From 20f83d963b214e3bd7a226fdc2e3e6e70388c58a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?D=C3=A1niel=20B=C3=A1tyai?= <daniel.batyai@h-lab.eu>
Date: Tue, 28 Jul 2020 10:47:37 +0200
Subject: [PATCH] Fix a use-after-free in RegExp.prototype.compile (#4068)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Fixes #4056.

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai daniel.batyai@h-lab.eu
---
 .../ecma-builtin-regexp-prototype.c           |  9 ++++---
 tests/jerry/regression-test-issue-4056.js     | 26 +++++++++++++++++++
 2 files changed, 31 insertions(+), 4 deletions(-)
 create mode 100644 tests/jerry/regression-test-issue-4056.js

diff --git a/jerry-core/ecma/builtin-objects/ecma-builtin-regexp-prototype.c b/jerry-core/ecma/builtin-objects/ecma-builtin-regexp-prototype.c
index d01fca15f..eb81b00c9 100644
--- a/jerry-core/ecma/builtin-objects/ecma-builtin-regexp-prototype.c
+++ b/jerry-core/ecma/builtin-objects/ecma-builtin-regexp-prototype.c
@@ -301,6 +301,7 @@ ecma_builtin_regexp_prototype_compile (ecma_value_t this_arg, /**< this */
   }
 
   JERRY_ASSERT (ecma_is_value_true (status));
+  ecma_value_t ret_value;
 
   if (ecma_object_is_regexp_object (pattern_arg))
   {
@@ -314,13 +315,13 @@ ecma_builtin_regexp_prototype_compile (ecma_value_t this_arg, /**< this */
                                                                 pattern_obj_p->u.class_prop.u.value);
 
     ecma_ref_object (this_obj_p);
-    /* ecma_op_create_regexp_from_bytecode will never throw an error while re-initalizing the regexp object, so we
-     * can deref the old bytecode without leaving a dangling pointer. */
+    ret_value = ecma_op_create_regexp_from_bytecode (this_obj_p, bc_p);
+
     ecma_bytecode_deref ((ecma_compiled_code_t *) old_bc_p);
-    return ecma_op_create_regexp_from_bytecode (this_obj_p, bc_p);
+    return ret_value;
   }
 
-  ecma_value_t ret_value = ecma_op_create_regexp_from_pattern (this_obj_p, pattern_arg, flags_arg);
+  ret_value = ecma_op_create_regexp_from_pattern (this_obj_p, pattern_arg, flags_arg);
 
   if (!ECMA_IS_VALUE_ERROR (ret_value))
   {
diff --git a/tests/jerry/regression-test-issue-4056.js b/tests/jerry/regression-test-issue-4056.js
new file mode 100644
index 000000000..e26bd2704
--- /dev/null
+++ b/tests/jerry/regression-test-issue-4056.js
@@ -0,0 +1,26 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+var r = new RegExp('a');
+
+new RegExp('1');
+new RegExp('2');
+new RegExp('3');
+new RegExp('4');
+new RegExp('5');
+new RegExp('6');
+new RegExp('7');
+new RegExp('8');
+
+r.compile(r);