workqueue: Fix NULL pointer dereference

libin2015 · htejun · commit cef572ad9bd7 · 2017-10-30T07:56:01.000-07:00
When queue_work() is used in irq (not in task context), there is a potential case that trigger NULL pointer dereference. ---------------------------------------------------------------- worker_thread() |-spin_lock_irq() |-process_one_work() |-worker->current_pwq = pwq |-spin_unlock_irq() |-worker->current_func(work) |-spin_lock_irq() |-worker->current_pwq = NULL |-spin_unlock_irq() //interrupt here |-irq_handler |-__queue_work() //assuming that the wq is draining |-is_chained_work(wq) |-current_wq_worker() //Here, 'current' is the interrupted worker! |-current->current_pwq is NULL here! |-schedule() ---------------------------------------------------------------- Avoid it by checking for task context in current_wq_worker(), and if not in task context, we shouldn't use the 'current' to check the condition. Reported-by: Xiaofei Tan <tanxiaofei@huawei.com> Signed-off-by: Li Bin <huawei.libin@huawei.com> Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com> Signed-off-by: Tejun Heo <tj@kernel.org> Fixes: 8d03ecf ("workqueue: reimplement is_chained_work() using current_wq_worker()") Cc: stable@vger.kernel.org # v3.9+
diff --git a/kernel/workqueue_internal.h b/kernel/workqueue_internal.h
@@ -9,6 +9,7 @@
 
 #include <linux/workqueue.h>
 #include <linux/kthread.h>
+#include <linux/preempt.h>
 
 struct worker_pool;
 
@@ -59,7 +60,7 @@ struct worker {
  */
 static inline struct worker *current_wq_worker(void)
 {
-	if (current->flags & PF_WQ_WORKER)
+	if (in_task() && (current->flags & PF_WQ_WORKER))
 		return kthread_data(current);
 	return NULL;
 }

Original file line number	Diff line number	Diff line change
`@@ -9,6 +9,7 @@`
`9`	`9`
`10`	`10`	`#include <linux/workqueue.h>`
`11`	`11`	`#include <linux/kthread.h>`
	`12`	`+#include <linux/preempt.h>`
`12`	`13`
`13`	`14`	`struct worker_pool;`
`14`	`15`
`@@ -59,7 +60,7 @@ struct worker {`
`59`	`60`	`*/`
`60`	`61`	`static inline struct worker *current_wq_worker(void)`
`61`	`62`	`{`
`62`		`- if (current->flags & PF_WQ_WORKER)`
	`63`	`+ if (in_task() && (current->flags & PF_WQ_WORKER))`
`63`	`64`	`return kthread_data(current);`
`64`	`65`	`return NULL;`
`65`	`66`	`}`