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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/214857">214857</a></dd>
<dt>Author</dt> <dd>mark.lam@apple.com</dd>
<dt>Date</dt> <dd>2017-04-03 17:42:02 -0700 (Mon, 03 Apr 2017)</dd>
</dl>
<h3>Log Message</h3>
<pre>Fix incorrect capacity delta calculation reported in SparseArrayValueMap::add().
https://bugs.webkit.org/show_bug.cgi?id=170412
<rdar://problem/29697336>
Reviewed by Filip Pizlo.
JSTests:
* stress/regress-170412.js: Added.
Source/JavaScriptCore:
Here's an example of code that will trigger underflow in the "deprecatedExtraMemory"
reported by SparseArrayValueMap::add() that is added to Heap::m_deprecatedExtraMemorySize:
arr = new Array;
Object.defineProperty(arr, 18, ({writable: true, configurable: true}));
for (var i = 0; i < 3; ++i) {
Array.prototype.push.apply(arr, ["", () => {}, {}]);
Array.prototype.sort.apply(arr, [() => {}, []]);
}
However, Heap::m_deprecatedExtraMemorySize is only 1 of 3 values that are added
up to form the result of Heap::extraMemorySize(). Heap::m_extraMemorySize and
Heap::m_arrayBuffers.size() are the other 2.
While Heap::m_arrayBuffers.size() is bounded by actual allocated memory, both
Heap::m_deprecatedExtraMemorySize and Heap::m_extraMemorySize are added to
without any bounds checks, and they are only reset to 0 at the start of a full
GC. As a result, if we have a long sequence of eden GCs with a lot of additions
to Heap::m_extraMemorySize and/or Heap::m_deprecatedExtraMemorySize, then these
values could theoretically overflow. Coupling this with the underflow from
SparseArrayValueMap::add(), the result for Heap::extraMemorySize() can easily
overflow. Note: Heap::extraMemorySize() is used to compute the value
currentHeapSize.
If multiple conditions line up just right, the above overflows can result in this
debug assertion failure during an eden GC:
ASSERT(currentHeapSize >= m_sizeAfterLastCollect);
Otherwise, the effects of the overflows will only result in the computed
currentHeapSize not being representative of actual memory usage, and therefore,
a full GC may be triggered earlier or later than is ideal.
This patch ensures that SparseArrayValueMap::add() cannot underflow
Heap::m_deprecatedExtraMemorySize. It also adds overflows checks in the
calculations of Heap::m_deprecatedExtraMemorySize, Heap::m_extraMemorySize, and
Heap::extraMemorySize() so that their values are saturated appropriately to
ensure that GC collections are triggered based on representative memory usage.
* heap/Heap.cpp:
(JSC::Heap::deprecatedReportExtraMemorySlowCase):
(JSC::Heap::extraMemorySize):
(JSC::Heap::updateAllocationLimits):
(JSC::Heap::reportExtraMemoryVisited):
* runtime/SparseArrayValueMap.cpp:
(JSC::SparseArrayValueMap::add):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkJSTestsChangeLog">trunk/JSTests/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreheapHeapcpp">trunk/Source/JavaScriptCore/heap/Heap.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeSparseArrayValueMapcpp">trunk/Source/JavaScriptCore/runtime/SparseArrayValueMap.cpp</a></li>
</ul>
<h3>Added Paths</h3>
<ul>
<li><a href="#trunkJSTestsstressregress170412js">trunk/JSTests/stress/regress-170412.js</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkJSTestsChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/JSTests/ChangeLog (214856 => 214857)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/JSTests/ChangeLog 2017-04-04 00:41:19 UTC (rev 214856)
+++ trunk/JSTests/ChangeLog 2017-04-04 00:42:02 UTC (rev 214857)
</span><span class="lines">@@ -1,3 +1,13 @@
</span><ins>+2017-04-03 Mark Lam <mark.lam@apple.com>
+
+ Fix incorrect capacity delta calculation reported in SparseArrayValueMap::add().
+ https://bugs.webkit.org/show_bug.cgi?id=170412
+ <rdar://problem/29697336>
+
+ Reviewed by Filip Pizlo.
+
+ * stress/regress-170412.js: Added.
+
</ins><span class="cx"> 2017-04-03 Keith Miller <keith_miller@apple.com>
</span><span class="cx">
</span><span class="cx"> WebAssembly: Update spec tests
</span></span></pre></div>
<a id="trunkJSTestsstressregress170412js"></a>
<div class="addfile"><h4>Added: trunk/JSTests/stress/regress-170412.js (0 => 214857)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/JSTests/stress/regress-170412.js (rev 0)
+++ trunk/JSTests/stress/regress-170412.js 2017-04-04 00:42:02 UTC (rev 214857)
</span><span class="lines">@@ -0,0 +1,8 @@
</span><ins>+// This test passes if it does not crash.
