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//== DivZeroChecker.cpp - Division by zero 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 defines DivZeroChecker, a builtin check in ExprEngine that performs
// checks for division by zeros.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Checkers/Taint.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/BugReporter/CommonBugCategories.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include <optional>
using namespace clang;
using namespace ento;
using namespace taint;
namespace {
class DivZeroChecker : public Checker< check::PreStmt<BinaryOperator> > {
const BugType BT{this, "Division by zero"};
const BugType TaintBT{this, "Division by zero", categories::TaintedData};
void reportBug(StringRef Msg, ProgramStateRef StateZero,
CheckerContext &C) const;
void reportTaintBug(StringRef Msg, ProgramStateRef StateZero,
CheckerContext &C,
llvm::ArrayRef<SymbolRef> TaintedSyms) const;
public:
void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
};
} // end anonymous namespace
static const Expr *getDenomExpr(const ExplodedNode *N) {
const Stmt *S = N->getLocationAs<PreStmt>()->getStmt();
if (const auto *BE = dyn_cast<BinaryOperator>(S))
return BE->getRHS();
return nullptr;
}
void DivZeroChecker::reportBug(StringRef Msg, ProgramStateRef StateZero,
CheckerContext &C) const {
if (ExplodedNode *N = C.generateErrorNode(StateZero)) {
auto R = std::make_unique<PathSensitiveBugReport>(BT, Msg, N);
bugreporter::trackExpressionValue(N, getDenomExpr(N), *R);
C.emitReport(std::move(R));
}
}
void DivZeroChecker::reportTaintBug(
StringRef Msg, ProgramStateRef StateZero, CheckerContext &C,
llvm::ArrayRef<SymbolRef> TaintedSyms) const {
if (ExplodedNode *N = C.generateErrorNode(StateZero)) {
auto R = std::make_unique<PathSensitiveBugReport>(TaintBT, Msg, N);
bugreporter::trackExpressionValue(N, getDenomExpr(N), *R);
for (auto Sym : TaintedSyms)
R->markInteresting(Sym);
C.emitReport(std::move(R));
}
}
void DivZeroChecker::checkPreStmt(const BinaryOperator *B,
CheckerContext &C) const {
BinaryOperator::Opcode Op = B->getOpcode();
if (Op != BO_Div &&
Op != BO_Rem &&
Op != BO_DivAssign &&
Op != BO_RemAssign)
return;
if (!B->getRHS()->getType()->isScalarType())
return;
SVal Denom = C.getSVal(B->getRHS());
std::optional<DefinedSVal> DV = Denom.getAs<DefinedSVal>();
// Divide-by-undefined handled in the generic checking for uses of
// undefined values.
if (!DV)
return;
// Check for divide by zero.
ConstraintManager &CM = C.getConstraintManager();
ProgramStateRef stateNotZero, stateZero;
std::tie(stateNotZero, stateZero) = CM.assumeDual(C.getState(), *DV);
if (!stateNotZero) {
assert(stateZero);
reportBug("Division by zero", stateZero, C);
return;
}
if ((stateNotZero && stateZero)) {
std::vector<SymbolRef> taintedSyms = getTaintedSymbols(C.getState(), *DV);
if (!taintedSyms.empty()) {
reportTaintBug("Division by a tainted value, possibly zero", stateZero, C,
taintedSyms);
return;
}
}
// If we get here, then the denom should not be zero. We abandon the implicit
// zero denom case for now.
C.addTransition(stateNotZero);
}
void ento::registerDivZeroChecker(CheckerManager &mgr) {
mgr.registerChecker<DivZeroChecker>();
}
bool ento::shouldRegisterDivZeroChecker(const CheckerManager &mgr) {
return true;
}
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