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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/203729">203729</a></dd>
<dt>Author</dt> <dd>commit-queue@webkit.org</dd>
<dt>Date</dt> <dd>2016-07-26 11:58:32 -0700 (Tue, 26 Jul 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>Infinite Canvas context save() causes WebKit to crash
https://bugs.webkit.org/show_bug.cgi?id=159586
<rdar://problem/26759984>
Patch by Said Abou-Hallawa <sabouhallawa@apple.com> on 2016-07-26
Reviewed by Simon Fraser.
Source/WebCore:
Limit the size of the canvas context state stack to 1024 * 16 saves. All
the saves which come after that limit will stay unrealized. The restore()
should not have any effect till there is no unrealized saves.
Test: fast/canvas/canvas-context-save-limit.html
* html/canvas/CanvasRenderingContext2D.cpp:
(WebCore::CanvasRenderingContext2D::realizeSaves):
(WebCore::CanvasRenderingContext2D::realizeSavesLoop):
* html/canvas/CanvasRenderingContext2D.h:
LayoutTests:
* fast/canvas/canvas-context-save-limit-expected.txt: Added.
* fast/canvas/canvas-context-save-limit.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="#trunkSourceWebCorehtmlcanvasCanvasRenderingContext2Dcpp">trunk/Source/WebCore/html/canvas/CanvasRenderingContext2D.cpp</a></li>
<li><a href="#trunkSourceWebCorehtmlcanvasCanvasRenderingContext2Dh">trunk/Source/WebCore/html/canvas/CanvasRenderingContext2D.h</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#trunkLayoutTestsfastcanvascanvascontextsavelimitexpectedtxt">trunk/LayoutTests/fast/canvas/canvas-context-save-limit-expected.txt</a></li>
<li><a href="#trunkLayoutTestsfastcanvascanvascontextsavelimithtml">trunk/LayoutTests/fast/canvas/canvas-context-save-limit.html</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkLayoutTestsChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/LayoutTests/ChangeLog (203728 => 203729)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/ChangeLog        2016-07-26 18:00:57 UTC (rev 203728)
+++ trunk/LayoutTests/ChangeLog        2016-07-26 18:58:32 UTC (rev 203729)
</span><span class="lines">@@ -1,3 +1,14 @@
</span><ins>+2016-07-26 Said Abou-Hallawa <sabouhallawa@apple.com>
+
+ Infinite Canvas context save() causes WebKit to crash
+ https://bugs.webkit.org/show_bug.cgi?id=159586
+ <rdar://problem/26759984>
+
+ Reviewed by Simon Fraser.
+
+ * fast/canvas/canvas-context-save-limit-expected.txt: Added.
+ * fast/canvas/canvas-context-save-limit.html: Added.
+
</ins><span class="cx"> 2016-07-26 Youenn Fablet <youenn@apple.com>
</span><span class="cx">
</span><span class="cx"> DOMTokenList should be iterable
</span></span></pre></div>
<a id="trunkLayoutTestsfastcanvascanvascontextsavelimitexpectedtxt"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/fast/canvas/canvas-context-save-limit-expected.txt (0 => 203729)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/fast/canvas/canvas-context-save-limit-expected.txt         (rev 0)
+++ trunk/LayoutTests/fast/canvas/canvas-context-save-limit-expected.txt        2016-07-26 18:58:32 UTC (rev 203729)
</span><span class="lines">@@ -0,0 +1,14 @@
</span><ins>+CONSOLE MESSAGE: line 29: CanvasRenderingContext2D.save() has been called without a matching restore() too many times. Ignoring save().
+CONSOLE MESSAGE: line 29: CanvasRenderingContext2D.save() has been called without a matching restore() too many times. Ignoring save().
+This test verifies that the size of CanvasRenderingContext2D state stack does not grow beyond a certain limit.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS ctx.fillStyle is "#ff0000"
+PASS ctx.fillStyle is "#0000ff"
+PASS ctx.fillStyle is "#00ff00"
+PASS successfullyParsed is true
+
+TEST COMPLETE
+
</ins></span></pre></div>
<a id="trunkLayoutTestsfastcanvascanvascontextsavelimithtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/fast/canvas/canvas-context-save-limit.html (0 => 203729)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/fast/canvas/canvas-context-save-limit.html         (rev 0)
+++ trunk/LayoutTests/fast/canvas/canvas-context-save-limit.html        2016-07-26 18:58:32 UTC (rev 203729)
</span><span class="lines">@@ -0,0 +1,43 @@
</span><ins>+<!DOCTYPE HTML>
+<html>
+<head>
+ <script src="../../resources/js-test-pre.js"></script>
+</head>
+<body>
+ <canvas id="canvas"/>
+ <script>
+ description("This test verifies that the size of CanvasRenderingContext2D state stack does not grow beyond a certain limit.");
+ const RED = '#ff0000';
+ const GREEN = '#00ff00';
+ const BLUE = '#0000ff';
+ const SAVE_STACK_SIZE = 1024 * 16;
+ const MAX_SAVES = SAVE_STACK_SIZE - 1;
+
+ var c = document.getElementById("canvas");
+ var ctx = c.getContext("2d");
+
+ for (var i = 0; i < MAX_SAVES * 2; ++i) {
+ if (!i || i >= MAX_SAVES)
+ ctx.fillStyle = GREEN;
+ else if (i == MAX_SAVES - 1)
+ ctx.fillStyle = BLUE;
+ else
+ ctx.fillStyle = RED;
+ ctx.save();
+ }
+
+ ctx.fillStyle = RED;
+
+ for (var i = MAX_SAVES * 2 - 1; i >= 0; --i) {
+ ctx.restore();
+ if (i == MAX_SAVES * 2 - 1)
+ shouldBeEqualToString('ctx.fillStyle', RED);
+ else if (i == MAX_SAVES - 1)
+ shouldBeEqualToString('ctx.fillStyle', BLUE);
+ else if (!i)
+ shouldBeEqualToString('ctx.fillStyle', GREEN);
+ }
+ </script>
+ <script src="../../resources/js-test-post.js"></script>
+</body>
+</html>
</ins><span class="cx">\ No newline at end of file
</span></span></pre></div>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (203728 => 203729)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog        2016-07-26 18:00:57 UTC (rev 203728)
+++ trunk/Source/WebCore/ChangeLog        2016-07-26 18:58:32 UTC (rev 203729)
</span><span class="lines">@@ -1,3 +1,22 @@
</span><ins>+2016-07-26 Said Abou-Hallawa <sabouhallawa@apple.com>
+
+ Infinite Canvas context save() causes WebKit to crash
+ https://bugs.webkit.org/show_bug.cgi?id=159586
+ <rdar://problem/26759984>
+
+ Reviewed by Simon Fraser.
