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/CheckerContext.h" 19 #include "clang/StaticAnalyzer/Core/PathSensitive/ObjCMessage.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 mutable OwningPtr<BugType> BT_call_null; 32 mutable OwningPtr<BugType> BT_call_undef; 33 mutable OwningPtr<BugType> BT_call_arg; 34 mutable OwningPtr<BugType> BT_msg_undef; 35 mutable OwningPtr<BugType> BT_objc_prop_undef; 36 mutable OwningPtr<BugType> BT_msg_arg; 37 mutable OwningPtr<BugType> BT_msg_ret; 38 public: 39 40 void checkPreStmt(const CallExpr *CE, CheckerContext &C) const; 41 void checkPreObjCMessage(ObjCMessage msg, CheckerContext &C) const; 42 43 private: 44 static void PreVisitProcessArgs(CheckerContext &C,CallOrObjCMessage callOrMsg, 45 const char *BT_desc, OwningPtr<BugType> &BT); 46 static bool PreVisitProcessArg(CheckerContext &C, SVal V,SourceRange argRange, 47 const Expr *argEx, const char *BT_desc, OwningPtr<BugType> &BT); 48 49 static void EmitBadCall(BugType *BT, CheckerContext &C, const CallExpr *CE); 50 void emitNilReceiverBug(CheckerContext &C, const ObjCMessage &msg, 51 ExplodedNode *N) const; 52 53 void HandleNilReceiver(CheckerContext &C, 54 ProgramStateRef state, 55 ObjCMessage msg) const; 56 57 static void LazyInit_BT(const char *desc, OwningPtr<BugType> &BT) { 58 if (!BT) 59 BT.reset(new BuiltinBug(desc)); 60 } 61 }; 62 } // end anonymous namespace 63 64 void CallAndMessageChecker::EmitBadCall(BugType *BT, CheckerContext &C, 65 const CallExpr *CE) { 66 ExplodedNode *N = C.generateSink(); 67 if (!N) 68 return; 69 70 BugReport *R = new BugReport(*BT, BT->getName(), N); 71 R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, 72 bugreporter::GetCalleeExpr(N))); 73 C.EmitReport(R); 74 } 75 76 void CallAndMessageChecker::PreVisitProcessArgs(CheckerContext &C, 77 CallOrObjCMessage callOrMsg, 78 const char *BT_desc, 79 OwningPtr<BugType> &BT) { 80 for (unsigned i = 0, e = callOrMsg.getNumArgs(); i != e; ++i) 81 if (PreVisitProcessArg(C, callOrMsg.getArgSVal(i), 82 callOrMsg.getArgSourceRange(i), callOrMsg.getArg(i), 83 BT_desc, BT)) 84 return; 85 } 86 87 bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C, 88 SVal V, SourceRange argRange, 89 const Expr *argEx, 90 const char *BT_desc, 91 OwningPtr<BugType> &BT) { 92 93 if (V.isUndef()) { 94 if (ExplodedNode *N = C.generateSink()) { 95 LazyInit_BT(BT_desc, BT); 96 97 // Generate a report for this bug. 98 BugReport *R = new BugReport(*BT, BT->getName(), N); 99 R->addRange(argRange); 100 if (argEx) 101 R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, argEx)); 102 C.EmitReport(R); 103 } 104 return true; 105 } 106 107 if (const nonloc::LazyCompoundVal *LV = 108 dyn_cast<nonloc::LazyCompoundVal>(&V)) { 109 110 class FindUninitializedField { 111 public: 112 SmallVector<const FieldDecl *, 10> FieldChain; 113 private: 114 ASTContext &C; 115 StoreManager &StoreMgr; 116 MemRegionManager &MrMgr; 117 Store store; 118 public: 119 FindUninitializedField(ASTContext &c, StoreManager &storeMgr, 120 MemRegionManager &mrMgr, Store s) 121 : C(c), StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {} 122 123 bool Find(const TypedValueRegion *R) { 124 QualType T = R->getValueType(); 125 if (const RecordType *RT = T->getAsStructureType()) { 126 const RecordDecl *RD = RT->getDecl()->getDefinition(); 127 assert(RD && "Referred record has no definition"); 128 for (RecordDecl::field_iterator I = 129 RD->field_begin(), E = RD->field_end(); I!