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llvm-project/clang/lib/StaticAnalyzer/Checkers/IteratorRangeChecker.cpp

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//===-- 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, check::PreStmt<UnaryOperator>,
check::PreStmt<BinaryOperator>,
check::PreStmt<ArraySubscriptExpr>,
check::PreStmt<MemberExpr>> {
std::unique_ptr<BugType> OutOfRangeBugType;
void verifyDereference(CheckerContext &C, SVal Val) const;
void verifyIncrement(CheckerContext &C, SVal Iter) const;
void verifyDecrement(CheckerContext &C, SVal Iter) const;
void verifyRandomIncrOrDecr(CheckerContext &C, OverloadedOperatorKind Op,
SVal LHS, SVal RHS) const;
void verifyAdvance(CheckerContext &C, SVal LHS, SVal RHS) const;
void verifyPrev(CheckerContext &C, SVal LHS, SVal RHS) const;
void verifyNext(CheckerContext &C, SVal LHS, SVal RHS) const;
void reportBug(const StringRef &Message, SVal Val, CheckerContext &C,
ExplodedNode *ErrNode) const;
public:
IteratorRangeChecker();
void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
void checkPreStmt(const UnaryOperator *UO, CheckerContext &C) const;
void checkPreStmt(const BinaryOperator *BO, CheckerContext &C) const;
void checkPreStmt(const ArraySubscriptExpr *ASE, CheckerContext &C) const;
void checkPreStmt(const MemberExpr *ME, CheckerContext &C) const;
using AdvanceFn = void (IteratorRangeChecker::*)(CheckerContext &, SVal,
SVal) const;
CallDescriptionMap<AdvanceFn> AdvanceFunctions = {
{{{"std", "advance"}, 2}, &IteratorRangeChecker::verifyAdvance},
{{{"std", "prev"}, 2}, &IteratorRangeChecker::verifyPrev},
{{{"std", "next"}, 2}, &IteratorRangeChecker::verifyNext},
};
};
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));
}
}
} else {
const AdvanceFn *Verifier = AdvanceFunctions.lookup(Call);
if (Verifier) {
if (Call.getNumArgs() > 1) {
(this->**Verifier)(C, Call.getArgSVal(0), Call.getArgSVal(1));
} else {
auto &BVF = C.getSValBuilder().getBasicValueFactory();
(this->**Verifier)(
C, Call.getArgSVal(0),
nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(1))));
}
}
}
}
void IteratorRangeChecker::checkPreStmt(const UnaryOperator *UO,
CheckerContext &C) const {
if (isa<CXXThisExpr>(UO->getSubExpr()))
return;
ProgramStateRef State = C.getState();
UnaryOperatorKind OK = UO->getOpcode();
SVal SubVal = State->getSVal(UO->getSubExpr(), C.getLocationContext());
if (isDereferenceOperator(OK)) {
verifyDereference(C, SubVal);
} else if (isIncrementOperator(OK)) {
verifyIncrement(C, SubVal);
} else if (isDecrementOperator(OK)) {
verifyDecrement(C, SubVal);
}
}
void IteratorRangeChecker::checkPreStmt(const BinaryOperator *BO,
CheckerContext &C) const {
ProgramStateRef State = C.getState();
BinaryOperatorKind OK = BO->getOpcode();
SVal LVal = State->getSVal(BO->getLHS(), C.getLocationContext());
if (isDereferenceOperator(OK)) {
verifyDereference(C, LVal);
} else if (isRandomIncrOrDecrOperator(OK)) {
SVal RVal = State->getSVal(BO->getRHS(), C.getLocationContext());
if (!BO->getRHS()->getType()->isIntegralOrEnumerationType())
return;
verifyRandomIncrOrDecr(C, BinaryOperator::getOverloadedOperator(OK), LVal,
RVal);
}
}
void IteratorRangeChecker::checkPreStmt(const ArraySubscriptExpr *ASE,
CheckerContext &C) const {
ProgramStateRef State = C.getState();
SVal LVal = State->getSVal(ASE->getLHS(), C.getLocationContext());
verifyDereference(C, LVal);
}
void IteratorRangeChecker::checkPreStmt(const MemberExpr *ME,
CheckerContext &C) const {
if (!ME->isArrow() || ME->isImplicitAccess())
return;
ProgramStateRef State = C.getState();
SVal BaseVal = State->getSVal(ME->getBase(), C.getLocationContext());
verifyDereference(C, BaseVal);
}
void IteratorRangeChecker::verifyDereference(CheckerContext &C,
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, 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, 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,
SVal LHS, SVal RHS) const {
auto State = C.getState();
auto Value = RHS;
if (auto ValAsLoc = RHS.getAs<Loc>()) {
Value = State->getRawSVal(*ValAsLoc);
}
if (Value.isUnknownOrUndef())
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::verifyAdvance(CheckerContext &C, SVal LHS,
SVal RHS) const {
verifyRandomIncrOrDecr(C, OO_PlusEqual, LHS, RHS);
}
void IteratorRangeChecker::verifyPrev(CheckerContext &C, SVal LHS,
SVal RHS) const {
verifyRandomIncrOrDecr(C, OO_Minus, LHS, RHS);
}
void IteratorRangeChecker::verifyNext(CheckerContext &C, SVal LHS,
SVal RHS) const {
verifyRandomIncrOrDecr(C, OO_Plus, LHS, RHS);
}
void IteratorRangeChecker::reportBug(const StringRef &Message, SVal Val,
CheckerContext &C,
ExplodedNode *ErrNode) const {
auto R = std::make_unique<PathSensitiveBugReport>(*OutOfRangeBugType, Message,
ErrNode);
const auto *Pos = getIteratorPosition(C.getState(), Val);
assert(Pos && "Iterator without known position cannot be out-of-range.");
R->markInteresting(Val);
R->markInteresting(Pos->getContainer());
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 CheckerManager &mgr) {
return true;
}
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