1 // MallocSizeofChecker.cpp - Check for dubious malloc arguments ---*- 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 // Reports inconsistencies between the casted type of the return value of a 11 // malloc/calloc/realloc call and the operand of any sizeof expressions 12 // contained within its argument(s). 13 // 14 //===----------------------------------------------------------------------===// 15 16 #include "ClangSACheckers.h" 17 #include "clang/AST/StmtVisitor.h" 18 #include "clang/AST/TypeLoc.h" 19 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h" 20 #include "clang/StaticAnalyzer/Core/Checker.h" 21 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 22 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.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 31 typedef std::pair<const TypeSourceInfo *, const CallExpr *> TypeCallPair; 32 typedef llvm::PointerUnion<const Stmt *, const VarDecl *> ExprParent; 33 34 class CastedAllocFinder 35 : public ConstStmtVisitor<CastedAllocFinder, TypeCallPair> { 36 IdentifierInfo *II_malloc, *II_calloc, *II_realloc; 37 38 public: 39 struct CallRecord { 40 ExprParent CastedExprParent; 41 const Expr *CastedExpr; 42 const TypeSourceInfo *ExplicitCastType; 43 const CallExpr *AllocCall; 44 45 CallRecord(ExprParent CastedExprParent, const Expr *CastedExpr, 46 const TypeSourceInfo *ExplicitCastType, 47 const CallExpr *AllocCall) 48 : CastedExprParent(CastedExprParent), CastedExpr(CastedExpr), 49 ExplicitCastType(ExplicitCastType), AllocCall(AllocCall) {} 50 }; 51 52 typedef std::vector<CallRecord> CallVec; 53 CallVec Calls; 54 55 CastedAllocFinder(ASTContext *Ctx) : 56 II_malloc(&Ctx->Idents.get("malloc")), 57 II_calloc(&Ctx->Idents.get("calloc")), 58 II_realloc(&Ctx->Idents.get("realloc")) {} 59 60 void VisitChild(ExprParent Parent, const Stmt *S) { 61 TypeCallPair AllocCall = Visit(S); 62 if (AllocCall.second && AllocCall.second != S) 63 Calls.push_back(CallRecord(Parent, cast<Expr>(S), AllocCall.first, 64 AllocCall.second)); 65 } 66 67 void VisitChildren(const Stmt *S) { 68 for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end(); 69 I!=E; ++I) 70 if (const Stmt *child = *I) 71 VisitChild(S, child); 72 } 73 74 TypeCallPair VisitCastExpr(const CastExpr *E) { 75 return Visit(E->getSubExpr()); 76 } 77 78 TypeCallPair VisitExplicitCastExpr(const ExplicitCastExpr *E) { 79 return TypeCallPair(E->getTypeInfoAsWritten(), 80 Visit(E->getSubExpr()).second); 81 } 82 83 TypeCallPair VisitParenExpr(const ParenExpr *E) { 84 return Visit(E->getSubExpr()); 85 } 86 87 TypeCallPair VisitStmt(const Stmt *S) { 88 VisitChildren(S); 89 return TypeCallPair(); 90 } 91 92 TypeCallPair VisitCallExpr(const CallExpr *E) { 93 VisitChildren(E); 94 const FunctionDecl *FD = E->getDirectCallee(); 95 if (FD) { 96 IdentifierInfo *II = FD->getIdentifier(); 97 if (II == II_malloc || II == II_calloc || II == II_realloc) 98 return TypeCallPair((const TypeSourceInfo *)0, E); 99 } 100 return TypeCallPair(); 101 } 102 103 TypeCallPair VisitDeclStmt(const DeclStmt *S) { 104 for (DeclStmt::const_decl_iterator I = S->decl_begin(), E = S->decl_end(); 105 I!=E; ++I) 106 if (const VarDecl *VD = dyn_cast<VarDecl>(*I)) 107 if (const Expr *Init = VD->getInit()) 108 VisitChild(VD, Init); 109 return TypeCallPair(); 110 } 111 }; 112 113 class SizeofFinder : public ConstStmtVisitor<SizeofFinder> { 114 public: 115 std::vector<const UnaryExprOrTypeTraitExpr *> Sizeofs; 116 117 void VisitBinMul(const BinaryOperator *E) { 118 Visit(E->getLHS()); 119 Visit(E->getRHS()); 120 } 121 122 void VisitImplicitCastExpr(const ImplicitCastExpr *E) { 123 return Visit(E->getSubExpr()); 124 } 125 126 void VisitParenExpr(const ParenExpr *E) { 127 return Visit(E->getSubExpr()); 128 } 129 130 void VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *E) { 131 if (E->getKind() != UETT_SizeOf) 132 return; 133 134 Sizeofs.push_back(E); 135 } 136 }; 137 138 // Determine if the pointee and sizeof types are compatible. Here 139 // we ignore constness of pointer types. 