From 9cbaacad3264028f767b438a98c6f2f12098f3ef Mon Sep 17 00:00:00 2001
From: Paul Hinze <phinze@phinze.com>
Date: Sat, 16 Jan 2016 13:33:24 -0500
Subject: [PATCH] communicator/winrm: fix data race in io copy

As the command completes, the winrm.Command does not wait for its copy of
the remote.Command streams to report itself completed.

This adds an additional sync.WaitGroup to ensure that copy is finished up
before moving on, solving the data race.

Fixes the following data race:

```
==================
WARNING: DATA RACE
Read by goroutine 6:
  github.com/hashicorp/terraform/communicator/winrm.TestStart()
      /Users/phinze/go/src/github.com/hashicorp/terraform/communicator/winrm/communicator_test.go:79 +0xa44
  testing.tRunner()
      /private/var/folders/vd/7l9ys5k57l91x63sh28wl_kc0000gn/T/workdir/go/src/testing/testing.go:456 +0xdc

Previous write by goroutine 14:
  bytes.(*Buffer).ReadFrom()
      /private/var/folders/vd/7l9ys5k57l91x63sh28wl_kc0000gn/T/workdir/go/src/bytes/buffer.go:174 +0x465
  io.copyBuffer()
      /private/var/folders/vd/7l9ys5k57l91x63sh28wl_kc0000gn/T/workdir/go/src/io/io.go:375 +0x1a5
  io.Copy()
      /private/var/folders/vd/7l9ys5k57l91x63sh28wl_kc0000gn/T/workdir/go/src/io/io.go:351 +0x78

Goroutine 6 (running) created at:
  testing.RunTests()
      /private/var/folders/vd/7l9ys5k57l91x63sh28wl_kc0000gn/T/workdir/go/src/testing/testing.go:561 +0xaa3
  testing.(*M).Run()
      /private/var/folders/vd/7l9ys5k57l91x63sh28wl_kc0000gn/T/workdir/go/src/testing/testing.go:494 +0xe4
  main.main()
      github.com/hashicorp/terraform/communicator/winrm/_test/_testmain.go:62 +0x20f

Goroutine 14 (finished) created at:
  github.com/hashicorp/terraform/communicator/winrm.runCommand()
      /Users/phinze/go/src/github.com/hashicorp/terraform/communicator/winrm/communicator.go:151 +0xf8
==================
```
---
 communicator/winrm/communicator.go | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/communicator/winrm/communicator.go b/communicator/winrm/communicator.go
index 27ba31a83..30998e0b1 100644
--- a/communicator/winrm/communicator.go
+++ b/communicator/winrm/communicator.go
@@ -7,6 +7,7 @@ import (
 	"math/rand"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/hashicorp/terraform/communicator/remote"
@@ -148,10 +149,20 @@ func (c *Communicator) Start(rc *remote.Cmd) error {
 func runCommand(shell *winrm.Shell, cmd *winrm.Command, rc *remote.Cmd) {
 	defer shell.Close()
 
-	go io.Copy(rc.Stdout, cmd.Stdout)
-	go io.Copy(rc.Stderr, cmd.Stderr)
+	var wg sync.WaitGroup
+	go func() {
+		wg.Add(1)
+		io.Copy(rc.Stdout, cmd.Stdout)
+		wg.Done()
+	}()
+	go func() {
+		wg.Add(1)
+		io.Copy(rc.Stderr, cmd.Stderr)
+		wg.Done()
+	}()
 
 	cmd.Wait()
+	wg.Wait()
 	rc.SetExited(cmd.ExitCode())
 }