removed awk from kubeadm reset

removed awk from kubeadm reset in favor of native go lang calls
that are not vulnerable to expantion.

cmd/kubeadm/app/cmd/phases/reset/BUILD

@@ -7,6 +7,8 @@ go_library(
         "data.go",
         "preflight.go",
         "removeetcdmember.go",
+        "unmount.go",
+        "unmount_linux.go",
         "updateclusterstatus.go",
     ],
     importpath = "k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/reset",

cmd/kubeadm/app/cmd/phases/reset/cleanupnode.go

@@ -20,7 +20,6 @@ import (
 	"errors"
 	"fmt"
 	"os"
-	"os/exec"
 	"path/filepath"
 
 	"k8s.io/klog"
@@ -100,13 +99,10 @@ func absoluteKubeletRunDirectory() (string, error) {
 		klog.Warningf("[reset] Failed to evaluate the %q directory. Skipping its unmount and cleanup: %v\n", kubeadmconstants.KubeletRunDirectory, err)
 		return "", err
 	}
-
-	// Only unmount mount points which start with "/var/lib/kubelet" or absolute path of symbolic link, and avoid using empty absoluteKubeletRunDirectory
-	umountDirsCmd := fmt.Sprintf("awk '$2 ~ path {print $2}' path=%s/ /proc/mounts | xargs -r umount", absoluteKubeletRunDirectory)
-	klog.V(1).Infof("[reset] Executing command %q", umountDirsCmd)
-	umountOutputBytes, err := exec.Command("sh", "-c", umountDirsCmd).Output()
+	err = unmountKubeletDirectory(absoluteKubeletRunDirectory)
 	if err != nil {
-		klog.Warningf("[reset] Failed to unmount mounted directories in %s: %s\n", kubeadmconstants.KubeletRunDirectory, string(umountOutputBytes))
+		klog.Warningf("[reset] Failed to unmount mounted directories in %s \n", kubeadmconstants.KubeletRunDirectory)
+		return "", err
 	}
 	return absoluteKubeletRunDirectory, nil
 }

cmd/kubeadm/app/cmd/phases/reset/unmount.go

@@ -0,0 +1,29 @@
+// +build !linux
+
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package phases
+
+import (
+	"k8s.io/klog"
+)
+
+// unmountKubeletDirectory is a NOOP on all but linux.
+func unmountKubeletDirectory(absoluteKubeletRunDirectory string) error {
+	klog.Warning("Cannot unmount filesystems on current OS, all mounted file systems will need to be manually unmounted")
+	return nil
+}

cmd/kubeadm/app/cmd/phases/reset/unmount_linux.go

@@ -0,0 +1,46 @@
+// +build linux
+
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package phases
+
+import (
+	"io/ioutil"
+	"strings"
+	"syscall"
+
+	"k8s.io/klog"
+)
+
+// unmountKubeletDirectory unmounts all paths that contain KubeletRunDirectory
+func unmountKubeletDirectory(absoluteKubeletRunDirectory string) error {
+	raw, err := ioutil.ReadFile("/proc/mounts")
+	if err != nil {
+		return err
+	}
+	mounts := strings.Split(string(raw), "\n")
+	for _, mount := range mounts {
+		m := strings.Split(mount, " ")
+		if len(m) < 2 || !strings.HasPrefix(m[1], absoluteKubeletRunDirectory) {
+			continue
+		}
+		if err := syscall.Unmount(m[1], 0); err != nil {
+			klog.Warningf("[reset] Failed to unmount mounted directory in %s: %s", absoluteKubeletRunDirectory, m[1])
+		}
+	}
+	return nil
+}