When id is empty for overlay2/overlay, do not remove the directories.

Signed-off-by: fanjiyun <fan.jiyun@zte.com.cn>
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

daemon/graphdriver/overlay/overlay.go

@@ -366,6 +366,9 @@ func (d *Driver) dir(id string) string {
 
 // Remove cleans the directories that are created for this id.
 func (d *Driver) Remove(id string) error {
+	if id == "" {
+		return fmt.Errorf("refusing to remove the directories: id is empty")
+	}
 	d.locker.Lock(id)
 	defer d.locker.Unlock(id)
 	return system.EnsureRemoveAll(d.dir(id))

daemon/graphdriver/overlay2/overlay.go

@@ -513,12 +513,17 @@ func (d *Driver) getLowerDirs(id string) ([]string, error) {
 
 // Remove cleans the directories that are created for this id.
 func (d *Driver) Remove(id string) error {
+	if id == "" {
+		return fmt.Errorf("refusing to remove the directories: id is empty")
+	}
 	d.locker.Lock(id)
 	defer d.locker.Unlock(id)
 	dir := d.dir(id)
 	lid, err := ioutil.ReadFile(path.Join(dir, "link"))
 	if err == nil {
-		if err := os.RemoveAll(path.Join(d.home, linkDir, string(lid))); err != nil {
+		if len(lid) == 0 {
+			logrus.WithField("storage-driver", "overlay2").Errorf("refusing to remove empty link for layer %v", id)
+		} else if err := os.RemoveAll(path.Join(d.home, linkDir, string(lid))); err != nil {
 			logrus.WithField("storage-driver", "overlay2").Debugf("Failed to remove link: %v", err)
 		}
 	}