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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - UB when shifting at llvm/lib/Fuzzer/FuzzerTracePC.cpp:73"
href="https://llvm.org/bugs/show_bug.cgi?id=31457">31457</a>
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<tr>
<th>Summary</th>
<td>UB when shifting at llvm/lib/Fuzzer/FuzzerTracePC.cpp:73
</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>../../fuzz/libFuzzer/FuzzerTracePC.cpp:73:33: runtime error: shift exponent
8832 is too large for 64-bit type 'uint64_t' (aka 'unsigned long')
#0 0x540e84 in fuzzer::TracePC::FinalizeTrace(fuzzer::InputCorpus*,
unsigned long, bool)
/home/worker/nss/out/Debug/../../fuzz/libFuzzer/FuzzerTracePC.cpp:73:33
#1 0x52abd3 in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long)
/home/worker/nss/out/Debug/../../fuzz/libFuzzer/FuzzerLoop.cpp:475:32
#2 0x529ec4 in fuzzer::Fuzzer::RunOne(std::vector<unsigned char,
std::allocator<unsigned char> > const&)
/home/worker/nss/out/Debug/../../fuzz/libFuzzer/FuzzerInternal.h:113:41
#3 0x529ec4 in
fuzzer::Fuzzer::ShuffleAndMinimize(std::vector<std::vector<unsigned char,
std::allocator<unsigned char> >, std::allocator<std::vector<unsigned char,
std::allocator<unsigned char> > > >*)
/home/worker/nss/out/Debug/../../fuzz/libFuzzer/FuzzerLoop.cpp:451
#4 0x5142b2 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char
const*, unsigned long))
/home/worker/nss/out/Debug/../../fuzz/libFuzzer/FuzzerDriver.cpp:523:6
#5 0x508724 in main /home/worker/nss/out/Debug/../../fuzz/nssfuzz.cc:151:10
#6 0x7faea9fb082f in __libc_start_main
/build/glibc-t3gR2i/glibc-2.23/csu/../csu/libc-start.c:291
#7 0x41ee98 in _start (/home/worker/dist/Debug/bin/nssfuzz+0x41ee98)
SUMMARY: AddressSanitizer: undefined-behavior
../../fuzz/libFuzzer/FuzzerTracePC.cpp:73:33 in
Here's where it happens:
<span class="quote">> for (size_t Idx = 0; Idx < N; Idx += Step) {
> uint64_t Bundle = *reinterpret_cast<uint64_t*>(&Counters[Idx]);
> if (!Bundle) continue;
> for (size_t i = Idx; i < Idx + Step; i++) {
> uint8_t Counter = (Bundle >> (i * 8)) & 0xff;</span >
I'm not sure what the right fix would be, I don't understand the code well
enough to propose a fix.</pre>
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