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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/211124">211124</a></dd>
<dt>Author</dt> <dd>msaboff@apple.com</dd>
<dt>Date</dt> <dd>2017-01-24 17:04:26 -0800 (Tue, 24 Jan 2017)</dd>
</dl>
<h3>Log Message</h3>
<pre>InferredTypeTable entry manipulation is not TOCTOU race safe
https://bugs.webkit.org/show_bug.cgi?id=167344
Reviewed by Filip Pizlo.
Made the accesses to table values safe from Time of Check,
Time of Use races with local temporary values.
Fixed point that we set an entry in the table to access the
current table entry instead of using the local entry. In that case,
we reload the now changed entry.
* runtime/InferredTypeTable.cpp:
(JSC::InferredTypeTable::visitChildren):
(JSC::InferredTypeTable::get):
(JSC::InferredTypeTable::willStoreValue):
(JSC::InferredTypeTable::makeTop):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeInferredTypeTablecpp">trunk/Source/JavaScriptCore/runtime/InferredTypeTable.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (211123 => 211124)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2017-01-25 00:55:10 UTC (rev 211123)
+++ trunk/Source/JavaScriptCore/ChangeLog 2017-01-25 01:04:26 UTC (rev 211124)
</span><span class="lines">@@ -1,3 +1,23 @@
</span><ins>+2017-01-24 Michael Saboff <msaboff@apple.com>
+
+ InferredTypeTable entry manipulation is not TOCTOU race safe
+ https://bugs.webkit.org/show_bug.cgi?id=167344
+
+ Reviewed by Filip Pizlo.
+
+ Made the accesses to table values safe from Time of Check,
+ Time of Use races with local temporary values.
+
+ Fixed point that we set an entry in the table to access the
+ current table entry instead of using the local entry. In that case,
+ we reload the now changed entry.
+
+ * runtime/InferredTypeTable.cpp:
+ (JSC::InferredTypeTable::visitChildren):
+ (JSC::InferredTypeTable::get):
+ (JSC::InferredTypeTable::willStoreValue):
+ (JSC::InferredTypeTable::makeTop):
+
</ins><span class="cx"> 2017-01-24 Filip Pizlo <fpizlo@apple.com>
</span><span class="cx">
</span><span class="cx"> Atomics.store should return the int-converted value, not the value that it stored
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeInferredTypeTablecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/InferredTypeTable.cpp (211123 => 211124)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/InferredTypeTable.cpp 2017-01-25 00:55:10 UTC (rev 211123)
+++ trunk/Source/JavaScriptCore/runtime/InferredTypeTable.cpp 2017-01-25 01:04:26 UTC (rev 211124)
</span><span class="lines">@@ -57,10 +57,12 @@
</span><span class="cx"> ConcurrentJSLocker locker(inferredTypeTable->m_lock);
</span><span class="cx">
</span><span class="cx"> for (auto& entry : inferredTypeTable->m_table) {
</span><del>- if (!entry.value)
</del><ins>+ auto entryValue = entry.value;
+
+ if (!entryValue)
</ins><span class="cx"> continue;
</span><del>- if (entry.value->isRelevant())
- visitor.append(entry.value);
</del><ins>+ if (entryValue->isRelevant())
+ visitor.append(entryValue);
</ins><span class="cx"> else
</span><span class="cx"> entry.value.clear();
</span><span class="cx"> }
</span><span class="lines">@@ -69,16 +71,20 @@
</span><span class="cx"> InferredType* InferredTypeTable::get(const ConcurrentJSLocker&, UniquedStringImpl* uid)
</span><span class="cx"> {
</span><span class="cx"> auto iter = m_table.find(uid);
</span><del>- if (iter == m_table.end() || !iter->value)
</del><ins>+ if (iter == m_table.end())
</ins><span class="cx"> return nullptr;
</span><span class="cx">
</span><ins>+ InferredType* entryValue = iter->value.get();
+ if (!entryValue)
+ return nullptr;
+
</ins><span class="cx"> // Take this opportunity to prune invalidated types.
</span><del>- if (!iter->value->isRelevant()) {
</del><ins>+ if (!entryValue->isRelevant()) {
</ins><span class="cx"> iter->value.clear();
</span><span class="cx"> return nullptr;
</span><span class="cx"> }
</span><span class="cx">
</span><del>- return iter->value.get();
</del><ins>+ return entryValue;
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> InferredType* InferredTypeTable::get(UniquedStringImpl* uid)
</span><span class="lines">@@ -99,10 +105,14 @@
</span><span class="cx">
</span><span class="cx"> if (age == OldProperty) {
</span><span class="cx"> TableType::iterator iter = m_table.find(propertyName.uid());
</span><del>- if (iter == m_table.end() || !iter->value)
</del><ins>+ if (iter == m_table.end())
</ins><span class="cx"> return false; // Absence on replace => top.
</span><ins>+
+ InferredType* entryValue = iter->value.get();
+ if (!entryValue)
+ return false;
</ins><span class="cx">
</span><del>- if (iter->value->willStoreValue(vm, propertyName, value))
</del><ins>+ if (entryValue->willStoreValue(vm, propertyName, value))
</ins><span class="cx"> return true;
</span><span class="cx">
</span><span class="cx"> iter->value.clear();
</span><span class="lines">@@ -114,14 +124,17 @@
</span><span class="cx"> ConcurrentJSLocker locker(m_lock);
</span><span class="cx"> result = m_table.add(propertyName.uid(), WriteBarrier<InferredType>());
</span><span class="cx"> }
</span><ins>+ InferredType* entryValue = result.iterator->value.get();
+
</ins><span class="cx"> if (result.isNewEntry) {
</span><span class="cx"> InferredType* inferredType = InferredType::create(vm);
</span><span class="cx"> WTF::storeStoreFence();
</span><span class="cx"> result.iterator->value.set(vm, this, inferredType);
</span><del>- } else if (!result.iterator->value)
</del><ins>+ entryValue = inferredType;
+ } else if (!entryValue)
</ins><span class="cx"> return false;
</span><span class="cx">
</span><del>- if (result.iterator->value->willStoreValue(vm, propertyName, value))
</del><ins>+ if (entryValue->willStoreValue(vm, propertyName, value))
</ins><span class="cx"> return true;
</span><span class="cx">
</span><span class="cx"> result.iterator->value.clear();
</span><span class="lines">@@ -133,10 +146,15 @@
</span><span class="cx"> // The algorithm here relies on the fact that only one thread modifies the hash map.
</span><span class="cx"> if (age == OldProperty) {
</span><span class="cx"> TableType::iterator iter = m_table.find(propertyName.uid());
</span><del>- if (iter == m_table.end() || !iter->value)
</del><ins>+ if (iter == m_table.end())
</ins><span class="cx"> return; // Absence on replace => top.
</span><span class="cx">
</span><del>- iter->value->makeTop(vm, propertyName);
</del><ins>+ InferredType* entryValue = iter->value.get();
+
+ if (!entryValue)
+ return;
+
+ entryValue->makeTop(vm, propertyName);
</ins><span class="cx"> iter->value.clear();
</span><span class="cx"> return;
</span><span class="cx"> }
</span></span></pre>
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