Do not create exec fifo in factory.Create

It should not be binded to container creation, for
example, runc restore needs to create a
libcontainer.Container, but it won't need exec fifo.

So create exec fifo when container is started or run,
where we really need it.

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>

libcontainer/container_linux.go

@@ -191,17 +191,29 @@ func (c *linuxContainer) Start(process *Process) error {
 	if err != nil {
 		return err
 	}
-	return c.start(process, status == Stopped)
+	if status == Stopped {
+		if err := c.createExecFifo(); err != nil {
+			return err
+		}
+	}
+	if err := c.start(process, status == Stopped); err != nil {
+		if status == Stopped {
+			c.deleteExecFifo()
+		}
+		return err
+	}
+	return nil
 }
 
 func (c *linuxContainer) Run(process *Process) error {
 	c.m.Lock()
-	defer c.m.Unlock()
 	status, err := c.currentStatus()
 	if err != nil {
+		c.m.Unlock()
 		return err
 	}
-	if err := c.start(process, status == Stopped); err != nil {
+	c.m.Unlock()
+	if err := c.Start(process); err != nil {
 		return err
 	}
 	if status == Stopped {
@@ -291,6 +303,37 @@ func (c *linuxContainer) Signal(s os.Signal, all bool) error {
 	return nil
 }
 
+func (c *linuxContainer) createExecFifo() error {
+	rootuid, err := c.Config().HostUID()
+	if err != nil {
+		return err
+	}
+	rootgid, err := c.Config().HostGID()
+	if err != nil {
+		return err
+	}
+
+	fifoName := filepath.Join(c.root, execFifoFilename)
+	if _, err := os.Stat(fifoName); err == nil {
+		return fmt.Errorf("exec fifo %s already exists", fifoName)
+	}
+	oldMask := syscall.Umask(0000)
+	if err := syscall.Mkfifo(fifoName, 0622); err != nil {
+		syscall.Umask(oldMask)
+		return err
+	}
+	syscall.Umask(oldMask)
+	if err := os.Chown(fifoName, rootuid, rootgid); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (c *linuxContainer) deleteExecFifo() {
+	fifoName := filepath.Join(c.root, execFifoFilename)
+	os.Remove(fifoName)
+}
+
 func (c *linuxContainer) newParentProcess(p *Process, doInit bool) (parentProcess, error) {
 	parentPipe, childPipe, err := newPipe()
 	if err != nil {

libcontainer/factory_linux.go

@@ -169,16 +169,6 @@ func (l *LinuxFactory) Create(id string, config *configs.Config) (Container, err
 	if err := os.Chown(containerRoot, uid, gid); err != nil {
 		return nil, newGenericError(err, SystemError)
 	}
-	fifoName := filepath.Join(containerRoot, execFifoFilename)
-	oldMask := syscall.Umask(0000)
-	if err := syscall.Mkfifo(fifoName, 0622); err != nil {
-		syscall.Umask(oldMask)
-		return nil, newGenericError(err, SystemError)
-	}
-	syscall.Umask(oldMask)
-	if err := os.Chown(fifoName, uid, gid); err != nil {
-		return nil, newGenericError(err, SystemError)
-	}
 	c := &linuxContainer{
 		id:            id,
 		root:          containerRoot,