clang/lib/StaticAnalyzer/Checkers/IteratorRangeChecker.cpp

   1 //===-- IteratorRangeChecker.cpp ----------------------------------*- C++ -*--//
   2 //
   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
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Defines a checker for dereference of the past-the-end iterator and
  10 // out-of-range increments and decrements.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
  15 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
  16 #include "clang/StaticAnalyzer/Core/Checker.h"
  17 #include "clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h"
  18 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
  19 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
  20
  21 #include "Iterator.h"
  22
  23 using namespace clang;
  24 using namespace ento;
  25 using namespace iterator;
  26
  27 namespace {
  28
  29 class IteratorRangeChecker
  30   : public Checker<check::PreCall, check::PreStmt<UnaryOperator>,
  31                    check::PreStmt<BinaryOperator>,
  32                    check::PreStmt<ArraySubscriptExpr>,
  33                    check::PreStmt<MemberExpr>> {
  34
  35   std::unique_ptr<BugType> OutOfRangeBugType;
  36
  37   void verifyDereference(CheckerContext &C, SVal Val) const;
  38   void verifyIncrement(CheckerContext &C, SVal Iter) const;
  39   void verifyDecrement(CheckerContext &C, SVal Iter) const;
  40   void verifyRandomIncrOrDecr(CheckerContext &C, OverloadedOperatorKind Op,
  41                               SVal LHS, SVal RHS) const;
  42   void verifyAdvance(CheckerContext &C, SVal LHS, SVal RHS) const;
  43   void verifyPrev(CheckerContext &C, SVal LHS, SVal RHS) const;
  44   void verifyNext(CheckerContext &C, SVal LHS, SVal RHS) const;
  45   void reportBug(const StringRef &Message, SVal Val, CheckerContext &C,
  46                  ExplodedNode *ErrNode) const;
  47
  48 public:
  49   IteratorRangeChecker();
  50
  51   void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
  52   void checkPreStmt(const UnaryOperator *UO, CheckerContext &C) const;
  53   void checkPreStmt(const BinaryOperator *BO, CheckerContext &C) const;
  54   void checkPreStmt(const ArraySubscriptExpr *ASE, CheckerContext &C) const;
  55   void checkPreStmt(const MemberExpr *ME, CheckerContext &C) const;
  56
  57   using AdvanceFn = void (IteratorRangeChecker::*)(CheckerContext &, SVal,
  58                                                    SVal) const;
  59
  60   CallDescriptionMap<AdvanceFn> AdvanceFunctions = {
  61       {{{"std", "advance"}, 2}, &IteratorRangeChecker::verifyAdvance},
  62       {{{"std", "prev"}, 2}, &IteratorRangeChecker::verifyPrev},
  63       {{{"std", "next"}, 2}, &IteratorRangeChecker::verifyNext},
  64   };
  65 };
  66
  67 bool isPastTheEnd(ProgramStateRef State, const IteratorPosition &Pos);
  68 bool isAheadOfRange(ProgramStateRef State, const IteratorPosition &Pos);
  69 bool isBehindPastTheEnd(ProgramStateRef State, const IteratorPosition &Pos);
  70 bool isZero(ProgramStateRef State, const NonLoc &Val);
  71
  72 } //namespace
  73
  74 IteratorRangeChecker::IteratorRangeChecker() {
  75   OutOfRangeBugType.reset(
  76       new BugType(this, "Iterator out of range", "Misuse of STL APIs"));
  77 }
  78
