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