[ 19/19] Revert "memcg: avoid dangling reference count in creation failure"

From: Greg Kroah-Hartman
Date: Thu Jul 11 2013 - 18:03:40 EST


3.10-stable review patch. If anyone has any objections, please let me know.

------------------

From: Michal Hocko <mhocko@xxxxxxx>

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@xxxxxxx>
Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Glauber Costa <glommer@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
mm/memcontrol.c | 2 --
1 file changed, 2 deletions(-)

--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6303,8 +6303,6 @@ mem_cgroup_css_online(struct cgroup *con
* call __mem_cgroup_free, so return directly
*/
mem_cgroup_put(memcg);
- if (parent->use_hierarchy)
- mem_cgroup_put(parent);
}
return error;
}


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