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/StaticAnalyzer/Core/BugReporter/BugReporter.h" 18 #include "clang/StaticAnalyzer/Core/Checker.h" 19 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 20 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h" 21 #include "clang/AST/StmtVisitor.h" 22 #include "clang/AST/TypeLoc.h" 23 #include "llvm/ADT/SmallString.h" 24 25 using namespace clang; 26 using namespace ento; 27 28 namespace { 29 30 typedef std::pair<const TypeSourceInfo *, const CallExpr *> TypeCallPair; 31 typedef llvm::PointerUnion<const Stmt *, const VarDecl *> ExprParent; 32 33 class CastedAllocFinder 34 : public ConstStmtVisitor<CastedAllocFinder, TypeCallPair> { 35 IdentifierInfo *II_malloc, *II_calloc, *II_realloc; 36 37 public: 38 struct CallRecord { 39 ExprParent CastedExprParent; 40 const Expr *CastedExpr; 41 const TypeSourceInfo *ExplicitCastType; 42 const CallExpr *AllocCall; 43 44 CallRecord(ExprParent CastedExprParent, const Expr *CastedExpr, 45 const TypeSourceInfo *ExplicitCastType, 46 const CallExpr *AllocCall) 47 : CastedExprParent(CastedExprParent), CastedExpr(CastedExpr), 48 ExplicitCastType(ExplicitCastType), AllocCall(AllocCall) {} 49 }; 50 51 typedef std::vector<CallRecord> CallVec; 52 CallVec Calls; 53 54 CastedAllocFinder(ASTContext *Ctx) : 55 II_malloc(&Ctx->Idents.get("malloc")), 56 II_calloc(&Ctx->Idents.get("calloc")), 57 II_realloc(&Ctx->Idents.get("realloc")) {} 58 59 void VisitChild(ExprParent Parent, const Stmt *S) { 60 TypeCallPair AllocCall = Visit(S); 61 if (AllocCall.second && AllocCall.second != S) 62 Calls.push_back(CallRecord(Parent, cast<Expr>(S), AllocCall.first, 63 AllocCall.second)); 64 } 65 66 void VisitChildren(const Stmt *S) { 67 for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end(); 68 I!=E; ++I) 69 if (const Stmt *child = *I) 70 VisitChild(S, child); 71 } 72 73 TypeCallPair VisitCastExpr(const CastExpr *E) { 74 return Visit(E->getSubExpr()); 75 } 76 77 TypeCallPair VisitExplicitCastExpr(const ExplicitCastExpr *E) { 78 return TypeCallPair(E->getTypeInfoAsWritten(), 79 Visit(E->getSubExpr()).second); 80 } 81 82 TypeCallPair VisitParenExpr(const ParenExpr *E) { 83 return Visit(E->getSubExpr()); 84 } 85 86 TypeCallPair VisitStmt(const Stmt *S) { 87 VisitChildren(S); 88 return TypeCallPair(); 89 } 90 91 TypeCallPair VisitCallExpr(const CallExpr *E) { 92 VisitChildren(E); 93 const FunctionDecl *FD = E->getDirectCallee(); 94 if (FD) { 95 IdentifierInfo *II = FD->getIdentifier(); 96 if (II == II_malloc || II == II_calloc || II == II_realloc) 97 return TypeCallPair((const TypeSourceInfo *)0, E); 98 } 99 return TypeCallPair(); 100 } 101 102 TypeCallPair VisitDeclStmt(const DeclStmt *S) { 103 for (DeclStmt::const_decl_iterator I = S->decl_begin(), E = S->decl_end(); 104 I!=E; ++I) 105 if (const VarDecl *VD = dyn_cast<VarDecl>(*I)) 106 if (const Expr *Init = VD->getInit()) 107 VisitChild(VD, Init); 108 return TypeCallPair(); 109 } 110 }; 111 112 class SizeofFinder : public ConstStmtVisitor<SizeofFinder> { 113 public: 114 std::vector<const UnaryExprOrTypeTraitExpr *> Sizeofs; 115 116 void VisitBinMul(const BinaryOperator *E) { 117 Visit(E->getLHS()); 118 Visit(E->getRHS()); 119 } 120 121 void VisitImplicitCastExpr(const ImplicitCastExpr *E) { 122 return Visit(E->getSubExpr()); 123 } 124 125 void VisitParenExpr(const ParenExpr *E) { 126 return Visit(E->getSubExpr()); 127 } 128 129 void VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *E) { 130 if (E->getKind() != UETT_SizeOf) 131 return; 132 133 Sizeofs.push_back(E); 134 } 135 }; 136 137 // Determine if the pointee and sizeof types are compatible. Here 138 // we ignore constness of pointer types. 