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>, 32 check::PreStmt<CXXDeleteExpr>, 33 check::PreObjCMessage, 34 check::PreCall > { 35 mutable OwningPtr<BugType> BT_call_null; 36 mutable OwningPtr<BugType> BT_call_undef; 37 mutable OwningPtr<BugType> BT_cxx_call_null; 38 mutable OwningPtr<BugType> BT_cxx_call_undef; 39 mutable OwningPtr<BugType> BT_call_arg; 40 mutable OwningPtr<BugType> BT_cxx_delete_undef; 41 mutable OwningPtr<BugType> BT_msg_undef; 42 mutable OwningPtr<BugType> BT_objc_prop_undef; 43 mutable OwningPtr<BugType> BT_objc_subscript_undef; 44 mutable OwningPtr<BugType> BT_msg_arg; 45 mutable OwningPtr<BugType> BT_msg_ret; 46 mutable OwningPtr<BugType> BT_call_few_args; 47 public: 48 49 void checkPreStmt(const CallExpr *CE, CheckerContext &C) const; 50 void checkPreStmt(const CXXDeleteExpr *DE, CheckerContext &C) const; 51 void checkPreObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const; 52 void checkPreCall(const CallEvent &Call, CheckerContext &C) const; 53 54 private: 55 static bool PreVisitProcessArg(CheckerContext &C, SVal V, 56 SourceRange argRange, const Expr *argEx, 57 bool IsFirstArgument, bool checkUninitFields, 58 const CallEvent &Call, OwningPtr<BugType> &BT); 59 60 static void emitBadCall(BugType *BT, CheckerContext &C, const Expr *BadE); 61 void emitNilReceiverBug(CheckerContext &C, const ObjCMethodCall &msg, 62 ExplodedNode *N) const; 63 64 void HandleNilReceiver(CheckerContext &C, 65 ProgramStateRef state, 66 const ObjCMethodCall &msg) const; 67 68 static void LazyInit_BT(const char *desc, OwningPtr<BugType> &BT) { 69 if (!BT) 70 BT.reset(new BuiltinBug(desc)); 71 } 72 }; 73 } // end anonymous namespace 74 75 void CallAndMessageChecker::emitBadCall(BugType *BT, CheckerContext &C, 76 const Expr *BadE) { 77 ExplodedNode *N = C.generateSink(); 78 if (!N) 79 return; 80 81 BugReport *R = new BugReport(*BT, BT->getName(), N); 82 if (BadE) { 83 R->addRange(BadE->getSourceRange()); 84 if (BadE->isGLValue()) 85 BadE = bugreporter::getDerefExpr(BadE); 86 bugreporter::trackNullOrUndefValue(N, BadE, *R); 87 } 88 C.emitReport(R); 89 } 90 91 static StringRef describeUninitializedArgumentInCall(const CallEvent &Call, 92 bool IsFirstArgument) { 93 switch (Call.getKind()) { 94 case CE_ObjCMessage: { 95 const ObjCMethodCall &Msg = cast<ObjCMethodCall>(Call); 96 switch (Msg.getMessageKind()) { 97 case OCM_Message: 98 return "Argument in message expression is an uninitialized value"; 99 case OCM_PropertyAccess: 100 assert(Msg.isSetter() && "Getters have no args"); 101 return "Argument for property setter is an uninitialized value"; 102 case OCM_Subscript: 103 if (Msg.isSetter() && IsFirstArgument) 104 return "Argument for subscript setter is an uninitialized value"; 105 return "Subscript index is an uninitialized value"; 106 } 107 llvm_unreachable("Unknown message kind."); 108 } 109 case CE_Block: 110 return "Block call argument is an uninitialized value"; 111 default: 112 return "Function call argument is an uninitialized value"; 113 } 114 } 115 116 bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C, 117 SVal V, SourceRange argRange, 118 const Expr *argEx, 119 bool IsFirstArgument, 120 bool checkUninitFields, 121 const CallEvent &Call, 122 OwningPtr<BugType> &BT) { 123 if (V.isUndef()) { 124 if (ExplodedNode *N = C.generateSink()) { 125 LazyInit_BT("Uninitialized argument value", BT); 126 127 // Generate a report for this bug. 128 StringRef Desc = describeUninitializedArgumentInCall(Call, 129 IsFirstArgument); 130 BugReport *R = new BugReport(*BT, Desc, N); 131 R->addRange(argRange); 132 if (argEx) 133 bugreporter::trackNullOrUndefValue(N, argEx, *R); 134 C.emitReport(R); 135 } 136 return true; 137 } 138 139 if (!checkUninitFields) 140 return false; 141 142 if (Optional<nonloc::LazyCompoundVal> LV = 143 V.getAs<nonloc::LazyCompoundVal>()) { 144 145 class FindUninitializedField { 146 public: 147 SmallVector<const FieldDecl *, 10> FieldChain; 148 private: 149 StoreManager &StoreMgr; 150 MemRegionManager &MrMgr; 151 Store store; 152 public: 153 FindUninitializedField(StoreManager &storeMgr, 154 MemRegionManager &mrMgr, Store s) 155 : StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {} 156 157 bool Find(const TypedValueRegion *R) { 158 QualType T = R->getValueType(); 159 if (const RecordType *RT = T->getAsStructureType()) { 160 const RecordDecl *RD = RT->getDecl()->getDefinition(); 161 assert(RD && "Referred record has no definition"); 162 for (RecordDecl::field_iterator I = 163 RD->field_begin(), E = RD->field_end(); I!