[PATCH v2] mm/memory_hotplug: prevent accessing by index=-1

[Anastasia Belova]

nid may be equal to NUMA_NO_NODE=-1. Prevent accessing node_data
array by invalid index with check for nid.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: e83a437faa62 ("mm/memory_hotplug: introduce "auto-movable" online policy")
Signed-off-by: Anastasia Belova <abelova@xxxxxxxxxxxxx>
---
 mm/memory_hotplug.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 431b1f6753c0..db78d1b725fc 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -846,7 +846,6 @@ static bool auto_movable_can_online_movable(int nid, struct memory_group *group,
 	unsigned long kernel_early_pages, movable_pages;
 	struct auto_movable_group_stats group_stats = {};
 	struct auto_movable_stats stats = {};
-	pg_data_t *pgdat = NODE_DATA(nid);
 	struct zone *zone;
 	int i;
 
@@ -857,6 +856,8 @@ static bool auto_movable_can_online_movable(int nid, struct memory_group *group,
 			auto_movable_stats_account_zone(&stats, zone);
 	} else {
 		for (i = 0; i < MAX_NR_ZONES; i++) {
+			pg_data_t *pgdat = NODE_DATA(nid);
+
 			zone = pgdat->node_zones + i;
 			if (populated_zone(zone))
 				auto_movable_stats_account_zone(&stats, zone);
-- 
2.30.2