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llvm-project/llvm/lib/Fuzzer/FuzzerLoop.cpp

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//===- FuzzerLoop.cpp - Fuzzer's main loop --------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// Fuzzer's main loop.
//===----------------------------------------------------------------------===//
#include "FuzzerCorpus.h"
#include "FuzzerInternal.h"
#include "FuzzerIO.h"
#include "FuzzerMutate.h"
#include "FuzzerRandom.h"
#include "FuzzerTracePC.h"
#include <algorithm>
#include <cstring>
#include <memory>
#include <set>
#if defined(__has_include)
#if __has_include(<sanitizer / coverage_interface.h>)
#include <sanitizer/coverage_interface.h>
#endif
#if __has_include(<sanitizer / lsan_interface.h>)
#include <sanitizer/lsan_interface.h>
#endif
#endif
#define NO_SANITIZE_MEMORY
#if defined(__has_feature)
#if __has_feature(memory_sanitizer)
#undef NO_SANITIZE_MEMORY
#define NO_SANITIZE_MEMORY __attribute__((no_sanitize_memory))
#endif
#endif
namespace fuzzer {
static const size_t kMaxUnitSizeToPrint = 256;
thread_local bool Fuzzer::IsMyThread;
static void MissingExternalApiFunction(const char *FnName) {
Printf("ERROR: %s is not defined. Exiting.\n"
"Did you use -fsanitize-coverage=... to build your code?\n",
FnName);
exit(1);
}
#define CHECK_EXTERNAL_FUNCTION(fn) \
do { \
if (!(EF->fn)) \
MissingExternalApiFunction(#fn); \
} while (false)
// Only one Fuzzer per process.
static Fuzzer *F;
void Fuzzer::ResetEdgeCoverage() {
CHECK_EXTERNAL_FUNCTION(__sanitizer_reset_coverage);
EF->__sanitizer_reset_coverage();
}
void Fuzzer::ResetCounters() {
if (Options.UseCounters)
EF->__sanitizer_update_counter_bitset_and_clear_counters(0);
}
void Fuzzer::PrepareCounters(Fuzzer::Coverage *C) {
if (Options.UseCounters) {
size_t NumCounters = EF->__sanitizer_get_number_of_counters();
C->CounterBitmap.resize(NumCounters);
}
}
// Records data to a maximum coverage tracker. Returns true if additional
// coverage was discovered.
bool Fuzzer::RecordMaxCoverage(Fuzzer::Coverage *C) {
bool Res = false;
uint64_t NewBlockCoverage = EF->__sanitizer_get_total_unique_coverage();
if (NewBlockCoverage > C->BlockCoverage) {
Res = true;
C->BlockCoverage = NewBlockCoverage;
}
if (Options.UseIndirCalls &&
EF->__sanitizer_get_total_unique_caller_callee_pairs) {
uint64_t NewCallerCalleeCoverage =
EF->__sanitizer_get_total_unique_caller_callee_pairs();
if (NewCallerCalleeCoverage > C->CallerCalleeCoverage) {
Res = true;
C->CallerCalleeCoverage = NewCallerCalleeCoverage;
}
}
if (Options.UseCounters) {
uint64_t CounterDelta =
EF->__sanitizer_update_counter_bitset_and_clear_counters(
C->CounterBitmap.data());
if (CounterDelta > 0) {
Res = true;
C->CounterBitmapBits += CounterDelta;
}
}
return Res;
}
// Leak detection is expensive, so we first check if there were more mallocs
// than frees (using the sanitizer malloc hooks) and only then try to call lsan.
struct MallocFreeTracer {
void Start(int TraceLevel) {
this->TraceLevel = TraceLevel;
if (TraceLevel)
Printf("MallocFreeTracer: START\n");
Mallocs = 0;
Frees = 0;
}
// Returns true if there were more mallocs than frees.
