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

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//===-- IteratorChecker.cpp ---------------------------------------*- C++ -*--//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Defines a checker for using iterators outside their range (past end). Usage
// means here dereferencing, incrementing etc.
//
//===----------------------------------------------------------------------===//
//
// In the code, iterator can be represented as a:
// * type-I: typedef-ed pointer. Operations over such iterator, such as
// comparisons or increments, are modeled straightforwardly by the
// analyzer.
// * type-II: structure with its method bodies available. Operations over such
// iterator are inlined by the analyzer, and results of modeling
// these operations are exposing implementation details of the
// iterators, which is not necessarily helping.
// * type-III: completely opaque structure. Operations over such iterator are
// modeled conservatively, producing conjured symbols everywhere.
//
// To handle all these types in a common way we introduce a structure called
// IteratorPosition which is an abstraction of the position the iterator
// represents using symbolic expressions. The checker handles all the
// operations on this structure.
//
// Additionally, depending on the circumstances, operators of types II and III
// can be represented as:
// * type-IIa, type-IIIa: conjured structure symbols - when returned by value
// from conservatively evaluated methods such as
// `.begin()`.
// * type-IIb, type-IIIb: memory regions of iterator-typed objects, such as
// variables or temporaries, when the iterator object is
// currently treated as an lvalue.
// * type-IIc, type-IIIc: compound values of iterator-typed objects, when the
// iterator object is treated as an rvalue taken of a
// particular lvalue, eg. a copy of "type-a" iterator
// object, or an iterator that existed before the
// analysis has started.
//
// To handle any of these three different representations stored in an SVal we
// use setter and getters functions which separate the three cases. To store
// them we use a pointer union of symbol and memory region.
//
// The checker works the following way: We record the begin and the
// past-end iterator for all containers whenever their `.begin()` and `.end()`
// are called. Since the Constraint Manager cannot handle such SVals we need
// to take over its role. We post-check equality and non-equality comparisons
// and record that the two sides are equal if we are in the 'equal' branch
// (true-branch for `==` and false-branch for `!=`).
//
// In case of type-I or type-II iterators we get a concrete integer as a result
// of the comparison (1 or 0) but in case of type-III we only get a Symbol. In
// this latter case we record the symbol and reload it in evalAssume() and do
// the propagation there. We also handle (maybe double) negated comparisons
// which are represented in the form of (x == 0 or x != 0) where x is the
// comparison itself.
//
// Since `SimpleConstraintManager` cannot handle complex symbolic expressions
// we only use expressions of the format S, S+n or S-n for iterator positions
// where S is a conjured symbol and n is an unsigned concrete integer. When
// making an assumption e.g. `S1 + n == S2 + m` we store `S1 - S2 == m - n` as
// a constraint which we later retrieve when doing an actual comparison.
#include "ClangSACheckers.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"
using namespace clang;
using namespace ento;
namespace {
// Abstract position of an iterator. This helps to handle all three kinds
// of operators in a common way by using a symbolic position.
struct IteratorPosition {
private:
// Container the iterator belongs to
const MemRegion *Cont;
// Abstract offset
const SymbolRef Offset;
IteratorPosition(const MemRegion *C, SymbolRef Of)
: Cont(C), Offset(Of) {}
public:
const MemRegion *getContainer() const { return Cont; }
SymbolRef getOffset() const { return Offset; }
static IteratorPosition getPosition(const MemRegion *C, SymbolRef Of) {
return IteratorPosition(C, Of);
}
IteratorPosition setTo(SymbolRef NewOf) const {
return IteratorPosition(Cont, NewOf);
}
bool operator==(const IteratorPosition &X) const {
return Cont == X.Cont && Offset == X.Offset;
}
bool operator!=(const IteratorPosition &X) const {
return Cont != X.Cont || Offset != X.Offset;
}
void Profile(llvm::FoldingSetNodeID &ID) const {
ID.AddPointer(Cont);
ID.Add(Offset);
}
};
typedef llvm::PointerUnion<const MemRegion *, SymbolRef> RegionOrSymbol;
// Structure to record the symbolic begin and end position of a container
struct ContainerData {
private:
const SymbolRef Begin, End;
ContainerData(SymbolRef B, SymbolRef E) : Begin(B), End(E) {}
public:
static ContainerData fromBegin(SymbolRef B) {
return ContainerData(B, nullptr);
}
static ContainerData fromEnd(SymbolRef E) {
return ContainerData(nullptr, E);
}
SymbolRef getBegin() const { return Begin; }
SymbolRef getEnd() const { return End; }
ContainerData newBegin(SymbolRef B) const { return ContainerData(B, End); }
ContainerData newEnd(SymbolRef E) const { return ContainerData(Begin, E); }
bool operator==(const ContainerData &X) const {
return Begin == X.Begin && End == X.End;
}
bool operator!=(const ContainerData &X) const {
return Begin != X.Begin || End != X.End;
}
void Profile(llvm::FoldingSetNodeID &ID) const {
ID.Add(Begin);
ID.Add(End);
}
};
// Structure fo recording iterator comparisons. We needed to retrieve the
// original comparison expression in assumptions.
