@@ -159,7 +159,7 @@ func (daemon *Daemon) ContainerExecCreate(name string, options *containertypes.E

 // ContainerExecStart starts a previously set up exec instance. The

 // std streams are set up.

 // If ctx is cancelled, the process is terminated.

-func (daemon *Daemon) ContainerExecStart(ctx context.Context, name string, options backend.ExecStartConfig) (err error) {

+func (daemon *Daemon) ContainerExecStart(ctx context.Context, name string, options backend.ExecStartConfig) (retErr error) {

 	var (

 		cStdin           io.ReadCloser

 		cStdout, cStderr io.Writer

@@ -173,13 +173,12 @@ func (daemon *Daemon) ContainerExecStart(ctx context.Context, name string, optio

 	ec.Lock()

 	if ec.ExitCode != nil {

 		ec.Unlock()

-		err := fmt.Errorf("Error: Exec command %s has already run", ec.ID)

-		return errdefs.Conflict(err)

+		return errdefs.Conflict(fmt.Errorf("exec command %s has already run", ec.ID))

 	}

 	if ec.Running {

 		ec.Unlock()

-		return errdefs.Conflict(fmt.Errorf("Error: Exec command %s is already running", ec.ID))

+		return errdefs.Conflict(fmt.Errorf("exec command %s is already running", ec.ID))

 	}

 	ec.Running = true

 	ec.Unlock()

@@ -190,7 +189,7 @@ func (daemon *Daemon) ContainerExecStart(ctx context.Context, name string, optio

 	})

 	defer func() {

-		if err != nil {

+		if retErr != nil {

 			ec.Lock()

 			ec.Container.ExecCommands.Delete(ec.ID)

 			ec.Running = false

@@ -210,9 +209,11 @@ func (daemon *Daemon) ContainerExecStart(ctx context.Context, name string, optio

 	if ec.OpenStdin && options.Stdin != nil {

 		r, w := io.Pipe()

 		go func() {

-			defer w.Close()

-			defer log.G(ctx).Debug("Closing buffered stdin pipe")

-			pools.Copy(w, options.Stdin)

+			defer func() {

+				log.G(ctx).Debug("Closing buffered stdin pipe")

+				_ = w.Close()

+			}()

+			_, _ = pools.Copy(w, options.Stdin)

 		}()

 		cStdin = r

 	}

@@ -231,6 +232,9 @@ func (daemon *Daemon) ContainerExecStart(ctx context.Context, name string, optio

 	p := &specs.Process{}

 	if runtime.GOOS != "windows" {

+		// TODO(thaJeztah): also enable on Windows;

+		//  This was added in https://github.com/moby/moby/commit/7603c22c7365d7d7150597fe396e0707d6e561da,

+		//  which mentions that it failed on Windows "Probably needs to wait for container to be in running state"

 		ctr, err := daemon.containerdClient.LoadContainer(ctx, ec.Container.ID)

 		if err != nil {

 			return err

@@ -239,11 +243,16 @@ func (daemon *Daemon) ContainerExecStart(ctx context.Context, name string, optio

 		if err != nil {

 			return err

 		}

-		spec := specs.Spec{Process: p}

+

+		// Technically, this should be a [specs.Spec], but we're only

+		// interested in the Process field.

+		spec := struct{ Process *specs.Process }{p}

 		if err := json.Unmarshal(md.Spec.GetValue(), &spec); err != nil {

 			return err

 		}

 	}

+

+	// merge/override properties of the container's process with the exec-config.

 	p.Args = append([]string{ec.Entrypoint}, ec.Args...)

 	p.Env = ec.Env

 	p.Cwd = ec.WorkingDir

@@ -308,15 +317,15 @@ func (daemon *Daemon) ContainerExecStart(ctx context.Context, name string, optio

 	select {

 	case <-ctx.Done():

-		log := log.G(ctx).

-			WithField("container", ec.Container.ID).

-			WithField("exec", ec.ID)

-		log.Debug("Sending KILL signal to container process")

+		logger := log.G(ctx).WithFields(log.Fields{

+			"container": ec.Container.ID,

+			"exeec":     ec.ID,

+		})

+		logger.Debug("Sending KILL signal to container process")

 		sigCtx, cancelFunc := context.WithTimeout(context.Background(), 30*time.Second)

 		defer cancelFunc()

-		err := ec.Process.Kill(sigCtx, signal.SignalMap["KILL"])

-		if err != nil {

-			log.WithError(err).Error("Could not send KILL signal to container process")

+		if err := ec.Process.Kill(sigCtx, signal.SignalMap["KILL"]); err != nil {

+			logger.WithError(err).Error("Could not send KILL signal to container process")

 		}

 		return ctx.Err()

 	case err := <-attachErr: