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