Make kubelet never delete files on mounted filesystems

With bug kubernetes#27653, kubelet could remove mounted volumes and delete user data.
The bug itself is fixed, however our trust in kubelet is significantly lower.
Let's add an extra version of RemoveAll that does not cross mount boundary
(rm -rf --one-file-system).

It calls lstat(path) three times for each removed directory - once in
RemoveAllOneFilesystem and twice in IsLikelyNotMountPoint, however this way
it's platform independent and the directory that is being removed by kubelet
should be almost empty.

pkg/kubelet/BUILD

@@ -97,6 +97,7 @@ go_library(
         "//pkg/util/node:go_default_library",
         "//pkg/util/oom:go_default_library",
         "//pkg/util/procfs:go_default_library",
+        "//pkg/util/removeall:go_default_library",
         "//pkg/util/term:go_default_library",
         "//pkg/version:go_default_library",
         "//pkg/volume:go_default_library",

pkg/kubelet/kubelet_volumes.go

@@ -18,14 +18,14 @@ package kubelet
 
 import (
 	"fmt"
-	"os"
 
 	"github.com/golang/glog"
 	"k8s.io/apimachinery/pkg/types"
 	utilerrors "k8s.io/apimachinery/pkg/util/errors"
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/kubernetes/pkg/api/v1"
 	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
+	"k8s.io/kubernetes/pkg/util/removeall"
 	"k8s.io/kubernetes/pkg/volume"
 	volumetypes "k8s.io/kubernetes/pkg/volume/util/types"
 )
@@ -115,7 +115,7 @@ func (kl *Kubelet) cleanupOrphanedPodDirs(
 			continue
 		}
 		glog.V(3).Infof("Orphaned pod %q found, removing", uid)
-		if err := os.RemoveAll(kl.getPodDir(uid)); err != nil {
+		if err := removeall.RemoveAllOneFilesystem(kl.mounter, kl.getPodDir(uid)); err != nil {
 			glog.Errorf("Failed to remove orphaned pod %q dir; err: %v", uid, err)
 			errlist = append(errlist, err)
 		}

pkg/util/BUILD

@@ -81,6 +81,7 @@ filegroup(
         "//pkg/util/parsers:all-srcs",
         "//pkg/util/procfs:all-srcs",
         "//pkg/util/rand:all-srcs",
+        "//pkg/util/removeall:all-srcs",
         "//pkg/util/resourcecontainer:all-srcs",
         "//pkg/util/rlimit:all-srcs",
         "//pkg/util/runtime:all-srcs",

pkg/util/removeall/BUILD

@@ -0,0 +1,40 @@
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])
+
+load(
+    "@io_bazel_rules_go//go:def.bzl",
+    "go_library",
+    "go_test",
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = ["removeall_test.go"],
+    library = ":go_default_library",
+    tags = ["automanaged"],
+    deps = [
+        "//pkg/util/mount:go_default_library",
+        "//vendor:k8s.io/client-go/util/testing",
+    ],
+)
+
+go_library(
+    name = "go_default_library",
+    srcs = ["removeall.go"],
+    tags = ["automanaged"],
+    deps = ["//pkg/util/mount:go_default_library"],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+)

pkg/util/removeall/removeall.go

@@ -0,0 +1,108 @@
+/*
+Copyright 2017 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 removeall
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"syscall"
+
+	"k8s.io/kubernetes/pkg/util/mount"
+)
+
+// RemoveAllOneFilesystem removes path and any children it contains.
+// It removes everything it can but returns the first error
+// it encounters. If the path does not exist, RemoveAll
+// returns nil (no error).
+// It makes sure it does not cross mount boundary, i.e. it does *not* remove
+// files from another filesystems. Like 'rm -rf --one-file-system'.
+// It is copied from RemoveAll() sources, with IsLikelyNotMountPoint
+func RemoveAllOneFilesystem(mounter mount.Interface, path string) error {
+	// Simple case: if Remove works, we're done.
+	err := os.Remove(path)
+	if err == nil || os.IsNotExist(err) {
+		return nil
+	}
+
+	// Otherwise, is this a directory we need to recurse into?
+	dir, serr := os.Lstat(path)
+	if serr != nil {
+		if serr, ok := serr.(*os.PathError); ok && (os.IsNotExist(serr.Err) || serr.Err == syscall.ENOTDIR) {
+			return nil
+		}
+		return serr
+	}
+	if !dir.IsDir() {
+		// Not a directory; return the error from Remove.
+		return err
+	}
+
+	// Directory.
+	isNotMount, err := mounter.IsLikelyNotMountPoint(path)
+	if err != nil {
+		return err
+	}
+	if !isNotMount {
+		return fmt.Errorf("cannot delete directory %s: it is a mount point", path)
+	}
+
+	fd, err := os.Open(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			// Race. It was deleted between the Lstat and Open.
+			// Return nil per RemoveAll's docs.
+			return nil
+		}
+		return err
+	}
+
+	// Remove contents & return first error.
+	err = nil
+	for {
+		names, err1 := fd.Readdirnames(100)
+		for _, name := range names {
+			err1 := RemoveAllOneFilesystem(mounter, path+string(os.PathSeparator)+name)
+			if err == nil {
+				err = err1
+			}
+		}
+		if err1 == io.EOF {
+			break
+		}
+		// If Readdirnames returned an error, use it.
+		if err == nil {
+			err = err1
+		}
+		if len(names) == 0 {
+			break
+		}
+	}
+
+	// Close directory, because windows won't remove opened directory.
+	fd.Close()
+
+	// Remove directory.
+	err1 := os.Remove(path)
+	if err1 == nil || os.IsNotExist(err1) {
+		return nil
+	}
+	if err == nil {
+		err = err1
+	}
+	return err
+}

