You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
349 lines
12 KiB
349 lines
12 KiB
//=== PointerArithChecker.cpp - Pointer arithmetic 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 files defines PointerArithChecker, a builtin checker that checks for
|
|
// pointer arithmetic on locations other than array elements.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
|
|
#include "clang/AST/DeclCXX.h"
|
|
#include "clang/AST/ExprCXX.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/CheckerContext.h"
|
|
|
|
using namespace clang;
|
|
using namespace ento;
|
|
|
|
namespace {
|
|
enum class AllocKind {
|
|
SingleObject,
|
|
Array,
|
|
Unknown,
|
|
Reinterpreted // Single object interpreted as an array.
|
|
};
|
|
} // end namespace
|
|
|
|
namespace llvm {
|
|
template <> struct FoldingSetTrait<AllocKind> {
|
|
static inline void Profile(AllocKind X, FoldingSetNodeID &ID) {
|
|
ID.AddInteger(static_cast<int>(X));
|
|
}
|
|
};
|
|
} // end namespace llvm
|
|
|
|
namespace {
|
|
class PointerArithChecker
|
|
: public Checker<
|
|
check::PreStmt<BinaryOperator>, check::PreStmt<UnaryOperator>,
|
|
check::PreStmt<ArraySubscriptExpr>, check::PreStmt<CastExpr>,
|
|
check::PostStmt<CastExpr>, check::PostStmt<CXXNewExpr>,
|
|
check::PostStmt<CallExpr>, check::DeadSymbols> {
|
|
AllocKind getKindOfNewOp(const CXXNewExpr *NE, const FunctionDecl *FD) const;
|
|
const MemRegion *getArrayRegion(const MemRegion *Region, bool &Polymorphic,
|
|
AllocKind &AKind, CheckerContext &C) const;
|
|
const MemRegion *getPointedRegion(const MemRegion *Region,
|
|
CheckerContext &C) const;
|
|
void reportPointerArithMisuse(const Expr *E, CheckerContext &C,
|
|
bool PointedNeeded = false) const;
|
|
void initAllocIdentifiers(ASTContext &C) const;
|
|
|
|
mutable std::unique_ptr<BuiltinBug> BT_pointerArith;
|
|
mutable std::unique_ptr<BuiltinBug> BT_polyArray;
|
|
mutable llvm::SmallSet<IdentifierInfo *, 8> AllocFunctions;
|
|
|
|
public:
|
|
void checkPreStmt(const UnaryOperator *UOp, CheckerContext &C) const;
|
|
void checkPreStmt(const BinaryOperator *BOp, CheckerContext &C) const;
|
|
void checkPreStmt(const ArraySubscriptExpr *SubExpr, CheckerContext &C) const;
|
|
void checkPreStmt(const CastExpr *CE, CheckerContext &C) const;
|
|
void checkPostStmt(const CastExpr *CE, CheckerContext &C) const;
|
|
void checkPostStmt(const CXXNewExpr *NE, CheckerContext &C) const;
|
|
void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
|
|
void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const;
|
|
};
|
|
} // end namespace
|
|
|
|
REGISTER_MAP_WITH_PROGRAMSTATE(RegionState, const MemRegion *, AllocKind)
|
|
|
|
void PointerArithChecker::checkDeadSymbols(SymbolReaper &SR,
|
|
CheckerContext &C) const {
|
|
// TODO: intentional leak. Some information is garbage collected too early,
|
|
// see http://reviews.llvm.org/D14203 for further information.
|
|
/*ProgramStateRef State = C.getState();
|
|
RegionStateTy RegionStates = State->get<RegionState>();
|
|
for (RegionStateTy::iterator I = RegionStates.begin(), E = RegionStates.end();
|
|
I != E; ++I) {
|
|
if (!SR.isLiveRegion(I->first))
|
|
State = State->remove<RegionState>(I->first);
|
|
}
|
|
C.addTransition(State);*/
|
|
}
|
|
|
|
AllocKind PointerArithChecker::getKindOfNewOp(const CXXNewExpr *NE,
|
|
const FunctionDecl *FD) const {
|
|
// This checker try not to assume anything about placement and overloaded
|
|
// new to avoid false positives.