struct IteratorComparison {
private:
RegionOrSymbol Left, Right;
bool Equality;
public:
IteratorComparison(RegionOrSymbol L, RegionOrSymbol R, bool Eq)
: Left(L), Right(R), Equality(Eq) {}
RegionOrSymbol getLeft() const { return Left; }
RegionOrSymbol getRight() const { return Right; }
bool isEquality() const { return Equality; }
bool operator==(const IteratorComparison &X) const {
return Left == X.Left && Right == X.Right && Equality == X.Equality;
}
bool operator!=(const IteratorComparison &X) const {
return Left != X.Left || Right != X.Right || Equality != X.Equality;
}
void Profile(llvm::FoldingSetNodeID &ID) const { ID.AddInteger(Equality); }
};
class IteratorChecker
: public Checker<check::PreCall, check::PostCall,
check::PreStmt<CXXOperatorCallExpr>,
check::PostStmt<MaterializeTemporaryExpr>,
check::LiveSymbols, check::DeadSymbols,
eval::Assume> {
std::unique_ptr<BugType> OutOfRangeBugType;
void handleComparison(CheckerContext &C, const SVal &RetVal, const SVal &LVal,
const SVal &RVal, OverloadedOperatorKind Op) const;
void verifyDereference(CheckerContext &C, const SVal &Val) const;
void handleIncrement(CheckerContext &C, const SVal &RetVal, const SVal &Iter,
bool Postfix) const;
void handleDecrement(CheckerContext &C, const SVal &RetVal, const SVal &Iter,
bool Postfix) const;
void handleRandomIncrOrDecr(CheckerContext &C, OverloadedOperatorKind Op,
const SVal &RetVal, const SVal &LHS,
const SVal &RHS) const;
void handleBegin(CheckerContext &C, const Expr *CE, const SVal &RetVal,
const SVal &Cont) const;
void handleEnd(CheckerContext &C, const Expr *CE, const SVal &RetVal,
const SVal &Cont) const;
void assignToContainer(CheckerContext &C, const Expr *CE, const SVal &RetVal,
const MemRegion *Cont) const;
void verifyRandomIncrOrDecr(CheckerContext &C, OverloadedOperatorKind Op,
const SVal &RetVal, const SVal &LHS,
const SVal &RHS) const;
void reportOutOfRangeBug(const StringRef &Message, const SVal &Val,
CheckerContext &C, ExplodedNode *ErrNode) const;
public:
IteratorChecker();
enum CheckKind {
CK_IteratorRangeChecker,
CK_NumCheckKinds
};
DefaultBool ChecksEnabled[CK_NumCheckKinds];
CheckName CheckNames[CK_NumCheckKinds];
void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
void checkPostCall(const CallEvent &Call, CheckerContext &C) const;
void checkPreStmt(const CXXOperatorCallExpr *COCE, CheckerContext &C) const;
void checkPostStmt(const MaterializeTemporaryExpr *MTE,
CheckerContext &C) const;
void checkLiveSymbols(ProgramStateRef State, SymbolReaper &SR) const;
void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const;
ProgramStateRef evalAssume(ProgramStateRef State, SVal Cond,
bool Assumption) const;
};
} // namespace
REGISTER_MAP_WITH_PROGRAMSTATE(IteratorSymbolMap, SymbolRef, IteratorPosition)
REGISTER_MAP_WITH_PROGRAMSTATE(IteratorRegionMap, const MemRegion *,
IteratorPosition)
REGISTER_MAP_WITH_PROGRAMSTATE(ContainerMap, const MemRegion *, ContainerData)
REGISTER_MAP_WITH_PROGRAMSTATE(IteratorComparisonMap, const SymExpr *,
IteratorComparison)
namespace {
bool isIteratorType(const QualType &Type);
bool isIterator(const CXXRecordDecl *CRD);
bool isBeginCall(const FunctionDecl *Func);
bool isEndCall(const FunctionDecl *Func);
bool isSimpleComparisonOperator(OverloadedOperatorKind OK);
bool isDereferenceOperator(OverloadedOperatorKind OK);
bool isIncrementOperator(OverloadedOperatorKind OK);
bool isDecrementOperator(OverloadedOperatorKind OK);
bool isRandomIncrOrDecrOperator(OverloadedOperatorKind OK);
BinaryOperator::Opcode getOpcode(const SymExpr *SE);
const RegionOrSymbol getRegionOrSymbol(const SVal &Val);
const ProgramStateRef processComparison(ProgramStateRef State,
RegionOrSymbol LVal,
RegionOrSymbol RVal, bool Equal);
const ProgramStateRef saveComparison(ProgramStateRef State,
const SymExpr *Condition, const SVal &LVal,
const SVal &RVal, bool Eq);
const IteratorComparison *loadComparison(ProgramStateRef State,
const SymExpr *Condition);
SymbolRef getContainerBegin(ProgramStateRef State, const MemRegion *Cont);
SymbolRef getContainerEnd(ProgramStateRef State, const MemRegion *Cont);
ProgramStateRef createContainerBegin(ProgramStateRef State,
const MemRegion *Cont,
const SymbolRef Sym);
ProgramStateRef createContainerEnd(ProgramStateRef State, const MemRegion *Cont,
const SymbolRef Sym);
const IteratorPosition *getIteratorPosition(ProgramStateRef State,
const SVal &Val);
const IteratorPosition *getIteratorPosition(ProgramStateRef State,
RegionOrSymbol RegOrSym);
ProgramStateRef setIteratorPosition(ProgramStateRef State, const SVal &Val,
const IteratorPosition &Pos);
ProgramStateRef setIteratorPosition(ProgramStateRef State,
RegionOrSymbol RegOrSym,
const IteratorPosition &Pos);
ProgramStateRef removeIteratorPosition(ProgramStateRef State, const SVal &Val);
ProgramStateRef adjustIteratorPosition(ProgramStateRef State,
RegionOrSymbol RegOrSym,
const IteratorPosition &Pos, bool Equal);
ProgramStateRef relateIteratorPositions(ProgramStateRef State,
const IteratorPosition &Pos1,
const IteratorPosition &Pos2,
bool Equal);
const ContainerData *getContainerData(ProgramStateRef State,
const MemRegion *Cont);
ProgramStateRef setContainerData(ProgramStateRef State, const MemRegion *Cont,
const ContainerData &CData);
