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//== ValistChecker.cpp - stdarg.h macro usage checker -----------*- C++ -*--==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This defines checkers which detect usage of uninitialized va_list values
// and va_start calls with no matching va_end.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
using namespace clang;
using namespace ento;
REGISTER_SET_WITH_PROGRAMSTATE(InitializedVALists, const MemRegion *)
namespace {
typedef SmallVector<const MemRegion *, 2> RegionVector;
class ValistChecker : public Checker<check::PreCall, check::PreStmt<VAArgExpr>,
check::DeadSymbols> {
mutable std::unique_ptr<BugType> BT_leakedvalist, BT_uninitaccess;
struct VAListAccepter {
CallDescription Func;
int VAListPos;
};
static const SmallVector<VAListAccepter, 15> VAListAccepters;
static const CallDescription VaStart, VaEnd, VaCopy;
public:
enum CheckKind {
CK_Uninitialized,
CK_Unterminated,
CK_CopyToSelf,
CK_NumCheckKinds
};
DefaultBool ChecksEnabled[CK_NumCheckKinds];
CheckerNameRef CheckNames[CK_NumCheckKinds];
void checkPreStmt(const VAArgExpr *VAA, CheckerContext &C) const;
void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const;
private:
const MemRegion *getVAListAsRegion(SVal SV, const Expr *VAExpr,
bool &IsSymbolic, CheckerContext &C) const;
const ExplodedNode *getStartCallSite(const ExplodedNode *N,
const MemRegion *Reg) const;
void reportUninitializedAccess(const MemRegion *VAList, StringRef Msg,
CheckerContext &C) const;
void reportLeakedVALists(const RegionVector &LeakedVALists, StringRef Msg1,
StringRef Msg2, CheckerContext &C, ExplodedNode *N,
bool ReportUninit = false) const;
void checkVAListStartCall(const CallEvent &Call, CheckerContext &C,
bool IsCopy) const;
void checkVAListEndCall(const CallEvent &Call, CheckerContext &C) const;
class ValistBugVisitor : public BugReporterVisitor {
public:
ValistBugVisitor(const MemRegion *Reg, bool IsLeak = false)
: Reg(Reg), IsLeak(IsLeak) {}
void Profile(llvm::FoldingSetNodeID &ID) const override {
static int X = 0;
ID.AddPointer(&X);
ID.AddPointer(Reg);
}
PathDiagnosticPieceRef getEndPath(BugReporterContext &BRC,
const ExplodedNode *EndPathNode,
PathSensitiveBugReport &BR) override {
if (!IsLeak)
return nullptr;
PathDiagnosticLocation L = BR.getLocation();
// Do not add the statement itself as a range in case of leak.
return std::make_shared<PathDiagnosticEventPiece>(L, BR.getDescription(),
false);
}
PathDiagnosticPieceRef VisitNode(const ExplodedNode *N,
BugReporterContext &BRC,
PathSensitiveBugReport &BR) override;
private:
const MemRegion *Reg;
bool IsLeak;
};
};
const SmallVector<ValistChecker::VAListAccepter, 15>
ValistChecker::VAListAccepters = {
{{"vfprintf", 3}, 2},
{{"vfscanf", 3}, 2},
{{"vprintf", 2}, 1},
{{"vscanf", 2}, 1},
{{"vsnprintf", 4}, 3},
{{"vsprintf", 3}, 2},
{{"vsscanf", 3}, 2},
{{"vfwprintf", 3}, 2},
{{"vfwscanf", 3}, 2},
{{"vwprintf", 2}, 1},
{{"vwscanf", 2}, 1},
{{"vswprintf", 4}, 3},
// vswprintf is the wide version of vsnprintf,
// vsprintf has no wide version
{{"vswscanf", 3}, 2}};
const CallDescription
ValistChecker::VaStart("__builtin_va_start", /*Args=*/2, /*Params=*/1),
ValistChecker::VaCopy("__builtin_va_copy", 2),
ValistChecker::VaEnd("__builtin_va_end", 1);
} // end anonymous namespace
void ValistChecker::checkPreCall(const CallEvent &Call,
CheckerContext &C) const {
if (!Call.isGlobalCFunction())
return;
if (Call.isCalled(VaStart))
checkVAListStartCall(Call, C, false);
else if (Call.isCalled(VaCopy))
checkVAListStartCall(Call, C, true);
else if (Call.isCalled(VaEnd))
checkVAListEndCall(Call, C);
else {
for (auto FuncInfo : VAListAccepters) {
if (!Call.isCalled(FuncInfo.Func))
continue;
bool Symbolic;
const MemRegion *VAList =
getVAListAsRegion(Call.getArgSVal(FuncInfo.VAListPos),
Call.getArgExpr(FuncInfo.VAListPos), Symbolic, C);
if (!VAList)
return;
if (C.getState()->contains<InitializedVALists>(VAList))
return;
// We did not see va_start call, but the source of the region is unknown.
