1 //===--- CallAndMessageChecker.cpp ------------------------------*- C++ -*--==// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This defines CallAndMessageChecker, a builtin checker that checks for various 11 // errors of call and objc message expressions. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "ClangSACheckers.h" 16 #include "clang/AST/ParentMap.h" 17 #include "clang/Basic/TargetInfo.h" 18 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" 19 #include "clang/StaticAnalyzer/Core/Checker.h" 20 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 21 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h" 22 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 23 #include "llvm/ADT/SmallString.h" 24 #include "llvm/Support/raw_ostream.h" 25 26 using namespace clang; 27 using namespace ento; 28 29 namespace { 30 class CallAndMessageChecker 31 : public Checker< check::PreStmt<CallExpr>, check::PreObjCMessage, 32 check::PreCall > { 33 mutable OwningPtr<BugType> BT_call_null; 34 mutable OwningPtr<BugType> BT_call_undef; 35 mutable OwningPtr<BugType> BT_cxx_call_null; 36 mutable OwningPtr<BugType> BT_cxx_call_undef; 37 mutable OwningPtr<BugType> BT_call_arg; 38 mutable OwningPtr<BugType> BT_msg_undef; 39 mutable OwningPtr<BugType> BT_objc_prop_undef; 40 mutable OwningPtr<BugType> BT_objc_subscript_undef; 41 mutable OwningPtr<BugType> BT_msg_arg; 42 mutable OwningPtr<BugType> BT_msg_ret; 43 public: 44 45 void checkPreStmt(const CallExpr *CE, CheckerContext &C) const; 46 void checkPreObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const; 47 void checkPreCall(const CallEvent &Call, CheckerContext &C) const; 48 49 private: 50 static bool PreVisitProcessArg(CheckerContext &C, SVal V, 51 SourceRange argRange, const Expr *argEx, 52 bool IsFirstArgument, bool checkUninitFields, 53 const CallEvent &Call, OwningPtr<BugType> &BT); 54 55 static void emitBadCall(BugType *BT, CheckerContext &C, const Expr *BadE); 56 void emitNilReceiverBug(CheckerContext &C, const ObjCMethodCall &msg, 57 ExplodedNode *N) const; 58 59 void HandleNilReceiver(CheckerContext &C, 60 ProgramStateRef state, 61 const ObjCMethodCall &msg) const; 62 63 static void LazyInit_BT(const char *desc, OwningPtr<BugType> &BT) { 64 if (!BT) 65 BT.reset(new BuiltinBug(desc)); 66 } 67 }; 68 } // end anonymous namespace 69 70 void CallAndMessageChecker::emitBadCall(BugType *BT, CheckerContext &C, 71 const Expr *BadE) { 72 ExplodedNode *N = C.generateSink(); 73 if (!N) 74 return; 75 76 BugReport *R = new BugReport(*BT, BT->getName(), N); 77 if (BadE) { 78 R->addRange(BadE->getSourceRange()); 79 if (BadE->isGLValue()) 80 BadE = bugreporter::getDerefExpr(BadE); 81 bugreporter::trackNullOrUndefValue(N, BadE, *R); 82 } 83 C.emitReport(R); 84 } 85 86 static StringRef describeUninitializedArgumentInCall(const CallEvent &Call, 87 bool IsFirstArgument) { 88 switch (Call.getKind()) { 89 case CE_ObjCMessage: { 90 const ObjCMethodCall &Msg = cast<ObjCMethodCall>(Call); 91 switch (Msg.getMessageKind()) { 92 case OCM_Message: 93 return "Argument in message expression is an uninitialized value"; 94 case OCM_PropertyAccess: 95 assert(Msg.isSetter() && "Getters have no args"); 96 return "Argument for property setter is an uninitialized value"; 97 case OCM_Subscript: 98 if (Msg.isSetter() && IsFirstArgument) 99 return "Argument for subscript setter is an uninitialized value"; 100 return "Subscript index is an uninitialized value"; 101 } 102 llvm_unreachable("Unknown message kind."); 103 } 104 case CE_Block: 105 return "Block call argument is an uninitialized value"; 106 default: 107 return "Function call argument is an uninitialized value"; 108 } 109 } 110 111 bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C, 