bool Stop() {
if (TraceLevel)
Printf("MallocFreeTracer: STOP %zd %zd (%s)\n", Mallocs.load(),
Frees.load(), Mallocs == Frees ? "same" : "DIFFERENT");
bool Result = Mallocs > Frees;
Mallocs = 0;
Frees = 0;
TraceLevel = 0;
return Result;
}
std::atomic<size_t> Mallocs;
std::atomic<size_t> Frees;
int TraceLevel = 0;
};
static MallocFreeTracer AllocTracer;
ATTRIBUTE_NO_SANITIZE_MEMORY
void MallocHook(const volatile void *ptr, size_t size) {
size_t N = AllocTracer.Mallocs++;
F->HandleMalloc(size);
if (int TraceLevel = AllocTracer.TraceLevel) {
Printf("MALLOC[%zd] %p %zd\n", N, ptr, size);
if (TraceLevel >= 2 && EF)
EF->__sanitizer_print_stack_trace();
}
}
ATTRIBUTE_NO_SANITIZE_MEMORY
void FreeHook(const volatile void *ptr) {
size_t N = AllocTracer.Frees++;
if (int TraceLevel = AllocTracer.TraceLevel) {
Printf("FREE[%zd] %p\n", N, ptr);
if (TraceLevel >= 2 && EF)
EF->__sanitizer_print_stack_trace();
}
}
// Crash on a single malloc that exceeds the rss limit.
void Fuzzer::HandleMalloc(size_t Size) {
if (!Options.RssLimitMb || (Size >> 20) < (size_t)Options.RssLimitMb)
return;
Printf("==%d== ERROR: libFuzzer: out-of-memory (malloc(%zd))\n", GetPid(),
Size);
Printf(" To change the out-of-memory limit use -rss_limit_mb=<N>\n\n");
if (EF->__sanitizer_print_stack_trace)
EF->__sanitizer_print_stack_trace();
DumpCurrentUnit("oom-");
Printf("SUMMARY: libFuzzer: out-of-memory\n");
PrintFinalStats();
_Exit(Options.ErrorExitCode); // Stop right now.
}
Fuzzer::Fuzzer(UserCallback CB, InputCorpus &Corpus, MutationDispatcher &MD,
FuzzingOptions Options)
: CB(CB), Corpus(Corpus), MD(MD), Options(Options) {
SetDeathCallback();
InitializeTraceState();
assert(!F);
F = this;
TPC.ResetMaps();
ResetCoverage();
IsMyThread = true;
if (Options.DetectLeaks && EF->__sanitizer_install_malloc_and_free_hooks)
EF->__sanitizer_install_malloc_and_free_hooks(MallocHook, FreeHook);
TPC.SetUseCounters(Options.UseCounters);
TPC.SetUseValueProfile(Options.UseValueProfile);
TPC.SetPrintNewPCs(Options.PrintNewCovPcs);
if (Options.Verbosity)
TPC.PrintModuleInfo();
if (!Options.OutputCorpus.empty() && Options.ReloadIntervalSec)
EpochOfLastReadOfOutputCorpus = GetEpoch(Options.OutputCorpus);
MaxInputLen = MaxMutationLen = Options.MaxLen;
AllocateCurrentUnitData();
CurrentUnitSize = 0;
memset(BaseSha1, 0, sizeof(BaseSha1));
}
Fuzzer::~Fuzzer() { }
void Fuzzer::AllocateCurrentUnitData() {
if (CurrentUnitData || MaxInputLen == 0) return;
CurrentUnitData = new uint8_t[MaxInputLen];
}
void Fuzzer::SetDeathCallback() {
CHECK_EXTERNAL_FUNCTION(__sanitizer_set_death_callback);
EF->__sanitizer_set_death_callback(StaticDeathCallback);
}
void Fuzzer::StaticDeathCallback() {
assert(F);
F->DeathCallback();
}
static void WarnOnUnsuccessfullMerge(bool DoWarn) {
if (!DoWarn) return;
Printf(
"***\n"
"***\n"
"***\n"
"*** NOTE: merge did not succeed due to a failure on one of the inputs.\n"
"*** You will need to filter out crashes from the corpus, e.g. like this:\n"
"*** for f in WITH_CRASHES/*; do ./fuzzer $f && cp $f NO_CRASHES; done\n"
"*** Future versions may have crash-resistant merge, stay tuned.\n"
"***\n"
"***\n"
"***\n");
}
void Fuzzer::DumpCurrentUnit(const char *Prefix) {
WarnOnUnsuccessfullMerge(InMergeMode);
if (!CurrentUnitData) return; // Happens when running individual inputs.