// Be conservative and assume the best.
if (Symbolic)
return;
SmallString<80> Errmsg("Function '");
Errmsg += FuncInfo.Func.getFunctionName();
Errmsg += "' is called with an uninitialized va_list argument";
reportUninitializedAccess(VAList, Errmsg.c_str(), C);
break;
}
}
}
const MemRegion *ValistChecker::getVAListAsRegion(SVal SV, const Expr *E,
bool &IsSymbolic,
CheckerContext &C) const {
const MemRegion *Reg = SV.getAsRegion();
if (!Reg)
return nullptr;
// TODO: In the future this should be abstracted away by the analyzer.
bool VaListModelledAsArray = false;
if (const auto *Cast = dyn_cast<CastExpr>(E)) {
QualType Ty = Cast->getType();
VaListModelledAsArray =
Ty->isPointerType() && Ty->getPointeeType()->isRecordType();
}
if (const auto *DeclReg = Reg->getAs<DeclRegion>()) {
if (isa<ParmVarDecl>(DeclReg->getDecl()))
Reg = C.getState()->getSVal(SV.castAs<Loc>()).getAsRegion();
}
IsSymbolic = Reg && Reg->getAs<SymbolicRegion>();
// Some VarRegion based VA lists reach here as ElementRegions.
const auto *EReg = dyn_cast_or_null<ElementRegion>(Reg);
return (EReg && VaListModelledAsArray) ? EReg->getSuperRegion() : Reg;
}
void ValistChecker::checkPreStmt(const VAArgExpr *VAA,
CheckerContext &C) const {
ProgramStateRef State = C.getState();
const Expr *VASubExpr = VAA->getSubExpr();
SVal VAListSVal = C.getSVal(VASubExpr);
bool Symbolic;
const MemRegion *VAList =
getVAListAsRegion(VAListSVal, VASubExpr, Symbolic, C);
if (!VAList)
return;
if (Symbolic)
return;
if (!State->contains<InitializedVALists>(VAList))
reportUninitializedAccess(
VAList, "va_arg() is called on an uninitialized va_list", C);
}
void ValistChecker::checkDeadSymbols(SymbolReaper &SR,
CheckerContext &C) const {
ProgramStateRef State = C.getState();
InitializedVAListsTy TrackedVALists = State->get<InitializedVALists>();
RegionVector LeakedVALists;
for (auto Reg : TrackedVALists) {
if (SR.isLiveRegion(Reg))
continue;
LeakedVALists.push_back(Reg);
State = State->remove<InitializedVALists>(Reg);
}
if (ExplodedNode *N = C.addTransition(State))
reportLeakedVALists(LeakedVALists, "Initialized va_list", " is leaked", C,
N);
}
// This function traverses the exploded graph backwards and finds the node where
// the va_list is initialized. That node is used for uniquing the bug paths.
// It is not likely that there are several different va_lists that belongs to
// different stack frames, so that case is not yet handled.
const ExplodedNode *
ValistChecker::getStartCallSite(const ExplodedNode *N,
const MemRegion *Reg) const {
const LocationContext *LeakContext = N->getLocationContext();
const ExplodedNode *StartCallNode = N;
bool FoundInitializedState = false;
while (N) {
ProgramStateRef State = N->getState();
if (!State->contains<InitializedVALists>(Reg)) {
if (FoundInitializedState)
break;
} else {
FoundInitializedState = true;
}
const LocationContext *NContext = N->getLocationContext();
if (NContext == LeakContext || NContext->isParentOf(LeakContext))
StartCallNode = N;
N = N->pred_empty() ? nullptr : *(N->pred_begin());
}
return StartCallNode;
}
void ValistChecker::reportUninitializedAccess(const MemRegion *VAList,
StringRef Msg,
CheckerContext &C) const {
if (!ChecksEnabled[CK_Uninitialized])
return;
if (ExplodedNode *N = C.generateErrorNode()) {
if (!BT_uninitaccess)
BT_uninitaccess.reset(new BugType(CheckNames[CK_Uninitialized],
"Uninitialized va_list",
categories::MemoryError));
auto R = std::make_unique<PathSensitiveBugReport>(*BT_uninitaccess, Msg, N);
R->markInteresting(VAList);
R->addVisitor(std::make_unique<ValistBugVisitor>(VAList));
C.emitReport(std::move(R));
}
}
void ValistChecker::reportLeakedVALists(const RegionVector &LeakedVALists,
StringRef Msg1, StringRef Msg2,
CheckerContext &C, ExplodedNode *N,
bool ReportUninit) const {
if (!(ChecksEnabled[CK_Unterminated] ||
(ChecksEnabled[CK_Uninitialized] && ReportUninit)))
return;
for (auto Reg : LeakedVALists) {
if (!BT_leakedvalist) {
// FIXME: maybe creating a new check name for this type of bug is a better
// solution.
