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 24 using namespace clang; 25 using namespace ento; 26 27 namespace { 28 class CallAndMessageChecker 29 : public Checker< check::PreStmt<CallExpr>, check::PreObjCMessage > { 30 mutable llvm::OwningPtr<BugType> BT_call_null; 31 mutable llvm::OwningPtr<BugType> BT_call_undef; 32 mutable llvm::OwningPtr<BugType> BT_call_arg; 33 mutable llvm::OwningPtr<BugType> BT_msg_undef; 34 mutable llvm::OwningPtr<BugType> BT_msg_arg; 35 mutable llvm::OwningPtr<BugType> BT_msg_ret; 36 public: 37 38 void checkPreStmt(const CallExpr *CE, CheckerContext &C) const; 39 void checkPreObjCMessage(ObjCMessage msg, CheckerContext &C) const; 40 41 private: 42 static void PreVisitProcessArgs(CheckerContext &C,CallOrObjCMessage callOrMsg, 43 const char *BT_desc, llvm::OwningPtr<BugType> &BT); 44 static bool PreVisitProcessArg(CheckerContext &C, SVal V,SourceRange argRange, 45 const Expr *argEx, const char *BT_desc, llvm::OwningPtr<BugType> &BT); 46 47 static void EmitBadCall(BugType *BT, CheckerContext &C, const CallExpr *CE); 48 void emitNilReceiverBug(CheckerContext &C, const ObjCMessage &msg, 49 ExplodedNode *N) const; 50 51 void HandleNilReceiver(CheckerContext &C, 52 ProgramStateRef state, 53 ObjCMessage msg) const; 54 55 static void LazyInit_BT(const char *desc, llvm::OwningPtr<BugType> &BT) { 56 if (!BT) 57 BT.reset(new BuiltinBug(desc)); 58 } 59 }; 60 } // end anonymous namespace 61 62 void CallAndMessageChecker::EmitBadCall(BugType *BT, CheckerContext &C, 63 const CallExpr *CE) { 64 ExplodedNode *N = C.generateSink(); 65 if (!N) 66 return; 67 68 BugReport *R = new BugReport(*BT, BT->getName(), N); 69 R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, 70 bugreporter::GetCalleeExpr(N))); 71 C.EmitReport(R); 72 } 73 74 void CallAndMessageChecker::PreVisitProcessArgs(CheckerContext &C, 75 CallOrObjCMessage callOrMsg, 76 const char *BT_desc, 77 llvm::OwningPtr<BugType> &BT) { 78 for (unsigned i = 0, e = callOrMsg.getNumArgs(); i != e; ++i) 79 if (PreVisitProcessArg(C, callOrMsg.getArgSVal(i), 80 callOrMsg.getArgSourceRange(i), callOrMsg.getArg(i), 81 BT_desc, BT)) 82 return; 83 } 84 85 bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C, 86 SVal V, SourceRange argRange, 87 const Expr *argEx, 88 const char *BT_desc, 89 llvm::OwningPtr<BugType> &BT) { 90 91 if (V.isUndef()) { 92 if (ExplodedNode *N = C.generateSink()) { 93 LazyInit_BT(BT_desc, BT); 94 95 // Generate a report for this bug. 96 BugReport *R = new BugReport(*BT, BT->getName(), N); 97 R->addRange(argRange); 98 if (argEx) 99 R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, argEx)); 100 C.EmitReport(R); 101 } 102 return true; 103 } 104 105 if (const nonloc::LazyCompoundVal *LV = 106 dyn_cast<nonloc::LazyCompoundVal>(&V)) { 107 108 class FindUninitializedField { 109 public: 110 SmallVector<const FieldDecl *, 10> FieldChain; 111 private: 112 ASTContext &C; 113 StoreManager &StoreMgr; 114 MemRegionManager &MrMgr; 115 Store store; 116 public: 117 FindUninitializedField(ASTContext &c, StoreManager &storeMgr, 118 MemRegionManager &mrMgr, Store s) 119 : C(c), StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {} 120 121 bool Find(const TypedValueRegion *R) { 122 QualType T = R->getValueType(); 123 if (const RecordType *RT = T->getAsStructureType()) { 124 const RecordDecl *RD = RT->getDecl()->getDefinition(); 125 assert(RD && "Referred record has no definition"); 126 for (RecordDecl::field_iterator I = 127 RD->field_begin(), E = RD->field_end(); I!