1//=- NSErrorChecker.cpp - Coding conventions for uses of NSError -*- 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 file defines a CheckNSError, a flow-insenstive check 11// that determines if an Objective-C class interface correctly returns 12// a non-void return type. 13// 14// File under feature request PR 2600. 15// 16//===----------------------------------------------------------------------===// 17 18#include "ClangSACheckers.h" 19#include "clang/AST/Decl.h" 20#include "clang/AST/DeclObjC.h" 21#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" 22#include "clang/StaticAnalyzer/Core/Checker.h" 23#include "clang/StaticAnalyzer/Core/CheckerManager.h" 24#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 25#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h" 26#include "llvm/ADT/SmallString.h" 27#include "llvm/Support/raw_ostream.h" 28 29using namespace clang; 30using namespace ento; 31 32static bool IsNSError(QualType T, IdentifierInfo *II); 33static bool IsCFError(QualType T, IdentifierInfo *II); 34 35//===----------------------------------------------------------------------===// 36// NSErrorMethodChecker 37//===----------------------------------------------------------------------===// 38 39namespace { 40class NSErrorMethodChecker 41 : public Checker< check::ASTDecl<ObjCMethodDecl> > { 42 mutable IdentifierInfo *II; 43 44public: 45 NSErrorMethodChecker() : II(nullptr) {} 46 47 void checkASTDecl(const ObjCMethodDecl *D, 48 AnalysisManager &mgr, BugReporter &BR) const; 49}; 50} 51 52void NSErrorMethodChecker::checkASTDecl(const ObjCMethodDecl *D, 53 AnalysisManager &mgr, 54 BugReporter &BR) const { 55 if (!D->isThisDeclarationADefinition()) 56 return; 57 if (!D->getReturnType()->isVoidType()) 58 return; 59 60 if (!II) 61 II = &D->getASTContext().Idents.get("NSError"); 62 63 bool hasNSError = false; 64 for (const auto *I : D->parameters()) { 65 if (IsNSError(I->getType(), II)) { 66 hasNSError = true; 67 break; 68 } 69 } 70 71 if (hasNSError) { 72 const char *err = "Method accepting NSError** " 73 "should have a non-void return value to indicate whether or not an " 74 "error occurred"; 75 PathDiagnosticLocation L = 76 PathDiagnosticLocation::create(D, BR.getSourceManager()); 77 BR.EmitBasicReport(D, this, "Bad return type when passing NSError**", 78 "Coding conventions (Apple)", err, L); 79 } 80} 81 82//===----------------------------------------------------------------------===// 83// CFErrorFunctionChecker 84//===----------------------------------------------------------------------===// 85 86namespace { 87class CFErrorFunctionChecker 88 : public Checker< check::ASTDecl<FunctionDecl> > { 89 mutable IdentifierInfo *II; 90 91public: 92 CFErrorFunctionChecker() : II(nullptr) {} 93 94 void checkASTDecl(const FunctionDecl *D, 95 AnalysisManager &mgr, BugReporter &BR) const; 96}; 97} 98 99void CFErrorFunctionChecker::checkASTDecl(const FunctionDecl *D, 100 AnalysisManager &mgr, 101 BugReporter &BR) const { 102 if (!D->doesThisDeclarationHaveABody()) 103 return; 104 if (!D->getReturnType()->isVoidType()) 105 return; 106 107 if (!II) 108 II = &D->getASTContext().Idents.get("CFErrorRef"); 109 110 bool hasCFError = false; 111 for (auto I : D->parameters()) { 112 if (IsCFError(I->getType(), II)) { 