<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head><meta http-equiv="content-type" content="text/html; charset=utf-8" />
<title>[200062] trunk/Source/WebCore</title>
</head>
<body>
<style type="text/css"><!--
#msg dl.meta { border: 1px #006 solid; background: #369; padding: 6px; color: #fff; }
#msg dl.meta dt { float: left; width: 6em; font-weight: bold; }
#msg dt:after { content:':';}
#msg dl, #msg dt, #msg ul, #msg li, #header, #footer, #logmsg { font-family: verdana,arial,helvetica,sans-serif; font-size: 10pt; }
#msg dl a { font-weight: bold}
#msg dl a:link { color:#fc3; }
#msg dl a:active { color:#ff0; }
#msg dl a:visited { color:#cc6; }
h3 { font-family: verdana,arial,helvetica,sans-serif; font-size: 10pt; font-weight: bold; }
#msg pre { overflow: auto; background: #ffc; border: 1px #fa0 solid; padding: 6px; }
#logmsg { background: #ffc; border: 1px #fa0 solid; padding: 1em 1em 0 1em; }
#logmsg p, #logmsg pre, #logmsg blockquote { margin: 0 0 1em 0; }
#logmsg p, #logmsg li, #logmsg dt, #logmsg dd { line-height: 14pt; }
#logmsg h1, #logmsg h2, #logmsg h3, #logmsg h4, #logmsg h5, #logmsg h6 { margin: .5em 0; }
#logmsg h1:first-child, #logmsg h2:first-child, #logmsg h3:first-child, #logmsg h4:first-child, #logmsg h5:first-child, #logmsg h6:first-child { margin-top: 0; }
#logmsg ul, #logmsg ol { padding: 0; list-style-position: inside; margin: 0 0 0 1em; }
#logmsg ul { text-indent: -1em; padding-left: 1em; }#logmsg ol { text-indent: -1.5em; padding-left: 1.5em; }
#logmsg > ul, #logmsg > ol { margin: 0 0 1em 0; }
#logmsg pre { background: #eee; padding: 1em; }
#logmsg blockquote { border: 1px solid #fa0; border-left-width: 10px; padding: 1em 1em 0 1em; background: white;}
#logmsg dl { margin: 0; }
#logmsg dt { font-weight: bold; }
#logmsg dd { margin: 0; padding: 0 0 0.5em 0; }
#logmsg dd:before { content:'\00bb';}
#logmsg table { border-spacing: 0px; border-collapse: collapse; border-top: 4px solid #fa0; border-bottom: 1px solid #fa0; background: #fff; }
#logmsg table th { text-align: left; font-weight: normal; padding: 0.2em 0.5em; border-top: 1px dotted #fa0; }
#logmsg table td { text-align: right; border-top: 1px dotted #fa0; padding: 0.2em 0.5em; }
#logmsg table thead th { text-align: center; border-bottom: 1px solid #fa0; }
#logmsg table th.Corner { text-align: left; }
#logmsg hr { border: none 0; border-top: 2px dashed #fa0; height: 1px; }
#header, #footer { color: #fff; background: #636; border: 1px #300 solid; padding: 6px; }
#patch { width: 100%; }
#patch h4 {font-family: verdana,arial,helvetica,sans-serif;font-size:10pt;padding:8px;background:#369;color:#fff;margin:0;}
#patch .propset h4, #patch .binary h4 {margin:0;}
#patch pre {padding:0;line-height:1.2em;margin:0;}
#patch .diff {width:100%;background:#eee;padding: 0 0 10px 0;overflow:auto;}
#patch .propset .diff, #patch .binary .diff {padding:10px 0;}
#patch span {display:block;padding:0 10px;}
#patch .modfile, #patch .addfile, #patch .delfile, #patch .propset, #patch .binary, #patch .copfile {border:1px solid #ccc;margin:10px 0;}
#patch ins {background:#dfd;text-decoration:none;display:block;padding:0 10px;}
#patch del {background:#fdd;text-decoration:none;display:block;padding:0 10px;}
#patch .lines, .info {color:#888;background:#fff;}
--></style>
<div id="msg">
<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/200062">200062</a></dd>
<dt>Author</dt> <dd>cdumez@apple.com</dd>
<dt>Date</dt> <dd>2016-04-25 17:13:03 -0700 (Mon, 25 Apr 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>Crash under WebCore::MutationObserver::deliverAllMutations()
https://bugs.webkit.org/show_bug.cgi?id=156997
<rdar://problem/16542323>
Reviewed by Ryosuke Niwa.
The crash traces indicate that we may derefence a null pointer when
dereferencing MutationCallback::scriptExecutationContext() in
MutationObserver::canDeliver(). This can happen when the script
execution context gets destroyed as a JSMutationCallback is an
ActiveDOMObject, which is a ContextDestructionObserver.
This patch refactors the code so that MutationObserver::canDeliver()
now simply asks JSMutationCallback if it can invoke its callback.
JSMutationCallback makes this decision using
ActiveDOMCallback::canInvokeCallback() which does a proper null
check of the ScriptExecutationContext. This avoids some code
duplication and fixes the crash.
