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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/287417">287417</a></dd>
<dt>Author</dt> <dd>zalan@apple.com</dd>
<dt>Date</dt> <dd>2021-12-23 17:22:12 -0800 (Thu, 23 Dec 2021)</dd>
</dl>

<h3>Log Message</h3>
<pre>REGRESSION(Containment) nullptr deref in RenderBox::styleDidChange
https://bugs.webkit.org/show_bug.cgi?id=234647
<rdar://86841302>

Reviewed by Simon Fraser.

Source/WebCore:

Do not try to propagate the writing mode to the RenderView unless we are attached to one.

Test: fast/dynamic/document-elment-renderer-null-crash.html

* rendering/RenderBox.cpp:
(WebCore::RenderBox::styleDidChange):

LayoutTests:

* fast/dynamic/document-elment-renderer-null-crash-expected.txt: Added.
* fast/dynamic/document-elment-renderer-null-crash.html: Added.</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkLayoutTestsChangeLog">trunk/LayoutTests/ChangeLog</a></li>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCorerenderingRenderBoxcpp">trunk/Source/WebCore/rendering/RenderBox.cpp</a></li>
</ul>

<h3>Added Paths</h3>
<ul>
<li><a href="#trunkLayoutTestsfastdynamicdocumentelmentrenderernullcrashexpectedtxt">trunk/LayoutTests/fast/dynamic/document-elment-renderer-null-crash-expected.txt</a></li>
<li><a href="#trunkLayoutTestsfastdynamicdocumentelmentrenderernullcrashhtml">trunk/LayoutTests/fast/dynamic/document-elment-renderer-null-crash.html</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkLayoutTestsChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/LayoutTests/ChangeLog (287416 => 287417)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/ChangeLog      2021-12-23 23:46:51 UTC (rev 287416)
+++ trunk/LayoutTests/ChangeLog 2021-12-24 01:22:12 UTC (rev 287417)
</span><span class="lines">@@ -1,3 +1,14 @@
</span><ins>+2021-12-23  Alan Bujtas  <zalan@apple.com>
+
+        REGRESSION(Containment) nullptr deref in RenderBox::styleDidChange
+        https://bugs.webkit.org/show_bug.cgi?id=234647
+        <rdar://86841302>
+
+        Reviewed by Simon Fraser.
+
+        * fast/dynamic/document-elment-renderer-null-crash-expected.txt: Added.
+        * fast/dynamic/document-elment-renderer-null-crash.html: Added.
+
</ins><span class="cx"> 2021-12-23  Tim Nguyen  <ntim@apple.com>
</span><span class="cx"> 
</span><span class="cx">         Rebaseline getComputedStyle tests for iOS after r287356
</span></span></pre></div>
<a id="trunkLayoutTestsfastdynamicdocumentelmentrenderernullcrashexpectedtxt"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/fast/dynamic/document-elment-renderer-null-crash-expected.txt (0 => 287417)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/fast/dynamic/document-elment-renderer-null-crash-expected.txt                          (rev 0)
+++ trunk/LayoutTests/fast/dynamic/document-elment-renderer-null-crash-expected.txt     2021-12-24 01:22:12 UTC (rev 287417)
</span><span class="lines">@@ -0,0 +1 @@
</span><ins>+PASS if no crash
</ins></span></pre></div>
<a id="trunkLayoutTestsfastdynamicdocumentelmentrenderernullcrashhtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/fast/dynamic/document-elment-renderer-null-crash.html (0 => 287417)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/fast/dynamic/document-elment-renderer-null-crash.html                          (rev 0)
+++ trunk/LayoutTests/fast/dynamic/document-elment-renderer-null-crash.html     2021-12-24 01:22:12 UTC (rev 287417)
</span><span class="lines">@@ -0,0 +1,12 @@
</span><ins>+<div id=insertionPoint>PASS if no crash</div>
+<script>
+if (window.testRunner)
+  testRunner.dumpAsText();
+var iframe = document.createElement("iframe");
+insertionPoint.appendChild(iframe);
+
+var iframeDocument = iframe.contentWindow.document; 
+iframeDocument.open();
+iframeDocument.appendChild(document.createElement("script"));
+iframeDocument.close();
+</script>
</ins></span></pre></div>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (287416 => 287417)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog   2021-12-23 23:46:51 UTC (rev 287416)
+++ trunk/Source/WebCore/ChangeLog      2021-12-24 01:22:12 UTC (rev 287417)
</span><span class="lines">@@ -1,3 +1,18 @@
</span><ins>+2021-12-23  Alan Bujtas  <zalan@apple.com>
+
+        REGRESSION(Containment) nullptr deref in RenderBox::styleDidChange
+        https://bugs.webkit.org/show_bug.cgi?id=234647
+        <rdar://86841302>
+
+        Reviewed by Simon Fraser.
+
+        Do not try to propagate the writing mode to the RenderView unless we are attached to one.
+
+        Test: fast/dynamic/document-elment-renderer-null-crash.html
+
+        * rendering/RenderBox.cpp:
+        (WebCore::RenderBox::styleDidChange):
+