112 SVal V, SourceRange argRange, 113 const Expr *argEx, 114 bool IsFirstArgument, 115 bool checkUninitFields, 116 const CallEvent &Call, 117 OwningPtr<BugType> &BT) { 118 if (V.isUndef()) { 119 if (ExplodedNode *N = C.generateSink()) { 120 LazyInit_BT("Uninitialized argument value", BT); 121 122 // Generate a report for this bug. 123 StringRef Desc = describeUninitializedArgumentInCall(Call, 124 IsFirstArgument); 125 BugReport *R = new BugReport(*BT, Desc, N); 126 R->addRange(argRange); 127 if (argEx) 128 bugreporter::trackNullOrUndefValue(N, argEx, *R); 129 C.emitReport(R); 130 } 131 return true; 132 } 133 134 if (!checkUninitFields) 135 return false; 136 137 if (Optional<nonloc::LazyCompoundVal> LV = 138 V.getAs<nonloc::LazyCompoundVal>()) { 139 140 class FindUninitializedField { 141 public: 142 SmallVector<const FieldDecl *, 10> FieldChain; 143 private: 144 StoreManager &StoreMgr; 145 MemRegionManager &MrMgr; 146 Store store; 147 public: 148 FindUninitializedField(StoreManager &storeMgr, 149 MemRegionManager &mrMgr, Store s) 150 : StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {} 151 152 bool Find(const TypedValueRegion *R) { 153 QualType T = R->getValueType(); 154 if (const RecordType *RT = T->getAsStructureType()) { 155 const RecordDecl *RD = RT->getDecl()->getDefinition(); 156 assert(RD && "Referred record has no definition"); 157 for (RecordDecl::field_iterator I = 158 RD->field_begin(), E = RD->field_end(); I!=E; ++I) { 159 const FieldRegion *FR = MrMgr.getFieldRegion(*I, R); 160 FieldChain.push_back(*I); 161 T = I->getType(); 162 if (T->getAsStructureType()) { 163 if (Find(FR)) 164 return true; 165 } 166 else { 167 const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR)); 168 if (V.isUndef()) 169 return true; 170 } 171 FieldChain.pop_back(); 172 } 173 } 174 175 return false; 176 } 177 }; 178 179 const LazyCompoundValData *D = LV->getCVData(); 180 FindUninitializedField F(C.getState()->getStateManager().getStoreManager(), 181 C.getSValBuilder().getRegionManager(), 182 D->getStore()); 183 184 if (F.Find(D->getRegion())) { 185 if (ExplodedNode *N = C.generateSink()) { 186 LazyInit_BT("Uninitialized argument value", BT); 187 SmallString<512> Str; 188 llvm::raw_svector_ostream os(Str); 189 os << "Passed-by-value struct argument contains uninitialized data"; 190 191 if (F.FieldChain.size() == 1) 192 os << " (e.g., field: '" << *F.FieldChain[0] << "')"; 193 else { 194 os << " (e.g., via the field chain: '"; 195 bool first = true; 196 for (SmallVectorImpl<const FieldDecl *>::iterator 197 DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){ 198 if (first) 199 first = false; 200 else 201 os << '.'; 202 os << **DI; 203 } 204 os << "')"; 205 } 206 207 // Generate a report for this bug. 208 BugReport *R = new BugReport(*BT, os.str(), N); 209 R->addRange(argRange); 210 211 // FIXME: enhance track back for uninitialized value for arbitrary 212 // memregions 213 C.emitReport(R); 214 } 215 return true; 216 } 217 } 218 219 return false; 220 } 221 222 void CallAndMessageChecker::checkPreStmt(const CallExpr *CE, 223 CheckerContext &C) const{ 224 225 const Expr *Callee = CE->getCallee()->IgnoreParens(); 226 ProgramStateRef State = C.getState(); 227 const LocationContext *LCtx = C.getLocationContext(); 228 SVal L = State->getSVal(Callee, LCtx); 229 230 if (L.isUndef()) { 231 if (!BT_call_undef) 232 BT_call_undef.reset(new BuiltinBug("Called function pointer is an " 233 "uninitalized pointer value")); 234 emitBadCall(BT_call_undef.get(), C, Callee); 235 return; 236 } 237 238 ProgramStateRef StNonNull, StNull; 239 llvm::tie(StNonNull, StNull) = 240 State->assume(L.castAs<DefinedOrUnknownSVal>()); 241 242 if (StNull && !StNonNull) { 243 if (!BT_call_null) 244 BT_call_null.reset( 245 new BuiltinBug("Called function pointer is null (null dereference)")); 246 emitBadCall(BT_call_null.get(), C, Callee); 247 } 248 249 C.addTransition(StNonNull); 250 } 251 252 void CallAndMessageChecker::checkPreCall(const CallEvent &Call, 253 CheckerContext &C) const { 254 ProgramStateRef State = C.getState(); 255 256 // If this is a call to a C++ method, check if the callee is null or 257 // undefined. 