//===-- IteratorRangeChecker.cpp ----------------------------------*- 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
//
//===----------------------------------------------------------------------===//
//
// Defines a checker for dereference of the past-the-end iterator and
// out-of-range increments and decrements.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "Iterator.h"
using namespace clang;
using namespace ento;
using namespace iterator;
namespace {
class IteratorRangeChecker
: public Checker<check::PreCall> {
std::unique_ptr<BugType> OutOfRangeBugType;
void verifyDereference(CheckerContext &C, const SVal &Val) const;
void verifyIncrement(CheckerContext &C, const SVal &Iter) const;
void verifyDecrement(CheckerContext &C, const SVal &Iter) const;
void verifyRandomIncrOrDecr(CheckerContext &C, OverloadedOperatorKind Op,
const SVal &LHS, const SVal &RHS) const;
void reportBug(const StringRef &Message, const SVal &Val,
CheckerContext &C, ExplodedNode *ErrNode) const;
public:
IteratorRangeChecker();
void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
};
bool isPastTheEnd(ProgramStateRef State, const IteratorPosition &Pos);
bool isAheadOfRange(ProgramStateRef State, const IteratorPosition &Pos);
bool isBehindPastTheEnd(ProgramStateRef State, const IteratorPosition &Pos);
bool isZero(ProgramStateRef State, const NonLoc &Val);
} //namespace
IteratorRangeChecker::IteratorRangeChecker() {
OutOfRangeBugType.reset(
new BugType(this, "Iterator out of range", "Misuse of STL APIs"));
}
void IteratorRangeChecker::checkPreCall(const CallEvent &Call,
CheckerContext &C) const {
// Check for out of range access
const auto *Func = dyn_cast_or_null<FunctionDecl>(Call.getDecl());
if (!Func)
return;
if (Func->isOverloadedOperator()) {
if (isIncrementOperator(Func->getOverloadedOperator())) {
// Check for out-of-range incrementions
if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
verifyIncrement(C, InstCall->getCXXThisVal());
} else {
if (Call.getNumArgs() >= 1) {
verifyIncrement(C, Call.getArgSVal(0));
}
}
} else if (isDecrementOperator(Func->getOverloadedOperator())) {
// Check for out-of-range decrementions
if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
verifyDecrement(C, InstCall->getCXXThisVal());
} else {
if (Call.getNumArgs() >= 1) {
verifyDecrement(C, Call.getArgSVal(0));
}
}
} else if (isRandomIncrOrDecrOperator(Func->getOverloadedOperator())) {
if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
// Check for out-of-range incrementions and decrementions
if (Call.getNumArgs() >= 1 &&
Call.getArgExpr(0)->getType()->isIntegralOrEnumerationType()) {
verifyRandomIncrOrDecr(C, Func->getOverloadedOperator(),
InstCall->getCXXThisVal(),
Call.getArgSVal(0));
}
} else {
if (Call.getNumArgs() >= 2 &&
Call.getArgExpr(1)->getType()->isIntegralOrEnumerationType()) {
verifyRandomIncrOrDecr(C, Func->getOverloadedOperator(),
Call.getArgSVal(0), Call.getArgSVal(1));
}
}
} else if (isDereferenceOperator(Func->getOverloadedOperator())) {
// Check for dereference of out-of-range iterators
if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
verifyDereference(C, InstCall->getCXXThisVal());
} else {
verifyDereference(C, Call.getArgSVal(0));
}
}
}
}
void IteratorRangeChecker::verifyDereference(CheckerContext &C,
const SVal &Val) const {
auto State = C.getState();
const auto *Pos = getIteratorPosition(State, Val);
if (Pos && isPastTheEnd(State, *Pos)) {
auto *N = C.generateErrorNode(State);
if (!N)
return;
reportBug("Past-the-end iterator dereferenced.", Val, C, N);
return;
}
}
void IteratorRangeChecker::verifyIncrement(CheckerContext &C,
const SVal &Iter) const {
auto &BVF = C.getSValBuilder().getBasicValueFactory();
verifyRandomIncrOrDecr(C, OO_Plus, Iter,
nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(1))));
}
void IteratorRangeChecker::verifyDecrement(CheckerContext &C,
const SVal &Iter) const {
auto &BVF = C.getSValBuilder().getBasicValueFactory();
verifyRandomIncrOrDecr(C, OO_Minus, Iter,
nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(1))));
}
void IteratorRangeChecker::verifyRandomIncrOrDecr(CheckerContext &C,
OverloadedOperatorKind Op,
const SVal &LHS,
const SVal &RHS) const {
auto State = C.getState();
auto Value = RHS;
if (auto ValAsLoc = RHS.getAs<Loc>()) {
Value = State->getRawSVal(*ValAsLoc);
}
if (Value.isUnknown())
return;
// Incremention or decremention by 0 is never a bug.