</ins><span class="cx"> 2021-12-23  Tim Nguyen  <ntim@apple.com>
</span><span class="cx"> 
</span><span class="cx">         Update features.json for STP 134-137
</span></span></pre></div>
<a id="trunkSourceWebCorerenderingRenderBoxcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/rendering/RenderBox.cpp (287416 => 287417)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/rendering/RenderBox.cpp     2021-12-23 23:46:51 UTC (rev 287416)
+++ trunk/Source/WebCore/rendering/RenderBox.cpp        2021-12-24 01:22:12 UTC (rev 287417)
</span><span class="lines">@@ -350,33 +350,39 @@
</span><span class="cx">         bool rootStyleChanged = false;
</span><span class="cx">         bool viewDirectionOrWritingModeChanged = false;
</span><span class="cx">         auto* rootRenderer = isBodyRenderer ? documentElementRenderer : nullptr;
</span><del>-        if (!isBodyRenderer || !(shouldApplyAnyContainment(*this) || shouldApplyAnyContainment(*documentElementRenderer))) {
</del><ins>+
+        auto propagateWritingModeToRenderViewIfApplicable = [&] {
</ins><span class="cx">             // Propagate the new writing mode and direction up to the RenderView.
</span><del>-            if (viewStyle.direction() != newStyle.direction() && (isDocElementRenderer || !documentElementRenderer->style().hasExplicitlySetDirection())) {
-                viewStyle.setDirection(newStyle.direction());
-                viewDirectionOrWritingModeChanged = true;
-                if (isBodyRenderer) {
-                    rootRenderer->mutableStyle().setDirection(newStyle.direction());
-                    rootStyleChanged = true;
</del><ins>+            if (!documentElementRenderer)
+                return;
+            if (!isBodyRenderer || !(shouldApplyAnyContainment(*this) || shouldApplyAnyContainment(*documentElementRenderer))) {
+                if (viewStyle.direction() != newStyle.direction() && (isDocElementRenderer || !documentElementRenderer->style().hasExplicitlySetDirection())) {
+                    viewStyle.setDirection(newStyle.direction());
+                    viewDirectionOrWritingModeChanged = true;
+                    if (isBodyRenderer) {
+                        rootRenderer->mutableStyle().setDirection(newStyle.direction());
+                        rootStyleChanged = true;
+                    }
+                    setNeedsLayoutAndPrefWidthsRecalc();
+
+                    view().frameView().topContentDirectionDidChange();
</ins><span class="cx">                 }
</span><del>-                setNeedsLayoutAndPrefWidthsRecalc();
</del><span class="cx"> 
</span><del>-                view().frameView().topContentDirectionDidChange();
-            }
-
-            if (viewStyle.writingMode() != newStyle.writingMode() && (isDocElementRenderer || !documentElementRenderer->style().hasExplicitlySetWritingMode())) {
-                viewStyle.setWritingMode(newStyle.writingMode());
-                viewDirectionOrWritingModeChanged = true;
-                view().setHorizontalWritingMode(newStyle.isHorizontalWritingMode());
-                view().markAllDescendantsWithFloatsForLayout();
-                if (isBodyRenderer) {
-                    rootStyleChanged = true;
-                    rootRenderer->mutableStyle().setWritingMode(newStyle.writingMode());
-                    rootRenderer->setHorizontalWritingMode(newStyle.isHorizontalWritingMode());
</del><ins>+                if (viewStyle.writingMode() != newStyle.writingMode() && (isDocElementRenderer || !documentElementRenderer->style().hasExplicitlySetWritingMode())) {
+                    viewStyle.setWritingMode(newStyle.writingMode());
+                    viewDirectionOrWritingModeChanged = true;
+                    view().setHorizontalWritingMode(newStyle.isHorizontalWritingMode());
+                    view().markAllDescendantsWithFloatsForLayout();
+                    if (isBodyRenderer) {
+                        rootStyleChanged = true;
+                        rootRenderer->mutableStyle().setWritingMode(newStyle.writingMode());
+                        rootRenderer->setHorizontalWritingMode(newStyle.isHorizontalWritingMode());
+                    }
+                    setNeedsLayoutAndPrefWidthsRecalc();
</ins><span class="cx">                 }
</span><del>-                setNeedsLayoutAndPrefWidthsRecalc();
</del><span class="cx">             }
</span><del>-        }
</del><ins>+        };
+        propagateWritingModeToRenderViewIfApplicable();
</ins><span class="cx"> 
</span><span class="cx"> #if ENABLE(DARK_MODE_CSS)
</span><span class="cx">         view().frameView().recalculateBaseBackgroundColor();
</span></span></pre>
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