From 73d3bd9cd5e425c7422084172e63ed2eaa87d8ec Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Sun, 1 Sep 2019 21:32:28 -0600
Subject: [PATCH] wintun: take mutex first always

This prevents an ABA deadlock with setupapi's internal locks.
---
 tun/wintun/wintun_windows.go | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/tun/wintun/wintun_windows.go b/tun/wintun/wintun_windows.go
index c654b02..e2348c0 100644
--- a/tun/wintun/wintun_windows.go
+++ b/tun/wintun/wintun_windows.go
@@ -196,6 +196,15 @@ func (pool Pool) GetInterface(ifname string) (*Interface, error) {
 // interesting complications with its usage. This function returns the network
 // interface ID and a flag if reboot is required.
 func (pool Pool) CreateInterface(ifname string, requestedGUID *windows.GUID) (wintun *Interface, rebootRequired bool, err error) {
+	mutex, err := pool.takeNameMutex()
+	if err != nil {
+		return
+	}
+	defer func() {
+		windows.ReleaseMutex(mutex)
+		windows.CloseHandle(mutex)
+	}()
+
 	// Create an empty device info set for network adapter device class.
 	devInfoList, err := setupapi.SetupDiCreateDeviceInfoListEx(&deviceClassNetGUID, 0, "")
 	if err != nil {
@@ -281,15 +290,6 @@ func (pool Pool) CreateInterface(ifname string, requestedGUID *windows.GUID) (wi
 		return
 	}
 
-	mutex, err := pool.takeNameMutex()
-	if err != nil {
-		return
-	}
-	defer func() {
-		windows.ReleaseMutex(mutex)
-		windows.CloseHandle(mutex)
-	}()
-
 	defer func() {
 		if err != nil {
 			// The interface failed to install, or the interface ID was unobtainable. Clean-up.