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 25using namespace clang; 26using namespace ento; 27 28namespace { 29 30typedef std::pair<const TypeSourceInfo *, const CallExpr *> TypeCallPair; 31typedef llvm::PointerUnion<const Stmt *, const VarDecl *> ExprParent; 32 33class CastedAllocFinder 34 : public ConstStmtVisitor<CastedAllocFinder, TypeCallPair> { 35 IdentifierInfo *II_malloc, *II_calloc, *II_realloc; 36 37public: 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 112class SizeofFinder : public ConstStmtVisitor<SizeofFinder> { 113public: 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. 139static 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 160static bool compatibleWithArrayType(ASTContext &C, QualType PT, QualType T) { 161 // Ex: 'int a[10][2]' is compatible with 'int', 'int[2]', 'int[10][2]'. 162 while (const ArrayType *AT = T->getAsArrayTypeUnsafe()) { 163 QualType ElemType = AT->getElementType(); 164 if (typesCompatible(C, PT, AT->getElementType())) 165 return true; 166 T = ElemType; 167 } 168 169 return false; 170} 171 172class MallocSizeofChecker : public Checker<check::ASTCodeBody> { 173public: 174 void checkASTCodeBody(const Decl *D, AnalysisManager& mgr, 175 BugReporter &BR) const { 176 AnalysisDeclContext *ADC = mgr.getAnalysisDeclContext(D); 177 CastedAllocFinder Finder(&BR.getContext()); 178 Finder.Visit(D->getBody()); 179 for (CastedAllocFinder::CallVec::iterator i = Finder.Calls.begin(), 180 e = Finder.Calls.end(); i != e; ++i) { 181 QualType CastedType = i->CastedExpr->getType(); 182 if (!CastedType->isPointerType()) 183 continue; 184 QualType PointeeType = CastedType->getAs<PointerType>()->getPointeeType(); 185 if (PointeeType->isVoidType()) 186 continue; 187 188 for (CallExpr::const_arg_iterator ai = i->AllocCall->arg_begin(), 189 ae = i->AllocCall->arg_end(); ai != ae; ++ai) { 190 if (!(*ai)->getType()->isIntegerType()) 191 continue; 192 193 SizeofFinder SFinder; 194 SFinder.Visit(*ai); 195 if (SFinder.Sizeofs.size() != 1) 196 continue; 197 198 QualType SizeofType = SFinder.Sizeofs[0]->getTypeOfArgument(); 199 200 if (typesCompatible(BR.getContext(), PointeeType, SizeofType)) 201 continue; 202 203 // If the argument to sizeof is an array, the result could be a 204 // pointer to any array element. 205 if (compatibleWithArrayType(BR.getContext(), PointeeType, SizeofType)) 206 continue; 207 208 const TypeSourceInfo *TSI = 0; 209 if (i->CastedExprParent.is<const VarDecl *>()) { 210 TSI = 211 i->CastedExprParent.get<const VarDecl *>()->getTypeSourceInfo(); 212 } else { 213 TSI = i->ExplicitCastType; 214 } 215 216 SmallString<64> buf; 217 llvm::raw_svector_ostream OS(buf); 218 219 OS << "Result of "; 220 const FunctionDecl *Callee = i->AllocCall->getDirectCallee(); 221 if (Callee && Callee->getIdentifier()) 222 OS << '\'' << Callee->getIdentifier()->getName() << '\''; 223 else 224 OS << "call"; 225 OS << " is converted to a pointer of type '" 226 << PointeeType.getAsString() << "', which is incompatible with " 227 << "sizeof operand type '" << SizeofType.getAsString() << "'"; 228 llvm::SmallVector<SourceRange, 4> Ranges; 229 Ranges.push_back(i->AllocCall->getCallee()->getSourceRange()); 230 Ranges.push_back(SFinder.Sizeofs[0]->getSourceRange()); 231 if (TSI) 232 Ranges.push_back(TSI->getTypeLoc().getSourceRange()); 233 234 PathDiagnosticLocation L = 235 PathDiagnosticLocation::createBegin(i->AllocCall->getCallee(), 236 BR.getSourceManager(), ADC); 237 238 BR.EmitBasicReport(D, "Allocator sizeof operand mismatch", 239 categories::UnixAPI, 240 OS.str(), 241 L, Ranges.data(), Ranges.size()); 242 } 243 } 244 } 245}; 246 247} 248 249void ento::registerMallocSizeofChecker(CheckerManager &mgr) { 250 mgr.registerChecker<MallocSizeofChecker>(); 251} 252