From 9a19c8412446933d529eb883abcd68ea04eba92a Mon Sep 17 00:00:00 2001
From: Aaron Lehmann <aaron.lehmann@docker.com>
Date: Thu, 3 Dec 2015 16:04:58 -0800
Subject: [PATCH] Fix race in RunCommandWithOutputForDuration

This function was starting a goroutine that modifies one of its return
values. The intent is for the goroutine to only influence the return
value when it's causing the function to return, but it's racy and can
also modify the return value when the function is returning due to the
timeout. Fix the goroutine to not modify return values directly.

Also, give the channel a buffer so that the goroutine doesn't block
forever after a timeout.

Fixes #18305

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
Upstream-commit: 2704fd9156bfb0fb8dc16c42902bb18ea5aa94a9
Component: engine
---
 components/engine/pkg/integration/utils.go | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/components/engine/pkg/integration/utils.go b/components/engine/pkg/integration/utils.go
index 6fe1c0afe6..330a533904 100644
--- a/components/engine/pkg/integration/utils.go
+++ b/components/engine/pkg/integration/utils.go
@@ -104,19 +104,25 @@ func RunCommandWithOutputForDuration(cmd *exec.Cmd, duration time.Duration) (out
 	}
 	cmd.Stderr = &outputBuffer
 
-	done := make(chan error)
-
 	// Start the command in the main thread..
 	err = cmd.Start()
 	if err != nil {
 		err = fmt.Errorf("Fail to start command %v : %v", cmd, err)
 	}
 
+	type exitInfo struct {
+		exitErr  error
+		exitCode int
+	}
+
+	done := make(chan exitInfo, 1)
+
 	go func() {
 		// And wait for it to exit in the goroutine :)
-		exitErr := cmd.Wait()
-		exitCode = ProcessExitCode(exitErr)
-		done <- exitErr
+		info := exitInfo{}
+		info.exitErr = cmd.Wait()
+		info.exitCode = ProcessExitCode(info.exitErr)
+		done <- info
 	}()
 
 	select {
@@ -126,9 +132,9 @@ func RunCommandWithOutputForDuration(cmd *exec.Cmd, duration time.Duration) (out
 			fmt.Printf("failed to kill (pid=%d): %v\n", cmd.Process.Pid, killErr)
 		}
 		timedOut = true
-		break
-	case err = <-done:
-		break
+	case info := <-done:
+		err = info.exitErr
+		exitCode = info.exitCode
 	}
 	output = outputBuffer.String()
 	return