+
+ Limit the size of the canvas context state stack to 1024 * 16 saves. All
+ the saves which come after that limit will stay unrealized. The restore()
+ should not have any effect till there is no unrealized saves.
+
+ Test: fast/canvas/canvas-context-save-limit.html
+
+ * html/canvas/CanvasRenderingContext2D.cpp:
+ (WebCore::CanvasRenderingContext2D::realizeSaves):
+ (WebCore::CanvasRenderingContext2D::realizeSavesLoop):
+ * html/canvas/CanvasRenderingContext2D.h:
+
</ins><span class="cx"> 2016-07-26 Youenn Fablet <youenn@apple.com>
</span><span class="cx">
</span><span class="cx"> DOMTokenList should be iterable
</span></span></pre></div>
<a id="trunkSourceWebCorehtmlcanvasCanvasRenderingContext2Dcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/html/canvas/CanvasRenderingContext2D.cpp (203728 => 203729)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/html/canvas/CanvasRenderingContext2D.cpp        2016-07-26 18:00:57 UTC (rev 203728)
+++ trunk/Source/WebCore/html/canvas/CanvasRenderingContext2D.cpp        2016-07-26 18:58:32 UTC (rev 203729)
</span><span class="lines">@@ -351,6 +351,17 @@
</span><span class="cx"> context.drawBidiText(m_font, run, point, action);
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+void CanvasRenderingContext2D::realizeSaves()
+{
+ if (m_unrealizedSaveCount)
+ realizeSavesLoop();
+
+ if (m_unrealizedSaveCount) {
+ static NeverDestroyed<String> consoleMessage(ASCIILiteral("CanvasRenderingContext2D.save() has been called without a matching restore() too many times. Ignoring save()."));
+ canvas()->document().addConsoleMessage(MessageSource::Rendering, MessageLevel::Error, consoleMessage);
+ }
+}
+
</ins><span class="cx"> void CanvasRenderingContext2D::realizeSavesLoop()
</span><span class="cx"> {
</span><span class="cx"> ASSERT(m_unrealizedSaveCount);
</span><span class="lines">@@ -357,6 +368,8 @@
</span><span class="cx"> ASSERT(m_stateStack.size() >= 1);
</span><span class="cx"> GraphicsContext* context = drawingContext();
</span><span class="cx"> do {
</span><ins>+ if (m_stateStack.size() > MaxSaveCount)
+ break;
</ins><span class="cx"> m_stateStack.append(state());
</span><span class="cx"> if (context)
</span><span class="cx"> context->save();
</span></span></pre></div>
<a id="trunkSourceWebCorehtmlcanvasCanvasRenderingContext2Dh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/html/canvas/CanvasRenderingContext2D.h (203728 => 203729)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/html/canvas/CanvasRenderingContext2D.h        2016-07-26 18:00:57 UTC (rev 203728)
+++ trunk/Source/WebCore/html/canvas/CanvasRenderingContext2D.h        2016-07-26 18:58:32 UTC (rev 203729)
</span><span class="lines">@@ -309,7 +309,7 @@
</span><span class="cx"> CanvasDidDrawApplyAll = 0xffffffff
</span><span class="cx"> };
</span><span class="cx">
</span><del>- State& modifiableState() { ASSERT(!m_unrealizedSaveCount); return m_stateStack.last(); }
</del><ins>+ State& modifiableState() { ASSERT(!m_unrealizedSaveCount || m_stateStack.size() >= MaxSaveCount); return m_stateStack.last(); }
</ins><span class="cx"> const State& state() const { return m_stateStack.last(); }
</span><span class="cx">
</span><span class="cx"> void applyLineDash() const;
</span><span class="lines">@@ -325,11 +325,7 @@
</span><span class="cx"> GraphicsContext* drawingContext() const;
</span><span class="cx">
</span><span class="cx"> void unwindStateStack();
</span><del>- void realizeSaves()
- {
- if (m_unrealizedSaveCount)
- realizeSavesLoop();
- }
</del><ins>+ void realizeSaves();
</ins><span class="cx"> void realizeSavesLoop();
</span><span class="cx">
</span><span class="cx"> void applyStrokePattern();
</span><span class="lines">@@ -385,6 +381,7 @@
</span><span class="cx"> PlatformLayer* platformLayer() const override;
</span><span class="cx"> #endif
</span><span class="cx">
</span><ins>+ static const unsigned MaxSaveCount = 1024 * 16;
</ins><span class="cx"> Vector<State, 1> m_stateStack;
</span><span class="cx"> unsigned m_unrealizedSaveCount { 0 };
</span><span class="cx"> bool m_usesCSSCompatibilityParseMode;
</span></span></pre>
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