=E; ++I) { 164 const FieldRegion *FR = MrMgr.getFieldRegion(*I, R); 165 FieldChain.push_back(*I); 166 T = I->getType(); 167 if (T->getAsStructureType()) { 168 if (Find(FR)) 169 return true; 170 } 171 else { 172 const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR)); 173 if (V.isUndef()) 174 return true; 175 } 176 FieldChain.pop_back(); 177 } 178 } 179 180 return false; 181 } 182 }; 183 184 const LazyCompoundValData *D = LV->getCVData(); 185 FindUninitializedField F(C.getState()->getStateManager().getStoreManager(), 186 C.getSValBuilder().getRegionManager(), 187 D->getStore()); 188 189 if (F.Find(D->getRegion())) { 190 if (ExplodedNode *N = C.generateSink()) { 191 LazyInit_BT("Uninitialized argument value", BT); 192 SmallString<512> Str; 193 llvm::raw_svector_ostream os(Str); 194 os << "Passed-by-value struct argument contains uninitialized data"; 195 196 if (F.FieldChain.size() == 1) 197 os << " (e.g., field: '" << *F.FieldChain[0] << "')"; 198 else { 199 os << " (e.g., via the field chain: '"; 200 bool first = true; 201 for (SmallVectorImpl<const FieldDecl *>::iterator 202 DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){ 203 if (first) 204 first = false; 205 else 206 os << '.'; 207 os << **DI; 208 } 209 os << "')"; 210 } 211 212 // Generate a report for this bug. 213 BugReport *R = new BugReport(*BT, os.str(), N); 214 R->addRange(argRange); 215 216 // FIXME: enhance track back for uninitialized value for arbitrary 217 // memregions 218 C.emitReport(R); 219 } 220 return true; 221 } 222 } 223 224 return false; 225 } 226 227 void CallAndMessageChecker::checkPreStmt(const CallExpr *CE, 228 CheckerContext &C) const{ 229 230 const Expr *Callee = CE->getCallee()->IgnoreParens(); 231 ProgramStateRef State = C.getState(); 232 const LocationContext *LCtx = C.getLocationContext(); 233 SVal L = State->getSVal(Callee, LCtx); 234 235 if (L.isUndef()) { 236 if (!BT_call_undef) 237 BT_call_undef.reset(new BuiltinBug("Called function pointer is an " 238 "uninitalized pointer value")); 239 emitBadCall(BT_call_undef.get(), C, Callee); 240 return; 241 } 242 243 ProgramStateRef StNonNull, StNull; 244 llvm::tie(StNonNull, StNull) = 245 State->assume(L.castAs<DefinedOrUnknownSVal>()); 246 247 if (StNull && !StNonNull) { 248 if (!BT_call_null) 249 BT_call_null.reset( 250 new BuiltinBug("Called function pointer is null (null dereference)")); 251 emitBadCall(BT_call_null.get(), C, Callee); 252 } 253 254 C.addTransition(StNonNull); 255 } 256 257 void CallAndMessageChecker::checkPreStmt(const CXXDeleteExpr *DE, 258 CheckerContext &C) const { 259 260 SVal Arg = C.getSVal(DE->getArgument()); 261 if (Arg.isUndef()) { 262 StringRef Desc; 263 ExplodedNode *N = C.generateSink(); 264 if (!N) 265 return; 266 if (!BT_cxx_delete_undef) 267 BT_cxx_delete_undef.reset(new BuiltinBug("Uninitialized argument value")); 268 if (DE->isArrayFormAsWritten()) 269 Desc = "Argument to 'delete[]' is uninitialized"; 270 else 271 Desc = "Argument to 'delete' is uninitialized"; 272 BugType *BT = BT_cxx_delete_undef.get(); 273 BugReport *R = new BugReport(*BT, Desc, N); 274 bugreporter::trackNullOrUndefValue(N, DE, *R); 275 C.emitReport(R); 276 return; 277 } 278 } 279 280 281 void CallAndMessageChecker::checkPreCall(const CallEvent &Call, 282 CheckerContext &C) const { 283 ProgramStateRef State = C.getState(); 284 285 // If this is a call to a C++ method, check if the callee is null or 286 // undefined. 