From 2df47c918bffd71e263058b49302bc7970bf0684 Mon Sep 17 00:00:00 2001
From: Joe Tsai <joetsai@digital-static.net>
Date: Mon, 9 Sep 2019 16:52:28 -0700
Subject: [PATCH] internal/impl: fix race ExtensionInfo.lazyInitSlow

The xi.init flag should not be set until after we have truly
initialized everything.

Change-Id: I43dcb300917145ce19a7199fa871acd0df325c6c
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/194439
Reviewed-by: Damien Neil <dneil@google.com>
---
 internal/impl/extension.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/internal/impl/extension.go b/internal/impl/extension.go
index c64f8f5e..40074fc4 100644
--- a/internal/impl/extension.go
+++ b/internal/impl/extension.go
@@ -145,7 +145,7 @@ func (xi *ExtensionInfo) lazyInitSlow() {
 	if xi.init == extensionInfoFullInit {
 		return
 	}
-	atomic.StoreUint32(&xi.init, extensionInfoFullInit)
+	defer atomic.StoreUint32(&xi.init, extensionInfoFullInit)
 
 	if xi.desc == nil {
 		xi.initFromLegacy()