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| // 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;
}
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