all calls to cp should be escaped

builder/docker/communicator.go

@@ -166,7 +166,7 @@ func (c *Communicator) UploadDir(dst string, src string, exclude []string) error
 
 	// Make the directory, then copy into it
 	cmd := &packer.RemoteCmd{
-		Command: fmt.Sprintf("set -e; mkdir -p %s; cp -R %s/* %s",
+		Command: fmt.Sprintf("set -e; mkdir -p %s; command cp -R %s/* %s",
 			containerDst, containerSrc, containerDst),
 	}
 	if err := c.Start(cmd); err != nil {