| // MallocSizeofChecker.cpp - Check for dubious malloc arguments ---*- C++ -*-=// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // Reports inconsistencies between the casted type of the return value of a |
| // malloc/calloc/realloc call and the operand of any sizeof expressions |
| // contained within its argument(s). |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h" |
| #include "clang/AST/StmtVisitor.h" |
| #include "clang/AST/TypeLoc.h" |
| #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h" |
| #include "clang/StaticAnalyzer/Core/Checker.h" |
| #include "clang/StaticAnalyzer/Core/CheckerManager.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h" |
| #include "llvm/ADT/SmallString.h" |
| #include "llvm/Support/raw_ostream.h" |
| |
| using namespace clang; |
| using namespace ento; |
| |
| namespace { |
| |
| typedef std::pair<const TypeSourceInfo *, const CallExpr *> TypeCallPair; |
| typedef llvm::PointerUnion<const Stmt *, const VarDecl *> ExprParent; |
| |
| class CastedAllocFinder |
| : public ConstStmtVisitor<CastedAllocFinder, TypeCallPair> { |
| IdentifierInfo *II_malloc, *II_calloc, *II_realloc; |
| |
| public: |
| struct CallRecord { |
| ExprParent CastedExprParent; |
| const Expr *CastedExpr; |
| const TypeSourceInfo *ExplicitCastType; |
| const CallExpr *AllocCall; |
| |
| CallRecord(ExprParent CastedExprParent, const Expr *CastedExpr, |
| const TypeSourceInfo *ExplicitCastType, |
| const CallExpr *AllocCall) |
| : CastedExprParent(CastedExprParent), CastedExpr(CastedExpr), |
| ExplicitCastType(ExplicitCastType), AllocCall(AllocCall) {} |
| }; |
| |
| typedef std::vector<CallRecord> CallVec; |
| CallVec Calls; |
| |
| CastedAllocFinder(ASTContext *Ctx) : |
| II_malloc(&Ctx->Idents.get("malloc")), |
| II_calloc(&Ctx->Idents.get("calloc")), |
| II_realloc(&Ctx->Idents.get("realloc")) {} |
| |
| void VisitChild(ExprParent Parent, const Stmt *S) { |
| TypeCallPair AllocCall = Visit(S); |
| if (AllocCall.second && AllocCall.second != S) |
| Calls.push_back(CallRecord(Parent, cast<Expr>(S), AllocCall.first, |
| AllocCall.second)); |
| } |
| |
| void VisitChildren(const Stmt *S) { |
| for (const Stmt *Child : S->children()) |
| if (Child) |
| VisitChild(S, Child); |
| } |
| |
| TypeCallPair VisitCastExpr(const CastExpr *E) { |
| return Visit(E->getSubExpr()); |
| } |
| |
| TypeCallPair VisitExplicitCastExpr(const ExplicitCastExpr *E) { |
| return TypeCallPair(E->getTypeInfoAsWritten(), |
| Visit(E->getSubExpr()).second); |
| } |
| |
| TypeCallPair VisitParenExpr(const ParenExpr *E) { |
| return Visit(E->getSubExpr()); |
| } |
| |
| TypeCallPair VisitStmt(const Stmt *S) { |
| VisitChildren(S); |
| return TypeCallPair(); |
| } |
| |
| TypeCallPair VisitCallExpr(const CallExpr *E) { |
| VisitChildren(E); |
| const FunctionDecl *FD = E->getDirectCallee(); |
| if (FD) { |
| IdentifierInfo *II = FD->getIdentifier(); |
| if (II == II_malloc || II == II_calloc || II == II_realloc) |
| return TypeCallPair((const TypeSourceInfo *)nullptr, E); |
| } |
| return TypeCallPair(); |
| } |
| |
| TypeCallPair VisitDeclStmt(const DeclStmt *S) { |
| for (const auto *I : S->decls()) |
| if (const VarDecl *VD = dyn_cast<VarDecl>(I)) |
| if (const Expr *Init = VD->getInit()) |
| VisitChild(VD, Init); |
| return TypeCallPair(); |
| } |
| }; |
| |
| class SizeofFinder : public ConstStmtVisitor<SizeofFinder> { |
| public: |
| std::vector<const UnaryExprOrTypeTraitExpr *> Sizeofs; |
| |
| void VisitBinMul(const BinaryOperator *E) { |
| Visit(E->getLHS()); |
| Visit(E->getRHS()); |
| } |
| |
| void VisitImplicitCastExpr(const ImplicitCastExpr *E) { |
| return Visit(E->getSubExpr()); |
| } |
| |
| void VisitParenExpr(const ParenExpr *E) { |
| return Visit(E->getSubExpr()); |
| } |
| |
| void VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *E) { |
| if (E->getKind() != UETT_SizeOf) |
| return; |
| |
| Sizeofs.push_back(E); |