140 static bool typesCompatible(ASTContext &C, QualType A, QualType B) { 141 while (true) { 142 A = A.getCanonicalType(); 143 B = B.getCanonicalType(); 144 145 if (A.getTypePtr() == B.getTypePtr()) 146 return true; 147 148 if (const PointerType *ptrA = A->getAs<PointerType>()) 149 if (const PointerType *ptrB = B->getAs<PointerType>()) { 150 A = ptrA->getPointeeType(); 151 B = ptrB->getPointeeType(); 152 continue; 153 } 154 155 break; 156 } 157 158 return false; 159 } 160 161 static bool compatibleWithArrayType(ASTContext &C, QualType PT, QualType T) { 162 // Ex: 'int a[10][2]' is compatible with 'int', 'int[2]', 'int[10][2]'. 163 while (const ArrayType *AT = T->getAsArrayTypeUnsafe()) { 164 QualType ElemType = AT->getElementType(); 165 if (typesCompatible(C, PT, AT->getElementType())) 166 return true; 167 T = ElemType; 168 } 169 170 return false; 171 } 172 173 class MallocSizeofChecker : public Checker<check::ASTCodeBody> { 174 public: 175 void checkASTCodeBody(const Decl *D, AnalysisManager& mgr, 176 BugReporter &BR) const { 177 AnalysisDeclContext *ADC = mgr.getAnalysisDeclContext(D); 178 CastedAllocFinder Finder(&BR.getContext()); 179 Finder.Visit(D->getBody()); 180 for (CastedAllocFinder::CallVec::iterator i = Finder.Calls.begin(), 181 e = Finder.Calls.end(); i != e; ++i) { 182 QualType CastedType = i->CastedExpr->getType(); 183 if (!CastedType->isPointerType()) 184 continue; 185 QualType PointeeType = CastedType->getAs<PointerType>()->getPointeeType(); 186 if (PointeeType->isVoidType()) 187 continue; 188 189 for (CallExpr::const_arg_iterator ai = i->AllocCall->arg_begin(), 190 ae = i->AllocCall->arg_end(); ai != ae; ++ai) { 191 if (!(*ai)->getType()->isIntegralOrUnscopedEnumerationType()) 192 continue; 193 194 SizeofFinder SFinder; 195 SFinder.Visit(*ai); 196 if (SFinder.Sizeofs.size() != 1) 197 continue; 198 199 QualType SizeofType = SFinder.Sizeofs[0]->getTypeOfArgument(); 200 201 if (typesCompatible(BR.getContext(), PointeeType, SizeofType)) 202 continue; 203 204 // If the argument to sizeof is an array, the result could be a 205 // pointer to any array element. 206 if (compatibleWithArrayType(BR.getContext(), PointeeType, SizeofType)) 207 continue; 208 209 const TypeSourceInfo *TSI = 0; 210 if (i->CastedExprParent.is<const VarDecl *>()) { 211 TSI = 212 i->CastedExprParent.get<const VarDecl *>()->getTypeSourceInfo(); 213 } else { 214 TSI = i->ExplicitCastType; 215 } 216 217 SmallString<64> buf; 218 llvm::raw_svector_ostream OS(buf); 219 220 OS << "Result of "; 221 const FunctionDecl *Callee = i->AllocCall->getDirectCallee(); 222 if (Callee && Callee->getIdentifier()) 223 OS << '\'' << Callee->getIdentifier()->getName() << '\''; 224 else 225 OS << "call"; 226 OS << " is converted to a pointer of type '" 227 << PointeeType.getAsString() << "', which is incompatible with " 228 << "sizeof operand type '" << SizeofType.getAsString() << "'"; 229 SmallVector<SourceRange, 4> Ranges; 230 Ranges.push_back(i->AllocCall->getCallee()->getSourceRange()); 231 Ranges.push_back(SFinder.Sizeofs[0]->getSourceRange()); 232 if (TSI) 233 Ranges.push_back(TSI->getTypeLoc().getSourceRange()); 234 235 PathDiagnosticLocation L = 236 PathDiagnosticLocation::createBegin(i->AllocCall->getCallee(), 237 BR.getSourceManager(), ADC); 238 239 BR.EmitBasicReport(D, "Allocator sizeof operand mismatch", 240 categories::UnixAPI, 241 OS.str(), 242 L, Ranges.data(), Ranges.size()); 243 } 244 } 245 } 246 }; 247 248 } 249 250 void ento::registerMallocSizeofChecker(CheckerManager &mgr) { 251 mgr.registerChecker<MallocSizeofChecker>(); 252 } 253