bool hasLiveIterators(ProgramStateRef State, const MemRegion *Cont);
bool isOutOfRange(ProgramStateRef State, const IteratorPosition &Pos);
bool isZero(ProgramStateRef State, const NonLoc &Val);
} // namespace
IteratorChecker::IteratorChecker() {
OutOfRangeBugType.reset(
new BugType(this, "Iterator out of range", "Misuse of STL APIs"));
OutOfRangeBugType->setSuppressOnSink(true);
}
void IteratorChecker::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 (ChecksEnabled[CK_IteratorRangeChecker] &&
isRandomIncrOrDecrOperator(Func->getOverloadedOperator())) {
if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
// Check for out-of-range incrementions and decrementions
if (Call.getNumArgs() >= 1) {
verifyRandomIncrOrDecr(C, Func->getOverloadedOperator(),
Call.getReturnValue(),
InstCall->getCXXThisVal(), Call.getArgSVal(0));
}
} else {
if (Call.getNumArgs() >= 2) {
verifyRandomIncrOrDecr(C, Func->getOverloadedOperator(),
Call.getReturnValue(), Call.getArgSVal(0),
Call.getArgSVal(1));
}
}
} else if (ChecksEnabled[CK_IteratorRangeChecker] &&
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 IteratorChecker::checkPostCall(const CallEvent &Call,
CheckerContext &C) const {
// Record new iterator positions and iterator position changes
const auto *Func = dyn_cast_or_null<FunctionDecl>(Call.getDecl());
if (!Func)
return;
if (Func->isOverloadedOperator()) {
const auto Op = Func->getOverloadedOperator();
if (isSimpleComparisonOperator(Op)) {
if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
handleComparison(C, Call.getReturnValue(), InstCall->getCXXThisVal(),
Call.getArgSVal(0), Op);
} else {
handleComparison(C, Call.getReturnValue(), Call.getArgSVal(0),
Call.getArgSVal(1), Op);
}
} else if (isRandomIncrOrDecrOperator(Func->getOverloadedOperator())) {
if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
if (Call.getNumArgs() >= 1) {
handleRandomIncrOrDecr(C, Func->getOverloadedOperator(),
Call.getReturnValue(),
InstCall->getCXXThisVal(), Call.getArgSVal(0));
}
} else {
if (Call.getNumArgs() >= 2) {
handleRandomIncrOrDecr(C, Func->getOverloadedOperator(),
Call.getReturnValue(), Call.getArgSVal(0),
Call.getArgSVal(1));
}
}
} else if (isIncrementOperator(Func->getOverloadedOperator())) {
if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
handleIncrement(C, Call.getReturnValue(), InstCall->getCXXThisVal(),
Call.getNumArgs());
} else {
handleIncrement(C, Call.getReturnValue(), Call.getArgSVal(0),
Call.getNumArgs());
}
} else if (isDecrementOperator(Func->getOverloadedOperator())) {
if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
handleDecrement(C, Call.getReturnValue(), InstCall->getCXXThisVal(),
Call.getNumArgs());
} else {
handleDecrement(C, Call.getReturnValue(), Call.getArgSVal(0),
Call.getNumArgs());
}
}
} else {
const auto *OrigExpr = Call.getOriginExpr();
if (!OrigExpr)
return;
if (!isIteratorType(Call.getResultType()))
return;
auto State = C.getState();
// Already bound to container?
if (getIteratorPosition(State, Call.getReturnValue()))
return;
if (const auto *InstCall = dyn_cast<CXXInstanceCall>(&Call)) {
if (isBeginCall(Func)) {
handleBegin(C, OrigExpr, Call.getReturnValue(),
InstCall->getCXXThisVal());
return;
}
if (isEndCall(Func)) {
handleEnd(C, OrigExpr, Call.getReturnValue(),
InstCall->getCXXThisVal());
return;
}
}
// Copy-like and move constructors
if (isa<CXXConstructorCall>(&Call) && Call.getNumArgs() == 1) {
if (const auto *Pos = getIteratorPosition(State, Call.getArgSVal(0))) {
State = setIteratorPosition(State, Call.getReturnValue(), *Pos);
if (cast<CXXConstructorDecl>(Func)->isMoveConstructor()) {
State = removeIteratorPosition(State, Call.getArgSVal(0));
}
C.addTransition(State);
return;
}
}
// Assumption: if return value is an iterator which is not yet bound to a
// container, then look for the first iterator argument, and
// bind the return value to the same container. This approach
// works for STL algorithms.
// FIXME: Add a more conservative mode
for (unsigned i = 0; i < Call.getNumArgs(); ++i) {
if (isIteratorType(Call.getArgExpr(i)->getType())) {
if (const auto *Pos = getIteratorPosition(State, Call.getArgSVal(i))) {
assignToContainer(C, OrigExpr, Call.getReturnValue(),
Pos->getContainer());
return;
}
}
}
}
}
void IteratorChecker::checkPreStmt(const CXXOperatorCallExpr *COCE,
CheckerContext &C) const {
const auto *ThisExpr = COCE->getArg(0);
auto State = C.getState();
const auto *LCtx = C.getLocationContext();
const auto CurrentThis = State->getSVal(ThisExpr, LCtx);
if (const auto *Reg = CurrentThis.getAsRegion()) {
if (!Reg->getAs<CXXTempObjectRegion>())
return;
const auto OldState = C.getPredecessor()->getFirstPred()->getState();
const auto OldThis = OldState->getSVal(ThisExpr, LCtx);
// FIXME: This solution is unreliable. It may happen that another checker
// subscribes to the pre-statement check of `CXXOperatorCallExpr`
// and adds a transition before us. The proper fix is to make the
// CFG provide a `ConstructionContext` for the `CXXOperatorCallExpr`,
// which would turn the corresponding `CFGStmt` element into a
// `CFGCXXRecordTypedCall` element, which will allow `ExprEngine` to
// foresee that the `begin()`/`end()` call constructs the object
// directly in the temporary region that `CXXOperatorCallExpr` takes
// as its implicit object argument.
