<html>
<head>
<base href="https://llvm.org/bugs/" />
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - libFuzzer buffer overrun in Fuzzer::RecordMaxCoverage()"
href="https://llvm.org/bugs/show_bug.cgi?id=31318">31318</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>libFuzzer buffer overrun in Fuzzer::RecordMaxCoverage()
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>ttaubert@mozilla.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=17741" name="attach_17741" title="Possible patch to properly resize C->CounterBitmap">attachment 17741</a> <a href="attachment.cgi?id=17741&action=edit" title="Possible patch to properly resize C->CounterBitmap">[details]</a></span>
Possible patch to properly resize C->CounterBitmap
I've been running into weird fuzzer behavior until I realized the libFuzzer
itself is overriding the fuzzing corpora held in memory.
>From FuzzerLoop.cpp:102:
EF->__sanitizer_update_counter_bitset_and_clear_counters(
C->CounterBitmap.data());
C->CounterBitmap.size() is smaller than the number returned by
EF->__sanitizer_get_number_of_counters().
A possible fix that seems to work well for us is attached. In
Fuzzer::ShuffleAndMinimize(), calling PrepareCounters() after
ExecuteCallback(&dummy, 0) resizes C->CounterBitmap to the appropriate size.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>