Error if a box override changes the box setting...

lib/vagrant/environment.rb

@@ -336,6 +336,7 @@ module Vagrant
       # Set this variable in order to keep track of if the box changes
       # too many times.
       original_box = config.vm.box
+      box_changed  = false
 
       load_box_and_overrides = lambda do
         # If a box was found, then we attempt to load the Vagrantfile for
@@ -366,11 +367,17 @@ module Vagrant
         end
 
         if config.vm.box && original_box != config.vm.box
+          if box_changed
+            # We already changed boxes once, so report an error that a
+            # box is attempting to change boxes again.
+            raise Errors::BoxConfigChangingBox
+          end
+
           # The box changed, probably due to the provider override. Let's
           # run the configuration one more time with the new box.
-          # TODO: previous original box
           @logger.info("Box changed to: #{config.vm.box}. Reloading configurations.")
           original_box = config.vm.box
+          box_changed  = true
           box          = find_box(config.vm.box, box_formats)
 
           # Recurse so that we reload all the configurations

lib/vagrant/errors.rb

@@ -103,6 +103,10 @@ module Vagrant
       error_key(:already_exists, "vagrant.actions.box.unpackage")
     end
 
+    class BoxConfigChangingBox < VagrantError
+      error_key(:box_config_changing_box)
+    end
+
     class BoxMetadataFileNotFound < VagrantError
       error_key(:box_metadata_file_not_found)
     end

templates/locales/en.yml

@@ -120,6 +120,11 @@ en:
         Any errors that occurred are shown below.
 
         %{message}
+      box_config_changing_box: |-
+        While loading the Vagrantfile, the provider override specified
+        a new box. This box, in turn, specified a different box. This isn't
+        allowed, as it could lead to infinite recursion of Vagrant configuration
+        loading. Please fix this.
       box_metadata_file_not_found: |-
         The "metadata.json" file for the box '%{name}' was not found.
         Boxes require this file in order for Vagrant to determine the