Make sure plugin mounts are cleaned up

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

plugin/manager.go

@@ -19,6 +19,7 @@ import (
 	"github.com/docker/docker/layer"
 	"github.com/docker/docker/pkg/authorization"
 	"github.com/docker/docker/pkg/ioutils"
+	"github.com/docker/docker/pkg/mount"
 	"github.com/docker/docker/pkg/pubsub"
 	"github.com/docker/docker/pkg/system"
 	"github.com/docker/docker/plugin/v2"
@@ -155,6 +156,10 @@ func (pm *Manager) HandleExitEvent(id string) error {
 
 	if restart {
 		pm.enable(p, c, true)
+	} else {
+		if err := mount.RecursiveUnmount(filepath.Join(pm.config.Root, id)); err != nil {
+			return errors.Wrap(err, "error cleaning up plugin mounts")
+		}
 	}
 	return nil
 }

plugin/manager_linux.go

@@ -187,6 +187,9 @@ func (pm *Manager) Shutdown() {
 			shutdownPlugin(p, c, pm.executor)
 		}
 	}
+	if err := mount.RecursiveUnmount(pm.config.Root); err != nil {
+		logrus.WithError(err).Warn("error cleaning up plugin mounts")
+	}
 }
 
 func (pm *Manager) upgradePlugin(p *v2.Plugin, configDigest digest.Digest, blobsums []digest.Digest, tmpRootFSDir string, privileges *types.PluginPrivileges) (err error) {