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//=== PointerSubChecker.cpp - Pointer subtraction checker ------*- 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
//
//===----------------------------------------------------------------------===//
//
// This files defines PointerSubChecker, a builtin checker that checks for
// pointer subtractions on two pointers pointing to different memory chunks.
// This check corresponds to CWE-469.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "llvm/ADT/StringRef.h"
using namespace clang;
using namespace ento;
namespace {
class PointerSubChecker
: public Checker< check::PreStmt<BinaryOperator> > {
const BugType BT{this, "Pointer subtraction"};
public:
void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
};
}
void PointerSubChecker::checkPreStmt(const BinaryOperator *B,
CheckerContext &C) const {
// When doing pointer subtraction, if the two pointers do not point to the
// same memory chunk, emit a warning.
if (B->getOpcode() != BO_Sub)
return;
SVal LV = C.getSVal(B->getLHS());
SVal RV = C.getSVal(B->getRHS());
const MemRegion *LR = LV.getAsRegion();
const MemRegion *RR = RV.getAsRegion();
if (!(LR && RR))
return;
const MemRegion *BaseLR = LR->getBaseRegion();
const MemRegion *BaseRR = RR->getBaseRegion();
if (BaseLR == BaseRR)
return;
// Allow arithmetic on different symbolic regions.
if (isa<SymbolicRegion>(BaseLR) || isa<SymbolicRegion>(BaseRR))
return;
if (ExplodedNode *N = C.generateNonFatalErrorNode()) {
constexpr llvm::StringLiteral Msg =
"Subtraction of two pointers that do not point to the same memory "
"chunk may cause incorrect result.";
auto R = std::make_unique<PathSensitiveBugReport>(BT, Msg, N);
R->addRange(B->getSourceRange());
C.emitReport(std::move(R));
}
}
void ento::registerPointerSubChecker(CheckerManager &mgr) {
mgr.registerChecker<PointerSubChecker>();
}
bool ento::shouldRegisterPointerSubChecker(const CheckerManager &mgr) {
return true;
}
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