MD.PrintMutationSequence();
Printf("; base unit: %s\n", Sha1ToString(BaseSha1).c_str());
size_t UnitSize = CurrentUnitSize;
if (UnitSize <= kMaxUnitSizeToPrint) {
PrintHexArray(CurrentUnitData, UnitSize, "\n");
PrintASCII(CurrentUnitData, UnitSize, "\n");
}
WriteUnitToFileWithPrefix({CurrentUnitData, CurrentUnitData + UnitSize},
Prefix);
}
NO_SANITIZE_MEMORY
void Fuzzer::DeathCallback() {
DumpCurrentUnit("crash-");
PrintFinalStats();
}
void Fuzzer::StaticAlarmCallback() {
assert(F);
F->AlarmCallback();
}
void Fuzzer::StaticCrashSignalCallback() {
assert(F);
F->CrashCallback();
}
void Fuzzer::StaticInterruptCallback() {
assert(F);
F->InterruptCallback();
}
void Fuzzer::StaticFileSizeExceedCallback() {
Printf("==%lu== ERROR: libFuzzer: file size exceeded\n", GetPid());
exit(1);
}
void Fuzzer::CrashCallback() {
Printf("==%lu== ERROR: libFuzzer: deadly signal\n", GetPid());
if (EF->__sanitizer_print_stack_trace)
EF->__sanitizer_print_stack_trace();
Printf("NOTE: libFuzzer has rudimentary signal handlers.\n"
" Combine libFuzzer with AddressSanitizer or similar for better "
"crash reports.\n");
Printf("SUMMARY: libFuzzer: deadly signal\n");
DumpCurrentUnit("crash-");
PrintFinalStats();
exit(Options.ErrorExitCode);
}
void Fuzzer::InterruptCallback() {
Printf("==%lu== libFuzzer: run interrupted; exiting\n", GetPid());
PrintFinalStats();
_Exit(0); // Stop right now, don't perform any at-exit actions.
}
NO_SANITIZE_MEMORY
void Fuzzer::AlarmCallback() {
assert(Options.UnitTimeoutSec > 0);
if (!InFuzzingThread()) return;
if (!RunningCB)
return; // We have not started running units yet.
size_t Seconds =
duration_cast<seconds>(system_clock::now() - UnitStartTime).count();
if (Seconds == 0)
return;
if (Options.Verbosity >= 2)
Printf("AlarmCallback %zd\n", Seconds);
if (Seconds >= (size_t)Options.UnitTimeoutSec) {
Printf("ALARM: working on the last Unit for %zd seconds\n", Seconds);
Printf(" and the timeout value is %d (use -timeout=N to change)\n",
Options.UnitTimeoutSec);
DumpCurrentUnit("timeout-");
Printf("==%lu== ERROR: libFuzzer: timeout after %d seconds\n", GetPid(),
Seconds);
if (EF->__sanitizer_print_stack_trace)
EF->__sanitizer_print_stack_trace();
Printf("SUMMARY: libFuzzer: timeout\n");
PrintFinalStats();
_Exit(Options.TimeoutExitCode); // Stop right now.