113 hasCFError = true; 114 break; 115 } 116 } 117 118 if (hasCFError) { 119 const char *err = "Function accepting CFErrorRef* " 120 "should have a non-void return value to indicate whether or not an " 121 "error occurred"; 122 PathDiagnosticLocation L = 123 PathDiagnosticLocation::create(D, BR.getSourceManager()); 124 BR.EmitBasicReport(D, this, "Bad return type when passing CFErrorRef*", 125 "Coding conventions (Apple)", err, L); 126 } 127} 128 129//===----------------------------------------------------------------------===// 130// NSOrCFErrorDerefChecker 131//===----------------------------------------------------------------------===// 132 133namespace { 134 135class NSErrorDerefBug : public BugType { 136public: 137 NSErrorDerefBug(const CheckerBase *Checker) 138 : BugType(Checker, "NSError** null dereference", 139 "Coding conventions (Apple)") {} 140}; 141 142class CFErrorDerefBug : public BugType { 143public: 144 CFErrorDerefBug(const CheckerBase *Checker) 145 : BugType(Checker, "CFErrorRef* null dereference", 146 "Coding conventions (Apple)") {} 147}; 148 149} 150 151namespace { 152class NSOrCFErrorDerefChecker 153 : public Checker< check::Location, 154 check::Event<ImplicitNullDerefEvent> > { 155 mutable IdentifierInfo *NSErrorII, *CFErrorII; 156 mutable std::unique_ptr<NSErrorDerefBug> NSBT; 157 mutable std::unique_ptr<CFErrorDerefBug> CFBT; 158public: 159 bool ShouldCheckNSError, ShouldCheckCFError; 160 NSOrCFErrorDerefChecker() : NSErrorII(nullptr), CFErrorII(nullptr), 161 ShouldCheckNSError(0), ShouldCheckCFError(0) { } 162 163 void checkLocation(SVal loc, bool isLoad, const Stmt *S, 164 CheckerContext &C) const; 165 void checkEvent(ImplicitNullDerefEvent event) const; 166}; 167} 168 169typedef llvm::ImmutableMap<SymbolRef, unsigned> ErrorOutFlag; 170REGISTER_TRAIT_WITH_PROGRAMSTATE(NSErrorOut, ErrorOutFlag) 171REGISTER_TRAIT_WITH_PROGRAMSTATE(CFErrorOut, ErrorOutFlag) 172 173template <typename T> 174static bool hasFlag(SVal val, ProgramStateRef state) { 175 if (SymbolRef sym = val.getAsSymbol()) 176 if (const unsigned *attachedFlags = state->get<T>(sym)) 177 return *attachedFlags; 178 return false; 179} 180 181template <typename T> 182static void setFlag(ProgramStateRef state, SVal val, CheckerContext &C) { 183 // We tag the symbol that the SVal wraps. 184 if (SymbolRef sym = val.getAsSymbol()) 185 C.addTransition(state->set<T>(sym, true)); 186} 187 188static QualType parameterTypeFromSVal(SVal val, CheckerContext &C) { 189 const StackFrameContext * 190 SFC = C.getLocationContext()->getCurrentStackFrame(); 191 if (Optional<loc::MemRegionVal> X = val.getAs<loc::MemRegionVal>()) { 192 const MemRegion* R = X->getRegion(); 193 if (const VarRegion *VR = R->getAs<VarRegion>()) 194 if (const StackArgumentsSpaceRegion * 195 stackReg = dyn_cast<StackArgumentsSpaceRegion>(VR->getMemorySpace())) 196 if (stackReg->getStackFrame() == SFC) 197 return VR->getValueType(); 198 } 199 200 return QualType(); 201} 202 203void NSOrCFErrorDerefChecker::checkLocation(SVal loc, bool isLoad, 204 const Stmt *S, 205 CheckerContext &C) const { 206 if (!isLoad) 207 return; 208 if (loc.isUndef() || !loc.getAs<Loc>()) 209 return; 210 211 ASTContext &Ctx = C.getASTContext(); 212 ProgramStateRef state = C.getState(); 213 214 // If we are loading from NSError**/CFErrorRef* parameter, mark the resulting 215 // SVal so that we can later check it when handling the 216 // ImplicitNullDerefEvent event. 