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107 lines
3.4 KiB
107 lines
3.4 KiB
//== DivZeroChecker.cpp - Division by zero checker --------------*- C++ -*--==//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This defines DivZeroChecker, a builtin check in ExprEngine that performs
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// checks for division by zeros.
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//
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//===----------------------------------------------------------------------===//
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#include "Taint.h"
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#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
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#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
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#include "clang/StaticAnalyzer/Core/Checker.h"
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#include "clang/StaticAnalyzer/Core/CheckerManager.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
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using namespace clang;
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using namespace ento;
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using namespace taint;
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namespace {
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class DivZeroChecker : public Checker< check::PreStmt<BinaryOperator> > {
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mutable std::unique_ptr<BuiltinBug> BT;
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void reportBug(const char *Msg, ProgramStateRef StateZero, CheckerContext &C,
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std::unique_ptr<BugReporterVisitor> Visitor = nullptr) const;
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public:
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void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
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};
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} // end anonymous namespace
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static const Expr *getDenomExpr(const ExplodedNode *N) {
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const Stmt *S = N->getLocationAs<PreStmt>()->getStmt();
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if (const auto *BE = dyn_cast<BinaryOperator>(S))
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return BE->getRHS();
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return nullptr;
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}
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void DivZeroChecker::reportBug(
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const char *Msg, ProgramStateRef StateZero, CheckerContext &C,
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std::unique_ptr<BugReporterVisitor> Visitor) const {
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if (ExplodedNode *N = C.generateErrorNode(StateZero)) {
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if (!BT)
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BT.reset(new BuiltinBug(this, "Division by zero"));
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auto R = std::make_unique<PathSensitiveBugReport>(*BT, Msg, N);
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R->addVisitor(std::move(Visitor));
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bugreporter::trackExpressionValue(N, getDenomExpr(N), *R);
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C.emitReport(std::move(R));
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}
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}
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void DivZeroChecker::checkPreStmt(const BinaryOperator *B,
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CheckerContext &C) const {
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BinaryOperator::Opcode Op = B->getOpcode();
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if (Op != BO_Div &&
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Op != BO_Rem &&
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Op != BO_DivAssign &&
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Op != BO_RemAssign)
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return;
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if (!B->getRHS()->getType()->isScalarType())
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return;
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SVal Denom = C.getSVal(B->getRHS());
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Optional<DefinedSVal> DV = Denom.getAs<DefinedSVal>();
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// Divide-by-undefined handled in the generic checking for uses of
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// undefined values.
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if (!DV)
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return;
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// Check for divide by zero.
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ConstraintManager &CM = C.getConstraintManager();
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ProgramStateRef stateNotZero, stateZero;
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std::tie(stateNotZero, stateZero) = CM.assumeDual(C.getState(), *DV);
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if (!stateNotZero) {
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assert(stateZero);
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reportBug("Division by zero", stateZero, C);
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return;
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}
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bool TaintedD = isTainted(C.getState(), *DV);
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if ((stateNotZero && stateZero && TaintedD)) {
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reportBug("Division by a tainted value, possibly zero", stateZero, C,
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std::make_unique<taint::TaintBugVisitor>(*DV));
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return;
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}
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// If we get here, then the denom should not be zero. We abandon the implicit
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// zero denom case for now.
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C.addTransition(stateNotZero);
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}
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void ento::registerDivZeroChecker(CheckerManager &mgr) {
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mgr.registerChecker<DivZeroChecker>();
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}
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bool ento::shouldRegisterDivZeroChecker(const CheckerManager &mgr) {
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return true;
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}
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