}
}
void Fuzzer::RssLimitCallback() {
Printf(
"==%lu== ERROR: libFuzzer: out-of-memory (used: %zdMb; limit: %zdMb)\n",
GetPid(), GetPeakRSSMb(), Options.RssLimitMb);
Printf(" To change the out-of-memory limit use -rss_limit_mb=<N>\n\n");
if (EF->__sanitizer_print_memory_profile)
EF->__sanitizer_print_memory_profile(95);
DumpCurrentUnit("oom-");
Printf("SUMMARY: libFuzzer: out-of-memory\n");
PrintFinalStats();
_Exit(Options.ErrorExitCode); // Stop right now.
}
void Fuzzer::PrintStats(const char *Where, const char *End, size_t Units) {
size_t ExecPerSec = execPerSec();
if (Options.OutputCSV) {
static bool csvHeaderPrinted = false;
if (!csvHeaderPrinted) {
csvHeaderPrinted = true;
Printf("runs,block_cov,bits,cc_cov,corpus,execs_per_sec,tbms,reason\n");
}
Printf("%zd,%zd,%zd,%zd,%zd,%zd,%s\n", TotalNumberOfRuns,
MaxCoverage.BlockCoverage, MaxCoverage.CounterBitmapBits,
MaxCoverage.CallerCalleeCoverage, Corpus.size(), ExecPerSec, Where);
}
if (!Options.Verbosity)
return;
Printf("#%zd\t%s", TotalNumberOfRuns, Where);
if (MaxCoverage.BlockCoverage)
Printf(" cov: %zd", MaxCoverage.BlockCoverage);
if (size_t N = MaxCoverage.VPMap.GetNumBitsSinceLastMerge())
Printf(" vp: %zd", N);
if (size_t N = TPC.GetTotalPCCoverage())
Printf(" cov: %zd", N);
if (auto TB = MaxCoverage.CounterBitmapBits)
Printf(" bits: %zd", TB);
if (size_t N = Corpus.NumFeatures())
Printf( " ft: %zd", N);
if (MaxCoverage.CallerCalleeCoverage)
Printf(" indir: %zd", MaxCoverage.CallerCalleeCoverage);
if (!Corpus.empty()) {
Printf(" corp: %zd", Corpus.NumActiveUnits());
if (size_t N = Corpus.SizeInBytes()) {
if (N < (1<<14))
Printf("/%zdb", N);
else if (N < (1 << 24))
Printf("/%zdKb", N >> 10);
else
Printf("/%zdMb", N >> 20);
}
}
if (Units)
Printf(" units: %zd", Units);
Printf(" exec/s: %zd", ExecPerSec);
Printf(" rss: %zdMb", GetPeakRSSMb());
Printf("%s", End);
}
void Fuzzer::PrintFinalStats() {
if (Options.PrintCoverage)
TPC.PrintCoverage();
if (Options.DumpCoverage)
TPC.DumpCoverage();
if (Options.PrintCorpusStats)
Corpus.PrintStats();
if (!Options.PrintFinalStats) return;
size_t ExecPerSec = execPerSec();
Printf("stat::number_of_executed_units: %zd\n", TotalNumberOfRuns);
Printf("stat::average_exec_per_sec: %zd\n", ExecPerSec);
Printf("stat::new_units_added: %zd\n", NumberOfNewUnitsAdded);
Printf("stat::slowest_unit_time_sec: %zd\n", TimeOfLongestUnitInSeconds);
Printf("stat::peak_rss_mb: %zd\n", GetPeakRSSMb());
}
void Fuzzer::SetMaxInputLen(size_t MaxInputLen) {
assert(this->MaxInputLen == 0); // Can only reset MaxInputLen from 0 to non-0.