|
|
if (isa<CXXMethodDecl>(FD))
|
|
return AllocKind::Unknown;
|
|
if (FD->getNumParams() != 1 || FD->isVariadic())
|
|
return AllocKind::Unknown;
|
|
if (NE->isArray())
|
|
return AllocKind::Array;
|
|
|
|
return AllocKind::SingleObject;
|
|
}
|
|
|
|
const MemRegion *
|
|
PointerArithChecker::getPointedRegion(const MemRegion *Region,
|
|
CheckerContext &C) const {
|
|
assert(Region);
|
|
ProgramStateRef State = C.getState();
|
|
SVal S = State->getSVal(Region);
|
|
return S.getAsRegion();
|
|
}
|
|
|
|
/// Checks whether a region is the part of an array.
|
|
/// In case there is a derived to base cast above the array element, the
|
|
/// Polymorphic output value is set to true. AKind output value is set to the
|
|
/// allocation kind of the inspected region.
|
|
const MemRegion *PointerArithChecker::getArrayRegion(const MemRegion *Region,
|
|
bool &Polymorphic,
|
|
AllocKind &AKind,
|
|
CheckerContext &C) const {
|
|
assert(Region);
|
|
while (const auto *BaseRegion = dyn_cast<CXXBaseObjectRegion>(Region)) {
|
|
Region = BaseRegion->getSuperRegion();
|
|
Polymorphic = true;
|
|
}
|
|
if (const auto *ElemRegion = dyn_cast<ElementRegion>(Region)) {
|
|
Region = ElemRegion->getSuperRegion();
|
|
}
|
|
|
|
ProgramStateRef State = C.getState();
|
|
if (const AllocKind *Kind = State->get<RegionState>(Region)) {
|
|
AKind = *Kind;
|
|
if (*Kind == AllocKind::Array)
|
|
return Region;
|
|
else
|
|
return nullptr;
|
|
}
|
|
// When the region is symbolic and we do not have any information about it,
|
|
// assume that this is an array to avoid false positives.
|
|
if (isa<SymbolicRegion>(Region))
|
|
return Region;
|
|
|
|
// No AllocKind stored and not symbolic, assume that it points to a single
|
|
// object.
|
|
return nullptr;
|
|
}
|
|
|
|
void PointerArithChecker::reportPointerArithMisuse(const Expr *E,
|
|
CheckerContext &C,
|
|
bool PointedNeeded) const {
|
|
SourceRange SR = E->getSourceRange();
|
|
if (SR.isInvalid())
|
|
return;
|
|
|
|
ProgramStateRef State = C.getState();
|
|
const MemRegion *Region = C.getSVal(E).getAsRegion();
|
|
if (!Region)
|
|
return;
|
|
if (PointedNeeded)
|
|
Region = getPointedRegion(Region, C);
|
|
if (!Region)
|
|
return;
|
|
|
|
bool IsPolymorphic = false;
|
|
AllocKind Kind = AllocKind::Unknown;
|
|
if (const MemRegion *ArrayRegion =
|
|
getArrayRegion(Region, IsPolymorphic, Kind, C)) {
|
|
if (!IsPolymorphic)
|
|
return;
|
|
if (ExplodedNode *N = C.generateNonFatalErrorNode()) {
|
|
if (!BT_polyArray)
|
|
BT_polyArray.reset(new BuiltinBug(
|
|
this, "Dangerous pointer arithmetic",
|
|
"Pointer arithmetic on a pointer to base class is dangerous "
|
|
"because derived and base class may have different size."));
|
|
auto R = std::make_unique<PathSensitiveBugReport>(
|
|
*BT_polyArray, BT_polyArray->getDescription(), N);
|
|
R->addRange(E->getSourceRange());
|
|
R->markInteresting(ArrayRegion);
|
|
C.emitReport(std::move(R));
|
|
}
|
|
return;
|
|
}
|
|
|
|
if (Kind == AllocKind::Reinterpreted)
|
|
return;
|
|
|
|
// We might not have enough information about symbolic regions.
