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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/244181">244181</a></dd>
<dt>Author</dt> <dd>rniwa@webkit.org</dd>
<dt>Date</dt> <dd>2019-04-10 19:12:56 -0700 (Wed, 10 Apr 2019)</dd>
</dl>

<h3>Log Message</h3>
<pre>Nullptr crash in CompositeEditCommand::moveParagraphs when root editable element goes away
https://bugs.webkit.org/show_bug.cgi?id=193027

Reviewed by Wenson Hsieh.

Source/WebCore:

Added an early exit when the root editable element (editing host in HTML5 spec terminology) is null
during CompositeEditCommand::moveParagraphs. This could happen when the website does something crazy
like removing contenteditable content attribute during DOM mutations or when the destination becomes
disconnected (orphaned) from the document due to bugs elsewhere in the codebase.

Test: editing/deleting/merge-paragraphs-null-root-editable-element-crash.html

* editing/CompositeEditCommand.cpp:
(WebCore::CompositeEditCommand::moveParagraphs): Added an early exit.

LayoutTests:

Added a regression test. Note that the test works around debug assertions in moveParagraphs.
These assertions are generally correct & useful unless the website does something crazy like
removing the contenteditable content attribute during editing operations.

* editing/deleting/merge-paragraphs-null-root-editable-element-crash-expected.txt: Added.
* editing/deleting/merge-paragraphs-null-root-editable-element-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="#trunkSourceWebCoreeditingCompositeEditCommandcpp">trunk/Source/WebCore/editing/CompositeEditCommand.cpp</a></li>
</ul>

