From: Li Zefan <lizf@cn.fujitsu.com>
Date: Wed, 18 Feb 2009 22:48:20 +0000 (-0800)
Subject: cgroups: fix possible use after free
X-Git-Tag: firefly_0821_release~15516
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=67e055d144c5b2acdc1c63811fde031263bf92c5;p=firefly-linux-kernel-4.4.55.git

cgroups: fix possible use after free

In cgroup_kill_sb(), root is freed before sb is detached from the list, so
another sget() may find this sb and call cgroup_test_super(), which will
access the root that has been freed.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index e14db9c089b9..9edb5c4b79b4 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1122,8 +1122,8 @@ static void cgroup_kill_sb(struct super_block *sb) {
 
 	mutex_unlock(&cgroup_mutex);
 
-	kfree(root);
 	kill_litter_super(sb);
+	kfree(root);
 }
 
 static struct file_system_type cgroup_fs_type = {