linux-kernel - Re: [patch] x86, mm: Fix size of numa

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Date:	Thu, 24 Feb 2011 15:31:24 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Tejun Heo <tj@...nel.org>, Ingo Molnar <mingo@...e.hu>
cc:	Yinghai Lu <yinghai@...nel.org>, tglx@...utronix.de,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [patch] x86, mm: Fix size of numa_distance array

On Thu, 24 Feb 2011, David Rientjes wrote:

> numa_distance should be sized like the SLIT, an NxN matrix where N is the
> highest node id.  This patch fixes the calulcation to avoid overflowing
> the array on the subsequent iteration.
> 
> Signed-off-by: David Rientjes <rientjes@...gle.com>
> ---
>  arch/x86/mm/numa_64.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
> index cccc01d..abf0131 100644
> --- a/arch/x86/mm/numa_64.c
> +++ b/arch/x86/mm/numa_64.c
> @@ -414,7 +414,7 @@ static int __init numa_alloc_distance(void)
>  
>  	for_each_node_mask(i, nodes_parsed)
>  		cnt = i;
> -	size = ++cnt * sizeof(numa_distance[0]);
> +	size = cnt * cnt * sizeof(numa_distance[0]);
>  
>  	phys = memblock_find_in_range(0, (u64)max_pfn_mapped << PAGE_SHIFT,
>  				      size, PAGE_SIZE);
> 

This also looks like it needs the following to not erroneously consider a 
node id to be out of bounds.  Why were we oversizing cnt in the old code 
above by 1?

diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
--- a/arch/x86/mm/numa_64.c
+++ b/arch/x86/mm/numa_64.c
@@ -454,7 +454,7 @@ void __init numa_set_distance(int from, int to, int distance)
 	if (!numa_distance && numa_alloc_distance() < 0)
 		return;
 
-	if (from >= numa_distance_cnt || to >= numa_distance_cnt) {
+	if (from > numa_distance_cnt || to > numa_distance_cnt) {
 		printk_once(KERN_DEBUG "NUMA: Debug: distance out of bound, from=%d to=%d distance=%d\n",
 			    from, to, distance);
 		return;
@@ -472,7 +472,7 @@ void __init numa_set_distance(int from, int to, int distance)
 
 int __node_distance(int from, int to)
 {
-	if (from >= numa_distance_cnt || to >= numa_distance_cnt)
+	if (from > numa_distance_cnt || to > numa_distance_cnt)
 		return from == to ? LOCAL_DISTANCE : REMOTE_DISTANCE;
 	return numa_distance[from * numa_distance_cnt + to];
 }
--
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