<h3>Added Paths</h3>
<ul>
<li><a href="#trunkLayoutTestseditingdeletingmergeparagraphsnullrooteditableelementcrashexpectedtxt">trunk/LayoutTests/editing/deleting/merge-paragraphs-null-root-editable-element-crash-expected.txt</a></li>
<li><a href="#trunkLayoutTestseditingdeletingmergeparagraphsnullrooteditableelementcrashhtml">trunk/LayoutTests/editing/deleting/merge-paragraphs-null-root-editable-element-crash.html</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkLayoutTestsChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/LayoutTests/ChangeLog (244180 => 244181)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/ChangeLog      2019-04-11 02:04:57 UTC (rev 244180)
+++ trunk/LayoutTests/ChangeLog 2019-04-11 02:12:56 UTC (rev 244181)
</span><span class="lines">@@ -1,3 +1,17 @@
</span><ins>+2019-04-10  Ryosuke Niwa  <rniwa@webkit.org>
+
+        Nullptr crash in CompositeEditCommand::moveParagraphs when root editable element goes away
+        https://bugs.webkit.org/show_bug.cgi?id=193027
+
+        Reviewed by Wenson Hsieh.
+
+        Added a regression test. Note that the test works around debug assertions in moveParagraphs.
+        These assertions are generally correct & useful unless the website does something crazy like
+        removing the contenteditable content attribute during editing operations.
+
+        * editing/deleting/merge-paragraphs-null-root-editable-element-crash-expected.txt: Added.
+        * editing/deleting/merge-paragraphs-null-root-editable-element-crash.html: Added.
+
</ins><span class="cx"> 2019-04-10  Alicia Boya GarcĂ­a  <aboya@igalia.com>
</span><span class="cx"> 
</span><span class="cx">         [GTK] Unreviewed test gardening
</span></span></pre></div>
<a id="trunkLayoutTestseditingdeletingmergeparagraphsnullrooteditableelementcrashexpectedtxt"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/editing/deleting/merge-paragraphs-null-root-editable-element-crash-expected.txt (0 => 244181)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/editing/deleting/merge-paragraphs-null-root-editable-element-crash-expected.txt                                (rev 0)
+++ trunk/LayoutTests/editing/deleting/merge-paragraphs-null-root-editable-element-crash-expected.txt   2019-04-11 02:12:56 UTC (rev 244181)
</span><span class="lines">@@ -0,0 +1,5 @@
</span><ins>+This test is for the root editable element being nullptr in CompositeEditCommand::moveParagraph. WebKit should not crash.
+
+
+
+PASS. WebKit did not crash
</ins></span></pre></div>
<a id="trunkLayoutTestseditingdeletingmergeparagraphsnullrooteditableelementcrashhtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/editing/deleting/merge-paragraphs-null-root-editable-element-crash.html (0 => 244181)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/editing/deleting/merge-paragraphs-null-root-editable-element-crash.html                                (rev 0)
+++ trunk/LayoutTests/editing/deleting/merge-paragraphs-null-root-editable-element-crash.html   2019-04-11 02:12:56 UTC (rev 244181)
</span><span class="lines">@@ -0,0 +1,28 @@
</span><ins>+<!DOCTYPE html>
+<html>
+<body>
+<p>This test is for the root editable element being nullptr in CompositeEditCommand::moveParagraph. WebKit should not crash.</p>
+<div id="editor" contenteditable><span id="start">hello</span><span id="end"> world</span><span id="text"> WebKit</span></div>
+<script>
+
+if (window.testRunner)
+    testRunner.dumpAsText();
+
+const frame = document.createElement('iframe');
+start.appendChild(frame);
+frame.contentWindow.addEventListener('unload', () => {
+    editor.removeAttribute('contenteditable');
+    end.innerHTML = '<div><br></div>';
+
+    // Avoid hitting debug assertions in CompositeEditCommand::moveParagraph
+    text.firstChild.data = ' ';
+    text.prepend(document.createElement('br'));
+});
+getSelection().setBaseAndExtent(start, 0, end, 1);
+document.execCommand('delete', false, null);
+
+document.write('PASS. WebKit did not crash');
+
+</script>
+</body>
+</html>
</ins></span></pre></div>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (244180 => 244181)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog   2019-04-11 02:04:57 UTC (rev 244180)
+++ trunk/Source/WebCore/ChangeLog      2019-04-11 02:12:56 UTC (rev 244181)
</span><span class="lines">@@ -1,3 +1,20 @@
</span><ins>+2019-04-10  Ryosuke Niwa  <rniwa@webkit.org>
+
+        Nullptr crash in CompositeEditCommand::moveParagraphs when root editable element goes away
+        https://bugs.webkit.org/show_bug.cgi?id=193027
+
+        Reviewed by Wenson Hsieh.
+
+        Added an early exit when the root editable element (editing host in HTML5 spec terminology) is null
+        during CompositeEditCommand::moveParagraphs. This could happen when the website does something crazy
+        like removing contenteditable content attribute during DOM mutations or when the destination becomes
+        disconnected (orphaned) from the document due to bugs elsewhere in the codebase.
+
+        Test: editing/deleting/merge-paragraphs-null-root-editable-element-crash.html
+
+        * editing/CompositeEditCommand.cpp:
+        (WebCore::CompositeEditCommand::moveParagraphs): Added an early exit.
+
</ins><span class="cx"> 2019-04-10  Devin Rousso  <drousso@apple.com>
</span><span class="cx"> 
</span><span class="cx">         Web Inspector: save sheet should be anchored underneath the tab bar when detached
</span></span></pre></div>
<a id="trunkSourceWebCoreeditingCompositeEditCommandcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/editing/CompositeEditCommand.cpp (244180 => 244181)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/editing/CompositeEditCommand.cpp    2019-04-11 02:04:57 UTC (rev 244180)
+++ trunk/Source/WebCore/editing/CompositeEditCommand.cpp       2019-04-11 02:12:56 UTC (rev 244181)
</span><span class="lines">@@ -1504,10 +1504,13 @@
</span><span class="cx">         document().updateLayoutIgnorePendingStylesheets();
</span><span class="cx">     }
</span><span class="cx"> 
</span><del>-    auto editableRoot = destination.rootEditableElement();
-    RefPtr<Range> startToDestinationRange(Range::create(document(), firstPositionInNode(editableRoot), destination.deepEquivalent().parentAnchoredEquivalent()));
-    destinationIndex = TextIterator::rangeLength(startToDestinationRange.get(), true);
</del><ins>+    RefPtr<ContainerNode> editableRoot = destination.rootEditableElement();
+    if (!editableRoot)
+        editableRoot = &document();
</ins><span class="cx"> 
</span><ins>+    auto startToDestinationRange = Range::create(document(), firstPositionInNode(editableRoot.get()), destination.deepEquivalent().parentAnchoredEquivalent());
+    destinationIndex = TextIterator::rangeLength(startToDestinationRange.ptr(), true);
+
</ins><span class="cx">     setEndingSelection(VisibleSelection(destination, originalIsDirectional));
</span><span class="cx">     ASSERT(endingSelection().isCaretOrRange());
</span><span class="cx">     OptionSet<ReplaceSelectionCommand::CommandOption> options { ReplaceSelectionCommand::SelectReplacement, ReplaceSelectionCommand::MovingParagraph };
</span><span class="lines">@@ -1528,8 +1531,8 @@
</span><span class="cx">         // causes spaces to be collapsed during the move operation.  This results
</span><span class="cx">         // in a call to rangeFromLocationAndLength with a location past the end
</span><span class="cx">         // of the document (which will return null).
</span><del>-        RefPtr<Range> start = TextIterator::rangeFromLocationAndLength(editableRoot, destinationIndex + startIndex, 0, true);
-        RefPtr<Range> end = TextIterator::rangeFromLocationAndLength(editableRoot, destinationIndex + endIndex, 0, true);
</del><ins>+        RefPtr<Range> start = TextIterator::rangeFromLocationAndLength(editableRoot.get(), destinationIndex + startIndex, 0, true);
+        RefPtr<Range> end = TextIterator::rangeFromLocationAndLength(editableRoot.get(), destinationIndex + endIndex, 0, true);
</ins><span class="cx">         if (start && end)
</span><span class="cx">             setEndingSelection(VisibleSelection(start->startPosition(), end->startPosition(), DOWNSTREAM, originalIsDirectional));
</span><span class="cx">     }
</span></span></pre>
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