const auto *Pos = getIteratorPosition(OldState, OldThis);
if (!Pos)
return;
State = setIteratorPosition(State, CurrentThis, *Pos);
C.addTransition(State);
}
}
void IteratorChecker::checkPostStmt(const MaterializeTemporaryExpr *MTE,
CheckerContext &C) const {
/* Transfer iterator state to temporary objects */
auto State = C.getState();
const auto *Pos =
getIteratorPosition(State, C.getSVal(MTE->GetTemporaryExpr()));
if (!Pos)
return;
State = setIteratorPosition(State, C.getSVal(MTE), *Pos);
C.addTransition(State);
}
void IteratorChecker::checkLiveSymbols(ProgramStateRef State,
SymbolReaper &SR) const {
// Keep symbolic expressions of iterator positions, container begins and ends
// alive
auto RegionMap = State->get<IteratorRegionMap>();
for (const auto Reg : RegionMap) {
const auto Offset = Reg.second.getOffset();
for (auto i = Offset->symbol_begin(); i != Offset->symbol_end(); ++i)
if (isa<SymbolData>(*i))
SR.markLive(*i);
}
auto SymbolMap = State->get<IteratorSymbolMap>();
for (const auto Sym : SymbolMap) {
const auto Offset = Sym.second.getOffset();
for (auto i = Offset->symbol_begin(); i != Offset->symbol_end(); ++i)
if (isa<SymbolData>(*i))
SR.markLive(*i);
}
auto ContMap = State->get<ContainerMap>();
for (const auto Cont : ContMap) {
const auto CData = Cont.second;
if (CData.getBegin()) {
SR.markLive(CData.getBegin());
}
if (CData.getEnd()) {
SR.markLive(CData.getEnd());
}
}
}
void IteratorChecker::checkDeadSymbols(SymbolReaper &SR,
CheckerContext &C) const {
// Cleanup
auto State = C.getState();
auto RegionMap = State->get<IteratorRegionMap>();
for (const auto Reg : RegionMap) {
if (!SR.isLiveRegion(Reg.first)) {
State = State->remove<IteratorRegionMap>(Reg.first);
}
}
auto SymbolMap = State->get<IteratorSymbolMap>();
for (const auto Sym : SymbolMap) {
if (!SR.isLive(Sym.first)) {
State = State->remove<IteratorSymbolMap>(Sym.first);
}
}
auto ContMap = State->get<ContainerMap>();
for (const auto Cont : ContMap) {
if (!SR.isLiveRegion(Cont.first)) {
// We must keep the container data while it has live iterators to be able
// to compare them to the begin and the end of the container.
if (!hasLiveIterators(State, Cont.first)) {
State = State->remove<ContainerMap>(Cont.first);
}
}
}
auto ComparisonMap = State->get<IteratorComparisonMap>();
for (const auto Comp : ComparisonMap) {
if (!SR.isLive(Comp.first)) {
State = State->remove<IteratorComparisonMap>(Comp.first);
}
}
C.addTransition(State);
}
ProgramStateRef IteratorChecker::evalAssume(ProgramStateRef State, SVal Cond,
bool Assumption) const {
// Load recorded comparison and transfer iterator state between sides
// according to comparison operator and assumption
const auto *SE = Cond.getAsSymExpr();
if (!SE)
return State;
auto Opc = getOpcode(SE);
if (Opc != BO_EQ && Opc != BO_NE)
return State;
bool Negated = false;
const auto *Comp = loadComparison(State, SE);
if (!Comp) {
// Try negated comparison, which is a SymExpr to 0 integer comparison
const auto *SIE = dyn_cast<SymIntExpr>(SE);
if (!SIE)
return State;
if (SIE->getRHS() != 0)
return State;
SE = SIE->getLHS();
Negated = SIE->getOpcode() == BO_EQ; // Equal to zero means negation
Opc = getOpcode(SE);
if (Opc != BO_EQ && Opc != BO_NE)
return State;
Comp = loadComparison(State, SE);
if (!Comp)
return State;
}
return processComparison(State, Comp->getLeft(), Comp->getRight(),
(Comp->isEquality() == Assumption) != Negated);
}
void IteratorChecker::handleComparison(CheckerContext &C, const SVal &RetVal,
const SVal &LVal, const SVal &RVal,
OverloadedOperatorKind Op) const {
// Record the operands and the operator of the comparison for the next
// evalAssume, if the result is a symbolic expression. If it is a concrete
// value (only one branch is possible), then transfer the state between
// the operands according to the operator and the result
auto State = C.getState();
if (const auto *Condition = RetVal.getAsSymbolicExpression()) {
const auto *LPos = getIteratorPosition(State, LVal);
const auto *RPos = getIteratorPosition(State, RVal);
if (!LPos && !RPos)
return;
State = saveComparison(State, Condition, LVal, RVal, Op == OO_EqualEqual);
C.addTransition(State);
} else if (const auto TruthVal = RetVal.getAs<nonloc::ConcreteInt>()) {
if ((State = processComparison(
State, getRegionOrSymbol(LVal), getRegionOrSymbol(RVal),
(Op == OO_EqualEqual) == (TruthVal->getValue() != 0)))) {
C.addTransition(State);
} else {
C.generateSink(State, C.getPredecessor());
}
}
}
void IteratorChecker::verifyDereference(CheckerContext &C,
const SVal &Val) const {
auto State = C.getState();
const auto *Pos = getIteratorPosition(State, Val);
if (Pos && isOutOfRange(State, *Pos)) {
// If I do not put a tag here, some range tests will fail
static CheckerProgramPointTag Tag("IteratorRangeChecker",
"IteratorOutOfRange");
auto *N = C.generateNonFatalErrorNode(State, &Tag);
if (!N)
return;
reportOutOfRangeBug("Iterator accessed outside of its range.", Val, C, N);
}
}
void IteratorChecker::handleIncrement(CheckerContext &C, const SVal &RetVal,
const SVal &Iter, bool Postfix) const {
// Increment the symbolic expressions which represents the position of the
// iterator
auto State = C.getState();
const auto *Pos = getIteratorPosition(State, Iter);
if (Pos) {
auto &SymMgr = C.getSymbolManager();
auto &BVF = SymMgr.getBasicVals();
auto &SVB = C.getSValBuilder();
const auto OldOffset = Pos->getOffset();
auto NewOffset =
SVB.evalBinOp(State, BO_Add,
nonloc::SymbolVal(OldOffset),
nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(1))),
SymMgr.getType(OldOffset)).getAsSymbol();
auto NewPos = Pos->setTo(NewOffset);
State = setIteratorPosition(State, Iter, NewPos);
State = setIteratorPosition(State, RetVal, Postfix ? *Pos : NewPos);
C.addTransition(State);
}
}
void IteratorChecker::handleDecrement(CheckerContext &C, const SVal &RetVal,
const SVal &Iter, bool Postfix) const {
// Decrement the symbolic expressions which represents the position of the
// iterator
auto State = C.getState();
const auto *Pos = getIteratorPosition(State, Iter);
if (Pos) {
auto &SymMgr = C.getSymbolManager();
auto &BVF = SymMgr.getBasicVals();
auto &SVB = C.getSValBuilder();
const auto OldOffset = Pos->getOffset();
auto NewOffset =
SVB.evalBinOp(State, BO_Sub,
nonloc::SymbolVal(OldOffset),
nonloc::ConcreteInt(BVF.getValue(llvm::APSInt::get(1))),
SymMgr.getType(OldOffset)).getAsSymbol();
auto NewPos = Pos->setTo(NewOffset);
State = setIteratorPosition(State, Iter, NewPos);
State = setIteratorPosition(State, RetVal, Postfix ? *Pos : NewPos);
C.addTransition(State);
}
}
// This function tells the analyzer's engine that symbols produced by our
// checker, most notably iterator positions, are relatively small.