=E; ++I) { 128 const FieldRegion *FR = MrMgr.getFieldRegion(*I, R); 129 FieldChain.push_back(*I); 130 T = (*I)->getType(); 131 if (T->getAsStructureType()) { 132 if (Find(FR)) 133 return true; 134 } 135 else { 136 const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR)); 137 if (V.isUndef()) 138 return true; 139 } 140 FieldChain.pop_back(); 141 } 142 } 143 144 return false; 145 } 146 }; 147 148 const LazyCompoundValData *D = LV->getCVData(); 149 FindUninitializedField F(C.getASTContext(), 150 C.getState()->getStateManager().getStoreManager(), 151 C.getSValBuilder().getRegionManager(), 152 D->getStore()); 153 154 if (F.Find(D->getRegion())) { 155 if (ExplodedNode *N = C.generateSink()) { 156 LazyInit_BT(BT_desc, BT); 157 llvm::SmallString<512> Str; 158 llvm::raw_svector_ostream os(Str); 159 os << "Passed-by-value struct argument contains uninitialized data"; 160 161 if (F.FieldChain.size() == 1) 162 os << " (e.g., field: '" << *F.FieldChain[0] << "')"; 163 else { 164 os << " (e.g., via the field chain: '"; 165 bool first = true; 166 for (SmallVectorImpl<const FieldDecl *>::iterator 167 DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){ 168 if (first) 169 first = false; 170 else 171 os << '.'; 172 os << **DI; 173 } 174 os << "')"; 175 } 176 177 // Generate a report for this bug. 178 BugReport *R = new BugReport(*BT, os.str(), N); 179 R->addRange(argRange); 180 181 // FIXME: enhance track back for uninitialized value for arbitrary 182 // memregions 183 C.EmitReport(R); 184 } 185 return true; 186 } 187 } 188 189 return false; 190 } 191 192 void CallAndMessageChecker::checkPreStmt(const CallExpr *CE, 193 CheckerContext &C) const{ 194 195 const Expr *Callee = CE->getCallee()->IgnoreParens(); 196 const LocationContext *LCtx = C.getLocationContext(); 197 SVal L = C.getState()->getSVal(Callee, LCtx); 198 199 if (L.isUndef()) { 200 if (!BT_call_undef) 201 BT_call_undef.reset(new BuiltinBug("Called function pointer is an " 202 "uninitalized pointer value")); 203 EmitBadCall(BT_call_undef.get(), C, CE); 204 return; 205 } 206 207 if (isa<loc::ConcreteInt>(L)) { 208 if (!BT_call_null) 209 BT_call_null.reset( 210 new BuiltinBug("Called function pointer is null (null dereference)")); 211 EmitBadCall(BT_call_null.get(), C, CE); 212 } 213 214 PreVisitProcessArgs(C, CallOrObjCMessage(CE, C.getState(), LCtx), 215 "Function call argument is an uninitialized value", 216 BT_call_arg); 217 } 218 219 void CallAndMessageChecker::checkPreObjCMessage(ObjCMessage msg, 220 CheckerContext &C) const { 221 222 ProgramStateRef state = C.getState(); 223 const LocationContext *LCtx = C.getLocationContext(); 224 225 // FIXME: Handle 'super'? 226 if (const Expr *receiver = msg.getInstanceReceiver()) { 227 SVal recVal = state->getSVal(receiver, LCtx); 228 if (recVal.isUndef()) { 229 if (ExplodedNode *N = C.generateSink()) { 230 if (!BT_msg_undef) 231 BT_msg_undef.reset(new BuiltinBug("Receiver in message expression is " 232 "an uninitialized value")); 233 BugReport *R = 234 new BugReport(*BT_msg_undef, BT_msg_undef->getName(), N); 235 R->addRange(receiver->getSourceRange()); 236 R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, 237 receiver)); 238 C.EmitReport(R); 239 } 240 return; 241 } else { 242 // Bifurcate the state into nil and non-nil ones. 243 DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal); 244 245 ProgramStateRef notNilState, nilState; 246 llvm::tie(notNilState, nilState) = state->assume(receiverVal); 247 248 // Handle receiver must be nil. 249 if (nilState && !notNilState) { 250 HandleNilReceiver(C, state, msg); 251 return; 252 } 253 } 254 } 255 256 const char *bugDesc = msg.isPropertySetter() ? 257 "Argument for property setter is an uninitialized value" 258 : "Argument in message expression is an uninitialized value"; 259 // Check for any arguments that are uninitialized/undefined. 