CallAndMessageChecker.cpp revision 7453624b98817f06d28ed2abe39c98805cfec623
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 26using namespace clang; 27using namespace ento; 28 29namespace { 30class 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; 47public: 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 54private: 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 75void 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 91static 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 116bool 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 227void 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 return; 253 } 254 255 C.addTransition(StNonNull); 256} 257 258void CallAndMessageChecker::checkPreStmt(const CXXDeleteExpr *DE, 259 CheckerContext &C) const { 260 261 SVal Arg = C.getSVal(DE->getArgument()); 262 if (Arg.isUndef()) { 263 StringRef Desc; 264 ExplodedNode *N = C.generateSink(); 265 if (!N) 266 return; 267 if (!BT_cxx_delete_undef) 268 BT_cxx_delete_undef.reset(new BuiltinBug("Uninitialized argument value")); 269 if (DE->isArrayFormAsWritten()) 270 Desc = "Argument to 'delete[]' is uninitialized"; 271 else 272 Desc = "Argument to 'delete' is uninitialized"; 273 BugType *BT = BT_cxx_delete_undef.get(); 274 BugReport *R = new BugReport(*BT, Desc, N); 275 bugreporter::trackNullOrUndefValue(N, DE, *R); 276 C.emitReport(R); 277 return; 278 } 279} 280 281 282void CallAndMessageChecker::checkPreCall(const CallEvent &Call, 283 CheckerContext &C) const { 284 ProgramStateRef State = C.getState(); 285 286 // If this is a call to a C++ method, check if the callee is null or 287 // undefined. 288 if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) { 289 SVal V = CC->getCXXThisVal(); 290 if (V.isUndef()) { 291 if (!BT_cxx_call_undef) 292 BT_cxx_call_undef.reset(new BuiltinBug("Called C++ object pointer is " 293 "uninitialized")); 294 emitBadCall(BT_cxx_call_undef.get(), C, CC->getCXXThisExpr()); 295 return; 296 } 297 298 ProgramStateRef StNonNull, StNull; 299 llvm::tie(StNonNull, StNull) = 300 State->assume(V.castAs<DefinedOrUnknownSVal>()); 301 302 if (StNull && !StNonNull) { 303 if (!BT_cxx_call_null) 304 BT_cxx_call_null.reset(new BuiltinBug("Called C++ object pointer " 305 "is null")); 306 emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr()); 307 return; 308 } 309 310 State = StNonNull; 311 } 312 313 const Decl *D = Call.getDecl(); 314 if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D)) { 315 // If we have a declaration, we can make sure we pass enough parameters to 316 // the function. 317 unsigned Params = FD->getNumParams(); 318 if (Call.getNumArgs() < Params) { 319 ExplodedNode *N = C.generateSink(); 320 if (!N) 321 return; 322 323 LazyInit_BT("Function call with too few arguments", BT_call_few_args); 324 325 SmallString<512> Str; 326 llvm::raw_svector_ostream os(Str); 327 os << "Function taking " << Params << " argument" 328 << (Params == 1 ? "" : "s") << " is called with less (" 329 << Call.getNumArgs() << ")"; 330 331 BugReport *R = new BugReport(*BT_call_few_args, os.str(), N); 332 C.emitReport(R); 333 } 334 } 335 336 // Don't check for uninitialized field values in arguments if the 337 // caller has a body that is available and we have the chance to inline it. 338 // This is a hack, but is a reasonable compromise betweens sometimes warning 339 // and sometimes not depending on if we decide to inline a function. 340 const bool checkUninitFields = 341 !(C.getAnalysisManager().shouldInlineCall() && (D && D->getBody())); 342 343 OwningPtr<BugType> *BT; 344 if (isa<ObjCMethodCall>(Call)) 345 BT = &BT_msg_arg; 346 else 347 BT = &BT_call_arg; 348 349 for (unsigned i = 0, e = Call.getNumArgs(); i != e; ++i) 350 if (PreVisitProcessArg(C, Call.getArgSVal(i), Call.getArgSourceRange(i), 351 Call.getArgExpr(i), /*IsFirstArgument=*/i == 0, 352 checkUninitFields, Call, *BT)) 353 return; 354 355 // If we make it here, record our assumptions about the callee. 356 C.addTransition(State); 357} 358 359void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg, 360 CheckerContext &C) const { 361 SVal recVal = msg.getReceiverSVal(); 362 if (recVal.isUndef()) { 363 if (ExplodedNode *N = C.generateSink()) { 364 BugType *BT = 0; 365 switch (msg.getMessageKind()) { 366 case OCM_Message: 367 if (!BT_msg_undef) 368 BT_msg_undef.reset(new BuiltinBug("Receiver in message expression " 369 "is an uninitialized value")); 370 BT = BT_msg_undef.get(); 371 break; 372 case OCM_PropertyAccess: 373 if (!BT_objc_prop_undef) 374 BT_objc_prop_undef.reset(new BuiltinBug("Property access on an " 375 "uninitialized object " 376 "pointer")); 377 BT = BT_objc_prop_undef.get(); 378 break; 379 case OCM_Subscript: 380 if (!BT_objc_subscript_undef) 381 BT_objc_subscript_undef.reset(new