use zend_string_safe_alloc

Author: LamentXU123

Zend/zend_string.c

@@ -475,8 +475,8 @@ ZEND_API zend_string *zend_string_concat2(
 		const char *str1, size_t str1_len,
 		const char *str2, size_t str2_len)
 {
-	size_t len = zend_safe_address_guarded(1, str1_len, str2_len);
-	zend_string *res = zend_string_alloc(len, 0);
+	size_t len = str1_len + str2_len;
+	zend_string *res = zend_string_safe_alloc(len, 0);
 
 	char *p = ZSTR_VAL(res);
 	p = zend_mempcpy(p, str1, str1_len);