|
|
if (Kind != AllocKind::SingleObject &&
|
|
Region->getKind() == MemRegion::Kind::SymbolicRegionKind)
|
|
return;
|
|
|
|
if (ExplodedNode *N = C.generateNonFatalErrorNode()) {
|
|
if (!BT_pointerArith)
|
|
BT_pointerArith.reset(new BuiltinBug(this, "Dangerous pointer arithmetic",
|
|
"Pointer arithmetic on non-array "
|
|
"variables relies on memory layout, "
|
|
"which is dangerous."));
|
|
auto R = std::make_unique<PathSensitiveBugReport>(
|
|
*BT_pointerArith, BT_pointerArith->getDescription(), N);
|
|
R->addRange(SR);
|
|
R->markInteresting(Region);
|
|
C.emitReport(std::move(R));
|
|
}
|
|
}
|
|
|
|
void PointerArithChecker::initAllocIdentifiers(ASTContext &C) const {
|
|
if (!AllocFunctions.empty())
|
|
return;
|
|
AllocFunctions.insert(&C.Idents.get("alloca"));
|
|
AllocFunctions.insert(&C.Idents.get("malloc"));
|
|
AllocFunctions.insert(&C.Idents.get("realloc"));
|
|
AllocFunctions.insert(&C.Idents.get("calloc"));
|
|
AllocFunctions.insert(&C.Idents.get("valloc"));
|
|
}
|
|
|
|
void PointerArithChecker::checkPostStmt(const CallExpr *CE,
|
|
CheckerContext &C) const {
|
|
ProgramStateRef State = C.getState();
|
|
const FunctionDecl *FD = C.getCalleeDecl(CE);
|
|
if (!FD)
|
|
return;
|
|
IdentifierInfo *FunI = FD->getIdentifier();
|
|
initAllocIdentifiers(C.getASTContext());
|
|
if (AllocFunctions.count(FunI) == 0)
|
|
return;
|
|
|
|
SVal SV = C.getSVal(CE);
|
|
const MemRegion *Region = SV.getAsRegion();
|
|
if (!Region)
|
|
return;
|
|
// Assume that C allocation functions allocate arrays to avoid false
|
|
// positives.
|
|
// TODO: Add heuristics to distinguish alloc calls that allocates single
|
|
// objecs.
|
|
State = State->set<RegionState>(Region, AllocKind::Array);
|
|
C.addTransition(State);
|
|
}
|
|
|
|
void PointerArithChecker::checkPostStmt(const CXXNewExpr *NE,
|
|
CheckerContext &C) const {
|
|
const FunctionDecl *FD = NE->getOperatorNew();
|
|
if (!FD)
|
|
return;
|
|
|
|
AllocKind Kind = getKindOfNewOp(NE, FD);
|
|
|
|
ProgramStateRef State = C.getState();
|
|
SVal AllocedVal = C.getSVal(NE);
|
|
const MemRegion *Region = AllocedVal.getAsRegion();
|
|
if (!Region)
|
|
return;
|
|
State = State->set<RegionState>(Region, Kind);
|
|
C.addTransition(State);
|
|
}
|
|
|
|
void PointerArithChecker::checkPostStmt(const CastExpr *CE,
|
|
CheckerContext &C) const {
|
|
if (CE->getCastKind() != CastKind::CK_BitCast)
|
|
return;
|
|
|
|
const Expr *CastedExpr = CE->getSubExpr();
|
|
ProgramStateRef State = C.getState();
|
|
SVal CastedVal = C.getSVal(CastedExpr);
|
|
|
|
const MemRegion *Region = CastedVal.getAsRegion();
|
|
if (!Region)
|
|
return;
|
|
|
|
// Suppress reinterpret casted hits.