// A distance between items in the container should not be very large.
// By assuming that it is within around 1/8 of the address space,
// we can help the analyzer perform operations on these symbols
// without being afraid of integer overflows.
// FIXME: Should we provide it as an API, so that all checkers could use it?
static ProgramStateRef assumeNoOverflow(ProgramStateRef State, SymbolRef Sym,
long Scale) {
SValBuilder &SVB = State->getStateManager().getSValBuilder();
BasicValueFactory &BV = SVB.getBasicValueFactory();
QualType T = Sym->getType();
assert(T->isSignedIntegerOrEnumerationType());
APSIntType AT = BV.getAPSIntType(T);
ProgramStateRef NewState = State;
llvm::APSInt Max = AT.getMaxValue() / AT.getValue(Scale);
SVal IsCappedFromAbove =
SVB.evalBinOpNN(State, BO_LE, nonloc::SymbolVal(Sym),
nonloc::ConcreteInt(Max), SVB.getConditionType());
if (auto DV = IsCappedFromAbove.getAs<DefinedSVal>()) {
NewState = NewState->assume(*DV, true);
if (!NewState)
return State;
}
llvm::APSInt Min = -Max;
SVal IsCappedFromBelow =
SVB.evalBinOpNN(State, BO_GE, nonloc::SymbolVal(Sym),
nonloc::ConcreteInt(Min), SVB.getConditionType());
if (auto DV = IsCappedFromBelow.getAs<DefinedSVal>()) {
NewState = NewState->assume(*DV, true);
if (!NewState)
return State;
}
return NewState;
}
void IteratorChecker::handleRandomIncrOrDecr(CheckerContext &C,
OverloadedOperatorKind Op,
const SVal &RetVal,
const SVal &LHS,
const SVal &RHS) const {
// Increment or decrement the symbolic expressions which represents the
// position of the iterator
auto State = C.getState();
const auto *Pos = getIteratorPosition(State, LHS);
if (!Pos)
return;
const auto *value = &RHS;
if (auto loc = RHS.getAs<Loc>()) {
const auto val = State->getRawSVal(*loc);
value = &val;
}
auto &SymMgr = C.getSymbolManager();
auto &SVB = C.getSValBuilder();
auto BinOp = (Op == OO_Plus || Op == OO_PlusEqual) ? BO_Add : BO_Sub;
const auto OldOffset = Pos->getOffset();
SymbolRef NewOffset;
if (const auto intValue = value->getAs<nonloc::ConcreteInt>()) {
// For concrete integers we can calculate the new position
NewOffset = SVB.evalBinOp(State, BinOp, nonloc::SymbolVal(OldOffset),
*intValue,
SymMgr.getType(OldOffset)).getAsSymbol();
} else {
// For other symbols create a new symbol to keep expressions simple
const auto &LCtx = C.getLocationContext();
NewOffset = SymMgr.conjureSymbol(nullptr, LCtx, SymMgr.getType(OldOffset),
C.blockCount());
State = assumeNoOverflow(State, NewOffset, 4);
}
auto NewPos = Pos->setTo(NewOffset);
auto &TgtVal = (Op == OO_PlusEqual || Op == OO_MinusEqual) ? LHS : RetVal;
State = setIteratorPosition(State, TgtVal, NewPos);
C.addTransition(State);
}
void IteratorChecker::verifyRandomIncrOrDecr(CheckerContext &C,
OverloadedOperatorKind Op,
const SVal &RetVal,
const SVal &LHS,
const SVal &RHS) const {
auto State = C.getState();
// If the iterator is initially inside its range, then the operation is valid
const auto *Pos = getIteratorPosition(State, LHS);
if (!Pos || !isOutOfRange(State, *Pos))
return;
auto value = RHS;
if (auto loc = RHS.getAs<Loc>()) {
value = State->getRawSVal(*loc);
}
// Incremention or decremention by 0 is never bug
if (isZero(State, value.castAs<NonLoc>()))
return;
auto &SymMgr = C.getSymbolManager();
auto &SVB = C.getSValBuilder();
auto BinOp = (Op == OO_Plus || Op == OO_PlusEqual) ? BO_Add : BO_Sub;
const auto OldOffset = Pos->getOffset();
const auto intValue = value.getAs<nonloc::ConcreteInt>();
if (!intValue)
return;
auto NewOffset = SVB.evalBinOp(State, BinOp, nonloc::SymbolVal(OldOffset),
*intValue,
SymMgr.getType(OldOffset)).getAsSymbol();
auto NewPos = Pos->setTo(NewOffset);
// If out of range, the only valid operation is to step into the range
if (isOutOfRange(State, NewPos)) {
auto *N = C.generateNonFatalErrorNode(State);
if (!N)
return;
reportOutOfRangeBug("Iterator accessed past its end.", LHS, C, N);
}
}
void IteratorChecker::handleBegin(CheckerContext &C, const Expr *CE,
const SVal &RetVal, const SVal &Cont) const {
const auto *ContReg = Cont.getAsRegion();
if (!ContReg)
return;
while (const auto *CBOR = ContReg->getAs<CXXBaseObjectRegion>()) {
ContReg = CBOR->getSuperRegion();
}
// If the container already has a begin symbol then use it. Otherwise first
// create a new one.
