merge revision(s) 54c4694994cc3bcfea9058b22ba3e68af6aaf740: [Backport #21961]

	marshal.c: properly freeze linked strings

2 files changed, 17 insertions, 0 deletions

diff --git a/marshal.c b/marshal.c
index 8cd4dc6079..a94d90fbbe 100644
--- a/marshal.c
+++ b/marshal.c
@@ -1879,6 +1879,9 @@ r_object_for(struct load_arg *arg, bool partial, int *ivp, VALUE extmod, int typ
         }
         v = (VALUE)link;
         if (!st_lookup(arg->partial_objects, (st_data_t)v, &link)) {
+            if (arg->freeze && RB_TYPE_P(v, T_STRING)) {
+                v = rb_str_to_interned_str(v);
+            }
             v = r_post_proc(v, arg);
         }
         break;
diff --git a/test/ruby/test_marshal.rb b/test/ruby/test_marshal.rb
index eb66994801..05d3ceb60a 100644
--- a/test/ruby/test_marshal.rb
+++ b/test/ruby/test_marshal.rb
@@ -1002,5 +1002,19 @@ class TestMarshal < Test::Unit::TestCase
       refute_predicate Object, :frozen?
       refute_predicate Kernel, :frozen?
     end
+
+    def test_linked_strings_are_frozen
+      str = "test"
+      str.instance_variable_set(:@self, str)
+      source = [str, str]
+
+      objects = Marshal.load(encode(source), freeze: true)
+      assert_predicate objects[0], :frozen?
+      assert_predicate objects[1], :frozen?
+      assert_same objects[0], objects[1]
+      assert_same objects[0], objects[0].instance_variable_get(:@self)
+      assert_same objects[1], objects[1].instance_variable_get(:@self)
+      assert_same objects[0].instance_variable_get(:@self), objects[1].instance_variable_get(:@self)
+    end
   end
 end