Revert "memcg: avoid dangling reference count in creation failure"

commit fa460c2d37870e0a6f94c70e8b76d05ca11b6db0 upstream.

This reverts commit e4715f01be697a.

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.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 0 insertions, 2 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 194721839cf5..fd79df5d3152 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6303,8 +6303,6 @@ 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;
 }