Ensure that mass assignment options are preserved

There are two possible scenarios where the @mass_assignment_options
instance variable can become corrupted:

1. If the assign_attributes doesn't complete correctly, then
   subsequent calls to a nested attribute assignment method will use
   whatever options were passed to the previous assign_attributes call.

2. With nested assign_attributes calls, the inner call will overwrite
   the current options. This will only affect nested attributes as the
   attribute hash is sanitized before any methods are called.

To fix this we save the current options in a local variable and then
restore these options in an ensure block.

2 files changed, 13 insertions, 10 deletions

diff --git a/activerecord/lib/active_record/attribute_assignment.rb b/activerecord/lib/active_record/attribute_assignment.rb
index bf9fe70b31..e0bf80142a 100644
--- a/activerecord/lib/active_record/attribute_assignment.rb
+++ b/activerecord/lib/active_record/attribute_assignment.rb
@@ -69,6 +69,7 @@ module ActiveRecord
       attributes = new_attributes.stringify_keys
       multi_parameter_attributes = []
       nested_parameter_attributes = []
+      previous_options = @mass_assignment_options
       @mass_assignment_options = options
 
       unless options[:without_protection]
@@ -94,8 +95,9 @@ module ActiveRecord
         send("#{k}=", v)
       end
 
-      @mass_assignment_options = nil
       assign_multiparameter_attributes(multi_parameter_attributes)
+    ensure
+      @mass_assignment_options = previous_options
     end
 
     protected
diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 1fa6c701bb..dbad561ca2 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -380,15 +380,16 @@ module ActiveRecord
 
       @attributes[pk] = nil unless @attributes.key?(pk)
 
-      @aggregation_cache      = {}
-      @association_cache      = {}
-      @attributes_cache       = {}
-      @previously_changed     = {}
-      @changed_attributes     = {}
-      @readonly               = false
-      @destroyed              = false
-      @marked_for_destruction = false
-      @new_record             = true
+      @aggregation_cache       = {}
+      @association_cache       = {}
+      @attributes_cache        = {}
+      @previously_changed      = {}
+      @changed_attributes      = {}
+      @readonly                = false
+      @destroyed               = false
+      @marked_for_destruction  = false
+      @new_record              = true
+      @mass_assignment_options = nil
     end
   end
 end