assert(MaxInputLen);
this->MaxInputLen = MaxInputLen;
this->MaxMutationLen = MaxInputLen;
AllocateCurrentUnitData();
Printf("INFO: -max_len is not provided, using %zd\n", MaxInputLen);
}
void Fuzzer::SetMaxMutationLen(size_t MaxMutationLen) {
assert(MaxMutationLen && MaxMutationLen <= MaxInputLen);
this->MaxMutationLen = MaxMutationLen;
}
void Fuzzer::CheckExitOnSrcPosOrItem() {
if (!Options.ExitOnSrcPos.empty()) {
static auto *PCsSet = new std::set<uintptr_t>;
for (size_t i = 1, N = TPC.GetNumPCs(); i < N; i++) {
uintptr_t PC = TPC.GetPC(i);
if (!PC) continue;
if (!PCsSet->insert(PC).second) continue;
std::string Descr = DescribePC("%L", PC);
if (Descr.find(Options.ExitOnSrcPos) != std::string::npos) {
Printf("INFO: found line matching '%s', exiting.\n",
Options.ExitOnSrcPos.c_str());
_Exit(0);
}
}
}
if (!Options.ExitOnItem.empty()) {
if (Corpus.HasUnit(Options.ExitOnItem)) {
Printf("INFO: found item with checksum '%s', exiting.\n",
Options.ExitOnItem.c_str());
_Exit(0);
}
}
}
void Fuzzer::RereadOutputCorpus(size_t MaxSize) {
if (Options.OutputCorpus.empty() || !Options.ReloadIntervalSec) return;
std::vector<Unit> AdditionalCorpus;
ReadDirToVectorOfUnits(Options.OutputCorpus.c_str(), &AdditionalCorpus,
&EpochOfLastReadOfOutputCorpus, MaxSize,
/*ExitOnError*/ false);
if (Options.Verbosity >= 2)
Printf("Reload: read %zd new units.\n", AdditionalCorpus.size());
bool Reloaded = false;
for (auto &U : AdditionalCorpus) {
if (U.size() > MaxSize)
U.resize(MaxSize);
if (!Corpus.HasUnit(U)) {
if (size_t NumFeatures = RunOne(U)) {
CheckExitOnSrcPosOrItem();
Corpus.AddToCorpus(U, NumFeatures);
Reloaded = true;
}
}
}
if (Reloaded)
PrintStats("RELOAD");
}
void Fuzzer::ShuffleCorpus(UnitVector *V) {
std::random_shuffle(V->begin(), V->end(), MD.GetRand());
if (Options.PreferSmall)
std::stable_sort(V->begin(), V->end(), [](const Unit &A, const Unit &B) {
return A.size() < B.size();
});
}
void Fuzzer::ShuffleAndMinimize(UnitVector *InitialCorpus) {
Printf("#0\tREAD units: %zd\n", InitialCorpus->size());
if (Options.ShuffleAtStartUp)
ShuffleCorpus(InitialCorpus);
// Test the callback with empty input and never try it again.
uint8_t dummy;
ExecuteCallback(&dummy, 0);
for (const auto &U : *InitialCorpus) {
if (size_t NumFeatures = RunOne(U)) {
CheckExitOnSrcPosOrItem();
Corpus.AddToCorpus(U, NumFeatures);
if (Options.Verbosity >= 2)
Printf("NEW0: %zd L %zd\n", MaxCoverage.BlockCoverage, U.size());
}
TryDetectingAMemoryLeak(U.data(), U.size(),
/*DuringInitialCorpusExecution*/ true);
}
PrintStats("INITED");
if (Corpus.empty()) {
Printf("ERROR: no interesting inputs were found. "
"Is the code instrumented for coverage? Exiting.\n");
exit(1);
}
}
size_t Fuzzer::RunOne(const uint8_t *Data, size_t Size) {
if (!Size) return 0;
TotalNumberOfRuns++;
ExecuteCallback(Data, Size);
size_t Res = 0;
if (size_t NumFeatures = TPC.CollectFeatures([&](size_t Feature) -> bool {
return Corpus.AddFeature(Feature, Size, Options.Shrink);
}))
Res = NumFeatures;
if (!TPC.UsingTracePcGuard()) {
if (TPC.UpdateValueProfileMap(&MaxCoverage.VPMap))
Res = 1;
if (!Res && RecordMaxCoverage(&MaxCoverage))
Res = 1;
}
auto TimeOfUnit =
duration_cast<seconds>(UnitStopTime - UnitStartTime).count();
if (!(TotalNumberOfRuns & (TotalNumberOfRuns - 1)) &&
secondsSinceProcessStartUp() >= 2)
PrintStats("pulse ");
if (TimeOfUnit > TimeOfLongestUnitInSeconds * 1.1 &&
TimeOfUnit >= Options.ReportSlowUnits) {
TimeOfLongestUnitInSeconds = TimeOfUnit;
Printf("Slowest unit: %zd s:\n", TimeOfLongestUnitInSeconds);
WriteUnitToFileWithPrefix({Data, Data + Size}, "slow-unit-");
}
return Res;
}
size_t Fuzzer::GetCurrentUnitInFuzzingThead(const uint8_t **Data) const {
assert(InFuzzingThread());
*Data = CurrentUnitData;
return CurrentUnitSize;
}
void Fuzzer::ExecuteCallback(const uint8_t *Data, size_t Size) {
assert(InFuzzingThread());
// We copy the contents of Unit into a separate heap buffer
// so that we reliably find buffer overflows in it.
