2022-09-09 09:47:27

by Miaohe Lin

Subject: [PATCH 06/16] mm/page_alloc: fix freeing static percpu memory

The size of struct per_cpu_zonestat can be 0 on !SMP && !NUMA. In that
case, zone->per_cpu_zonestats will always equal to boot_zonestats. But
in zone_pcp_reset(), zone->per_cpu_zonestats is freed via free_percpu()
directly without checking against boot_zonestats first. boot_zonestats
will be released by free_percpu() unexpectedly.

Fixes: 28f836b6777b ("mm/page_alloc: split per cpu page lists and zone stats")
Signed-off-by: Miaohe Lin <[email protected]>
---
mm/page_alloc.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3497919f4ef5..a35ef385d906 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -9510,9 +9510,11 @@ void zone_pcp_reset(struct zone *zone)
drain_zonestat(zone, pzstats);
}
free_percpu(zone->per_cpu_pageset);
- free_percpu(zone->per_cpu_zonestats);
zone->per_cpu_pageset = &boot_pageset;
- zone->per_cpu_zonestats = &boot_zonestats;
+ if (zone->per_cpu_zonestats != &boot_zonestats) {
+ free_percpu(zone->per_cpu_zonestats);
+ zone->per_cpu_zonestats = &boot_zonestats;
+ }
}
}

--
2.23.0

2022-09-09 12:02:37

by David Hildenbrand

Subject: Re: [PATCH 06/16] mm/page_alloc: fix freeing static percpu memory

On 09.09.22 11:24, Miaohe Lin wrote:
> The size of struct per_cpu_zonestat can be 0 on !SMP && !NUMA. In that
> case, zone->per_cpu_zonestats will always equal to boot_zonestats. But
> in zone_pcp_reset(), zone->per_cpu_zonestats is freed via free_percpu()
> directly without checking against boot_zonestats first. boot_zonestats
> will be released by free_percpu() unexpectedly.
>
> Fixes: 28f836b6777b ("mm/page_alloc: split per cpu page lists and zone stats")
> Signed-off-by: Miaohe Lin <[email protected]>
> ---
> mm/page_alloc.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 3497919f4ef5..a35ef385d906 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -9510,9 +9510,11 @@ void zone_pcp_reset(struct zone *zone)
> drain_zonestat(zone, pzstats);
> }
> free_percpu(zone->per_cpu_pageset);
> - free_percpu(zone->per_cpu_zonestats);
> zone->per_cpu_pageset = &boot_pageset;
> - zone->per_cpu_zonestats = &boot_zonestats;
> + if (zone->per_cpu_zonestats != &boot_zonestats) {
> + free_percpu(zone->per_cpu_zonestats);
> + zone->per_cpu_zonestats = &boot_zonestats;
> + }
> }
> }
>

Reviewed-by: David Hildenbrand <[email protected]>

--
Thanks,

David / dhildenb

2022-09-15 05:11:26

by Oscar Salvador

Subject: Re: [PATCH 06/16] mm/page_alloc: fix freeing static percpu memory

On Fri, Sep 09, 2022 at 05:24:41PM +0800, Miaohe Lin wrote:
> The size of struct per_cpu_zonestat can be 0 on !SMP && !NUMA. In that
> case, zone->per_cpu_zonestats will always equal to boot_zonestats. But
> in zone_pcp_reset(), zone->per_cpu_zonestats is freed via free_percpu()
> directly without checking against boot_zonestats first. boot_zonestats
> will be released by free_percpu() unexpectedly.
>
> Fixes: 28f836b6777b ("mm/page_alloc: split per cpu page lists and zone stats")
> Signed-off-by: Miaohe Lin <[email protected]>

Reviewed-by: Oscar Salvador <[email protected]>


--
Oscar Salvador
SUSE Labs