Return nil when argument to ObjectSpace.internal_class_of is T_IMEMO

The added test case crashes the interpreter because it makes
ObjectSpace.internal_class_of return the second VALUE slot of an AST
imemo object. The second VALUE slot of `struct rb_ast_struct` is
not a VALUE and not a pointer to a Ruby object.

1 files changed, 7 insertions, 2 deletions

diff --git a/ext/objspace/objspace.c b/ext/objspace/objspace.c
index 262640d30c..3bfb79dc1f 100644
--- a/ext/objspace/objspace.c
+++ b/ext/objspace/objspace.c
@@ -895,8 +895,13 @@ objspace_internal_class_of(VALUE self, VALUE obj)
 	obj = (VALUE)DATA_PTR(obj);
     }
 
-    klass = CLASS_OF(obj);
-    return wrap_klass_iow(klass);
+    if (RB_TYPE_P(obj, T_IMEMO)) {
+        return Qnil;
+    }
+    else {
+        klass = CLASS_OF(obj);
+        return wrap_klass_iow(klass);
+    }
 }
 
 /*