernel yet 
Dave tested it as good.  I'm suspicious of the changelog that indicates 
this nodemask is the result of a stack overflow itself which only manages 
to reproduce itself in the init patch slightly more than 50% of the time.  
How is that possible?

I think the changelog should indicate this also fixes an uninitialized 
nodemask issue.
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