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//=== PointerSubChecker.cpp - Pointer subtraction checker ------*- C++ -*--===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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 "ClangSACheckers.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
using namespace clang;
using namespace ento;
namespace {
class PointerSubChecker
: public Checker< check::PreStmt<BinaryOperator> > {
mutable OwningPtr<BuiltinBug> BT;
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;
ProgramStateRef state = C.getState();
const LocationContext *LCtx = C.getLocationContext();
SVal LV = state->getSVal(B->getLHS(), LCtx);
SVal RV = state->getSVal(B->getRHS(), LCtx);
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.addTransition()) {
if (!BT)
BT.reset(new BuiltinBug("Pointer subtraction",
"Subtraction of two pointers that do not point to "
"the same memory chunk may cause incorrect result."));
BugReport *R = new BugReport(*BT, BT->getDescription(), N);
R->addRange(B->getSourceRange());
C.EmitReport(R);
}
}
void ento::registerPointerSubChecker(CheckerManager &mgr) {
mgr.registerChecker<PointerSubChecker>();
}
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