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