=E; ++I) { 130 const FieldRegion *FR = MrMgr.getFieldRegion(*I, R); 131 FieldChain.push_back(*I); 132 T = (*I)->getType(); 133 if (T->getAsStructureType()) { 134 if (Find(FR)) 135 return true; 136 } 137 else { 138 const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR)); 139 if (V.isUndef()) 140 return true; 141 } 142 FieldChain.pop_back(); 143 } 144 } 145 146 return false; 147 } 148 }; 149 150 const LazyCompoundValData *D = LV->getCVData(); 151 FindUninitializedField F(C.getASTContext(), 152 C.getState()->getStateManager().getStoreManager(), 153 C.getSValBuilder().getRegionManager(), 154 D->getStore()); 155 156 if (F.Find(D->getRegion())) { 157 if (ExplodedNode *N = C.generateSink()) { 158 LazyInit_BT(BT_desc, BT); 159 SmallString<512> Str; 160 llvm::raw_svector_ostream os(Str); 161 os << "Passed-by-value struct argument contains uninitialized data"; 162 163 if (F.FieldChain.size() == 1) 164 os << " (e.g., field: '" << *F.FieldChain[0] << "')"; 165 else { 166 os << " (e.g., via the field chain: '"; 167 bool first = true; 168 for (SmallVectorImpl<const FieldDecl *>::iterator 169 DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){ 170 if (first) 171 first = false; 172 else 173 os << '.'; 174 os << **DI; 175 } 176 os << "')"; 177 } 178 179 // Generate a report for this bug. 180 BugReport *R = new BugReport(*BT, os.str(), N); 181 R->addRange(argRange); 182 183 // FIXME: enhance track back for uninitialized value for arbitrary 184 // memregions 185 C.EmitReport(R); 186 } 187 return true; 188 } 189 } 190 191 return false; 192 } 193 194 void CallAndMessageChecker::checkPreStmt(const CallExpr *CE, 195 CheckerContext &C) const{ 196 197 const Expr *Callee = CE->getCallee()->IgnoreParens(); 198 const LocationContext *LCtx = C.getLocationContext(); 199 SVal L = C.getState()->getSVal(Callee, LCtx); 200 201 if (L.isUndef()) { 202 if (!BT_call_undef) 203 BT_call_undef.reset(new BuiltinBug("Called function pointer is an " 204 "uninitalized pointer value")); 205 EmitBadCall(BT_call_undef.get(), C, CE); 206 return; 207 } 208 209 if (isa<loc::ConcreteInt>(L)) { 210 if (!BT_call_null) 211 BT_call_null.reset( 212 new BuiltinBug("Called function pointer is null (null dereference)")); 213 EmitBadCall(BT_call_null.get(), C, CE); 214 } 215 216 PreVisitProcessArgs(C, CallOrObjCMessage(CE, C.getState(), LCtx), 217 "Function call argument is an uninitialized value", 218 BT_call_arg); 219 } 220 221 void CallAndMessageChecker::checkPreObjCMessage(ObjCMessage msg, 222 CheckerContext &C) const { 223 224 ProgramStateRef state = C.getState(); 225 const LocationContext *LCtx = C.getLocationContext(); 226 227 // FIXME: Handle 'super'? 228 if (const Expr *receiver = msg.getInstanceReceiver()) { 229 SVal recVal = state->getSVal(receiver, LCtx); 230 if (recVal.isUndef()) { 231 if (ExplodedNode *N = C.generateSink()) { 232 BugType *BT = 0; 233 if (msg.isPureMessageExpr()) { 234 if (!BT_msg_undef) 235 BT_msg_undef.reset(new BuiltinBug("Receiver in message expression " 236 "is an uninitialized value")); 237 BT = BT_msg_undef.get(); 238 } 239 else { 240 if (!BT_objc_prop_undef) 241 BT_objc_prop_undef.reset(new BuiltinBug("Property access on an " 242 "uninitialized object pointer")); 243 BT = BT_objc_prop_undef.get(); 244 } 245 BugReport *R = 246 new BugReport(*BT, BT->getName(), N); 247 R->addRange(receiver->getSourceRange()); 248 R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, 249 receiver)); 250 C.EmitReport(R); 251 } 252 return; 253 } else { 254 // Bifurcate the state into nil and non-nil ones. 255 DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal); 256 257 ProgramStateRef notNilState, nilState; 258 llvm::tie(notNilState, nilState) = state->assume(receiverVal); 259 260 // Handle receiver must be nil. 261 if (nilState && !notNilState) { 262 HandleNilReceiver(C, state, msg); 263 return; 264 } 265 } 266 } 267 268 const char *bugDesc = msg.isPropertySetter() ? 