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[3.8,31/86] cpuset: fix a race condition in __cpuset_node_allowed_softwall()

Message ID 1396368519-12728-32-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa April 1, 2014, 4:07 p.m. UTC 
3.8.13.21 -stable review patch.  If anyone has any objections, please let me know.

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

From: Li Zefan <lizefan@huawei.com>

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: Kamal Mostafa <kamal@canonical.com>
---
 kernel/cpuset.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index aa4ec01..47e7595 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2370,9 +2370,9 @@  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;
 }