+
+arr = new Array;
+Object.defineProperty(arr, 18, ({writable: true, configurable: true}));
+for (var i = 0; i < 3; ++i) {
+ Array.prototype.push.apply(arr, ["", () => { }, {}]);
+ Array.prototype.sort.apply(arr, [edenGC, []]);
+}
</ins></span></pre></div>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (214856 => 214857)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2017-04-04 00:41:19 UTC (rev 214856)
+++ trunk/Source/JavaScriptCore/ChangeLog 2017-04-04 00:42:02 UTC (rev 214857)
</span><span class="lines">@@ -1,3 +1,58 @@
</span><ins>+2017-04-03 Mark Lam <mark.lam@apple.com>
+
+ Fix incorrect capacity delta calculation reported in SparseArrayValueMap::add().
+ https://bugs.webkit.org/show_bug.cgi?id=170412
+ <rdar://problem/29697336>
+
+ Reviewed by Filip Pizlo.
+
+ Here's an example of code that will trigger underflow in the "deprecatedExtraMemory"
+ reported by SparseArrayValueMap::add() that is added to Heap::m_deprecatedExtraMemorySize:
+
+ arr = new Array;
+ Object.defineProperty(arr, 18, ({writable: true, configurable: true}));
+ for (var i = 0; i < 3; ++i) {
+ Array.prototype.push.apply(arr, ["", () => {}, {}]);
+ Array.prototype.sort.apply(arr, [() => {}, []]);
+ }
+
+ However, Heap::m_deprecatedExtraMemorySize is only 1 of 3 values that are added
+ up to form the result of Heap::extraMemorySize(). Heap::m_extraMemorySize and
+ Heap::m_arrayBuffers.size() are the other 2.
+
+ While Heap::m_arrayBuffers.size() is bounded by actual allocated memory, both
+ Heap::m_deprecatedExtraMemorySize and Heap::m_extraMemorySize are added to
+ without any bounds checks, and they are only reset to 0 at the start of a full
+ GC. As a result, if we have a long sequence of eden GCs with a lot of additions
+ to Heap::m_extraMemorySize and/or Heap::m_deprecatedExtraMemorySize, then these
+ values could theoretically overflow. Coupling this with the underflow from
+ SparseArrayValueMap::add(), the result for Heap::extraMemorySize() can easily
+ overflow. Note: Heap::extraMemorySize() is used to compute the value
+ currentHeapSize.
+
+ If multiple conditions line up just right, the above overflows can result in this
+ debug assertion failure during an eden GC:
+
+ ASSERT(currentHeapSize >= m_sizeAfterLastCollect);
+
+ Otherwise, the effects of the overflows will only result in the computed
+ currentHeapSize not being representative of actual memory usage, and therefore,
+ a full GC may be triggered earlier or later than is ideal.
+
+ This patch ensures that SparseArrayValueMap::add() cannot underflow
+ Heap::m_deprecatedExtraMemorySize. It also adds overflows checks in the
+ calculations of Heap::m_deprecatedExtraMemorySize, Heap::m_extraMemorySize, and
+ Heap::extraMemorySize() so that their values are saturated appropriately to
+ ensure that GC collections are triggered based on representative memory usage.
+
+ * heap/Heap.cpp:
+ (JSC::Heap::deprecatedReportExtraMemorySlowCase):
+ (JSC::Heap::extraMemorySize):
+ (JSC::Heap::updateAllocationLimits):
+ (JSC::Heap::reportExtraMemoryVisited):
+ * runtime/SparseArrayValueMap.cpp:
+ (JSC::SparseArrayValueMap::add):
+
</ins><span class="cx"> 2017-04-03 Filip Pizlo <fpizlo@apple.com>
</span><span class="cx">
</span><span class="cx"> Move the Liveness<> adapters from AirLiveness.h to AirLivenessAdapter.h.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreheapHeapcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/heap/Heap.cpp (214856 => 214857)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/heap/Heap.cpp 2017-04-04 00:41:19 UTC (rev 214856)
+++ trunk/Source/JavaScriptCore/heap/Heap.cpp 2017-04-04 00:42:02 UTC (rev 214857)
</span><span class="lines">@@ -458,7 +458,11 @@
</span><span class="cx">
</span><span class="cx"> void Heap::deprecatedReportExtraMemorySlowCase(size_t size)
</span><span class="cx"> {
</span><del>- m_deprecatedExtraMemorySize += size;
</del><ins>+ // FIXME: Change this to use SaturatedArithmetic when available.
