[PATCH 2/6] workqueue: Protect wq_unbound_cpumask with wq_pool_attach_mutex in init_rescuer()

[Lai Jiangshan]

From: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>

wq_unbound_cpumask can be possibly changed without wq_pool_attach_mutex
or wq_pool_mutex held in init_rescuer().

Use wq_pool_attach_mutex to protect it.

Fixes: 49584bb8ddbe("workqueue: Bind unbound workqueue rescuer to wq_unbound_cpumask")
Signed-off-by: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
---
 kernel/workqueue.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index c738b3024cc2..cf1a129eb547 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5533,6 +5533,9 @@ static int init_rescuer(struct workqueue_struct *wq)
 		return ret;
 	}
 
+	/* lock wq_pool_attach_mutex for wq_unbound_cpumask */
+	mutex_lock(&wq_pool_attach_mutex);
+
 	wq->rescuer = rescuer;
 	if (wq->flags & WQ_UNBOUND)
 		kthread_bind_mask(rescuer->task, wq_unbound_cpumask);
@@ -5540,6 +5543,8 @@ static int init_rescuer(struct workqueue_struct *wq)
 		kthread_bind_mask(rescuer->task, cpu_possible_mask);
 	wake_up_process(rescuer->task);
 
+	mutex_unlock(&wq_pool_attach_mutex);
+
 	return 0;
 }
 
-- 
2.19.1.6.gb485710b