BuiltinBug("Subscript access on an " 382 "uninitialized object " 383 "pointer")); 384 BT = BT_objc_subscript_undef.get(); 385 break; 386 } 387 assert(BT && "Unknown message kind."); 388 389 BugReport *R = new BugReport(*BT, BT->getName(), N); 390 const ObjCMessageExpr *ME = msg.getOriginExpr(); 391 R->addRange(ME->getReceiverRange()); 392 393 // FIXME: getTrackNullOrUndefValueVisitor can't handle "super" yet. 394 if (const Expr *ReceiverE = ME->getInstanceReceiver()) 395 bugreporter::trackNullOrUndefValue(N, ReceiverE, *R); 396 C.emitReport(R); 397 } 398 return; 399 } else { 400 // Bifurcate the state into nil and non-nil ones. 401 DefinedOrUnknownSVal receiverVal = recVal.castAs<DefinedOrUnknownSVal>(); 402 403 ProgramStateRef state = C.getState(); 404 ProgramStateRef notNilState, nilState; 405 llvm::tie(notNilState, nilState) = state->assume(receiverVal); 406 407 // Handle receiver must be nil. 408 if (nilState && !notNilState) { 409 HandleNilReceiver(C, state, msg); 410 return; 411 } 412 } 413} 414 415void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C, 416 const ObjCMethodCall &msg, 417 ExplodedNode *N) const { 418 419 if (!BT_msg_ret) 420 BT_msg_ret.reset( 421 new BuiltinBug("Receiver in message expression is 'nil'")); 422 423 const ObjCMessageExpr *ME = msg.getOriginExpr(); 424 425 QualType ResTy = msg.getResultType(); 426 427 SmallString<200> buf; 428 llvm::raw_svector_ostream os(buf); 429 os << "The receiver of message '" << ME->getSelector().getAsString() 430 << "' is nil"; 431 if (ResTy->isReferenceType()) { 432 os << ", which results in forming a null reference"; 433 } else { 434 os << " and returns a value of type '"; 435 msg.getResultType().print(os, C.getLangOpts()); 436 os << "' that will be garbage"; 437 } 438 439 BugReport *report = new BugReport(*BT_msg_ret, os.str(), N); 440 report->addRange(ME->getReceiverRange()); 441 // FIXME: This won't track "self" in messages to super. 442 if (const Expr *receiver = ME->getInstanceReceiver()) { 443 bugreporter::trackNullOrUndefValue(N, receiver, *report); 444 } 445 C.emitReport(report); 446} 447 448static bool supportsNilWithFloatRet(const llvm::Triple &triple) { 449 return (triple.getVendor() == llvm::Triple::Apple && 450 (triple.isiOS() || !triple.isMacOSXVersionLT(10,5))); 451} 452 453void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C, 454 ProgramStateRef state, 455 const ObjCMethodCall &Msg) const { 456 ASTContext &Ctx = C.getASTContext(); 457 static SimpleProgramPointTag Tag("CallAndMessageChecker : NilReceiver"); 458 459 // Check the return type of the message expression. A message to nil will 460 // return different values depending on the return type and the architecture. 461 QualType RetTy = Msg.getResultType(); 462 CanQualType CanRetTy = Ctx.getCanonicalType(RetTy); 463 const LocationContext *LCtx = C.getLocationContext(); 464 465 if (CanRetTy->isStructureOrClassType()) { 466 // Structure returns are safe since the compiler zeroes them out. 467 SVal V = C.getSValBuilder().makeZeroVal(RetTy); 468 C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag); 469 return; 470 } 471 472 // Other cases: check if sizeof(return type) > sizeof(void*) 473 if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap() 474 .isConsumedExpr(Msg.getOriginExpr())) { 475 // Compute: sizeof(void *) and sizeof(return type) 476 const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy); 477 const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy); 478 479 if (CanRetTy.getTypePtr()->isReferenceType()|| 480 (voidPtrSize < returnTypeSize && 481 !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) && 482 (Ctx.FloatTy == CanRetTy || 483 Ctx.DoubleTy == CanRetTy || 484 Ctx.LongDoubleTy == CanRetTy || 485 Ctx.LongLongTy == CanRetTy || 486 Ctx.UnsignedLongLongTy == CanRetTy)))) { 487 if (ExplodedNode *N = C.generateSink(state, 0 , &Tag)) 488 emitNilReceiverBug(C, Msg, N); 489 return; 490 } 491 492 // Handle the safe cases where the return value is 0 if the 493 // receiver is nil. 494 // 495 // FIXME: For now take the conservative approach that we only 496 // return null values if we *know* that the receiver is nil. 497 // This is because we can have surprises like: 498 // 499 // ... = [[NSScreens screens] objectAtIndex:0]; 500 // 501 // What can happen is that [... screens] could return nil, but 502 // it most likely isn't nil. We should assume the semantics 503 // of this case unless we have *a lot* more knowledge. 504 // 505 SVal V = C.getSValBuilder().makeZeroVal(RetTy); 506 C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag); 507 return; 508 } 509 510 C.addTransition(state); 511} 512 513void ento::registerCallAndMessageChecker(CheckerManager &mgr) { 514 mgr.registerChecker<CallAndMessageChecker>(); 515} 516