Fix #81351: xml_parse may fail, but has no error code

The fix for bug #73151[1] cured the symptoms, but not the root cause,
namely xmlParse() must not be called recursively.  Since that bugfix
also messed up the error handling, we basically revert it (but also
simplify the return), and then prevent calling the parser recursively.

[1] <php@f2a8a8c>

Co-authored-by: Nikita Popov <[email protected]>

Closes phpGH-7363.

Author: cmb69

Diff for: NEWS

@@ -7,6 +7,9 @@ PHP                                                                        NEWS
   . Fixed bug #81346 (Non-seekable streams don't update position after write).
     (cmb)
 
+- XML:
+  . Fixed bug #81351 (xml_parse may fail, but has no error code). (cmb, Nikita)
+
 26 Aug 2021, PHP 7.4.23
 
 - Core:

Diff for: ext/xml/compat.c

@@ -565,16 +565,8 @@ XML_Parse(XML_Parser parser, const XML_Char *data, int data_len, int is_final)
 {
 	int error;
 
-	if (parser->parser->lastError.level >= XML_ERR_WARNING) {
-		return 0;
-	}
-
 	error = xmlParseChunk(parser->parser, (char *) data, data_len, is_final);
-	if (error) {
-		return 0;
-	} else {
-		return 1;
-	}
+	return !error && parser->parser->lastError.level <= XML_ERR_WARNING;
 }
 
 PHP_XML_API int

Diff for: ext/xml/tests/bug73135.phpt

@@ -21,6 +21,10 @@ HERE;
     xml_parse($parser, $xml);
 ?>
 --EXPECTF--
+Warning: xml_parse(): Parser must not be called recursively in %s%ebug73135.php on line %d
+
+Warning: xml_parse(): Parser must not be called recursively in %s%ebug73135.php on line %d
+
 Warning: xml_parse(): Unable to call handler ahihi() in %s%ebug73135.php on line %d
 
 Warning: xml_parse(): Unable to call handler ahihi() in %s%ebug73135.php on line %d

Diff for: ext/xml/tests/bug81351.phpt

@@ -0,0 +1,28 @@
+--TEST--
+Bug #81351 (xml_parse may fail, but has no error code)
+--SKIPIF--
+<?php
+if (!extension_loaded('xml')) die("skip xml extension not available");
+?>
+--FILE--
+<?php
+$xml = <<<XML
+<?xml version="1.0" encoding="utf-8"?>
+<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
+ <soap:Body>
+  <X xmlns="example.org">
+XML;
+
+$parser = xml_parser_create_ns('UTF-8');
+$success = xml_parse($parser, $xml, false);
+$code = xml_get_error_code($parser);
+$error = xml_error_string($code);
+echo "xml_parse returned $success, xml_get_error_code = $code, xml_error_string = $error\r\n";
+$success = xml_parse($parser, 'Y>', true);
+$code = xml_get_error_code($parser);
+$error = xml_error_string($code);
+echo "xml_parse returned $success, xml_get_error_code = $code, xml_error_string = $error\r\n";
+?>
+--EXPECT--
+xml_parse returned 1, xml_get_error_code = 0, xml_error_string = No error
+xml_parse returned 0, xml_get_error_code = 5, xml_error_string = Invalid document end

Diff for: ext/xml/xml.c

@@ -1416,6 +1416,10 @@ PHP_FUNCTION(xml_parse)
 		RETURN_FALSE;
 	}
 
+	if (parser->isparsing) {
+		php_error_docref(NULL, E_WARNING, "Parser must not be called recursively");
+		RETURN_FALSE;
+	}
 	parser->isparsing = 1;
 	ret = XML_Parse(parser->parser, (XML_Char*)data, data_len, isFinal);
 	parser->isparsing = 0;
@@ -1467,6 +1471,10 @@ PHP_FUNCTION(xml_parse_into_struct)
 	XML_SetElementHandler(parser->parser, _xml_startElementHandler, _xml_endElementHandler);
 	XML_SetCharacterDataHandler(parser->parser, _xml_characterDataHandler);
 
+	if (parser->isparsing) {
+		php_error_docref(NULL, E_WARNING, "Parser must not be called recursively");
+		RETURN_FALSE;
+	}
 	parser->isparsing = 1;
 	ret = XML_Parse(parser->parser, (XML_Char*)data, data_len, 1);
 	parser->isparsing = 0;