  79 void IteratorRangeChecker::checkPreCall(const CallEvent &Call,
  80                                         CheckerContext &C) const {
  81   // Check for out of range access
  82   const auto *Func = dyn_cast_or_null<FunctionDecl>(Call.getDecl());
  83   if (!Func)
  84     return;
  85
  86   if (Func->isOverloadedOperator()) {
  87     if (isIncrementOperator(Func->getOverloadedOperator())) {
  88       // Check for out-of-range incrementions
  89       if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
  90         verifyIncrement(C, InstCall->getCXXThisVal());
  91       } else {
  92         if (Call.getNumArgs() >= 1) {
  93           verifyIncrement(C, Call.getArgSVal(0));
  94         }
  95       }
  96     } else if (isDecrementOperator(Func->getOverloadedOperator())) {
  97       // Check for out-of-range decrementions
  98       if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
  99         verifyDecrement(C, InstCall->getCXXThisVal());
 100       } else {
 101         if (Call.getNumArgs() >= 1) {
 102           verifyDecrement(C, Call.getArgSVal(0));
 103         }
 104       }
 105     } else if (isRandomIncrOrDecrOperator(Func->getOverloadedOperator())) {
 106       if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
 107         // Check for out-of-range incrementions and decrementions
 108         if (Call.getNumArgs() >= 1 &&
 109             Call.getArgExpr(0)->getType()->isIntegralOrEnumerationType()) {
 110           verifyRandomIncrOrDecr(C, Func->getOverloadedOperator(),
 111                                  InstCall->getCXXThisVal(),
 112                                  Call.getArgSVal(0));
 113         }
 114       } else {
 115         if (Call.getNumArgs() >= 2 &&
 116             Call.getArgExpr(1)->getType()->isIntegralOrEnumerationType()) {
 117           verifyRandomIncrOrDecr(C, Func->getOverloadedOperator(),
 118                                  Call.getArgSVal(0), Call.getArgSVal(1));
 119         }
 120       }
 121     } else if (isDereferenceOperator(Func->getOverloadedOperator())) {
 122       // Check for dereference of out-of-range iterators
 123       if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
 124         verifyDereference(C, InstCall->getCXXThisVal());
 125       } else {
 126         verifyDereference(C, Call.getArgSVal(0));
 127       }
 128     }
 129   } else {
 130     const AdvanceFn *Verifier = AdvanceFunctions.lookup(Call);
 131     if (Verifier) {
 132       if (Call.getNumArgs() > 1) {
 133         (this->**Verifier)(C, Call.getArgSVal(0), Call.getArgSVal(1));
 134       } else {
 135         auto &BVF = C.getSValBuilder().getBasicValueFactory();
 136         (this->**Verifier)(
 137             C, Call.getArgSVal(0),
 138             nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(1))));
 139       }
 140     }
 141   }
 142 }
 143
 144 void IteratorRangeChecker::checkPreStmt(const UnaryOperator *UO,
 145                                         CheckerContext &C) const {
 146   if (isa<CXXThisExpr>(UO->getSubExpr()))
 147     return;
 148
 149   ProgramStateRef State = C.getState();
 150   UnaryOperatorKind OK = UO->getOpcode();
 151   SVal SubVal = State->getSVal(UO->getSubExpr(), C.getLocationContext());
 152
 153   if (isDereferenceOperator(OK)) {
