From: Christoph M. Becker <cmbecker69@gmx.de>
Date: Fri, 31 Jul 2020 07:12:22 +0000 (+0200)
Subject: Fix #79919: Stack use-after-scope in define()
X-Git-Tag: php-7.3.22RC1~22
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=1e0bc6e30f9fb327cd06383c8290a8afab1e484d;p=php

Fix #79919: Stack use-after-scope in define()

Instead of the temporary `rv`, we use the `val_free` which is there for
this purpose.
---

diff --git a/NEWS b/NEWS
index 1a5d787307..ebdb9601ee 100644
--- a/NEWS
+++ b/NEWS
@@ -8,6 +8,7 @@ PHP                                                                        NEWS
   . Fixed bug #79806 (realpath() erroneously resolves link to link). (cmb)
   . Fixed bug #79895 (PHP_CHECK_GCC_ARG does not allow flags with equal sign).
     (Santiago M. Mola)
+  . Fixed bug #79919 (Stack use-after-scope in define()). (cmb)
 
 - LDAP:
   . Fixed memory leaks. (ptomulik)
diff --git a/Zend/tests/bug79919.phpt b/Zend/tests/bug79919.phpt
new file mode 100644
index 0000000000..c135722675
--- /dev/null
+++ b/Zend/tests/bug79919.phpt
@@ -0,0 +1,14 @@
+--TEST--
+Bug #79919 (Stack use-after-scope in define())
+--SKIPIF--
+<?php
+if (!extension_loaded('simplexml')) die('skip simplexml extension not available');
+?>
+--FILE--
+<?php
+$b = error_log(0);
+$b = simplexml_load_string('<xml/>', null, $b);
+define(0, $b);
+?>
+--EXPECT--
+0
diff --git a/Zend/zend_builtin_functions.c b/Zend/zend_builtin_functions.c
index bc3649a622..468a7c3446 100644
--- a/Zend/zend_builtin_functions.c
+++ b/Zend/zend_builtin_functions.c
@@ -882,9 +882,7 @@ repeat:
 		case IS_OBJECT:
 			if (Z_TYPE(val_free) == IS_UNDEF) {
 				if (Z_OBJ_HT_P(val)->get) {
-					zval rv;
-					val = Z_OBJ_HT_P(val)->get(val, &rv);
-					ZVAL_COPY_VALUE(&val_free, val);
+					val = Z_OBJ_HT_P(val)->get(val, &val_free);
 					goto repeat;
 				} else if (Z_OBJ_HT_P(val)->cast_object) {
 					if (Z_OBJ_HT_P(val)->cast_object(val, &val_free, IS_STRING) == SUCCESS) {