139 static bool typesCompatible(ASTContext &C, QualType A, QualType B) { 140 while (true) { 141 A = A.getCanonicalType(); 142 B = B.getCanonicalType(); 143 144 if (A.getTypePtr() == B.getTypePtr()) 145 return true; 146 147 if (const PointerType *ptrA = A->getAs<PointerType>()) 148 if (const PointerType *ptrB = B->getAs<PointerType>()) { 149 A = ptrA->getPointeeType(); 150 B = ptrB->getPointeeType(); 151 continue; 152 } 153 154 break; 155 } 156 157 return false; 158 } 159 160 class MallocSizeofChecker : public Checker<check::ASTCodeBody> { 161 public: 162 void checkASTCodeBody(const Decl *D, AnalysisManager& mgr, 163 BugReporter &BR) const { 164 AnalysisDeclContext *ADC = mgr.getAnalysisDeclContext(D); 165 CastedAllocFinder Finder(&BR.getContext()); 166 Finder.Visit(D->getBody()); 167 for (CastedAllocFinder::CallVec::iterator i = Finder.Calls.begin(), 168 e = Finder.Calls.end(); i != e; ++i) { 169 QualType CastedType = i->CastedExpr->getType(); 170 if (!CastedType->isPointerType()) 171 continue; 172 QualType PointeeType = CastedType->getAs<PointerType>()->getPointeeType(); 173 if (PointeeType->isVoidType()) 174 continue; 175 176 for (CallExpr::const_arg_iterator ai = i->AllocCall->arg_begin(), 177 ae = i->AllocCall->arg_end(); ai != ae; ++ai) { 178 if (!(*ai)->getType()->isIntegerType()) 179 continue; 180 181 SizeofFinder SFinder; 182 SFinder.Visit(*ai); 183 if (SFinder.Sizeofs.size() != 1) 184 continue; 185 186 QualType SizeofType = SFinder.Sizeofs[0]->getTypeOfArgument(); 187 if (!typesCompatible(BR.getContext(), PointeeType, SizeofType)) { 188 const TypeSourceInfo *TSI = 0; 189 if (i->CastedExprParent.is<const VarDecl *>()) { 190 TSI = 191 i->CastedExprParent.get<const VarDecl *>()->getTypeSourceInfo(); 192 } else { 193 TSI = i->ExplicitCastType; 194 } 195 196 SmallString<64> buf; 197 llvm::raw_svector_ostream OS(buf); 198 199 OS << "Result of "; 200 const FunctionDecl *Callee = i->AllocCall->getDirectCallee(); 201 if (Callee && Callee->getIdentifier()) 202 OS << '\'' << Callee->getIdentifier()->getName() << '\''; 203 else 204 OS << "call"; 205 OS << " is converted to a pointer of type '" 206 << PointeeType.getAsString() << "', which is incompatible with " 207 << "sizeof operand type '" << SizeofType.getAsString() << "'"; 208 llvm::SmallVector<SourceRange, 4> Ranges; 209 Ranges.push_back(i->AllocCall->getCallee()->getSourceRange()); 210 Ranges.push_back(SFinder.Sizeofs[0]->getSourceRange()); 211 if (TSI) 212 Ranges.push_back(TSI->getTypeLoc().getSourceRange()); 213 214 PathDiagnosticLocation L = 215 PathDiagnosticLocation::createBegin(i->AllocCall->getCallee(), 216 BR.getSourceManager(), ADC); 217 218 BR.EmitBasicReport(D, "Allocator sizeof operand mismatch", 219 categories::UnixAPI, 220 OS.str(), 221 L, Ranges.data(), Ranges.size()); 222 } 223 } 224 } 225 } 226 }; 227 228 } 229 230 void ento::registerMallocSizeofChecker(CheckerManager &mgr) { 231 mgr.registerChecker<MallocSizeofChecker>(); 232 } 233