Fix GH-15551: Segmentation fault (access null pointer) in ext/dom/xml_common.h

Closes GH-15556.

NEWS

@@ -8,6 +8,10 @@ PHP                                                                        NEWS
   . Fixed bug GH-15515 (Configure error grep illegal option q). (Peter Kokot)
   . Fixed bug GH-15514 (Configure error: genif.sh: syntax error). (Peter Kokot)
 
+- DOM:
+  . Fixed bug GH-15551 (Segmentation fault (access null pointer) in
+    ext/dom/xml_common.h). (nielsdos)
+
 - MySQLnd:
   . Fixed bug GH-15432 (Heap corruption when querying a vector). (cmb,
     Kamil Tekiela)

ext/dom/dom_iterators.c

@@ -184,13 +184,15 @@ static void php_dom_iterator_move_forward(zend_object_iterator *iter) /* {{{ */
 	bool do_curobj_undef = 1;
 
 	php_dom_iterator *iterator = (php_dom_iterator *)iter;
+	if (Z_ISUNDEF(iterator->curobj)) {
+		return;
+	}
 
+	intern = Z_DOMOBJ_P(&iterator->curobj);
 	object = &iterator->intern.data;
 	nnmap = Z_DOMOBJ_P(object);
 	objmap = (dom_nnodemap_object *)nnmap->ptr;
 
-	intern = Z_DOMOBJ_P(&iterator->curobj);
-
 	if (intern != NULL && intern->ptr != NULL) {
 		if (objmap->nodetype != XML_ENTITY_NODE &&
 			objmap->nodetype != XML_NOTATION_NODE) {

ext/dom/tests/gh15551.phpt

@@ -0,0 +1,14 @@
+--TEST--
+GH-15551 (Segmentation fault (access null pointer) in ext/dom/xml_common.h)
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+$fragment = new DOMDocumentFragment();
+$nodes = $fragment->childNodes;
+$iter = $nodes->getIterator();
+$iter->next();
+var_dump($iter->valid());
+?>
+--EXPECT--
+bool(false)