* bindings/js/JSMutationCallback.h:
* dom/MutationCallback.h:
* dom/MutationObserver.cpp:
(WebCore::MutationObserver::canDeliver):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCorebindingsjsJSMutationCallbackh">trunk/Source/WebCore/bindings/js/JSMutationCallback.h</a></li>
<li><a href="#trunkSourceWebCoredomMutationCallbackh">trunk/Source/WebCore/dom/MutationCallback.h</a></li>
<li><a href="#trunkSourceWebCoredomMutationObservercpp">trunk/Source/WebCore/dom/MutationObserver.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (200061 => 200062)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog 2016-04-26 00:12:22 UTC (rev 200061)
+++ trunk/Source/WebCore/ChangeLog 2016-04-26 00:13:03 UTC (rev 200062)
</span><span class="lines">@@ -1,3 +1,29 @@
</span><ins>+2016-04-25 Chris Dumez <cdumez@apple.com>
+
+ Crash under WebCore::MutationObserver::deliverAllMutations()
+ https://bugs.webkit.org/show_bug.cgi?id=156997
+ <rdar://problem/16542323>
+
+ Reviewed by Ryosuke Niwa.
+
+ The crash traces indicate that we may derefence a null pointer when
+ dereferencing MutationCallback::scriptExecutationContext() in
+ MutationObserver::canDeliver(). This can happen when the script
+ execution context gets destroyed as a JSMutationCallback is an
+ ActiveDOMObject, which is a ContextDestructionObserver.
+
+ This patch refactors the code so that MutationObserver::canDeliver()
+ now simply asks JSMutationCallback if it can invoke its callback.
+ JSMutationCallback makes this decision using
+ ActiveDOMCallback::canInvokeCallback() which does a proper null
+ check of the ScriptExecutationContext. This avoids some code
+ duplication and fixes the crash.
+
+ * bindings/js/JSMutationCallback.h:
+ * dom/MutationCallback.h:
+ * dom/MutationObserver.cpp:
+ (WebCore::MutationObserver::canDeliver):
+
</ins><span class="cx"> 2016-04-25 Brady Eidson <beidson@apple.com>
</span><span class="cx">
</span><span class="cx"> Fix a flaky test after r200032
</span></span></pre></div>
<a id="trunkSourceWebCorebindingsjsJSMutationCallbackh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/bindings/js/JSMutationCallback.h (200061 => 200062)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/bindings/js/JSMutationCallback.h 2016-04-26 00:12:22 UTC (rev 200061)
+++ trunk/Source/WebCore/bindings/js/JSMutationCallback.h 2016-04-26 00:13:03 UTC (rev 200062)
</span><span class="lines">@@ -37,7 +37,7 @@
</span><span class="cx">
</span><span class="cx"> class JSDOMGlobalObject;
</span><span class="cx">
</span><del>-class JSMutationCallback : public MutationCallback, public ActiveDOMCallback {
</del><ins>+class JSMutationCallback final : public MutationCallback, public ActiveDOMCallback {
</ins><span class="cx"> public:
</span><span class="cx"> static Ref<JSMutationCallback> create(JSC::JSObject* callback, JSDOMGlobalObject* globalObject)
</span><span class="cx"> {
</span><span class="lines">@@ -47,9 +47,8 @@
</span><span class="cx"> virtual ~JSMutationCallback();
</span><span class="cx">
</span><span class="cx"> void call(const Vector<Ref<MutationRecord>>&, MutationObserver*) override;
</span><ins>+ bool canInvokeCallback() const override { return ActiveDOMCallback::canInvokeCallback(); }
</ins><span class="cx">
</span><del>- ScriptExecutionContext* scriptExecutionContext() const override { return ContextDestructionObserver::scriptExecutionContext(); }
-
</del><span class="cx"> private:
</span><span class="cx"> JSMutationCallback(JSC::JSObject* callback, JSDOMGlobalObject*);
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceWebCoredomMutationCallbackh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/dom/MutationCallback.h (200061 => 200062)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/dom/MutationCallback.h 2016-04-26 00:12:22 UTC (rev 200061)
+++ trunk/Source/WebCore/dom/MutationCallback.h 2016-04-26 00:13:03 UTC (rev 200062)
</span><span class="lines">@@ -45,7 +45,7 @@
</span><span class="cx"> virtual ~MutationCallback() { }
</span><span class="cx">
</span><span class="cx"> virtual void call(const Vector<Ref<MutationRecord>>&, MutationObserver*) = 0;
</span><del>- virtual ScriptExecutionContext* scriptExecutionContext() const = 0;
</del><ins>+ virtual bool canInvokeCallback() const = 0;
</ins><span class="cx"> };
</span><span class="cx">
</span><span class="cx"> }
</span></span></pre></div>
<a id="trunkSourceWebCoredomMutationObservercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/dom/MutationObserver.cpp (200061 => 200062)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/dom/MutationObserver.cpp 2016-04-26 00:12:22 UTC (rev 200061)
+++ trunk/Source/WebCore/dom/MutationObserver.cpp 2016-04-26 00:13:03 UTC (rev 200062)
</span><span class="lines">@@ -211,7 +211,7 @@
</span><span class="cx">
</span><span class="cx"> bool MutationObserver::canDeliver()
</span><span class="cx"> {
</span><del>- return !m_callback->scriptExecutionContext()->activeDOMObjectsAreSuspended();
</del><ins>+ return m_callback->canInvokeCallback();
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> void MutationObserver::deliver()
</span></span></pre>
</div>
</div>
</body>
</html>