1 //=== PointerArithChecker.cpp - Pointer arithmetic checker -----*- C++ -*--===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // This files defines PointerArithChecker, a builtin checker that checks for
10 // pointer arithmetic on locations other than array elements.
12 //===----------------------------------------------------------------------===//
14 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
15 #include "clang/AST/DeclCXX.h"
16 #include "clang/AST/ExprCXX.h"
17 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
18 #include "clang/StaticAnalyzer/Core/Checker.h"
19 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
20 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
22 using namespace clang;
26 enum class AllocKind {
30 Reinterpreted // Single object interpreted as an array.
35 template <> struct FoldingSetTrait<AllocKind> {
36 static inline void Profile(AllocKind X, FoldingSetNodeID &ID) {
37 ID.AddInteger(static_cast<int>(X));
40 } // end namespace llvm
43 class PointerArithChecker
45 check::PreStmt<BinaryOperator>, check::PreStmt<UnaryOperator>,
46 check::PreStmt<ArraySubscriptExpr>, check::PreStmt<CastExpr>,
47 check::PostStmt<CastExpr>, check::PostStmt<CXXNewExpr>,
48 check::PostStmt<CallExpr>, check::DeadSymbols> {
49 AllocKind getKindOfNewOp(const CXXNewExpr *NE, const FunctionDecl *FD) const;
50 const MemRegion *getArrayRegion(const MemRegion *Region, bool &Polymorphic,
51 AllocKind &AKind, CheckerContext &C) const;
52 const MemRegion *getPointedRegion(const MemRegion *Region,
53 CheckerContext &C) const;
54 void reportPointerArithMisuse(const Expr *E, CheckerContext &C,
55 bool PointedNeeded = false) const;
56 void initAllocIdentifiers(ASTContext &C) const;
58 mutable std::unique_ptr<BuiltinBug> BT_pointerArith;
59 mutable std::unique_ptr<BuiltinBug> BT_polyArray;
60 mutable llvm::SmallSet<IdentifierInfo *, 8> AllocFunctions;
63 void checkPreStmt(const UnaryOperator *UOp, CheckerContext &C) const;
64 void checkPreStmt(const BinaryOperator *BOp, CheckerContext &C) const;
65 void checkPreStmt(const ArraySubscriptExpr *SubExpr, CheckerContext &C) const;
66 void checkPreStmt(const CastExpr *CE, CheckerContext &C) const;
67 void checkPostStmt(const CastExpr *CE, CheckerContext &C) const;
68 void checkPostStmt(const CXXNewExpr *NE, CheckerContext &C) const;
69 void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
70 void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const;
74 REGISTER_MAP_WITH_PROGRAMSTATE(RegionState, const MemRegion *, AllocKind)
76 void PointerArithChecker::checkDeadSymbols(SymbolReaper &SR,
77 CheckerContext &C) const {
78 // TODO: intentional leak. Some information is garbage collected too early,
79 // see http://reviews.llvm.org/D14203 for further information.
80 /*ProgramStateRef State = C.getState();
81 RegionStateTy RegionStates = State->get<RegionState>();
82 for (RegionStateTy::iterator I = RegionStates.begin(), E = RegionStates.end();
84 if (!SR.isLiveRegion(I->first))
85 State = State->remove<RegionState>(I->first);
87 C.addTransition(State);*/
90 AllocKind PointerArithChecker::getKindOfNewOp(const CXXNewExpr *NE,
91 const FunctionDecl *FD) const {
92 // This checker try not to assume anything about placement and overloaded
93 // new to avoid false positives.
94 if (isa<CXXMethodDecl>(FD))
95 return AllocKind::Unknown;
96 if (FD->getNumParams() != 1 || FD->isVariadic())
97 return AllocKind::Unknown;
99 return AllocKind::Array;
101 return AllocKind::SingleObject;
105 PointerArithChecker::getPointedRegion(const MemRegion *Region,
106 CheckerContext &C) const {
108 ProgramStateRef State = C.getState();
109 SVal S = State->getSVal(Region);
110 return S.getAsRegion();
113 /// Checks whether a region is the part of an array.