287 if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) { 288 SVal V = CC->getCXXThisVal(); 289 if (V.isUndef()) { 290 if (!BT_cxx_call_undef) 291 BT_cxx_call_undef.reset(new BuiltinBug("Called C++ object pointer is " 292 "uninitialized")); 293 emitBadCall(BT_cxx_call_undef.get(), C, CC->getCXXThisExpr()); 294 return; 295 } 296 297 ProgramStateRef StNonNull, StNull; 298 llvm::tie(StNonNull, StNull) = 299 State->assume(V.castAs<DefinedOrUnknownSVal>()); 300 301 if (StNull && !StNonNull) { 302 if (!BT_cxx_call_null) 303 BT_cxx_call_null.reset(new BuiltinBug("Called C++ object pointer " 304 "is null")); 305 emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr()); 306 return; 307 } 308 309 State = StNonNull; 310 } 311 312 const Decl *D = Call.getDecl(); 313 if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D)) { 314 // If we have a declaration, we can make sure we pass enough parameters to 315 // the function. 316 unsigned Params = FD->getNumParams(); 317 if (Call.getNumArgs() < Params) { 318 ExplodedNode *N = C.generateSink(); 319 if (!N) 320 return; 321 322 LazyInit_BT("Function call with too few arguments", BT_call_few_args); 323 324 SmallString<512> Str; 325 llvm::raw_svector_ostream os(Str); 326 os << "Function taking " << Params << " argument" 327 << (Params == 1 ? "" : "s") << " is called with less (" 328 << Call.getNumArgs() << ")"; 329 330 BugReport *R = new BugReport(*BT_call_few_args, os.str(), N); 331 C.emitReport(R); 332 } 333 } 334 335 // Don't check for uninitialized field values in arguments if the 336 // caller has a body that is available and we have the chance to inline it. 337 // This is a hack, but is a reasonable compromise betweens sometimes warning 338 // and sometimes not depending on if we decide to inline a function. 339 const bool checkUninitFields = 340 !(C.getAnalysisManager().shouldInlineCall() && (D && D->getBody())); 341 342 OwningPtr<BugType> *BT; 343 if (isa<ObjCMethodCall>(Call)) 344 BT = &BT_msg_arg; 345 else 346 BT = &BT_call_arg; 347 348 for (unsigned i = 0, e = Call.getNumArgs(); i != e; ++i) 349 if (PreVisitProcessArg(C, Call.getArgSVal(i), Call.getArgSourceRange(i), 350 Call.getArgExpr(i), /*IsFirstArgument=*/i == 0, 351 checkUninitFields, Call, *BT)) 352 return; 353 354 // If we make it here, record our assumptions about the callee. 355 C.addTransition(State); 356 } 357 358 void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg, 359 CheckerContext &C) const { 360 SVal recVal = msg.getReceiverSVal(); 361 if (recVal.isUndef()) { 362 if (ExplodedNode *N = C.generateSink()) { 363 BugType *BT = 0; 364 switch (msg.getMessageKind()) { 365 case OCM_Message: 366 if (!BT_msg_undef) 367 BT_msg_undef.reset(new BuiltinBug("Receiver in message expression " 368 "is an uninitialized value")); 369 BT = BT_msg_undef.get(); 370 break; 371 case OCM_PropertyAccess: 372 if (!BT_objc_prop_undef) 373 BT_objc_prop_undef.reset(new BuiltinBug("Property access on an " 374 "uninitialized object " 375 "pointer")); 376 BT = BT_objc_prop_undef.get(); 377 break; 378 case OCM_Subscript: 379 if (!BT_objc_subscript_undef) 380 BT_objc_subscript_undef.reset(new BuiltinBug("Subscript access on an " 381 "uninitialized object " 382 "pointer")); 383 BT = BT_objc_subscript_undef.get(); 384 break; 385 } 386 assert(BT && "Unknown message kind."); 387 388 BugReport *R = new BugReport(*BT, BT->getName(), N); 389 const ObjCMessageExpr *ME = msg.getOriginExpr(); 390 R->addRange(ME->getReceiverRange()); 391 392 // FIXME: getTrackNullOrUndefValueVisitor can't handle "super" yet. 393 if (const Expr *ReceiverE = ME->getInstanceReceiver()) 394 bugreporter::trackNullOrUndefValue(N, ReceiverE, *R); 395 C.emitReport(R); 396 } 397 return; 398 } else { 399 // Bifurcate the state into nil and non-nil ones. 400 DefinedOrUnknownSVal receiverVal = recVal.castAs<DefinedOrUnknownSVal>(); 401 402 ProgramStateRef state = C.getState(); 403 ProgramStateRef notNilState, nilState; 