linux-kernel - Re: [PATCH v2] mm: fix a possible null pointer dereference in setup_zone

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Message-ID: <00d84e12-4c14-4a6b-a5cd-83d81ac90855@redhat.com>
Date: Thu, 7 Nov 2024 13:53:26 +0100
From: David Hildenbrand <david@...hat.com>
To: Qiu-ji Chen <chenqiuji666@...il.com>, akpm@...ux-foundation.org
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, baijiaju1990@...il.com,
 stable@...r.kernel.org
Subject: Re: [PATCH v2] mm: fix a possible null pointer dereference in
 setup_zone_pageset()

On 07.11.24 13:41, Qiu-ji Chen wrote:
> The function call alloc_percpu() returns a pointer to the memory address,
> but it hasn't been checked. Our static analysis tool indicates that null
> pointer dereference may exist in pointer zone->per_cpu_pageset. It is
> always safe to judge the null pointer before use.
> 
> Signed-off-by: Qiu-ji Chen <chenqiuji666@...il.com>
> Cc: stable@...r.kernel.org
> Fixes: 9420f89db2dd ("mm: move most of core MM initialization to mm/mm_init.c")
> ---
> V2:
> Fixed the incorrect code logic.
> Thanks David Hildenbrand for helpful suggestion.
> ---
>   mm/page_alloc.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 8afab64814dc..7c8a74fd02d6 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5703,8 +5703,14 @@ void __meminit setup_zone_pageset(struct zone *zone)
>   	/* Size may be 0 on !SMP && !NUMA */
>   	if (sizeof(struct per_cpu_zonestat) > 0)
>   		zone->per_cpu_zonestats = alloc_percpu(struct per_cpu_zonestat);
> +	if (!zone->per_cpu_zonestats)
> +		return;
>   
>   	zone->per_cpu_pageset = alloc_percpu(struct per_cpu_pages);
> +	if (!zone->per_cpu_pageset) {
> +		free_percpu(zone->per_cpu_zonestats);
> +		return;
> +	}
>   	for_each_possible_cpu(cpu) {
>   		struct per_cpu_pages *pcp;
>   		struct per_cpu_zonestat *pzstats;

Unmodified patch, likely not what you wanted to send?


-- 
Cheers,

David / dhildenb