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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - InferredTypeTable entry manipulation is not TOCTOU race safe"
href="https://bugs.webkit.org/show_bug.cgi?id=167344">167344</a>
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<th>Summary</th>
<td>InferredTypeTable entry manipulation is not TOCTOU race safe
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<th>Classification</th>
<td>Unclassified
</td>
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<th>Product</th>
<td>WebKit
</td>
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<th>Version</th>
<td>WebKit Nightly Build
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<th>Hardware</th>
<td>Unspecified
</td>
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<th>OS</th>
<td>Unspecified
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>Normal
</td>
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<th>Priority</th>
<td>P2
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<th>Component</th>
<td>JavaScriptCore
</td>
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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<th>Reporter</th>
<td>msaboff@apple.com
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<p>
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<pre>InferredTypeTable.cpp has Time of Check, Time of Use (TOCTOU) races in code that accesses and modifies the values stored in the table. Consider:
void InferredTypeTable::visitChildren(JSCell* cell, SlotVisitor& visitor)
{
InferredTypeTable* inferredTypeTable = jsCast<InferredTypeTable*>(cell);
ConcurrentJSLocker locker(inferredTypeTable->m_lock);
for (auto& entry : inferredTypeTable->m_table) {
if (!entry.value)
continue;
if (entry.value->isRelevant())
visitor.append(entry.value);
else
entry.value.clear();
}
}
Between the null check at the top of the loop and call to isRelevant(), the entry can be cleared by another thread.
<rdar://problem/30156092></pre>
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