258 if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) { 259 SVal V = CC->getCXXThisVal(); 260 if (V.isUndef()) { 261 if (!BT_cxx_call_undef) 262 BT_cxx_call_undef.reset(new BuiltinBug("Called C++ object pointer is " 263 "uninitialized")); 264 emitBadCall(BT_cxx_call_undef.get(), C, CC->getCXXThisExpr()); 265 return; 266 } 267 268 ProgramStateRef StNonNull, StNull; 269 llvm::tie(StNonNull, StNull) = 270 State->assume(V.castAs<DefinedOrUnknownSVal>()); 271 272 if (StNull && !StNonNull) { 273 if (!BT_cxx_call_null) 274 BT_cxx_call_null.reset(new BuiltinBug("Called C++ object pointer " 275 "is null")); 276 emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr()); 277 return; 278 } 279 280 State = StNonNull; 281 } 282 283 // Don't check for uninitialized field values in arguments if the 284 // caller has a body that is available and we have the chance to inline it. 285 // This is a hack, but is a reasonable compromise betweens sometimes warning 286 // and sometimes not depending on if we decide to inline a function. 287 const Decl *D = Call.getDecl(); 288 const bool checkUninitFields = 289 !(C.getAnalysisManager().shouldInlineCall() && (D && D->getBody())); 290 291 OwningPtr<BugType> *BT; 292 if (isa<ObjCMethodCall>(Call)) 293 BT = &BT_msg_arg; 294 else 295 BT = &BT_call_arg; 296 297 for (unsigned i = 0, e = Call.getNumArgs(); i != e; ++i) 298 if (PreVisitProcessArg(C, Call.getArgSVal(i), Call.getArgSourceRange(i), 299 Call.getArgExpr(i), /*IsFirstArgument=*/i == 0, 300 checkUninitFields, Call, *BT)) 301 return; 302 303 // If we make it here, record our assumptions about the callee. 304 C.addTransition(State); 305 } 306 307 void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg, 308 CheckerContext &C) const { 309 SVal recVal = msg.getReceiverSVal(); 310 if (recVal.isUndef()) { 311 if (ExplodedNode *N = C.generateSink()) { 312 BugType *BT = 0; 313 switch (msg.getMessageKind()) { 314 case OCM_Message: 315 if (!BT_msg_undef) 316 BT_msg_undef.reset(new BuiltinBug("Receiver in message expression " 317 "is an uninitialized value")); 318 BT = BT_msg_undef.get(); 319 break; 320 case OCM_PropertyAccess: 321 if (!BT_objc_prop_undef) 322 BT_objc_prop_undef.reset(new BuiltinBug("Property access on an " 323 "uninitialized object " 324 "pointer")); 325 BT = BT_objc_prop_undef.get(); 326 break; 327 case OCM_Subscript: 328 if (!BT_objc_subscript_undef) 329 BT_objc_subscript_undef.reset(new BuiltinBug("Subscript access on an " 330 "uninitialized object " 331 "pointer")); 332 BT = BT_objc_subscript_undef.get(); 333 break; 334 } 335 assert(BT && "Unknown message kind."); 336 337 BugReport *R = new BugReport(*BT, BT->getName(), N); 338 const ObjCMessageExpr *ME = msg.getOriginExpr(); 339 R->addRange(ME->getReceiverRange()); 340 341 // FIXME: getTrackNullOrUndefValueVisitor can't handle "super" yet. 342 if (const Expr *ReceiverE = ME->getInstanceReceiver()) 343 bugreporter::trackNullOrUndefValue(N, ReceiverE, *R); 344 C.emitReport(R); 345 } 346 return; 347 } else { 348 // Bifurcate the state into nil and non-nil ones. 349 DefinedOrUnknownSVal receiverVal = recVal.castAs<DefinedOrUnknownSVal>(); 350 351 ProgramStateRef state = C.getState(); 352 ProgramStateRef notNilState, nilState; 353 