linux-kernel - Re: [PATCH v2] NUMA x86: add constraints check for nid parameters

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Message-ID: <alpine.DEB.2.00.1112071342450.27360@chino.kir.corp.google.com>
Date:	Wed, 7 Dec 2011 13:46:03 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Petr Holasek <pholasek@...hat.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	Anton Arapov <anton@...hat.com>
Subject: Re: [PATCH v2] NUMA x86: add constraints check for nid parameters

On Wed, 7 Dec 2011, Petr Holasek wrote:

> This patch adds constraints checks for numa_set_distance()
> function. It emits warning when pxms are used uninitialized
> when parsing the SRAT.
> 

The changelog also needs to indicate that, in addition to emitting the 
warning, that this will avoid a store to a negative index in the 
numa_distance[] array, that's the real thing you're trying to catch.  This 
would happen if pxm_to_node() is returning NUMA_NO_NODE which is what the 
pxm-to-node mapping is initialized to.

> Signed-off-by: Petr Holasek <pholasek@...hat.com>
> ---
>  arch/x86/mm/numa.c |    8 +++++---
>  1 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> index fbeaaf4..42c12b6 100644
> --- a/arch/x86/mm/numa.c
> +++ b/arch/x86/mm/numa.c
> @@ -430,8 +430,9 @@ static int __init numa_alloc_distance(void)
>   * calls are ignored until the distance table is reset with
>   * numa_reset_distance().
>   *
> - * If @from or @to is higher than the highest known node at the time of
> - * table creation or @distance doesn't make sense, the call is ignored.
> + * If @from or @to is higher than the highest known node or lower than zero
> + * at the time of table creation or @distance doesn't make sense, the call
> + * is ignored.
>   * This is to allow simplification of specific NUMA config implementations.
>   */
>  void __init numa_set_distance(int from, int to, int distance)
> @@ -439,7 +440,8 @@ 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 ||
> +			from < 0 || to < 0) {
>  		printk_once(KERN_DEBUG "NUMA: Debug: distance out of bound, from=%d to=%d distance=%d\n",
>  			    from, to, distance);

That warning doesn't look appropriate for negative node ids, it should be 
modified to say the node ids or distance are out of bounds.  One more 
revision?

>  		return;
--
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