114 /// In case there is a derived to base cast above the array element, the
115 /// Polymorphic output value is set to true. AKind output value is set to the
116 /// allocation kind of the inspected region.
117 const MemRegion *PointerArithChecker::getArrayRegion(const MemRegion *Region,
120 CheckerContext &C) const {
122 while (Region->getKind() == MemRegion::Kind::CXXBaseObjectRegionKind) {
123 Region = Region->getAs<CXXBaseObjectRegion>()->getSuperRegion();
126 if (Region->getKind() == MemRegion::Kind::ElementRegionKind) {
127 Region = Region->getAs<ElementRegion>()->getSuperRegion();
130 ProgramStateRef State = C.getState();
131 if (const AllocKind *Kind = State->get<RegionState>(Region)) {
133 if (*Kind == AllocKind::Array)
138 // When the region is symbolic and we do not have any information about it,
139 // assume that this is an array to avoid false positives.
140 if (Region->getKind() == MemRegion::Kind::SymbolicRegionKind)
143 // No AllocKind stored and not symbolic, assume that it points to a single
148 void PointerArithChecker::reportPointerArithMisuse(const Expr *E,
150 bool PointedNeeded) const {
151 SourceRange SR = E->getSourceRange();
155 ProgramStateRef State = C.getState();
156 const MemRegion *Region = C.getSVal(E).getAsRegion();
160 Region = getPointedRegion(Region, C);
164 bool IsPolymorphic = false;
165 AllocKind Kind = AllocKind::Unknown;
166 if (const MemRegion *ArrayRegion =
167 getArrayRegion(Region, IsPolymorphic, Kind, C)) {
170 if (ExplodedNode *N = C.generateNonFatalErrorNode()) {
172 BT_polyArray.reset(new BuiltinBug(
173 this, "Dangerous pointer arithmetic",
174 "Pointer arithmetic on a pointer to base class is dangerous "
175 "because derived and base class may have different size."));
176 auto R = llvm::make_unique<BugReport>(*BT_polyArray,
177 BT_polyArray->getDescription(), N);
178 R->addRange(E->getSourceRange());
179 R->markInteresting(ArrayRegion);
180 C.emitReport(std::move(R));
185 if (Kind == AllocKind::Reinterpreted)
188 // We might not have enough information about symbolic regions.
189 if (Kind != AllocKind::SingleObject &&
190 Region->getKind() == MemRegion::Kind::SymbolicRegionKind)
193 if (ExplodedNode *N = C.generateNonFatalErrorNode()) {
194 if (!BT_pointerArith)
195 BT_pointerArith.reset(new BuiltinBug(this, "Dangerous pointer arithmetic",
196 "Pointer arithmetic on non-array "
197 "variables relies on memory layout, "
198 "which is dangerous."));
199 auto R = llvm::make_unique<BugReport>(*BT_pointerArith,
200 BT_pointerArith->getDescription(), N);
202 R->markInteresting(Region);
203 C.emitReport(std::move(R));
207 void PointerArithChecker::initAllocIdentifiers(ASTContext &C) const {
208 if (!AllocFunctions.empty())
210 AllocFunctions.insert(&C.Idents.get("alloca"));
211 AllocFunctions.insert(&C.Idents.get("malloc"));
212 AllocFunctions.insert(&C.Idents.get("realloc"));
213 AllocFunctions.insert(&C.Idents.get("calloc"));
214 AllocFunctions.insert(&C.Idents.get("valloc"));
217 void PointerArithChecker::checkPostStmt(const CallExpr *CE,
218 CheckerContext &C) const {
219 ProgramStateRef State = C.getState();
220 const FunctionDecl *FD = C.getCalleeDecl(CE);
223 IdentifierInfo *FunI = FD->getIdentifier();
224 initAllocIdentifiers(C.getASTContext());
225 if (AllocFunctions.count(FunI) == 0)
228 SVal SV = C.getSVal(CE);
229 const MemRegion *Region = SV.getAsRegion();
232 // Assume that C allocation functions allocate arrays to avoid false
234 // TODO: Add heuristics to distinguish alloc calls that allocates single
236 State = State->set<RegionState>(Region, AllocKind::Array);
237 C.addTransition(State);
240 void PointerArithChecker::checkPostStmt(const CXXNewExpr *NE,
241 CheckerContext &C) const {
242 const FunctionDecl *FD = NE->getOperatorNew();
246 AllocKind Kind = getKindOfNewOp(NE, FD);
248 ProgramStateRef State = C.getState();
249 SVal AllocedVal = C.getSVal(NE);
250 const MemRegion *Region = AllocedVal.getAsRegion();
253 State = State->set<RegionState>(Region, Kind);
254 C.addTransition(State);
257 void PointerArithChecker::checkPostStmt(const CastExpr *CE,
258 CheckerContext &C) const {
259 if (CE->getCastKind() != CastKind::CK_BitCast)
262 const Expr *CastedExpr = CE->getSubExpr();
263 ProgramStateRef State = C.getState();
264 SVal CastedVal = C.getSVal(CastedExpr);
266 const MemRegion *Region = CastedVal.getAsRegion();
270 // Suppress reinterpret casted hits.