if (isZero(State, Value.castAs<NonLoc>()))
return;
// The result may be the past-end iterator of the container, but any other
// out of range position is undefined behaviour
auto StateAfter = advancePosition(State, LHS, Op, Value);
if (!StateAfter)
return;
const auto *PosAfter = getIteratorPosition(StateAfter, LHS);
assert(PosAfter &&
"Iterator should have position after successful advancement");
if (isAheadOfRange(State, *PosAfter)) {
auto *N = C.generateErrorNode(State);
if (!N)
return;
reportBug("Iterator decremented ahead of its valid range.", LHS,
C, N);
}
if (isBehindPastTheEnd(State, *PosAfter)) {
auto *N = C.generateErrorNode(State);
if (!N)
return;
reportBug("Iterator incremented behind the past-the-end "
"iterator.", LHS, C, N);
}
}
void IteratorRangeChecker::reportBug(const StringRef &Message,
const SVal &Val, CheckerContext &C,
ExplodedNode *ErrNode) const {
auto R = std::make_unique<PathSensitiveBugReport>(*OutOfRangeBugType, Message,
ErrNode);
R->markInteresting(Val);
C.emitReport(std::move(R));
}
namespace {
bool isLess(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2);
bool isGreater(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2);
bool isEqual(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2);
bool isZero(ProgramStateRef State, const NonLoc &Val) {
auto &BVF = State->getBasicVals();
return compare(State, Val,
nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(0))),
BO_EQ);
}
bool isPastTheEnd(ProgramStateRef State, const IteratorPosition &Pos) {
const auto *Cont = Pos.getContainer();
const auto *CData = getContainerData(State, Cont);
if (!CData)
return false;
const auto End = CData->getEnd();
if (End) {
if (isEqual(State, Pos.getOffset(), End)) {
return true;
}
}
return false;
}
bool isAheadOfRange(ProgramStateRef State, const IteratorPosition &Pos) {
const auto *Cont = Pos.getContainer();
const auto *CData = getContainerData(State, Cont);
if (!CData)
return false;
const auto Beg = CData->getBegin();
if (Beg) {
if (isLess(State, Pos.getOffset(), Beg)) {
return true;
}
}
return false;
}
bool isBehindPastTheEnd(ProgramStateRef State, const IteratorPosition &Pos) {
const auto *Cont = Pos.getContainer();
const auto *CData = getContainerData(State, Cont);
if (!CData)
return false;
const auto End = CData->getEnd();
if (End) {
if (isGreater(State, Pos.getOffset(), End)) {
return true;
}
}
return false;
}
bool isLess(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2) {
return compare(State, Sym1, Sym2, BO_LT);
}
bool isGreater(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2) {
return compare(State, Sym1, Sym2, BO_GT);
}
bool isEqual(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2) {
return compare(State, Sym1, Sym2, BO_EQ);
}
} // namespace
void ento::registerIteratorRangeChecker(CheckerManager &mgr) {
mgr.registerChecker<IteratorRangeChecker>();
}
bool ento::shouldRegisterIteratorRangeChecker(const LangOptions &LO) {
return true;
}