uint8_t *DataCopy = new uint8_t[Size];
memcpy(DataCopy, Data, Size);
if (CurrentUnitData && CurrentUnitData != Data)
memcpy(CurrentUnitData, Data, Size);
CurrentUnitSize = Size;
AllocTracer.Start(Options.TraceMalloc);
UnitStartTime = system_clock::now();
ResetCounters(); // Reset coverage right before the callback.
TPC.ResetMaps();
RunningCB = true;
int Res = CB(DataCopy, Size);
RunningCB = false;
UnitStopTime = system_clock::now();
(void)Res;
assert(Res == 0);
HasMoreMallocsThanFrees = AllocTracer.Stop();
CurrentUnitSize = 0;
delete[] DataCopy;
}
void Fuzzer::WriteToOutputCorpus(const Unit &U) {
if (Options.OnlyASCII)
assert(IsASCII(U));
if (Options.OutputCorpus.empty())
return;
std::string Path = DirPlusFile(Options.OutputCorpus, Hash(U));
WriteToFile(U, Path);
if (Options.Verbosity >= 2)
Printf("Written to %s\n", Path.c_str());
}
void Fuzzer::WriteUnitToFileWithPrefix(const Unit &U, const char *Prefix) {
if (!Options.SaveArtifacts)
return;
std::string Path = Options.ArtifactPrefix + Prefix + Hash(U);
if (!Options.ExactArtifactPath.empty())
Path = Options.ExactArtifactPath; // Overrides ArtifactPrefix.
WriteToFile(U, Path);
Printf("artifact_prefix='%s'; Test unit written to %s\n",
Options.ArtifactPrefix.c_str(), Path.c_str());
if (U.size() <= kMaxUnitSizeToPrint)
Printf("Base64: %s\n", Base64(U).c_str());
}
void Fuzzer::PrintStatusForNewUnit(const Unit &U) {
if (!Options.PrintNEW)
return;
PrintStats("NEW ", "");
if (Options.Verbosity) {
Printf(" L: %zd ", U.size());
MD.PrintMutationSequence();
Printf("\n");
}
}
void Fuzzer::ReportNewCoverage(InputInfo *II, const Unit &U) {
II->NumSuccessfullMutations++;
MD.RecordSuccessfulMutationSequence();
PrintStatusForNewUnit(U);
WriteToOutputCorpus(U);
NumberOfNewUnitsAdded++;
TPC.PrintNewPCs();
}
// Finds minimal number of units in 'Extra' that add coverage to 'Initial'.
// We do it by actually executing the units, sometimes more than once,
// because we may be using different coverage-like signals and the only
// common thing between them is that we can say "this unit found new stuff".