269 "Argument for property setter is an uninitialized value" 270 : "Argument in message expression is an uninitialized value"; 271 // Check for any arguments that are uninitialized/undefined. 272 PreVisitProcessArgs(C, CallOrObjCMessage(msg, state, LCtx), 273 bugDesc, BT_msg_arg); 274 } 275 276 void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C, 277 const ObjCMessage &msg, 278 ExplodedNode *N) const { 279 280 if (!BT_msg_ret) 281 BT_msg_ret.reset( 282 new BuiltinBug("Receiver in message expression is " 283 "'nil' and returns a garbage value")); 284 285 SmallString<200> buf; 286 llvm::raw_svector_ostream os(buf); 287 os << "The receiver of message '" << msg.getSelector().getAsString() 288 << "' is nil and returns a value of type '" 289 << msg.getType(C.getASTContext()).getAsString() << "' that will be garbage"; 290 291 BugReport *report = new BugReport(*BT_msg_ret, os.str(), N); 292 if (const Expr *receiver = msg.getInstanceReceiver()) { 293 report->addRange(receiver->getSourceRange()); 294 report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, 295 receiver)); 296 } 297 C.EmitReport(report); 298 } 299 300 static bool supportsNilWithFloatRet(const llvm::Triple &triple) { 301 return (triple.getVendor() == llvm::Triple::Apple && 302 (triple.getOS() == llvm::Triple::IOS || 303 !triple.isMacOSXVersionLT(10,5))); 304 } 305 306 void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C, 307 ProgramStateRef state, 308 ObjCMessage msg) const { 309 ASTContext &Ctx = C.getASTContext(); 310 311 // Check the return type of the message expression. A message to nil will 312 // return different values depending on the return type and the architecture. 313 QualType RetTy = msg.getType(Ctx); 314 CanQualType CanRetTy = Ctx.getCanonicalType(RetTy); 315 const LocationContext *LCtx = C.getLocationContext(); 316 317 if (CanRetTy->isStructureOrClassType()) { 318 // Structure returns are safe since the compiler zeroes them out. 319 SVal V = C.getSValBuilder().makeZeroVal(msg.getType(Ctx)); 320 C.addTransition(state->BindExpr(msg.getMessageExpr(), LCtx, V)); 321 return; 322 } 323 324 // Other cases: check if sizeof(return type) > sizeof(void*) 325 if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap() 326 .isConsumedExpr(msg.getMessageExpr())) { 327 // Compute: sizeof(void *) and sizeof(return type) 328 const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy); 329 const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy); 330 331 if (voidPtrSize < returnTypeSize && 332 !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) && 333 (Ctx.FloatTy == CanRetTy || 334 Ctx.DoubleTy == CanRetTy || 335 Ctx.LongDoubleTy == CanRetTy || 336 Ctx.LongLongTy == CanRetTy || 337 Ctx.UnsignedLongLongTy == CanRetTy))) { 338 if (ExplodedNode *N = C.generateSink(state)) 339 emitNilReceiverBug(C, msg, N); 340 return; 341 } 342 343 // Handle the safe cases where the return value is 0 if the 344 // receiver is nil. 345 // 346 // FIXME: For now take the conservative approach that we only 347 // return null values if we *know* that the receiver is nil. 348 // This is because we can have surprises like: 349 // 350 // ... = [[NSScreens screens] objectAtIndex:0]; 351 // 352 // What can happen is that [... screens] could return nil, but 353 // it most likely isn't nil. We should assume the semantics 354 // of this case unless we have *a lot* more knowledge. 355 // 356 SVal V = C.getSValBuilder().makeZeroVal(msg.getType(Ctx)); 357 C.addTransition(state->BindExpr(msg.getMessageExpr(), LCtx, V)); 358 return; 359 } 360 361 C.addTransition(state); 362 } 363 364 void ento::registerCallAndMessageChecker(CheckerManager &mgr) { 365 mgr.registerChecker<CallAndMessageChecker>(); 366 } 367