4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Li Bin <huawei.libin@xxxxxxxxxx>
commit cef572ad9bd7f85035ba8272e5352040e8be0152 upstream.
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@xxxxxxxxxx>
Signed-off-by: Li Bin <huawei.libin@xxxxxxxxxx>
Reviewed-by: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Fixes: 8d03ecfe4718 ("workqueue: reimplement is_chained_work() using current_wq_worker()")
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/workqueue_internal.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- 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;
}