UnitVector Fuzzer::FindExtraUnits(const UnitVector &Initial,
const UnitVector &Extra) {
UnitVector Res = Extra;
UnitVector Tmp;
size_t OldSize = Res.size();
for (int Iter = 0; Iter < 10; Iter++) {
ShuffleCorpus(&Res);
TPC.ResetMaps();
Corpus.ResetFeatureSet();
ResetCoverage();
for (auto &U : Initial) {
TPC.ResetMaps();
RunOne(U);
}
Tmp.clear();
for (auto &U : Res) {
TPC.ResetMaps();
if (RunOne(U))
Tmp.push_back(U);
}
char Stat[7] = "MIN ";
Stat[3] = '0' + Iter;
PrintStats(Stat, "\n", Tmp.size());
size_t NewSize = Tmp.size();
assert(NewSize <= OldSize);
Res.swap(Tmp);
if (NewSize + 5 >= OldSize)
break;
OldSize = NewSize;
}
return Res;
}
void Fuzzer::Merge(const std::vector<std::string> &Corpora) {
if (Corpora.size() <= 1) {
Printf("Merge requires two or more corpus dirs\n");
return;
}
InMergeMode = true;
std::vector<std::string> ExtraCorpora(Corpora.begin() + 1, Corpora.end());
assert(MaxInputLen > 0);
UnitVector Initial, Extra;
ReadDirToVectorOfUnits(Corpora[0].c_str(), &Initial, nullptr, MaxInputLen,
true);
for (auto &C : ExtraCorpora)
ReadDirToVectorOfUnits(C.c_str(), &Extra, nullptr, MaxInputLen, true);
if (!Initial.empty()) {
Printf("=== Minimizing the initial corpus of %zd units\n", Initial.size());
Initial = FindExtraUnits({}, Initial);
}
Printf("=== Merging extra %zd units\n", Extra.size());
auto Res = FindExtraUnits(Initial, Extra);
for (auto &U: Res)
WriteToOutputCorpus(U);
Printf("=== Merge: written %zd units\n", Res.size());
}
// Tries detecting a memory leak on the particular input that we have just
// executed before calling this function.
void Fuzzer::TryDetectingAMemoryLeak(const uint8_t *Data, size_t Size,
bool DuringInitialCorpusExecution) {
if (!HasMoreMallocsThanFrees) return; // mallocs==frees, a leak is unlikely.
if (!Options.DetectLeaks) return;
if (!&(EF->__lsan_enable) || !&(EF->__lsan_disable) ||
!(EF->__lsan_do_recoverable_leak_check))
return; // No lsan.
// Run the target once again, but with lsan disabled so that if there is
// a real leak we do not report it twice.
EF->__lsan_disable();
ExecuteCallback(Data, Size);
EF->__lsan_enable();
if (!HasMoreMallocsThanFrees) return; // a leak is unlikely.
if (NumberOfLeakDetectionAttempts++ > 1000) {
Options.DetectLeaks = false;
Printf("INFO: libFuzzer disabled leak detection after every mutation.\n"
" Most likely the target function accumulates allocated\n"
" memory in a global state w/o actually leaking it.\n"
" You may try running this binary with -trace_malloc=[12]"
" to get a trace of mallocs and frees.\n"
" If LeakSanitizer is enabled in this process it will still\n"
" run on the process shutdown.\n");
return;
}
// Now perform the actual lsan pass. This is expensive and we must ensure
// we don't call it too often.
if (EF->__lsan_do_recoverable_leak_check()) { // Leak is found, report it.
if (DuringInitialCorpusExecution)
Printf("\nINFO: a leak has been found in the initial corpus.\n\n");
Printf("INFO: to ignore leaks on libFuzzer side use -detect_leaks=0.\n\n");
CurrentUnitSize = Size;
DumpCurrentUnit("leak-");
PrintFinalStats();
_Exit(Options.ErrorExitCode); // not exit() to disable lsan further on.