271 State = State->set<RegionState>(Region, AllocKind::Reinterpreted);
272 C.addTransition(State);
275 void PointerArithChecker::checkPreStmt(const CastExpr *CE,
276 CheckerContext &C) const {
277 if (CE->getCastKind() != CastKind::CK_ArrayToPointerDecay)
280 const Expr *CastedExpr = CE->getSubExpr();
281 ProgramStateRef State = C.getState();
282 SVal CastedVal = C.getSVal(CastedExpr);
284 const MemRegion *Region = CastedVal.getAsRegion();
288 if (const AllocKind *Kind = State->get<RegionState>(Region)) {
289 if (*Kind == AllocKind::Array || *Kind == AllocKind::Reinterpreted)
292 State = State->set<RegionState>(Region, AllocKind::Array);
293 C.addTransition(State);
296 void PointerArithChecker::checkPreStmt(const UnaryOperator *UOp,
297 CheckerContext &C) const {
298 if (!UOp->isIncrementDecrementOp() || !UOp->getType()->isPointerType())
300 reportPointerArithMisuse(UOp->getSubExpr(), C, true);
303 void PointerArithChecker::checkPreStmt(const ArraySubscriptExpr *SubsExpr,
304 CheckerContext &C) const {
305 SVal Idx = C.getSVal(SubsExpr->getIdx());
307 // Indexing with 0 is OK.
308 if (Idx.isZeroConstant())
311 // Indexing vector-type expressions is also OK.
312 if (SubsExpr->getBase()->getType()->isVectorType())
314 reportPointerArithMisuse(SubsExpr->getBase(), C);
317 void PointerArithChecker::checkPreStmt(const BinaryOperator *BOp,
318 CheckerContext &C) const {
319 BinaryOperatorKind OpKind = BOp->getOpcode();
320 if (!BOp->isAdditiveOp() && OpKind != BO_AddAssign && OpKind != BO_SubAssign)
323 const Expr *Lhs = BOp->getLHS();
324 const Expr *Rhs = BOp->getRHS();
325 ProgramStateRef State = C.getState();
327 if (Rhs->getType()->isIntegerType() && Lhs->getType()->isPointerType()) {
328 SVal RHSVal = C.getSVal(Rhs);
329 if (State->isNull(RHSVal).isConstrainedTrue())
331 reportPointerArithMisuse(Lhs, C, !BOp->isAdditiveOp());
333 // The int += ptr; case is not valid C++.
334 if (Lhs->getType()->isIntegerType() && Rhs->getType()->isPointerType()) {
335 SVal LHSVal = C.getSVal(Lhs);
336 if (State->isNull(LHSVal).isConstrainedTrue())
338 reportPointerArithMisuse(Rhs, C);
342 void ento::registerPointerArithChecker(CheckerManager &mgr) {
343 mgr.registerChecker<PointerArithChecker>();
346 bool ento::shouldRegisterPointerArithChecker(const LangOptions &LO) {