auto State = C.getState();
auto BeginSym = getContainerBegin(State, ContReg);
if (!BeginSym) {
auto &SymMgr = C.getSymbolManager();
BeginSym = SymMgr.conjureSymbol(CE, C.getLocationContext(),
C.getASTContext().LongTy, C.blockCount());
State = assumeNoOverflow(State, BeginSym, 4);
State = createContainerBegin(State, ContReg, BeginSym);
}
State = setIteratorPosition(State, RetVal,
IteratorPosition::getPosition(ContReg, BeginSym));
C.addTransition(State);
}
void IteratorChecker::handleEnd(CheckerContext &C, const Expr *CE,
const SVal &RetVal, const SVal &Cont) const {
const auto *ContReg = Cont.getAsRegion();
if (!ContReg)
return;
while (const auto *CBOR = ContReg->getAs<CXXBaseObjectRegion>()) {
ContReg = CBOR->getSuperRegion();
}
// If the container already has an end symbol then use it. Otherwise first
// create a new one.
auto State = C.getState();
auto EndSym = getContainerEnd(State, ContReg);
if (!EndSym) {
auto &SymMgr = C.getSymbolManager();
EndSym = SymMgr.conjureSymbol(CE, C.getLocationContext(),
C.getASTContext().LongTy, C.blockCount());
State = assumeNoOverflow(State, EndSym, 4);
State = createContainerEnd(State, ContReg, EndSym);
}
State = setIteratorPosition(State, RetVal,
IteratorPosition::getPosition(ContReg, EndSym));
C.addTransition(State);
}
void IteratorChecker::assignToContainer(CheckerContext &C, const Expr *CE,
const SVal &RetVal,
const MemRegion *Cont) const {
while (const auto *CBOR = Cont->getAs<CXXBaseObjectRegion>()) {
Cont = CBOR->getSuperRegion();
}
auto State = C.getState();
auto &SymMgr = C.getSymbolManager();
auto Sym = SymMgr.conjureSymbol(CE, C.getLocationContext(),
C.getASTContext().LongTy, C.blockCount());
State = assumeNoOverflow(State, Sym, 4);
State = setIteratorPosition(State, RetVal,
IteratorPosition::getPosition(Cont, Sym));
C.addTransition(State);
}
void IteratorChecker::reportOutOfRangeBug(const StringRef &Message,
const SVal &Val, CheckerContext &C,
ExplodedNode *ErrNode) const {
auto R = llvm::make_unique<BugReport>(*OutOfRangeBugType, Message, ErrNode);
R->markInteresting(Val);
C.emitReport(std::move(R));
}
namespace {
bool isLess(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2);
bool isGreaterOrEqual(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2);
bool compare(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2,
BinaryOperator::Opcode Opc);
bool compare(ProgramStateRef State, NonLoc NL1, NonLoc NL2,
BinaryOperator::Opcode Opc);
bool isIteratorType(const QualType &Type) {
if (Type->isPointerType())
return true;
const auto *CRD = Type->getUnqualifiedDesugaredType()->getAsCXXRecordDecl();
return isIterator(CRD);
}
bool isIterator(const CXXRecordDecl *CRD) {
if (!CRD)
return false;
const auto Name = CRD->getName();
if (!(Name.endswith_lower("iterator") || Name.endswith_lower("iter") ||
Name.endswith_lower("it")))
return false;
bool HasCopyCtor = false, HasCopyAssign = true, HasDtor = false,
HasPreIncrOp = false, HasPostIncrOp = false, HasDerefOp = false;
for (const auto *Method : CRD->methods()) {
if (const auto *Ctor = dyn_cast<CXXConstructorDecl>(Method)) {
if (Ctor->isCopyConstructor()) {
HasCopyCtor = !Ctor->isDeleted() && Ctor->getAccess() == AS_public;
}
continue;
}
if (const auto *Dtor = dyn_cast<CXXDestructorDecl>(Method)) {
HasDtor = !Dtor->isDeleted() && Dtor->getAccess() == AS_public;
continue;
}
if (Method->isCopyAssignmentOperator()) {
HasCopyAssign = !Method->isDeleted() && Method->getAccess() == AS_public;
continue;
}
if (!Method->isOverloadedOperator())
continue;
const auto OPK = Method->getOverloadedOperator();
if (OPK == OO_PlusPlus) {
HasPreIncrOp = HasPreIncrOp || (Method->getNumParams() == 0);
HasPostIncrOp = HasPostIncrOp || (Method->getNumParams() == 1);
continue;
}
if (OPK == OO_Star) {
HasDerefOp = (Method->getNumParams() == 0);
continue;
}
}
return HasCopyCtor && HasCopyAssign && HasDtor && HasPreIncrOp &&
HasPostIncrOp && HasDerefOp;
}
bool isBeginCall(const FunctionDecl *Func) {
const auto *IdInfo = Func->getIdentifier();
if (!IdInfo)
return false;
return IdInfo->getName().endswith_lower("begin");
}
bool isEndCall(const FunctionDecl *Func) {
const auto *IdInfo = Func->getIdentifier();
if (!IdInfo)
return false;
return IdInfo->getName().endswith_lower("end");
}
bool isSimpleComparisonOperator(OverloadedOperatorKind OK) {
return OK == OO_EqualEqual || OK == OO_ExclaimEqual;
}
bool isDereferenceOperator(OverloadedOperatorKind OK) {
return OK == OO_Star || OK == OO_Arrow || OK == OO_ArrowStar ||
OK == OO_Subscript;
}
bool isIncrementOperator(OverloadedOperatorKind OK) {
