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.

Link: https://lkml.kernel.org/r/20220916072257.9639-7-linmiaohe@huawei.com
Fixes: 28f836b6777b ("mm/page_alloc: split per cpu page lists and zone stats")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 21261f55dab1ed833278e8477f1aa65487d71be5..43114e172592d9754f41e02b704f609481ad7518 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -9513,9 +9513,11 @@ 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;
+               }
        }
 }