| } |
| }; |
| |
| // Determine if the pointee and sizeof types are compatible. Here |
| // we ignore constness of pointer types. |
| static bool typesCompatible(ASTContext &C, QualType A, QualType B) { |
| // sizeof(void*) is compatible with any other pointer. |
| if (B->isVoidPointerType() && A->getAs<PointerType>()) |
| return true; |
| |
| while (true) { |
| A = A.getCanonicalType(); |
| B = B.getCanonicalType(); |
| |
| if (A.getTypePtr() == B.getTypePtr()) |
| return true; |
| |
| if (const PointerType *ptrA = A->getAs<PointerType>()) |
| if (const PointerType *ptrB = B->getAs<PointerType>()) { |
| A = ptrA->getPointeeType(); |
| B = ptrB->getPointeeType(); |
| continue; |
| } |
| |
| break; |
| } |
| |
| return false; |
| } |
| |
| static bool compatibleWithArrayType(ASTContext &C, QualType PT, QualType T) { |
| // Ex: 'int a[10][2]' is compatible with 'int', 'int[2]', 'int[10][2]'. |
| while (const ArrayType *AT = T->getAsArrayTypeUnsafe()) { |
| QualType ElemType = AT->getElementType(); |
| if (typesCompatible(C, PT, AT->getElementType())) |
| return true; |
| T = ElemType; |
| } |
| |
| return false; |
| } |
| |
| class MallocSizeofChecker : public Checker<check::ASTCodeBody> { |
| public: |
| void checkASTCodeBody(const Decl *D, AnalysisManager& mgr, |
| BugReporter &BR) const { |
| AnalysisDeclContext *ADC = mgr.getAnalysisDeclContext(D); |
| CastedAllocFinder Finder(&BR.getContext()); |
| Finder.Visit(D->getBody()); |
| for (CastedAllocFinder::CallVec::iterator i = Finder.Calls.begin(), |
| e = Finder.Calls.end(); i != e; ++i) { |
| QualType CastedType = i->CastedExpr->getType(); |
| if (!CastedType->isPointerType()) |
| continue; |
| QualType PointeeType = CastedType->getPointeeType(); |
| if (PointeeType->isVoidType()) |
| continue; |
| |
| for (CallExpr::const_arg_iterator ai = i->AllocCall->arg_begin(), |
| ae = i->AllocCall->arg_end(); ai != ae; ++ai) { |
| if (!(*ai)->getType()->isIntegralOrUnscopedEnumerationType()) |
| continue; |
| |
| SizeofFinder SFinder; |
| SFinder.Visit(*ai); |
| if (SFinder.Sizeofs.size() != 1) |
| continue; |
| |
| QualType SizeofType = SFinder.Sizeofs[0]->getTypeOfArgument(); |
| |
| if (typesCompatible(BR.getContext(), PointeeType, SizeofType)) |
| continue; |
| |
| // If the argument to sizeof is an array, the result could be a |
| // pointer to any array element. |
| if (compatibleWithArrayType(BR.getContext(), PointeeType, SizeofType)) |
| continue; |
| |
| const TypeSourceInfo *TSI = nullptr; |
| if (i->CastedExprParent.is<const VarDecl *>()) { |
| TSI = |
| i->CastedExprParent.get<const VarDecl *>()->getTypeSourceInfo(); |
| } else { |
| TSI = i->ExplicitCastType; |
| } |
| |
| SmallString<64> buf; |
| llvm::raw_svector_ostream OS(buf); |
| |
| OS << "Result of "; |
| const FunctionDecl *Callee = i->AllocCall->getDirectCallee(); |
| if (Callee && Callee->getIdentifier()) |
| OS << '\'' << Callee->getIdentifier()->getName() << '\''; |
| else |
| OS << "call"; |
| OS << " is converted to a pointer of type '" |
| << PointeeType.getAsString() << "', which is incompatible with " |
| << "sizeof operand type '" << SizeofType.getAsString() << "'"; |
| SmallVector<SourceRange, 4> Ranges; |
| Ranges.push_back(i->AllocCall->getCallee()->getSourceRange()); |
| Ranges.push_back(SFinder.Sizeofs[0]->getSourceRange()); |
| if (TSI) |
| Ranges.push_back(TSI->getTypeLoc().getSourceRange()); |
| |
| PathDiagnosticLocation L = |
| PathDiagnosticLocation::createBegin(i->AllocCall->getCallee(), |
| BR.getSourceManager(), ADC); |
| |
| BR.EmitBasicReport(D, this, "Allocator sizeof operand mismatch", |
| categories::UnixAPI, OS.str(), L, Ranges); |
| } |
| } |
| } |
| }; |
| |
| } |
| |
| void ento::registerMallocSizeofChecker(CheckerManager &mgr) { |
| mgr.registerChecker<MallocSizeofChecker>(); |
| } |
| |
| bool ento::shouldRegisterMallocSizeofChecker(const LangOptions &LO) { |
| return true; |
| } |