 154     verifyDereference(C, SubVal);
 155   } else if (isIncrementOperator(OK)) {
 156     verifyIncrement(C, SubVal);
 157   } else if (isDecrementOperator(OK)) {
 158     verifyDecrement(C, SubVal);
 159   }
 160 }
 161
 162 void IteratorRangeChecker::checkPreStmt(const BinaryOperator *BO,
 163                                         CheckerContext &C) const {
 164   ProgramStateRef State = C.getState();
 165   BinaryOperatorKind OK = BO->getOpcode();
 166   SVal LVal = State->getSVal(BO->getLHS(), C.getLocationContext());
 167
 168   if (isDereferenceOperator(OK)) {
 169     verifyDereference(C, LVal);
 170   } else if (isRandomIncrOrDecrOperator(OK)) {
 171     SVal RVal = State->getSVal(BO->getRHS(), C.getLocationContext());
 172     if (!BO->getRHS()->getType()->isIntegralOrEnumerationType())
 173       return;
 174     verifyRandomIncrOrDecr(C, BinaryOperator::getOverloadedOperator(OK), LVal,
 175                            RVal);
 176   }
 177 }
 178
 179 void IteratorRangeChecker::checkPreStmt(const ArraySubscriptExpr *ASE,
 180                                         CheckerContext &C) const {
 181   ProgramStateRef State = C.getState();
 182   SVal LVal = State->getSVal(ASE->getLHS(), C.getLocationContext());
 183   verifyDereference(C, LVal);
 184 }
 185
 186 void IteratorRangeChecker::checkPreStmt(const MemberExpr *ME,
 187                                         CheckerContext &C) const {
 188   if (!ME->isArrow() || ME->isImplicitAccess())
 189     return;
 190
 191   ProgramStateRef State = C.getState();
 192   SVal BaseVal = State->getSVal(ME->getBase(), C.getLocationContext());
 193   verifyDereference(C, BaseVal);
 194 }
 195
 196 void IteratorRangeChecker::verifyDereference(CheckerContext &C,
 197                                              SVal Val) const {
 198   auto State = C.getState();
 199   const auto *Pos = getIteratorPosition(State, Val);
 200   if (Pos && isPastTheEnd(State, *Pos)) {
 201     auto *N = C.generateErrorNode(State);
 202     if (!N)
 203       return;
 204     reportBug("Past-the-end iterator dereferenced.", Val, C, N);
 205     return;
 206   }
 207 }
 208
 209 void IteratorRangeChecker::verifyIncrement(CheckerContext &C, SVal Iter) const {
 210   auto &BVF = C.getSValBuilder().getBasicValueFactory();
 211   verifyRandomIncrOrDecr(C, OO_Plus, Iter,
 212                      nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(1))));
 213 }
 214
 215 void IteratorRangeChecker::verifyDecrement(CheckerContext &C, SVal Iter) const {
 216   auto &BVF = C.getSValBuilder().getBasicValueFactory();
 217   verifyRandomIncrOrDecr(C, OO_Minus, Iter,
 218                      nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(1))));
 219 }
 220
 221 void IteratorRangeChecker::verifyRandomIncrOrDecr(CheckerContext &C,
 222                                                   OverloadedOperatorKind Op,
 223                                                   SVal LHS, SVal RHS) const {
 224   auto State = C.getState();
 225
 226   auto Value = RHS;
 227   if (auto ValAsLoc = RHS.getAs<Loc>()) {
 228     Value = State->getRawSVal(*ValAsLoc);
 229   }
 230
 231   if (Value.isUnknownOrUndef() || !isa<NonLoc>(Value))
 232     return;
 233
 234   // Incremention or decremention by 0 is never a bug.