+ // https://bugs.webkit.org/show_bug.cgi?id=170411
+ Checked<size_t, RecordOverflow> checkedNewSize = m_deprecatedExtraMemorySize;
+ checkedNewSize += size;
+ m_deprecatedExtraMemorySize = UNLIKELY(checkedNewSize.hasOverflowed()) ? std::numeric_limits<size_t>::max() : checkedNewSize.unsafeGet();
</ins><span class="cx"> reportExtraMemoryAllocatedSlowCase(size);
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -706,7 +710,15 @@
</span><span class="cx">
</span><span class="cx"> size_t Heap::extraMemorySize()
</span><span class="cx"> {
</span><del>- return m_extraMemorySize + m_deprecatedExtraMemorySize + m_arrayBuffers.size();
</del><ins>+ // FIXME: Change this to use SaturatedArithmetic when available.
+ // https://bugs.webkit.org/show_bug.cgi?id=170411
+ Checked<size_t, RecordOverflow> checkedTotal = m_extraMemorySize;
+ checkedTotal += m_deprecatedExtraMemorySize;
+ checkedTotal += m_arrayBuffers.size();
+ size_t total = UNLIKELY(checkedTotal.hasOverflowed()) ? std::numeric_limits<size_t>::max() : checkedTotal.unsafeGet();
+
+ ASSERT(m_objectSpace.capacity() >= m_objectSpace.size());
+ return std::min(total, std::numeric_limits<size_t>::max() - m_objectSpace.capacity());
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> size_t Heap::size()
</span><span class="lines">@@ -2112,6 +2124,11 @@
</span><span class="cx"> // It's up to the user to ensure that extraMemorySize() ends up corresponding to allocation-time
</span><span class="cx"> // extra memory reporting.
</span><span class="cx"> currentHeapSize += extraMemorySize();
</span><ins>+ if (!ASSERT_DISABLED) {
+ Checked<size_t, RecordOverflow> checkedCurrentHeapSize = m_totalBytesVisited;
+ checkedCurrentHeapSize += extraMemorySize();
+ ASSERT(!checkedCurrentHeapSize.hasOverflowed() && checkedCurrentHeapSize.unsafeGet() == currentHeapSize);
+ }
</ins><span class="cx">
</span><span class="cx"> if (verbose)
</span><span class="cx"> dataLog("extraMemorySize() = ", extraMemorySize(), ", currentHeapSize = ", currentHeapSize, "\n");
</span><span class="lines">@@ -2386,7 +2403,12 @@
</span><span class="cx">
</span><span class="cx"> for (;;) {
</span><span class="cx"> size_t oldSize = *counter;
</span><del>- if (WTF::atomicCompareExchangeWeakRelaxed(counter, oldSize, oldSize + size))
</del><ins>+ // FIXME: Change this to use SaturatedArithmetic when available.
+ // https://bugs.webkit.org/show_bug.cgi?id=170411
+ Checked<size_t, RecordOverflow> checkedNewSize = oldSize;
+ checkedNewSize += size;
+ size_t newSize = UNLIKELY(checkedNewSize.hasOverflowed()) ? std::numeric_limits<size_t>::max() : checkedNewSize.unsafeGet();
+ if (WTF::atomicCompareExchangeWeakRelaxed(counter, oldSize, newSize))
</ins><span class="cx"> return;
</span><span class="cx"> }
</span><span class="cx"> }
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeSparseArrayValueMapcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/SparseArrayValueMap.cpp (214856 => 214857)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/SparseArrayValueMap.cpp 2017-04-04 00:41:19 UTC (rev 214856)
+++ trunk/Source/JavaScriptCore/runtime/SparseArrayValueMap.cpp 2017-04-04 00:42:02 UTC (rev 214857)
</span><span class="lines">@@ -1,5 +1,5 @@
</span><span class="cx"> /*
</span><del>- * Copyright (C) 2011-2016 Apple Inc. All rights reserved.
</del><ins>+ * Copyright (C) 2011-2017 Apple Inc. All rights reserved.
</ins><span class="cx"> *
</span><span class="cx"> * Redistribution and use in source and binary forms, with or without
</span><span class="cx"> * modification, are permitted provided that the following conditions
</span><span class="lines">@@ -84,7 +84,7 @@
</span><span class="cx"> result = m_map.add(i, entry);
</span><span class="cx"> capacity = m_map.capacity();
</span><span class="cx"> }
</span><del>- if (capacity != m_reportedCapacity) {
</del><ins>+ if (capacity > m_reportedCapacity) {
</ins><span class="cx"> // FIXME: Adopt reportExtraMemoryVisited, and switch to reportExtraMemoryAllocated.
</span><span class="cx"> // https://bugs.webkit.org/show_bug.cgi?id=142595
</span><span class="cx"> Heap::heap(array)->deprecatedReportExtraMemory((capacity - m_reportedCapacity) * (sizeof(unsigned) + sizeof(WriteBarrier<Unknown>)));
</span></span></pre>
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