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Diffstat (limited to 'clang/lib/StaticAnalyzer/Checkers/PointerArithChecker.cpp')
| -rw-r--r-- | clang/lib/StaticAnalyzer/Checkers/PointerArithChecker.cpp | 348 |
1 files changed, 348 insertions, 0 deletions
diff --git a/clang/lib/StaticAnalyzer/Checkers/PointerArithChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/PointerArithChecker.cpp new file mode 100644 index 0000000000000..259f23abdc958 --- /dev/null +++ b/clang/lib/StaticAnalyzer/Checkers/PointerArithChecker.cpp @@ -0,0 +1,348 @@ +//=== 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 LangOptions &LO) { + return true; +} |