[PATCH] workqueue: Fix NULL current_pwq deref in current_is_workqueue_mem_reclaim()

[Bui Viet Dung]

current_wq_worker() indicates that %current is a kworker thread, but it
does not guarantee that the worker is currently executing a work item, as
worker->current_pwq is populated only while process_one_work() is actively
running the work function. Outside of that window (e.g. during worker idle,
initialization, or auxiliary execution paths), worker->current_pwq is NULL.

In current_is_workqueue_mem_reclaim(), worker->current_pwq->wq is
dereferenced without checking worker->current_pwq:

	return worker &&
		((worker->current_pwq->wq->flags &
		  (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM);

If current_is_workqueue_mem_reclaim() is called when worker->current_pwq
is NULL, the kernel triggers a NULL pointer dereference.

This mirrors the issue recently fixed in is_chained_work() by commit
980db94e3eee ("workqueue: Fix NULL current_pwq deref in chained work check").

Guard the check with worker->current_pwq before dereferencing ->wq.

Fixes: da729ddd4a1b ("NFS/localio: issue IO inline when not in a memory-reclaim context")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Bui Viet Dung <dungvn2345@xxxxxxxxx>
---
 kernel/workqueue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index c56c042d1c3..c1cb328bce3 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);
 }
-- 
2.43.0