ext/dom: fix use-after-free with XPath callback returning foreign-document node.

devnexen · devnexen · commit a97217d3693c · 2026-07-02T20:10:35.000+01:00
Fix GH-22554 A PHP XPath callback that returns a node belonging to a document created inside the callback (e.g. $d->documentElement of a throwaway DOMDocument) parks that node in the DOMXPath node_list to keep it alive. When a sibling callback consumes a node navigated into that foreign document, the proxy object was created with the DOMXPath's own dom as parent, so it took a reference on the wrong document and none on the foreign one. On teardown the foreign document could be freed while the proxy still referenced it. Route the proxy factory through dom_xpath_intern_for_doc() so the created object shares the ref_obj of the node's actual document, mirroring the query-result path.
diff --git a/ext/dom/tests/gh22554.phpt b/ext/dom/tests/gh22554.phpt
@@ -0,0 +1,36 @@
+--TEST--
+GH-22554 (Use-after-free when an XPath callback returns a node from a document created inside the callback)
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$doc = new DOMDocument;
+$doc->loadXML('<root/>');
+
+$xp = new DOMXPath($doc);
+$xp->registerNamespace('my', 'my.ns');
+
+$xp->registerPHPFunctionNS('my.ns', 'include', function () {
+    $d = new DOMDocument;
+    $d->loadXML('<r><uaf/></r>');
+
+    return $d->documentElement;
+});
+
+$xp->registerPHPFunctionNS('my.ns', 'process', function ($arg) {
+    echo "process arg: ", get_class($arg[0]), " ", $arg[0]->nodeName, "\n";
+    return 'x';
+});
+
+$result = $xp->query('my:process(my:include()/uaf)');
+var_dump($result->length);
+unset($xp);
+
+echo "Done\n";
+
+?>
+--EXPECT--
+process arg: DOMElement uaf
+int(0)
+Done
diff --git a/ext/dom/xpath.c b/ext/dom/xpath.c
@@ -77,7 +77,8 @@ static void dom_xpath_proxy_factory(xmlNodePtr node, zval *child, dom_object *in
 
 	ZEND_ASSERT(node->type != XML_NAMESPACE_DECL);
 
-	php_dom_create_object(node, child, intern);
+	dom_xpath_object *xobj = php_xpath_obj_from_obj(&intern->std);
+	php_dom_create_object(node, child, dom_xpath_intern_for_doc(xobj, node->doc));
 }
 
 static dom_xpath_object *dom_xpath_ext_fetch_intern(xmlXPathParserContextPtr ctxt)

Original file line number	Diff line number	Diff line change
`@@ -77,7 +77,8 @@ static void dom_xpath_proxy_factory(xmlNodePtr node, zval child, dom_object in`
`77`	`77`
`78`	`78`	`ZEND_ASSERT(node->type != XML_NAMESPACE_DECL);`
`79`	`79`
`80`		`- php_dom_create_object(node, child, intern);`
	`80`	`+ dom_xpath_object *xobj = php_xpath_obj_from_obj(&intern->std);`
	`81`	`+ php_dom_create_object(node, child, dom_xpath_intern_for_doc(xobj, node->doc));`
`81`	`82`	`}`
`82`	`83`
`83`	`84`	`static dom_xpath_object *dom_xpath_ext_fetch_intern(xmlXPathParserContextPtr ctxt)`