[PATCH 3.2 152/200] cpuset: fix a race condition in __cpuset_node_allowed_softwall()

From: Ben Hutchings
Date: Sun Mar 30 2014 - 19:48:44 EST


3.2.56-rc1 review patch. If anyone has any objections, please let me know.

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

From: Li Zefan <lizefan@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
kernel/cpuset.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2366,9 +2366,9 @@ int __cpuset_node_allowed_softwall(int n

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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