diff --git a/kernel/events/core.c b/kernel/events/core.c
index 18d7966..f491cc0 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11146,6 +11146,9 @@
 		 * Do not allow to attach to a group in a different task
 		 * or CPU context. If we're moving SW events, we'll fix
 		 * this up later, so allow that.
+		 *
+		 * Racy, not holding group_leader->ctx->mutex, see comment with
+		 * perf_event_ctx_lock().
 		 */
 		if (!move_group && group_leader->ctx != ctx)
 			goto err_context;
@@ -11213,6 +11216,7 @@
 			} else {
 				perf_event_ctx_unlock(group_leader, gctx);
 				move_group = 0;
+				goto not_move_group;
 			}
 		}
 
@@ -11229,7 +11233,17 @@
 		}
 	} else {
 		mutex_lock(&ctx->mutex);
+
+		/*
+		 * Now that we hold ctx->lock, (re)validate group_leader->ctx == ctx,
+		 * see the group_leader && !move_group test earlier.
+		 */
+		if (group_leader && group_leader->ctx != ctx) {
+			err = -EINVAL;
+			goto err_locked;
+		}
 	}
+not_move_group:
 
 	if (ctx->task == TASK_TOMBSTONE) {
 		err = -ESRCH;