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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/184190">184190</a></dd>
<dt>Author</dt> <dd>carlosgc@webkit.org</dd>
<dt>Date</dt> <dd>2015-05-12 02:25:39 -0700 (Tue, 12 May 2015)</dd>
</dl>

<h3>Log Message</h3>
<pre>Merge <a href="http://trac.webkit.org/projects/webkit/changeset/184104">r184104</a> - WebContent crash under com.apple.WebCore: WebCore::WebKitCSSResourceValue::isCSSValueNone const + 6
https://bugs.webkit.org/show_bug.cgi?id=144870
rdar://problem/20727702

Reviewed by Simon Fraser.

No repro but we are seeing null pointer crashes like this:

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   com.apple.WebCore   0x00007fff92da5706 WebCore::WebKitCSSResourceValue::isCSSValueNone() const + 6
1   com.apple.WebCore   0x00007fff93382b48 WebCore::MaskImageOperation::isCSSValueNone() const + 24
2   com.apple.WebCore   0x00007fff92e0475e WebCore::FillLayer::hasNonEmptyMaskImage() const + 30

* platform/graphics/MaskImageOperation.cpp:
(WebCore::MaskImageOperation::MaskImageOperation):
(WebCore::MaskImageOperation::isCSSValueNone):

    This would crash like this if both m_styleImage and m_cssMaskImageValue are null.
    There are no obvious guarantees that this doesn't happen. Two of the constructor variants allow it
    and there is setImage which may turn m_styleImage null later too.

    Fix by making null m_cssMaskImageValue always signify CSSValueNone.

(WebCore::MaskImageOperation::cssValue):</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#releasesWebKitGTKwebkit28SourceWebCoreChangeLog">releases/WebKitGTK/webkit-2.8/Source/WebCore/ChangeLog</a></li>
<li><a href="#releasesWebKitGTKwebkit28SourceWebCoreplatformgraphicsMaskImageOperationcpp">releases/WebKitGTK/webkit-2.8/Source/WebCore/platform/graphics/MaskImageOperation.cpp</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="releasesWebKitGTKwebkit28SourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.8/Source/WebCore/ChangeLog (184189 => 184190)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.8/Source/WebCore/ChangeLog        2015-05-12 09:24:49 UTC (rev 184189)
+++ releases/WebKitGTK/webkit-2.8/Source/WebCore/ChangeLog        2015-05-12 09:25:39 UTC (rev 184190)
</span><span class="lines">@@ -1,3 +1,30 @@
</span><ins>+2015-05-11  Antti Koivisto  &lt;antti@apple.com&gt;
+
+        WebContent crash under com.apple.WebCore: WebCore::WebKitCSSResourceValue::isCSSValueNone const + 6
+        https://bugs.webkit.org/show_bug.cgi?id=144870
+        rdar://problem/20727702
+
+        Reviewed by Simon Fraser.
+
+        No repro but we are seeing null pointer crashes like this:
+
+        Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
+        0   com.apple.WebCore   0x00007fff92da5706 WebCore::WebKitCSSResourceValue::isCSSValueNone() const + 6
+        1   com.apple.WebCore   0x00007fff93382b48 WebCore::MaskImageOperation::isCSSValueNone() const + 24
+        2   com.apple.WebCore   0x00007fff92e0475e WebCore::FillLayer::hasNonEmptyMaskImage() const + 30
+
+        * platform/graphics/MaskImageOperation.cpp:
+        (WebCore::MaskImageOperation::MaskImageOperation):
+        (WebCore::MaskImageOperation::isCSSValueNone):
+
+            This would crash like this if both m_styleImage and m_cssMaskImageValue are null.
+            There are no obvious guarantees that this doesn't happen. Two of the constructor variants allow it
+            and there is setImage which may turn m_styleImage null later too.
+
+            Fix by making null m_cssMaskImageValue always signify CSSValueNone.
+
+        (WebCore::MaskImageOperation::cssValue):
+
</ins><span class="cx"> 2015-05-11  Chris Fleizach  &lt;cfleizach@apple.com&gt;
</span><span class="cx"> 
</span><span class="cx">         AX: Crash at WebCore::AccessibilityMenuList::addChildren()
</span></span></pre></div>
<a id="releasesWebKitGTKwebkit28SourceWebCoreplatformgraphicsMaskImageOperationcpp"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.8/Source/WebCore/platform/graphics/MaskImageOperation.cpp (184189 => 184190)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.8/Source/WebCore/platform/graphics/MaskImageOperation.cpp        2015-05-12 09:24:49 UTC (rev 184189)
+++ releases/WebKitGTK/webkit-2.8/Source/WebCore/platform/graphics/MaskImageOperation.cpp        2015-05-12 09:25:39 UTC (rev 184190)
</span><span class="lines">@@ -27,6 +27,7 @@
</span><span class="cx"> #include &quot;config.h&quot;
</span><span class="cx"> #include &quot;MaskImageOperation.h&quot;
</span><span class="cx"> 
</span><ins>+#include &quot;CSSValuePool.h&quot;
</ins><span class="cx"> #include &quot;CachedImage.h&quot;
</span><span class="cx"> #include &quot;CachedSVGDocument.h&quot;
</span><span class="cx"> #include &quot;RenderBoxModelObject.h&quot;
</span><span class="lines">@@ -77,7 +78,6 @@
</span><span class="cx">     : m_isExternalDocument(false)
</span><span class="cx">     , m_renderLayerImageClient(nullptr)
</span><span class="cx"> {
</span><del>-    m_cssMaskImageValue = WebKitCSSResourceValue::create(CSSPrimitiveValue::createIdentifier(CSSValueNone));
</del><span class="cx"> }
</span><span class="cx"> 
</span><span class="cx"> MaskImageOperation::~MaskImageOperation()
</span><span class="lines">@@ -98,8 +98,7 @@
</span><span class="cx">     if (image())
</span><span class="cx">         return false;
</span><span class="cx"> 
</span><del>-    ASSERT(m_cssMaskImageValue.get());
-    return m_cssMaskImageValue-&gt;isCSSValueNone();
</del><ins>+    return !m_cssMaskImageValue || m_cssMaskImageValue-&gt;isCSSValueNone();
</ins><span class="cx"> }
</span><span class="cx"> 
</span><span class="cx"> PassRefPtr&lt;CSSValue&gt; MaskImageOperation::cssValue()
</span><span class="lines">@@ -108,7 +107,7 @@
</span><span class="cx">         return image()-&gt;cssValue();
</span><span class="cx">     
</span><span class="cx">     if (isCSSValueNone())
</span><del>-        return m_cssMaskImageValue-&gt;innerValue();
</del><ins>+        return cssValuePool().createIdentifierValue(CSSValueNone);
</ins><span class="cx"> 
</span><span class="cx">     ASSERT(m_cssMaskImageValue.get());
</span><span class="cx">     return m_cssMaskImageValue.get();
</span></span></pre>
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