BT_leakedvalist.reset(
new BugType(CheckNames[CK_Unterminated].getName().empty()
? CheckNames[CK_Uninitialized]
: CheckNames[CK_Unterminated],
"Leaked va_list", categories::MemoryError,
/*SuppressOnSink=*/true));
}
const ExplodedNode *StartNode = getStartCallSite(N, Reg);
PathDiagnosticLocation LocUsedForUniqueing;
if (const Stmt *StartCallStmt = StartNode->getStmtForDiagnostics())
LocUsedForUniqueing = PathDiagnosticLocation::createBegin(
StartCallStmt, C.getSourceManager(), StartNode->getLocationContext());
SmallString<100> Buf;
llvm::raw_svector_ostream OS(Buf);
OS << Msg1;
std::string VariableName = Reg->getDescriptiveName();
if (!VariableName.empty())
OS << " " << VariableName;
OS << Msg2;
auto R = std::make_unique<PathSensitiveBugReport>(
*BT_leakedvalist, OS.str(), N, LocUsedForUniqueing,
StartNode->getLocationContext()->getDecl());
R->markInteresting(Reg);
R->addVisitor(std::make_unique<ValistBugVisitor>(Reg, true));
C.emitReport(std::move(R));
}
}
void ValistChecker::checkVAListStartCall(const CallEvent &Call,
CheckerContext &C, bool IsCopy) const {
bool Symbolic;
const MemRegion *VAList =
getVAListAsRegion(Call.getArgSVal(0), Call.getArgExpr(0), Symbolic, C);
if (!VAList)
return;
ProgramStateRef State = C.getState();
if (IsCopy) {
const MemRegion *Arg2 =
getVAListAsRegion(Call.getArgSVal(1), Call.getArgExpr(1), Symbolic, C);
if (Arg2) {
if (ChecksEnabled[CK_CopyToSelf] && VAList == Arg2) {
RegionVector LeakedVALists{VAList};
if (ExplodedNode *N = C.addTransition(State))
reportLeakedVALists(LeakedVALists, "va_list",
" is copied onto itself", C, N, true);
return;
} else if (!State->contains<InitializedVALists>(Arg2) && !Symbolic) {
if (State->contains<InitializedVALists>(VAList)) {
State = State->remove<InitializedVALists>(VAList);
RegionVector LeakedVALists{VAList};
if (ExplodedNode *N = C.addTransition(State))
reportLeakedVALists(LeakedVALists, "Initialized va_list",
" is overwritten by an uninitialized one", C, N,
true);
} else {
reportUninitializedAccess(Arg2, "Uninitialized va_list is copied", C);
}
return;
}
}
}
if (State->contains<InitializedVALists>(VAList)) {
RegionVector LeakedVALists{VAList};
if (ExplodedNode *N = C.addTransition(State))
reportLeakedVALists(LeakedVALists, "Initialized va_list",
" is initialized again", C, N);
return;
}
State = State->add<InitializedVALists>(VAList);
C.addTransition(State);
}
void ValistChecker::checkVAListEndCall(const CallEvent &Call,
CheckerContext &C) const {
bool Symbolic;
const MemRegion *VAList =
getVAListAsRegion(Call.getArgSVal(0), Call.getArgExpr(0), Symbolic, C);
if (!VAList)
return;
// We did not see va_start call, but the source of the region is unknown.
// Be conservative and assume the best.
if (Symbolic)
return;
if (!C.getState()->contains<InitializedVALists>(VAList)) {
reportUninitializedAccess(
VAList, "va_end() is called on an uninitialized va_list", C);
return;
}
ProgramStateRef State = C.getState();
State = State->remove<InitializedVALists>(VAList);
C.addTransition(State);
}
PathDiagnosticPieceRef ValistChecker::ValistBugVisitor::VisitNode(
const ExplodedNode *N, BugReporterContext &BRC, PathSensitiveBugReport &) {
ProgramStateRef State = N->getState();
ProgramStateRef StatePrev = N->getFirstPred()->getState();
const Stmt *S = N->getStmtForDiagnostics();
if (!S)
return nullptr;
StringRef Msg;
if (State->contains<InitializedVALists>(Reg) &&
!StatePrev->contains<InitializedVALists>(Reg))
Msg = "Initialized va_list";
else if (!State->contains<InitializedVALists>(Reg) &&
StatePrev->contains<InitializedVALists>(Reg))
Msg = "Ended va_list";
if (Msg.empty())
return nullptr;
PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
N->getLocationContext());
return std::make_shared<PathDiagnosticEventPiece>(Pos, Msg, true);
}
void ento::registerValistBase(CheckerManager &mgr) {
mgr.registerChecker<ValistChecker>();
}
bool ento::shouldRegisterValistBase(const LangOptions &LO) {
return true;
}
#define REGISTER_CHECKER(name) \
void ento::register##name##Checker(CheckerManager &mgr) { \
ValistChecker *checker = mgr.getChecker<ValistChecker>(); \
checker->ChecksEnabled[ValistChecker::CK_##name] = true; \
checker->CheckNames[ValistChecker::CK_##name] = \
mgr.getCurrentCheckerName(); \
} \
\
bool ento::shouldRegister##name##Checker(const LangOptions &LO) { \
return true; \
}
REGISTER_CHECKER(Uninitialized)
REGISTER_CHECKER(Unterminated)
REGISTER_CHECKER(CopyToSelf)