Only dup Ruby's Hash and Array.

When calling `to_h` on an `ActionController::Parameters` instance it would
`deep_dup` its internal parameters.

This inadvertently called `dup` on a passed Active Record model which would
create new models. Fix by only dupping Ruby's Arrays and Hashes.

1 files changed, 18 insertions, 2 deletions

diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index 8bc3c271e2..957aa746c0 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -1,4 +1,5 @@
 require 'active_support/core_ext/hash/indifferent_access'
+require 'active_support/core_ext/hash/transform_values'
 require 'active_support/core_ext/array/wrap'
 require 'active_support/core_ext/string/filters'
 require 'active_support/rescuable'
@@ -175,7 +176,7 @@ module ActionController
     #   safe_params.to_h # => {"name"=>"Senjougahara Hitagi"}
     def to_h
       if permitted?
-        @parameters.deep_dup
+        convert_parameters_to_hashes(@parameters)
       else
         slice(*self.class.always_permitted_parameters).permit!.to_h
       end
@@ -185,7 +186,7 @@ module ActionController
     # <tt>ActiveSupport::HashWithIndifferentAccess</tt> representation of this
     # parameter.
     def to_unsafe_h
-      @parameters.deep_dup
+      convert_parameters_to_hashes(@parameters)
     end
     alias_method :to_unsafe_hash, :to_unsafe_h
 
@@ -594,6 +595,21 @@ module ActionController
         end
       end
 
+      def convert_parameters_to_hashes(value)
+        case value
+        when Array
+          value.map { |v| convert_parameters_to_hashes(v) }
+        when Hash
+          value.transform_values do |v|
+            convert_parameters_to_hashes(v)
+          end.with_indifferent_access
+        when Parameters
+          value.to_h
+        else
+          value
+        end
+      end
+
       def convert_hashes_to_parameters(key, value)
         converted = convert_value_to_parameters(value)
         @parameters[key] = converted unless converted.equal?(value)