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

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Message-Id: <20130711214832.785223221@linuxfoundation.org>
Date:	Thu, 11 Jul 2013 15:01:36 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Michal Hocko <mhocko@...e.cz>,
	Li Zefan <lizefan@...wei.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>, Tejun Heo <tj@...nel.org>,
	Glauber Costa <glommer@...nvz.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [ 19/19] Revert "memcg: avoid dangling reference count in creation failure"

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

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

From: Michal Hocko <mhocko@...e.cz>

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@...e.cz>
Signed-off-by: Li Zefan <lizefan@...wei.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Tejun Heo <tj@...nel.org>
Cc: Glauber Costa <glommer@...nvz.org>
Cc: Johannes Weiner <hannes@...xchg.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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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