Conditionally mount flexvolume

cmd/kubeadm/app/phases/controlplane/volumes.go

@@ -72,7 +72,9 @@ func getHostPathVolumesForTheControlPlane(cfg *kubeadmapi.MasterConfiguration) c
 	mounts.NewHostPathMount(kubeadmconstants.KubeControllerManager, kubeadmconstants.KubeConfigVolumeName, controllerManagerKubeConfigFile, controllerManagerKubeConfigFile, true, &hostPathFileOrCreate)
 	// Mount for the flexvolume directory (/usr/libexec/kubernetes/kubelet-plugins/volume/exec) directory
 	// Flexvolume dir must NOT be readonly as it is used for third-party plugins to integrate with their storage backends via unix domain socket.
-	mounts.NewHostPathMount(kubeadmconstants.KubeControllerManager, flexvolumeDirVolumeName, flexvolumeDirVolumePath, flexvolumeDirVolumePath, false, &hostPathDirectoryOrCreate)
+	if stat, err := os.Stat(flexvolumeDirVolumePath); err == nil && stat.IsDir() {
+		mounts.NewHostPathMount(kubeadmconstants.KubeControllerManager, flexvolumeDirVolumeName, flexvolumeDirVolumePath, flexvolumeDirVolumePath, false, &hostPathDirectoryOrCreate)
+	}
 
 	// HostPath volumes for the scheduler
 	// Read-only mount for the scheduler kubeconfig file