[PATCH v4 1/9] Revert "memcg: avoid dangling reference count in creationfailure."

[Li Zefan]

From: Michal Hocko <mhocko@xxxxxxx>

This reverts commit e4715f01be697a3730c78f8ffffb595591d6a88c

mem_cgroup_put is hierarchy aware so mem_cgroup_put(memcg) already drops
an additional reference from all parents so the additional
mem_cgrroup_put(parent) potentially causes use-after-free.

Cc: <stable@xxxxxxxxxxxxxxx> # 3.9+
Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
 mm/memcontrol.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2e851f4..0bacc0d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6332,8 +6332,6 @@ mem_cgroup_css_online(struct cgroup *cont)
 		 * call __mem_cgroup_free, so return directly
 		 */
 		mem_cgroup_put(memcg);
-		if (parent->use_hierarchy)
-			mem_cgroup_put(parent);
 	}
 	return error;
 }
-- 
1.8.0.2
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