260 PreVisitProcessArgs(C, CallOrObjCMessage(msg, state, LCtx), 261 bugDesc, BT_msg_arg); 262 } 263 264 void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C, 265 const ObjCMessage &msg, 266 ExplodedNode *N) const { 267 268 if (!BT_msg_ret) 269 BT_msg_ret.reset( 270 new BuiltinBug("Receiver in message expression is " 271 "'nil' and returns a garbage value")); 272 273 llvm::SmallString<200> buf; 274 llvm::raw_svector_ostream os(buf); 275 os << "The receiver of message '" << msg.getSelector().getAsString() 276 << "' is nil and returns a value of type '" 277 << msg.getType(C.getASTContext()).getAsString() << "' that will be garbage"; 278 279 BugReport *report = new BugReport(*BT_msg_ret, os.str(), N); 280 if (const Expr *receiver = msg.getInstanceReceiver()) { 281 report->addRange(receiver->getSourceRange()); 282 report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, 283 receiver)); 284 } 285 C.EmitReport(report); 286 } 287 288 static bool supportsNilWithFloatRet(const llvm::Triple &triple) { 289 return triple.getVendor() == llvm::Triple::Apple && 290 (!triple.isMacOSXVersionLT(10,5) || 291 triple.getArch() == llvm::Triple::arm || 292 triple.getArch() == llvm::Triple::thumb); 293 } 294 295 void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C, 296 ProgramStateRef state, 297 ObjCMessage msg) const { 298 ASTContext &Ctx = C.getASTContext(); 299 300 // Check the return type of the message expression. A message to nil will 301 // return different values depending on the return type and the architecture. 302 QualType RetTy = msg.getType(Ctx); 303 CanQualType CanRetTy = Ctx.getCanonicalType(RetTy); 304 const LocationContext *LCtx = C.getLocationContext(); 305 306 if (CanRetTy->isStructureOrClassType()) { 307 // Structure returns are safe since the compiler zeroes them out. 308 SVal V = C.getSValBuilder().makeZeroVal(msg.getType(Ctx)); 309 C.addTransition(state->BindExpr(msg.getOriginExpr(), LCtx, V)); 310 return; 311 } 312 313 // Other cases: check if sizeof(return type) > sizeof(void*) 314 if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap() 315 .isConsumedExpr(msg.getOriginExpr())) { 316 // Compute: sizeof(void *) and sizeof(return type) 317 const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy); 318 const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy); 319 320 if (voidPtrSize < returnTypeSize && 321 !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) && 322 (Ctx.FloatTy == CanRetTy || 323 Ctx.DoubleTy == CanRetTy || 324 Ctx.LongDoubleTy == CanRetTy || 325 Ctx.LongLongTy == CanRetTy || 326 Ctx.UnsignedLongLongTy == CanRetTy))) { 327 if (ExplodedNode *N = C.generateSink(state)) 328 emitNilReceiverBug(C, msg, N); 329 return; 330 } 331 332 // Handle the safe cases where the return value is 0 if the 333 // receiver is nil. 334 // 335 // FIXME: For now take the conservative approach that we only 336 // return null values if we *know* that the receiver is nil. 337 // This is because we can have surprises like: 338 // 339 // ... = [[NSScreens screens] objectAtIndex:0]; 340 // 341 // What can happen is that [... screens] could return nil, but 342 // it most likely isn't nil. We should assume the semantics 343 // of this case unless we have *a lot* more knowledge. 344 // 345 SVal V = C.getSValBuilder().makeZeroVal(msg.getType(Ctx)); 346 C.addTransition(state->BindExpr(msg.getOriginExpr(), LCtx, V)); 347 return; 348 } 349 350 C.addTransition(state); 351 } 352 353 void ento::registerCallAndMessageChecker(CheckerManager &mgr) { 354 mgr.registerChecker<CallAndMessageChecker>(); 355 } 356