linux-kernel - Re: [PATCH] arm64: numa: check the node id before accessing node_to_cpumask

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Message-ID: <20190830055528.GO28313@dhcp22.suse.cz>
Date:   Fri, 30 Aug 2019 07:55:28 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Yunsheng Lin <linyunsheng@...wei.com>
Cc:     will@...nel.org, akpm@...ux-foundation.org, rppt@...ux.ibm.com,
        anshuman.khandual@....com, adobriyan@...il.com, cai@....pw,
        robin.murphy@....com, tglx@...utronix.de,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linuxarm@...wei.com
Subject: Re: [PATCH] arm64: numa: check the node id before accessing
 node_to_cpumask_map

On Fri 30-08-19 10:26:31, Yunsheng Lin wrote:
> Some buggy bios may not set the device' numa id, and dev_to_node
> will return -1, which may cause global-out-of-bounds error
> detected by KASAN.

Why should we workaround a buggy bios like that? Is it so widespread and
no BIOS update available? Also, why is this arm64 specific?

> This patch changes cpumask_of_node to return cpu_none_mask if the
> node is not valid, and sync the cpumask_of_node between the
> cpumask_of_node function in numa.h and numa.c.

Why?

> Signed-off-by: Yunsheng Lin <linyunsheng@...wei.com>
> ---
>  arch/arm64/include/asm/numa.h | 6 ++++++
>  arch/arm64/mm/numa.c          | 2 +-
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/numa.h b/arch/arm64/include/asm/numa.h
> index 626ad01..da891ed 100644
> --- a/arch/arm64/include/asm/numa.h
> +++ b/arch/arm64/include/asm/numa.h
> @@ -25,6 +25,12 @@ const struct cpumask *cpumask_of_node(int node);
>  /* Returns a pointer to the cpumask of CPUs on Node 'node'. */
>  static inline const struct cpumask *cpumask_of_node(int node)
>  {
> +	if (node >= nr_node_ids || node < 0)
> +		return cpu_none_mask;
> +
> +	if (!node_to_cpumask_map[node])
> +		return cpu_online_mask;
> +
>  	return node_to_cpumask_map[node];
>  }
>  #endif
> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
> index 4f241cc..3846313 100644
> --- a/arch/arm64/mm/numa.c
> +++ b/arch/arm64/mm/numa.c
> @@ -46,7 +46,7 @@ EXPORT_SYMBOL(node_to_cpumask_map);
>   */
>  const struct cpumask *cpumask_of_node(int node)
>  {
> -	if (WARN_ON(node >= nr_node_ids))
> +	if (WARN_ON(node >= nr_node_ids || node < 0))
>  		return cpu_none_mask;
>  
>  	if (WARN_ON(node_to_cpumask_map[node] == NULL))
> -- 
> 2.8.1

-- 
Michal Hocko
SUSE Labs