}
}
static size_t ComputeMutationLen(size_t MaxInputSize, size_t MaxMutationLen,
Random &Rand) {
assert(MaxInputSize <= MaxMutationLen);
if (MaxInputSize == MaxMutationLen) return MaxMutationLen;
size_t Result = MaxInputSize;
size_t R = Rand.Rand();
if ((R % (1U << 7)) == 0)
Result++;
if ((R % (1U << 15)) == 0)
Result += 10 + Result / 2;
return Min(Result, MaxMutationLen);
}
void Fuzzer::MutateAndTestOne() {
MD.StartMutationSequence();
auto &II = Corpus.ChooseUnitToMutate(MD.GetRand());
const auto &U = II.U;
memcpy(BaseSha1, II.Sha1, sizeof(BaseSha1));
assert(CurrentUnitData);
size_t Size = U.size();
assert(Size <= MaxInputLen && "Oversized Unit");
memcpy(CurrentUnitData, U.data(), Size);
assert(MaxMutationLen > 0);
size_t CurrentMaxMutationLen =
Options.ExperimentalLenControl
? ComputeMutationLen(Corpus.MaxInputSize(), MaxMutationLen,
MD.GetRand())
: MaxMutationLen;
for (int i = 0; i < Options.MutateDepth; i++) {
if (TotalNumberOfRuns >= Options.MaxNumberOfRuns)
break;
size_t NewSize = 0;
NewSize = MD.Mutate(CurrentUnitData, Size, CurrentMaxMutationLen);
assert(NewSize > 0 && "Mutator returned empty unit");
assert(NewSize <= CurrentMaxMutationLen && "Mutator return overisized unit");
Size = NewSize;
if (i == 0)
StartTraceRecording();
II.NumExecutedMutations++;
if (size_t NumFeatures = RunOne(CurrentUnitData, Size)) {
Corpus.AddToCorpus({CurrentUnitData, CurrentUnitData + Size}, NumFeatures,
/*MayDeleteFile=*/true);
ReportNewCoverage(&II, {CurrentUnitData, CurrentUnitData + Size});
CheckExitOnSrcPosOrItem();
}
StopTraceRecording();
TryDetectingAMemoryLeak(CurrentUnitData, Size,
/*DuringInitialCorpusExecution*/ false);
}
}
void Fuzzer::ResetCoverage() {
ResetEdgeCoverage();
MaxCoverage.Reset();
PrepareCounters(&MaxCoverage);
}
void Fuzzer::Loop() {
TPC.InitializePrintNewPCs();
system_clock::time_point LastCorpusReload = system_clock::now();
if (Options.DoCrossOver)
MD.SetCorpus(&Corpus);
while (true) {
auto Now = system_clock::now();
if (duration_cast<seconds>(Now - LastCorpusReload).count() >=
Options.ReloadIntervalSec) {
RereadOutputCorpus(MaxInputLen);
LastCorpusReload = system_clock::now();
}
if (TotalNumberOfRuns >= Options.MaxNumberOfRuns)
break;
if (TimedOut()) break;
// Perform several mutations and runs.
MutateAndTestOne();
}
PrintStats("DONE ", "\n");
MD.PrintRecommendedDictionary();
}
void Fuzzer::MinimizeCrashLoop(const Unit &U) {
if (U.size() <= 2) return;
while (!TimedOut() && TotalNumberOfRuns < Options.MaxNumberOfRuns) {
MD.StartMutationSequence();
memcpy(CurrentUnitData, U.data(), U.size());
for (int i = 0; i < Options.MutateDepth; i++) {
size_t NewSize = MD.Mutate(CurrentUnitData, U.size(), MaxMutationLen);
assert(NewSize > 0 && NewSize <= MaxMutationLen);
RunOne(CurrentUnitData, NewSize);
TryDetectingAMemoryLeak(CurrentUnitData, NewSize,
/*DuringInitialCorpusExecution*/ false);
}
}
}
} // namespace fuzzer
extern "C" {
size_t LLVMFuzzerMutate(uint8_t *Data, size_t Size, size_t MaxSize) {
assert(fuzzer::F);
return fuzzer::F->GetMD().DefaultMutate(Data, Size, MaxSize);
}
} // extern "C"
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