diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index a9c11aa..72cec9e 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -584,6 +584,8 @@
 		}
 	} else {
 		/* signal bit not set -> a real page is missing. */
+		if (WARN_ON_ONCE(tsk != current))
+			goto out;
 		if (tsk->thread.pfault_wait == 1) {
 			/* Already on the list with a reference: put to sleep */
 			__set_task_state(tsk, TASK_UNINTERRUPTIBLE);
@@ -606,6 +608,7 @@
 			set_tsk_need_resched(tsk);
 		}
 	}
+out:
 	spin_unlock(&pfault_lock);
 	put_task_struct(tsk);
 }