From: Li Zefan <lizefan@huawei.com>
Date: Thu, 27 Feb 2014 10:19:36 +0000 (+0800)
Subject: cpuset: fix a race condition in __cpuset_node_allowed_softwall()
X-Git-Tag: firefly_0821_release~176^2~4274^2~1
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=99afb0fd5f05aac467ffa85c36778fec4396209b;p=firefly-linux-kernel-4.4.55.git

cpuset: fix a race condition in __cpuset_node_allowed_softwall()

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

Cc: <stable@vger.kernel.org>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
---

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index dba9e4aef69a..e6b1b66afe52 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2482,9 +2482,9 @@ 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;
 }