llvm::tie(notNilState, nilState) = state->assume(receiverVal); 354 355 // Handle receiver must be nil. 356 if (nilState && !notNilState) { 357 HandleNilReceiver(C, state, msg); 358 return; 359 } 360 } 361 } 362 363 void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C, 364 const ObjCMethodCall &msg, 365 ExplodedNode *N) const { 366 367 if (!BT_msg_ret) 368 BT_msg_ret.reset( 369 new BuiltinBug("Receiver in message expression is " 370 "'nil' and returns a garbage value")); 371 372 const ObjCMessageExpr *ME = msg.getOriginExpr(); 373 374 SmallString<200> buf; 375 llvm::raw_svector_ostream os(buf); 376 os << "The receiver of message '" << ME->getSelector().getAsString() 377 << "' is nil and returns a value of type '"; 378 msg.getResultType().print(os, C.getLangOpts()); 379 os << "' that will be garbage"; 380 381 BugReport *report = new BugReport(*BT_msg_ret, os.str(), N); 382 report->addRange(ME->getReceiverRange()); 383 // FIXME: This won't track "self" in messages to super. 384 if (const Expr *receiver = ME->getInstanceReceiver()) { 385 bugreporter::trackNullOrUndefValue(N, receiver, *report); 386 } 387 C.emitReport(report); 388 } 389 390 static bool supportsNilWithFloatRet(const llvm::Triple &triple) { 391 return (triple.getVendor() == llvm::Triple::Apple && 392 (triple.getOS() == llvm::Triple::IOS || 393 !triple.isMacOSXVersionLT(10,5))); 394 } 395 396 void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C, 397 ProgramStateRef state, 398 const ObjCMethodCall &Msg) const { 399 ASTContext &Ctx = C.getASTContext(); 400 401 // Check the return type of the message expression. A message to nil will 402 // return different values depending on the return type and the architecture. 403 QualType RetTy = Msg.getResultType(); 404 CanQualType CanRetTy = Ctx.getCanonicalType(RetTy); 405 const LocationContext *LCtx = C.getLocationContext(); 406 407 if (CanRetTy->isStructureOrClassType()) { 408 // Structure returns are safe since the compiler zeroes them out. 409 SVal V = C.getSValBuilder().makeZeroVal(RetTy); 410 C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V)); 411 return; 412 } 413 414 // Other cases: check if sizeof(return type) > sizeof(void*) 415 if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap() 416 .isConsumedExpr(Msg.getOriginExpr())) { 417 // Compute: sizeof(void *) and sizeof(return type) 418 const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy); 419 const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy); 420 421 if (voidPtrSize < returnTypeSize && 422 !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) && 423 (Ctx.FloatTy == CanRetTy || 424 Ctx.DoubleTy == CanRetTy || 425 Ctx.LongDoubleTy == CanRetTy || 426 Ctx.LongLongTy == CanRetTy || 427 Ctx.UnsignedLongLongTy == CanRetTy))) { 428 if (ExplodedNode *N = C.generateSink(state)) 429 emitNilReceiverBug(C, Msg, N); 430 return; 431 } 432 433 // Handle the safe cases where the return value is 0 if the 434 // receiver is nil. 435 // 436 // FIXME: For now take the conservative approach that we only 437 // return null values if we *know* that the receiver is nil. 438 // This is because we can have surprises like: 439 // 440 // ... = [[NSScreens screens] objectAtIndex:0]; 441 // 442 // What can happen is that [... screens] could return nil, but 443 // it most likely isn't nil. We should assume the semantics 444 // of this case unless we have *a lot* more knowledge. 445 // 446 SVal V = C.getSValBuilder().makeZeroVal(RetTy); 447 C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V)); 448 return; 449 } 450 451 C.addTransition(state); 452 } 453 454 void ento::registerCallAndMessageChecker(CheckerManager &mgr) { 455 mgr.registerChecker<CallAndMessageChecker>(); 456 } 457
