From d3615115129b0f8c930cda7bd31cfa5537bcad10 Mon Sep 17 00:00:00 2001
From: Dmytro Shynkevych <dmytro@tailscale.com>
Date: Wed, 15 Jul 2020 13:00:20 -0400
Subject: [PATCH] control/controlclient: eliminate race in loginGoal access.

This code is currently racy due to an incorrect assumption
that goal is never modified in-place, so does not require extra locking.
This change makes the assumption correct.

Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
---
 control/controlclient/auto.go | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/control/controlclient/auto.go b/control/controlclient/auto.go
index 0d7e247c8..50efeb2e3 100644
--- a/control/controlclient/auto.go
+++ b/control/controlclient/auto.go
@@ -355,12 +355,13 @@ func (c *Client) authRoutine() {
 					err = fmt.Errorf("weird: server required a new url?")
 					report(err, "WaitLoginURL")
 				}
-				goal.url = url
-				goal.token = nil
-				goal.flags = LoginDefault
 
 				c.mu.Lock()
-				c.loginGoal = goal
+				c.loginGoal = &LoginGoal{
+					wantLoggedIn: true,
+					flags:        LoginDefault,
+					url:          url,
+				}
 				c.state = StateURLVisitRequired
 				c.synced = false
 				c.mu.Unlock()