Fix GH-20840: crash on nested object with var_dump().

mitigate it with stack check limit.

Author: devnexen

ext/standard/var.c

@@ -39,6 +39,17 @@ struct php_serialize_data {
 
 #define COMMON (is_ref ? "&" : "")
 
+static zend_always_inline bool php_serialize_check_stack_limit(void)
+{
+#ifdef ZEND_CHECK_STACK_LIMIT
+	if (UNEXPECTED(zend_call_stack_overflowed(EG(stack_limit)))) {
+		zend_call_stack_size_error();
+		return true;
+	}
+#endif
+	return false;
+}
+
 static void php_array_element_dump(zval *zv, zend_ulong index, zend_string *key, int level) /* {{{ */
 {
 	if (key == NULL) { /* numeric key */
@@ -56,6 +67,10 @@ static void php_object_property_dump(zend_property_info *prop_info, zval *zv, ze
 {
 	const char *prop_name, *class_name;
 
+	if (UNEXPECTED(php_serialize_check_stack_limit())) {
+		return;
+	}
+
 	if (key == NULL) { /* numeric key */
 		php_printf("%*c[" ZEND_LONG_FMT "]=>\n", level + 1, ' ', index);
 	} else { /* string key */
@@ -1029,17 +1044,6 @@ static void php_var_serialize_class(smart_str *buf, zval *struc, HashTable *ht,
 }
 /* }}} */
 
-static zend_always_inline bool php_serialize_check_stack_limit(void)
-{
-#ifdef ZEND_CHECK_STACK_LIMIT
-	if (UNEXPECTED(zend_call_stack_overflowed(EG(stack_limit)))) {
-		zend_call_stack_size_error();
-		return true;
-	}
-#endif
-	return false;
-}
-
 static void php_var_serialize_intern(smart_str *buf, zval *struc, php_serialize_data_t var_hash, bool in_rcn_array, bool is_root) /* {{{ */
 {
 	zend_long var_already;