pkg/util/removeall/removeall_test.go

@@ -0,0 +1,157 @@
+/*
+Copyright 2017 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 removeall
+
+import (
+	"errors"
+	"os"
+	"path"
+	"strings"
+	"testing"
+
+	utiltesting "k8s.io/client-go/util/testing"
+	"k8s.io/kubernetes/pkg/util/mount"
+)
+
+type fakeMounter struct{}
+
+var _ mount.Interface = &fakeMounter{}
+
+func (mounter *fakeMounter) Mount(source string, target string, fstype string, options []string) error {
+	return errors.New("not implemented")
+}
+func (mounter *fakeMounter) Unmount(target string) error {
+	return errors.New("not implemented")
+}
+func (mounter *fakeMounter) List() ([]mount.MountPoint, error) {
+	return nil, errors.New("not implemented")
+}
+func (mounter fakeMounter) DeviceOpened(pathname string) (bool, error) {
+	return false, errors.New("not implemented")
+}
+func (mounter *fakeMounter) PathIsDevice(pathname string) (bool, error) {
+	return false, errors.New("not implemented")
+}
+func (mounter *fakeMounter) GetDeviceNameFromMount(mountPath, pluginDir string) (string, error) {
+	return "", errors.New("not implemented")
+}
+func (mounter *fakeMounter) IsLikelyNotMountPoint(file string) (bool, error) {
+	name := path.Base(file)
+	if strings.HasPrefix(name, "mount") {
+		return false, nil
+	}
+	if strings.HasPrefix(name, "err") {
+		return false, errors.New("mock error")
+	}
+	return true, nil
+}
+
+func TestRemoveAllOneFilesystem(t *testing.T) {
+	tests := []struct {
+		name string
+		// Items of the test directory. Directories end with "/".
+		// Directories starting with "mount" are considered to be mount points.
+		// Directories starting with "err" will cause an error in
+		// IsLikelyNotMountPoint.
+		items       []string
+		expectError bool
+	}{
+		{
+			"empty dir",
+			[]string{},
+			false,
+		},
+		{
+			"non-mount",
+			[]string{
+				"dir/",
+				"dir/file",
+				"dir2/",
+				"file2",
+			},
+			false,
+		},
+		{
+			"mount",
+			[]string{
+				"dir/",
+				"dir/file",
+				"dir2/",
+				"file2",
+				"mount/",
+				"mount/file3",
+			},
+			true,
+		},
+		{
+			"innermount",
+			[]string{
+				"dir/",
+				"dir/file",
+				"dir/dir2/",
+				"dir/dir2/file2",
+				"dir/dir2/mount/",
+				"dir/dir2/mount/file3",
+			},
+			true,
+		},
+		{
+			"error",
+			[]string{
+				"dir/",
+				"dir/file",
+				"dir2/",
+				"file2",
+				"err/",
+				"err/file3",
+			},
+			true,
+		},
+	}
+
+	for _, test := range tests {
+		tmpDir, err := utiltesting.MkTmpdir("removeall-" + test.name + "-")
+		if err != nil {
+			t.Fatalf("Can't make a tmp dir: %v", err)
+		}
+		defer os.RemoveAll(tmpDir)
+		// Create the directory structure
+		for _, item := range test.items {
+			if strings.HasSuffix(item, "/") {
+				item = strings.TrimRight(item, "/")
+				if err = os.Mkdir(path.Join(tmpDir, item), 0777); err != nil {
+					t.Fatalf("error creating %s: %v", item, err)
+				}
+			} else {
+				f, err := os.Create(path.Join(tmpDir, item))
+				if err != nil {
+					t.Fatalf("error creating %s: %v", item, err)
+				}
+				f.Close()
+			}
+		}
+
+		mounter := &fakeMounter{}
+		err = RemoveAllOneFilesystem(mounter, tmpDir)
+		if err == nil && test.expectError {
+			t.Errorf("test %q failed: expected error and got none", test.name)
+		}
+		if err != nil && !test.expectError {
+			t.Errorf("test %q failed: unexpected error: %v", test.name, err)
+		}
+	}
+}