return OK == OO_PlusPlus;
}
bool isDecrementOperator(OverloadedOperatorKind OK) {
return OK == OO_MinusMinus;
}
bool isRandomIncrOrDecrOperator(OverloadedOperatorKind OK) {
return OK == OO_Plus || OK == OO_PlusEqual || OK == OO_Minus ||
OK == OO_MinusEqual;
}
BinaryOperator::Opcode getOpcode(const SymExpr *SE) {
if (const auto *BSE = dyn_cast<BinarySymExpr>(SE)) {
return BSE->getOpcode();
} else if (const auto *SC = dyn_cast<SymbolConjured>(SE)) {
const auto *COE = dyn_cast_or_null<CXXOperatorCallExpr>(SC->getStmt());
if (!COE)
return BO_Comma; // Extremal value, neither EQ nor NE
if (COE->getOperator() == OO_EqualEqual) {
return BO_EQ;
} else if (COE->getOperator() == OO_ExclaimEqual) {
return BO_NE;
}
return BO_Comma; // Extremal value, neither EQ nor NE
}
return BO_Comma; // Extremal value, neither EQ nor NE
}
const RegionOrSymbol getRegionOrSymbol(const SVal &Val) {
if (const auto Reg = Val.getAsRegion()) {
return Reg;
} else if (const auto Sym = Val.getAsSymbol()) {
return Sym;
} else if (const auto LCVal = Val.getAs<nonloc::LazyCompoundVal>()) {
return LCVal->getRegion();
}
return RegionOrSymbol();
}
const ProgramStateRef processComparison(ProgramStateRef State,
RegionOrSymbol LVal,
RegionOrSymbol RVal, bool Equal) {
const auto *LPos = getIteratorPosition(State, LVal);
const auto *RPos = getIteratorPosition(State, RVal);
if (LPos && !RPos) {
State = adjustIteratorPosition(State, RVal, *LPos, Equal);
} else if (!LPos && RPos) {
State = adjustIteratorPosition(State, LVal, *RPos, Equal);
} else if (LPos && RPos) {
State = relateIteratorPositions(State, *LPos, *RPos, Equal);
}
return State;
}
const ProgramStateRef saveComparison(ProgramStateRef State,
const SymExpr *Condition, const SVal &LVal,
const SVal &RVal, bool Eq) {
const auto Left = getRegionOrSymbol(LVal);
const auto Right = getRegionOrSymbol(RVal);
if (!Left || !Right)
return State;
return State->set<IteratorComparisonMap>(Condition,
IteratorComparison(Left, Right, Eq));
}
const IteratorComparison *loadComparison(ProgramStateRef State,
const SymExpr *Condition) {
return State->get<IteratorComparisonMap>(Condition);
}
SymbolRef getContainerBegin(ProgramStateRef State, const MemRegion *Cont) {
const auto *CDataPtr = getContainerData(State, Cont);
if (!CDataPtr)
return nullptr;
return CDataPtr->getBegin();
}
SymbolRef getContainerEnd(ProgramStateRef State, const MemRegion *Cont) {
const auto *CDataPtr = getContainerData(State, Cont);
if (!CDataPtr)
return nullptr;
return CDataPtr->getEnd();
}
ProgramStateRef createContainerBegin(ProgramStateRef State,
const MemRegion *Cont,
const SymbolRef Sym) {
// Only create if it does not exist
const auto *CDataPtr = getContainerData(State, Cont);
if (CDataPtr) {
if (CDataPtr->getBegin()) {
return State;
}
const auto CData = CDataPtr->newBegin(Sym);
return setContainerData(State, Cont, CData);
}
const auto CData = ContainerData::fromBegin(Sym);
return setContainerData(State, Cont, CData);
}
ProgramStateRef createContainerEnd(ProgramStateRef State, const MemRegion *Cont,
const SymbolRef Sym) {
// Only create if it does not exist
const auto *CDataPtr = getContainerData(State, Cont);
if (CDataPtr) {
if (CDataPtr->getEnd()) {
return State;
}
const auto CData = CDataPtr->newEnd(Sym);
return setContainerData(State, Cont, CData);
}
const auto CData = ContainerData::fromEnd(Sym);
return setContainerData(State, Cont, CData);
}
const ContainerData *getContainerData(ProgramStateRef State,
const MemRegion *Cont) {
return State->get<ContainerMap>(Cont);
}
ProgramStateRef setContainerData(ProgramStateRef State, const MemRegion *Cont,
const ContainerData &CData) {
return State->set<ContainerMap>(Cont, CData);
}
const IteratorPosition *getIteratorPosition(ProgramStateRef State,
const SVal &Val) {
if (const auto Reg = Val.getAsRegion()) {
return State->get<IteratorRegionMap>(Reg);
} else if (const auto Sym = Val.getAsSymbol()) {
return State->get<IteratorSymbolMap>(Sym);
} else if (const auto LCVal = Val.getAs<nonloc::LazyCompoundVal>()) {
return State->get<IteratorRegionMap>(LCVal->getRegion());
}
return nullptr;
}
const IteratorPosition *getIteratorPosition(ProgramStateRef State,
RegionOrSymbol RegOrSym) {
if (RegOrSym.is<const MemRegion *>()) {
return State->get<IteratorRegionMap>(RegOrSym.get<const MemRegion *>());
} else if (RegOrSym.is<SymbolRef>()) {
return State->get<IteratorSymbolMap>(RegOrSym.get<SymbolRef>());
}
return nullptr;
}
ProgramStateRef setIteratorPosition(ProgramStateRef State, const SVal &Val,
const IteratorPosition &Pos) {
