@@ -135,6 +135,11 @@ func (d *Daemon) ContainerExecStart(name string, stdin io.ReadCloser, stdout io.

 	}

 	ec.Lock()

+	if ec.ExitCode != nil {

+		ec.Unlock()

+		return derr.ErrorCodeExecExited.WithArgs(ec.ID)

+	}

+

 	if ec.Running {

 		ec.Unlock()

 		return derr.ErrorCodeExecRunning.WithArgs(ec.ID)

@@ -214,7 +219,7 @@ func (d *Daemon) Exec(c *container.Container, execConfig *exec.Config, pipes *ex

 		exitStatus = 128

 	}

-	execConfig.ExitCode = exitStatus

+	execConfig.ExitCode = &exitStatus

 	execConfig.Running = false

 	return exitStatus, err

@@ -18,7 +18,7 @@ type Config struct {

 	*runconfig.StreamConfig

 	ID            string

 	Running       bool

-	ExitCode      int

+	ExitCode      *int

 	ProcessConfig *execdriver.ProcessConfig

 	OpenStdin     bool

 	OpenStderr    bool

@@ -742,6 +742,15 @@ var (

 		HTTPStatusCode: http.StatusInternalServerError,

 	})

+	// ErrorCodeExecExited is generated when we try to start an exec

+	// but its already running.

+	ErrorCodeExecExited = errcode.Register(errGroup, errcode.ErrorDescriptor{

+		Value:          "EXECEXITED",

+		Message:        "Error: Exec command %s has already run",

+		Description:    "An attempt to start an 'exec' was made, but 'exec' was already run",

+		HTTPStatusCode: http.StatusConflict,

+	})

+

 	// ErrorCodeExecCantRun is generated when we try to start an exec

 	// but it failed for some reason.

 	ErrorCodeExecCantRun = errcode.Register(errGroup, errcode.ErrorDescriptor{

@@ -8,6 +8,7 @@ import (

 	"fmt"

 	"net/http"

 	"strings"

+	"time"

 	"github.com/docker/docker/pkg/integration/checker"

 	"github.com/go-check/check"

@@ -66,33 +67,23 @@ func (s *DockerSuite) TestExecAPIStart(c *check.C) {

 	testRequires(c, DaemonIsLinux) // Uses pause/unpause but bits may be salvagable to Windows to Windows CI

 	dockerCmd(c, "run", "-d", "--name", "test", "busybox", "top")

-	startExec := func(id string, code int) {

-		resp, body, err := sockRequestRaw("POST", fmt.Sprintf("/exec/%s/start", id), strings.NewReader(`{"Detach": true}`), "application/json")

-		c.Assert(err, checker.IsNil)

-

-		b, err := readBody(body)

-		comment := check.Commentf("response body: %s", b)

-		c.Assert(err, checker.IsNil, comment)

-		c.Assert(resp.StatusCode, checker.Equals, code, comment)

-	}

-

 	id := createExec(c, "test")

-	startExec(id, http.StatusOK)

+	startExec(c, id, http.StatusOK)

 	id = createExec(c, "test")

 	dockerCmd(c, "stop", "test")

-	startExec(id, http.StatusNotFound)

+	startExec(c, id, http.StatusNotFound)

 	dockerCmd(c, "start", "test")

-	startExec(id, http.StatusNotFound)

+	startExec(c, id, http.StatusNotFound)

 	// make sure exec is created before pausing

 	id = createExec(c, "test")

 	dockerCmd(c, "pause", "test")

-	startExec(id, http.StatusConflict)

+	startExec(c, id, http.StatusConflict)

 	dockerCmd(c, "unpause", "test")

-	startExec(id, http.StatusOK)

+	startExec(c, id, http.StatusOK)

 }

 func (s *DockerSuite) TestExecAPIStartBackwardsCompatible(c *check.C) {

@@ -108,6 +99,30 @@ func (s *DockerSuite) TestExecAPIStartBackwardsCompatible(c *check.C) {

 	c.Assert(resp.StatusCode, checker.Equals, http.StatusOK, comment)

 }

+// #19362

+func (s *DockerSuite) TestExecAPIStartMultipleTimesError(c *check.C) {

+	dockerCmd(c, "run", "-d", "--name", "test", "busybox", "top")

+	execID := createExec(c, "test")

+	startExec(c, execID, http.StatusOK)

+

+	timeout := time.After(10 * time.Second)

+	var execJSON struct{ Running bool }

+	for {

+		select {

+		case <-timeout:

+			c.Fatal("timeout waiting for exec to start")

+		default:

+		}

+

+		inspectExec(c, execID, &execJSON)

+		if !execJSON.Running {

+			break

+		}

+	}

+

+	startExec(c, execID, http.StatusConflict)

+}

+

 func createExec(c *check.C, name string) string {

 	_, b, err := sockRequest("POST", fmt.Sprintf("/containers/%s/exec", name), map[string]interface{}{"Cmd": []string{"true"}})

 	c.Assert(err, checker.IsNil, check.Commentf(string(b)))

@@ -118,3 +133,22 @@ func createExec(c *check.C, name string) string {

 	c.Assert(json.Unmarshal(b, &createResp), checker.IsNil, check.Commentf(string(b)))

 	return createResp.ID

 }

+

+func startExec(c *check.C, id string, code int) {

+	resp, body, err := sockRequestRaw("POST", fmt.Sprintf("/exec/%s/start", id), strings.NewReader(`{"Detach": true}`), "application/json")

+	c.Assert(err, checker.IsNil)

+

+	b, err := readBody(body)

+	comment := check.Commentf("response body: %s", b)

+	c.Assert(err, checker.IsNil, comment)

+	c.Assert(resp.StatusCode, checker.Equals, code, comment)

+}

+

+func inspectExec(c *check.C, id string, out interface{}) {

+	resp, body, err := sockRequestRaw("GET", fmt.Sprintf("/exec/%s/json", id), nil, "")

+	c.Assert(err, checker.IsNil)

+	defer body.Close()

+	c.Assert(resp.StatusCode, checker.Equals, http.StatusOK)

+	err = json.NewDecoder(body).Decode(out)

+	c.Assert(err, checker.IsNil)

+}