217 // FIXME: Cumbersome! Maybe add hook at construction of SVals at start of 218 // function ? 219 220 QualType parmT = parameterTypeFromSVal(loc, C); 221 if (parmT.isNull()) 222 return; 223 224 if (!NSErrorII) 225 NSErrorII = &Ctx.Idents.get("NSError"); 226 if (!CFErrorII) 227 CFErrorII = &Ctx.Idents.get("CFErrorRef"); 228 229 if (ShouldCheckNSError && IsNSError(parmT, NSErrorII)) { 230 setFlag<NSErrorOut>(state, state->getSVal(loc.castAs<Loc>()), C); 231 return; 232 } 233 234 if (ShouldCheckCFError && IsCFError(parmT, CFErrorII)) { 235 setFlag<CFErrorOut>(state, state->getSVal(loc.castAs<Loc>()), C); 236 return; 237 } 238} 239 240void NSOrCFErrorDerefChecker::checkEvent(ImplicitNullDerefEvent event) const { 241 if (event.IsLoad) 242 return; 243 244 SVal loc = event.Location; 245 ProgramStateRef state = event.SinkNode->getState(); 246 BugReporter &BR = *event.BR; 247 248 bool isNSError = hasFlag<NSErrorOut>(loc, state); 249 bool isCFError = false; 250 if (!isNSError) 251 isCFError = hasFlag<CFErrorOut>(loc, state); 252 253 if (!(isNSError || isCFError)) 254 return; 255 256 // Storing to possible null NSError/CFErrorRef out parameter. 257 SmallString<128> Buf; 258 llvm::raw_svector_ostream os(Buf); 259 260 os << "Potential null dereference. According to coding standards "; 261 os << (isNSError 262 ? "in 'Creating and Returning NSError Objects' the parameter" 263 : "documented in CoreFoundation/CFError.h the parameter"); 264 265 os << " may be null"; 266 267 BugType *bug = nullptr; 268 if (isNSError) { 269 if (!NSBT) 270 NSBT.reset(new NSErrorDerefBug(this)); 271 bug = NSBT.get(); 272 } 273 else { 274 if (!CFBT) 275 CFBT.reset(new CFErrorDerefBug(this)); 276 bug = CFBT.get(); 277 } 278 BR.emitReport(llvm::make_unique<BugReport>(*bug, os.str(), event.SinkNode)); 279} 280 281static bool IsNSError(QualType T, IdentifierInfo *II) { 282 283 const PointerType* PPT = T->getAs<PointerType>(); 284 if (!PPT) 285 return false; 286 287 const ObjCObjectPointerType* PT = 288 PPT->getPointeeType()->getAs<ObjCObjectPointerType>(); 289 290 if (!PT) 291 return false; 292 293 const ObjCInterfaceDecl *ID = PT->getInterfaceDecl(); 294 295 // FIXME: Can ID ever be NULL? 296 if (ID) 297 return II == ID->getIdentifier(); 298 299 return false; 300} 301 302static bool IsCFError(QualType T, IdentifierInfo *II) { 303 const PointerType* PPT = T->getAs<PointerType>(); 304 if (!PPT) return false; 305 306 const TypedefType* TT = PPT->getPointeeType()->getAs<TypedefType>(); 307 if (!TT) return false; 308 309 return TT->getDecl()->getIdentifier() == II; 310} 311 312void ento::registerNSErrorChecker(CheckerManager &mgr) { 313 mgr.registerChecker<NSErrorMethodChecker>(); 314 NSOrCFErrorDerefChecker *checker = 315 mgr.registerChecker<NSOrCFErrorDerefChecker>(); 316 checker->ShouldCheckNSError = true; 317} 318 319void ento::registerCFErrorChecker(CheckerManager &mgr) { 320 mgr.registerChecker<CFErrorFunctionChecker>(); 321 NSOrCFErrorDerefChecker *checker = 322 mgr.registerChecker<NSOrCFErrorDerefChecker>(); 323 checker->ShouldCheckCFError = true; 324} 325