if (const auto Reg = Val.getAsRegion()) {
return State->set<IteratorRegionMap>(Reg, Pos);
} else if (const auto Sym = Val.getAsSymbol()) {
return State->set<IteratorSymbolMap>(Sym, Pos);
} else if (const auto LCVal = Val.getAs<nonloc::LazyCompoundVal>()) {
return State->set<IteratorRegionMap>(LCVal->getRegion(), Pos);
}
return nullptr;
}
ProgramStateRef setIteratorPosition(ProgramStateRef State,
RegionOrSymbol RegOrSym,
const IteratorPosition &Pos) {
if (RegOrSym.is<const MemRegion *>()) {
return State->set<IteratorRegionMap>(RegOrSym.get<const MemRegion *>(),
Pos);
} else if (RegOrSym.is<SymbolRef>()) {
return State->set<IteratorSymbolMap>(RegOrSym.get<SymbolRef>(), Pos);
}
return nullptr;
}
ProgramStateRef removeIteratorPosition(ProgramStateRef State, const SVal &Val) {
if (const auto Reg = Val.getAsRegion()) {
return State->remove<IteratorRegionMap>(Reg);
} else if (const auto Sym = Val.getAsSymbol()) {
return State->remove<IteratorSymbolMap>(Sym);
} else if (const auto LCVal = Val.getAs<nonloc::LazyCompoundVal>()) {
return State->remove<IteratorRegionMap>(LCVal->getRegion());
}
return nullptr;
}
ProgramStateRef adjustIteratorPosition(ProgramStateRef State,
RegionOrSymbol RegOrSym,
const IteratorPosition &Pos,
bool Equal) {
if (Equal) {
return setIteratorPosition(State, RegOrSym, Pos);
} else {
return State;
}
}
ProgramStateRef relateIteratorPositions(ProgramStateRef State,
const IteratorPosition &Pos1,
const IteratorPosition &Pos2,
bool Equal) {
auto &SVB = State->getStateManager().getSValBuilder();
// FIXME: This code should be reworked as follows:
// 1. Subtract the operands using evalBinOp().
// 2. Assume that the result doesn't overflow.
// 3. Compare the result to 0.
// 4. Assume the result of the comparison.
const auto comparison =
SVB.evalBinOp(State, BO_EQ, nonloc::SymbolVal(Pos1.getOffset()),
nonloc::SymbolVal(Pos2.getOffset()),
SVB.getConditionType());
assert(comparison.getAs<DefinedSVal>() &&
"Symbol comparison must be a `DefinedSVal`");
auto NewState = State->assume(comparison.castAs<DefinedSVal>(), Equal);
if (const auto CompSym = comparison.getAsSymbol()) {
assert(isa<SymIntExpr>(CompSym) &&
"Symbol comparison must be a `SymIntExpr`");
assert(BinaryOperator::isComparisonOp(
cast<SymIntExpr>(CompSym)->getOpcode()) &&
"Symbol comparison must be a comparison");
return assumeNoOverflow(NewState, cast<SymIntExpr>(CompSym)->getLHS(), 2);
}
return NewState;
}
bool hasLiveIterators(ProgramStateRef State, const MemRegion *Cont) {
auto RegionMap = State->get<IteratorRegionMap>();
for (const auto Reg : RegionMap) {
if (Reg.second.getContainer() == Cont)
return true;
}
auto SymbolMap = State->get<IteratorSymbolMap>();
for (const auto Sym : SymbolMap) {
if (Sym.second.getContainer() == Cont)
return true;
}
return false;
}
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 isOutOfRange(ProgramStateRef State, const IteratorPosition &Pos) {
const auto *Cont = Pos.getContainer();
const auto *CData = getContainerData(State, Cont);
if (!CData)
return false;
// Out of range means less than the begin symbol or greater or equal to the
// end symbol.
const auto Beg = CData->getBegin();
if (Beg) {
if (isLess(State, Pos.getOffset(), Beg)) {
return true;
}
}
const auto End = CData->getEnd();
if (End) {
if (isGreaterOrEqual(State, Pos.getOffset(), End)) {
return true;
}
}
return false;
}
bool isLess(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2) {
return compare(State, Sym1, Sym2, BO_LT);
}
bool isGreaterOrEqual(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2) {
return compare(State, Sym1, Sym2, BO_GE);
}
bool compare(ProgramStateRef State, SymbolRef Sym1, SymbolRef Sym2,
BinaryOperator::Opcode Opc) {
return compare(State, nonloc::SymbolVal(Sym1), nonloc::SymbolVal(Sym2), Opc);
}
bool compare(ProgramStateRef State, NonLoc NL1, NonLoc NL2,
BinaryOperator::Opcode Opc) {
auto &SVB = State->getStateManager().getSValBuilder();
const auto comparison =
SVB.evalBinOp(State, Opc, NL1, NL2, SVB.getConditionType());
assert(comparison.getAs<DefinedSVal>() &&
"Symbol comparison must be a `DefinedSVal`");
return !State->assume(comparison.castAs<DefinedSVal>(), false);
}
} // namespace
#define REGISTER_CHECKER(name) \
void ento::register##name(CheckerManager &Mgr) { \
auto *checker = Mgr.registerChecker<IteratorChecker>(); \
checker->ChecksEnabled[IteratorChecker::CK_##name] = true; \
checker->CheckNames[IteratorChecker::CK_##name] = \
Mgr.getCurrentCheckName(); \
}
REGISTER_CHECKER(IteratorRangeChecker)
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