From 44ba741a0f470c22c691586dea1e219df757fef2 Mon Sep 17 00:00:00 2001
From: Li Zefan <lizefan@huawei.com>
Date: Thu, 27 Feb 2014 18:19:36 +0800
Subject: cpuset: fix a race condition in __cpuset_node_allowed_softwall()

commit 99afb0fd5f05aac467ffa85c36778fec4396209b upstream.

It's not safe to access task's cpuset after releasing task_lock().
Holding callback_mutex won't help.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index bd1dfa2..5ae9f95 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2507,9 +2507,9 @@ int __cpuset_node_allowed_softwall(int node, gfp_t gfp_mask)
 
 	task_lock(current);
 	cs = nearest_hardwall_ancestor(task_cs(current));
+	allowed = node_isset(node, cs->mems_allowed);
 	task_unlock(current);
 
-	allowed = node_isset(node, cs->mems_allowed);
 	mutex_unlock(&callback_mutex);
 	return allowed;
 }
-- 
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