|
|
State = State->set<RegionState>(Region, AllocKind::Reinterpreted);
|
|
C.addTransition(State);
|
|
}
|
|
|
|
void PointerArithChecker::checkPreStmt(const CastExpr *CE,
|
|
CheckerContext &C) const {
|
|
if (CE->getCastKind() != CastKind::CK_ArrayToPointerDecay)
|
|
return;
|
|
|
|
const Expr *CastedExpr = CE->getSubExpr();
|
|
ProgramStateRef State = C.getState();
|
|
SVal CastedVal = C.getSVal(CastedExpr);
|
|
|
|
const MemRegion *Region = CastedVal.getAsRegion();
|
|
if (!Region)
|
|
return;
|
|
|
|
if (const AllocKind *Kind = State->get<RegionState>(Region)) {
|
|
if (*Kind == AllocKind::Array || *Kind == AllocKind::Reinterpreted)
|
|
return;
|
|
}
|
|
State = State->set<RegionState>(Region, AllocKind::Array);
|
|
C.addTransition(State);
|
|
}
|
|
|
|
void PointerArithChecker::checkPreStmt(const UnaryOperator *UOp,
|
|
CheckerContext &C) const {
|
|
if (!UOp->isIncrementDecrementOp() || !UOp->getType()->isPointerType())
|
|
return;
|
|
reportPointerArithMisuse(UOp->getSubExpr(), C, true);
|
|
}
|
|
|
|
void PointerArithChecker::checkPreStmt(const ArraySubscriptExpr *SubsExpr,
|
|
CheckerContext &C) const {
|
|
SVal Idx = C.getSVal(SubsExpr->getIdx());
|
|
|
|
// Indexing with 0 is OK.
|
|
if (Idx.isZeroConstant())
|
|
return;
|
|
|
|
// Indexing vector-type expressions is also OK.
|
|
if (SubsExpr->getBase()->getType()->isVectorType())
|
|
return;
|
|
reportPointerArithMisuse(SubsExpr->getBase(), C);
|
|
}
|
|
|
|
void PointerArithChecker::checkPreStmt(const BinaryOperator *BOp,
|
|
CheckerContext &C) const {
|
|
BinaryOperatorKind OpKind = BOp->getOpcode();
|
|
if (!BOp->isAdditiveOp() && OpKind != BO_AddAssign && OpKind != BO_SubAssign)
|
|
return;
|
|
|
|
const Expr *Lhs = BOp->getLHS();
|
|
const Expr *Rhs = BOp->getRHS();
|
|
ProgramStateRef State = C.getState();
|
|
|
|
if (Rhs->getType()->isIntegerType() && Lhs->getType()->isPointerType()) {
|
|
SVal RHSVal = C.getSVal(Rhs);
|
|
if (State->isNull(RHSVal).isConstrainedTrue())
|
|
return;
|
|
reportPointerArithMisuse(Lhs, C, !BOp->isAdditiveOp());
|
|
}
|
|
// The int += ptr; case is not valid C++.
|
|
if (Lhs->getType()->isIntegerType() && Rhs->getType()->isPointerType()) {
|
|
SVal LHSVal = C.getSVal(Lhs);
|
|
if (State->isNull(LHSVal).isConstrainedTrue())
|
|
return;
|
|
reportPointerArithMisuse(Rhs, C);
|
|
}
|
|
}
|
|
|
|
void ento::registerPointerArithChecker(CheckerManager &mgr) {
|
|
mgr.registerChecker<PointerArithChecker>();
|
|
}
|
|
|
|
bool ento::shouldRegisterPointerArithChecker(const CheckerManager &mgr) {
|
|
return true;
|
|
}
|