[PATCH] fix: mm: memcontrol: convert objcg to be per-memcg per-node type

[Qi Zheng]

From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>

Reset pn->orig_objcg to NULL to prevent obj_cgroup_put()
from being called agagin in __mem_cgroup_free().

Reported-by: Usama Arif <usama.arif@xxxxxxxxx>
Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
---
 mm/memcontrol.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 992a3f5caa62b..ad32639ea5959 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4140,8 +4140,14 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
 	for_each_node(nid) {
 		struct mem_cgroup_per_node *pn = memcg->nodeinfo[nid];
 
-		if (pn && pn->orig_objcg)
+		if (pn && pn->orig_objcg) {
 			obj_cgroup_put(pn->orig_objcg);
+			/*
+			 * Reset pn->orig_objcg to NULL to prevent obj_cgroup_put()
+			 * from being called agagin in __mem_cgroup_free().
+			 */
+			pn->orig_objcg = NULL;
+		}
 	}
 	free_shrinker_info(memcg);
 offline_kmem:
-- 
2.20.1