[3.5.y.z extended stable] Patch "cpuset: fix a race condition in __cpuset_node_allowed_softwall()" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    cpuset: fix a race condition in __cpuset_node_allowed_softwall()

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 3b13a0d049e70543de0f226ff2c715bd9cde721e Mon Sep 17 00:00:00 2001
From: Li Zefan <lizefan at 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 at huawei.com>
Signed-off-by: Tejun Heo <tj at kernel.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 kernel/cpuset.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 2627f0d0..f1dec4b 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2327,9 +2327,9 @@ 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;
 }
--
1.9.0