[PATCH] workqueue: Fix NULL current_pwq deref in mem-reclaim helper

[PATCH] workqueue: Fix NULL current_pwq deref in mem-reclaim helper

[Pavankumar Kondeti]

current_is_workqueue_mem_reclaim() uses current_wq_worker() to decide
whether %current is a workqueue worker and then checks the current
workqueue flags. However, current_wq_worker() only implies that %current
is a kworker; it does not imply that the worker is currently executing a
work item.

worker->current_pwq is set while process_one_work() runs the work
function and cleared afterwards. A kworker outside work-item execution can
therefore have PF_WQ_WORKER set with current_pwq cleared.

Guard the flag check with worker->current_pwq. Without a current_pwq, the
worker is not executing on a WQ_MEM_RECLAIM workqueue, so the helper
should return false.

Fixes: da729ddd4a1b ("NFS/localio: issue IO inline when not in a memory-reclaim context")
Signed-off-by: Pavankumar Kondeti <pavan.kondeti@oss.qualcomm.com>
---
 kernel/workqueue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 959525393739..3d0497639e79 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -6320,7 +6320,7 @@ bool current_is_workqueue_mem_reclaim(void)
 {
 	struct worker *worker = current_wq_worker();
 
-	return worker &&
+	return worker && worker->current_pwq &&
 		((worker->current_pwq->wq->flags &
 		  (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM);
 }

---
base-commit: 72d3fcf802c45d00b300f25b848a93c3a2bd7c7e
change-id: 20260928-wq_mem_reclaim_fix-39b357dfa4f0

Best regards,
-- 
Pavankumar Kondeti <pavan.kondeti@oss.qualcomm.com>

Re: [PATCH] workqueue: Fix NULL current_pwq deref in mem-reclaim helper

[Tejun Heo]

current_is_workqueue_mem_reclaim() came in through the NFS tree with
da729ddd4a1b ("NFS/localio: issue IO inline when not in a memory-reclaim
context"). Can you please take this fix through the NFS tree too?

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

--
tejun