 235   if (isZero(State, Value.castAs<NonLoc>()))
 236     return;
 237
 238   // The result may be the past-end iterator of the container, but any other
 239   // out of range position is undefined behaviour
 240   auto StateAfter = advancePosition(State, LHS, Op, Value);
 241   if (!StateAfter)
 242     return;
 243
 244   const auto *PosAfter = getIteratorPosition(StateAfter, LHS);
 245   assert(PosAfter &&
 246          "Iterator should have position after successful advancement");
 247   if (isAheadOfRange(State, *PosAfter)) {
 248     auto *N = C.generateErrorNode(State);
 249     if (!N)
 250       return;
 251     reportBug("Iterator decremented ahead of its valid range.", LHS,
 252                         C, N);
 253   }
 254   if (isBehindPastTheEnd(State, *PosAfter)) {
 255     auto *N = C.generateErrorNode(State);
 256     if (!N)
 257       return;
 258     reportBug("Iterator incremented behind the past-the-end "
 259                         "iterator.", LHS, C, N);
 260   }
 261 }
 262
 263 void IteratorRangeChecker::verifyAdvance(CheckerContext &C, SVal LHS,
 264                                          SVal RHS) const {
 265   verifyRandomIncrOrDecr(C, OO_PlusEqual, LHS, RHS);
 266 }
 267
 268 void IteratorRangeChecker::verifyPrev(CheckerContext &C, SVal LHS,
 269                                       SVal RHS) const {
 270   verifyRandomIncrOrDecr(C, OO_Minus, LHS, RHS);
 271 }
 272
 273 void IteratorRangeChecker::verifyNext(CheckerContext &C, SVal LHS,
 274                                       SVal RHS) const {
 275   verifyRandomIncrOrDecr(C, OO_Plus, LHS, RHS);
 276 }
 277
 278 void IteratorRangeChecker::reportBug(const StringRef &Message, SVal Val,
 279                                      CheckerContext &C,
 280                                      ExplodedNode *ErrNode) const {
 281   auto R = std::make_unique<PathSensitiveBugReport>(*OutOfRangeBugType, Message,
 282                                                     ErrNode);
 283
 284   const auto *Pos = getIteratorPosition(C.getState(), Val);
 285   assert(Pos && "Iterator without known position cannot be out-of-range.");
 286
 287   R->markInteresting(Val);
 288   R->markInteresting(Pos->getContainer());
 289   C.emitReport(std::move(R));
 290 }
 291
 292 namespace {
 293
 294 bool isLess(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2);
 295 bool isGreater(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2);
 296 bool isEqual(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2);
 297
 298 bool isZero(ProgramStateRef State, const NonLoc &Val) {
 299   auto &BVF = State->getBasicVals();
 300   return compare(State, Val,
 301                  nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(0))),
 302                  BO_EQ);
 303 }
 304
 305 bool isPastTheEnd(ProgramStateRef State, const IteratorPosition &Pos) {
 306   const auto *Cont = Pos.getContainer();
 307   const auto *CData = getContainerData(State, Cont);
 308   if (!CData)
 309     return false;
 310
 311   const auto End = CData->getEnd();
 312   if (End) {
 313     if (isEqual(State, Pos.getOffset(), End)) {
 314       return true;
 315     }
 316   }
 317
 318   return false;
 319 }
 320
 321 bool isAheadOfRange(ProgramStateRef State, const IteratorPosition &Pos) {
 322   const auto *Cont = Pos.getContainer();
 323   const auto *CData = getContainerData(State, Cont);
 324   if (!CData)
 325     return false;
 326
 327   const auto Beg = CData->getBegin();
 328   if (Beg) {
 329     if (isLess(State, Pos.getOffset(), Beg)) {
 330       return true;
 331     }
 332   }
 333
 334   return false;
 335 }
 336
 337 bool isBehindPastTheEnd(ProgramStateRef State, const IteratorPosition &Pos) {
 338   const auto *Cont = Pos.getContainer();
 339   const auto *CData = getContainerData(State, Cont);
 340   if (!CData)
 341     return false;
 342
 343   const auto End = CData->getEnd();
 344   if (End) {
 345     if (isGreater(State, Pos.getOffset(), End)) {
 346       return true;
 347     }
 348   }
 349
 350   return false;
 351 }
 352
 353 bool isLess(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2) {
 354   return compare(State, Sym1, Sym2, BO_LT);
 355 }
 356
 357 bool isGreater(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2) {
 358   return compare(State, Sym1, Sym2, BO_GT);
 359 }
 360
 361 bool isEqual(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2) {
 362   return compare(State, Sym1, Sym2, BO_EQ);
 363 }
 364
 365 } // namespace
 366
 367 void ento::registerIteratorRangeChecker(CheckerManager &mgr) {
 368   mgr.registerChecker<IteratorRangeChecker>();
 369 }
 370
 371 bool ento::shouldRegisterIteratorRangeChecker(const CheckerManager &mgr) {
 372   return true;
 373 }