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Fix bug #79451: Using DOMDocument->replaceChild on doctype causes double free #9201

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Fix bug #79451: Using DOMDocument->replaceChild on doctype causes double free #9201

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95e231d
fix bug #79451
NathanFreeman Jul 30, 2022
0f6831e
fix type
NathanFreeman Jul 30, 2022
e55b067
use bool
NathanFreeman Aug 4, 2022
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21 changes: 15 additions & 6 deletions ext/dom/node.c
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
#endif

#include "php.h"

#if defined(HAVE_LIBXML) && defined(HAVE_DOM)
#include "php_dom.h"

Expand Down Expand Up @@ -1000,7 +1001,7 @@ PHP_METHOD(DOMNode, replaceChild)
zval *id, *newnode, *oldnode;
xmlNodePtr children, newchild, oldchild, nodep;
dom_object *intern, *newchildobj, *oldchildobj;
int foundoldchild = 0, stricterror;
int foundoldchild = 0, stricterror, replacedoctype = 0;
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Suggested change
int foundoldchild = 0, stricterror, replacedoctype = 0;
int foundoldchild = 0, stricterror;
bool replacedoctype = false;

PHP 8.0 uses C99 so might as well use bool :)

But even better would to move into the branch where it is only relevant.


int ret;

Expand Down Expand Up @@ -1063,13 +1064,21 @@ PHP_METHOD(DOMNode, replaceChild)
dom_reconcile_ns(nodep->doc, newchild);
}
} else if (oldchild != newchild) {
xmlDtdPtr intSubset = xmlGetIntSubset(nodep->doc);
replacedoctype = (intSubset == (xmlDtd *) oldchild);

if (newchild->doc == NULL && nodep->doc != NULL) {
xmlSetTreeDoc(newchild, nodep->doc);
newchildobj->document = intern->document;
php_libxml_increment_doc_ref((php_libxml_node_object *)newchildobj, NULL);
}

xmlReplaceNode(oldchild, newchild);
dom_reconcile_ns(nodep->doc, newchild);

if (replacedoctype) {
nodep->doc->intSubset = (xmlDtd *) newchild;
}
}
DOM_RET_OBJ(oldchild, &ret, intern);
return;
Expand Down Expand Up @@ -1668,7 +1677,7 @@ static void dom_canonicalization(INTERNAL_FUNCTION_PARAMETERS, int mode) /* {{{
buf = xmlAllocOutputBuffer(NULL);
}

if (buf != NULL) {
if (buf != NULL) {
ret = xmlC14NDocSaveTo(docp, nodeset, exclusive, inclusive_ns_prefixes,
with_comments, buf);
}
Expand All @@ -1683,9 +1692,9 @@ static void dom_canonicalization(INTERNAL_FUNCTION_PARAMETERS, int mode) /* {{{
xmlXPathFreeContext(ctxp);
}

if (buf == NULL || ret < 0) {
RETVAL_FALSE;
} else {
if (buf == NULL || ret < 0) {
RETVAL_FALSE;
} else {
if (mode == 0) {
#ifdef LIBXML2_NEW_BUFFER
ret = xmlOutputBufferGetSize(buf);
Expand All @@ -1702,7 +1711,7 @@ static void dom_canonicalization(INTERNAL_FUNCTION_PARAMETERS, int mode) /* {{{
RETVAL_EMPTY_STRING();
}
}
}
}

if (buf) {
int bytes;
Expand Down
20 changes: 20 additions & 0 deletions ext/dom/tests/bug79451.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,20 @@
--TEST--
Bug #79451 (Using DOMDocument->replaceChild on doctype causes double free)
--SKIPIF--
<?php require_once('skipif.inc'); ?>
--FILE--
<?php
$dom = new \DOMDocument();
$dom->loadHTML("<!DOCTYPE html><p>hello</p>");
$impl = new \DOMImplementation();
$dt = $impl->createDocumentType("html_replace", "", "");
$dom->replaceChild($dt, $dom->doctype);

var_dump($dom->doctype->name);
echo $dom->saveXML();
?>
--EXPECTF--
string(12) "html_replace"
<?xml version="1.0" standalone="yes"?>
<!DOCTYPE html_replace>
<html><body><p>hello</p></body></html>