404 llvm::tie(notNilState, nilState) = state->assume(receiverVal); 405 406 // Handle receiver must be nil. 407 if (nilState && !notNilState) { 408 HandleNilReceiver(C, state, msg); 409 return; 410 } 411 } 412 } 413 414 void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C, 415 const ObjCMethodCall &msg, 416 ExplodedNode *N) const { 417 418 if (!BT_msg_ret) 419 BT_msg_ret.reset( 420 new BuiltinBug("Receiver in message expression is 'nil'")); 421 422 const ObjCMessageExpr *ME = msg.getOriginExpr(); 423 424 QualType ResTy = msg.getResultType(); 425 426 SmallString<200> buf; 427 llvm::raw_svector_ostream os(buf); 428 os << "The receiver of message '" << ME->getSelector().getAsString() 429 << "' is nil"; 430 if (ResTy->isReferenceType()) { 431 os << ", which results in forming a null reference"; 432 } else { 433 os << " and returns a value of type '"; 434 msg.getResultType().print(os, C.getLangOpts()); 435 os << "' that will be garbage"; 436 } 437 438 BugReport *report = new BugReport(*BT_msg_ret, os.str(), N); 439 report->addRange(ME->getReceiverRange()); 440 // FIXME: This won't track "self" in messages to super. 441 if (const Expr *receiver = ME->getInstanceReceiver()) { 442 bugreporter::trackNullOrUndefValue(N, receiver, *report); 443 } 444 C.emitReport(report); 445 } 446 447 static bool supportsNilWithFloatRet(const llvm::Triple &triple) { 448 return (triple.getVendor() == llvm::Triple::Apple && 449 (triple.isiOS() || !triple.isMacOSXVersionLT(10,5))); 450 } 451 452 void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C, 453 ProgramStateRef state, 454 const ObjCMethodCall &Msg) const { 455 ASTContext &Ctx = C.getASTContext(); 456 static SimpleProgramPointTag Tag("CallAndMessageChecker : NilReceiver"); 457 458 // Check the return type of the message expression. A message to nil will 459 // return different values depending on the return type and the architecture. 460 QualType RetTy = Msg.getResultType(); 461 CanQualType CanRetTy = Ctx.getCanonicalType(RetTy); 462 const LocationContext *LCtx = C.getLocationContext(); 463 464 if (CanRetTy->isStructureOrClassType()) { 465 // Structure returns are safe since the compiler zeroes them out. 466 SVal V = C.getSValBuilder().makeZeroVal(RetTy); 467 C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag); 468 return; 469 } 470 471 // Other cases: check if sizeof(return type) > sizeof(void*) 472 if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap() 473 .isConsumedExpr(Msg.getOriginExpr())) { 474 // Compute: sizeof(void *) and sizeof(return type) 475 const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy); 476 const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy); 477 478 if (CanRetTy.getTypePtr()->isReferenceType()|| 479 (voidPtrSize < returnTypeSize && 480 !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) && 481 (Ctx.FloatTy == CanRetTy || 482 Ctx.DoubleTy == CanRetTy || 483 Ctx.LongDoubleTy == CanRetTy || 484 Ctx.LongLongTy == CanRetTy || 485 Ctx.UnsignedLongLongTy == CanRetTy)))) { 486 if (ExplodedNode *N = C.generateSink(state, 0 , &Tag)) 487 emitNilReceiverBug(C, Msg, N); 488 return; 489 } 490 491 // Handle the safe cases where the return value is 0 if the 492 // receiver is nil. 493 // 494 // FIXME: For now take the conservative approach that we only 495 // return null values if we *know* that the receiver is nil. 496 // This is because we can have surprises like: 497 // 498 // ... = [[NSScreens screens] objectAtIndex:0]; 499 // 500 // What can happen is that [... screens] could return nil, but 501 // it most likely isn't nil. We should assume the semantics 502 // of this case unless we have *a lot* more knowledge. 503 // 504 SVal V = C.getSValBuilder().makeZeroVal(RetTy); 505 C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag); 506 return; 507 } 508 509 C.addTransition(state); 510 } 511 512 void ento::registerCallAndMessageChecker(CheckerManager &mgr) { 513 mgr.registerChecker<CallAndMessageChecker>(); 514 } 515