void ArrayBoundChecker::checkLocation(SVal l, bool isLoad,
CheckerContext &C) const {
// Check for out of bound array element access.
const MemRegion *R = l.getAsRegion();
if (!R)
return;
const ElementRegion *ER = dyn_cast<ElementRegion>(R);
if (!ER)
return;
// Get the index of the accessed element.
DefinedOrUnknownSVal Idx = cast<DefinedOrUnknownSVal>(ER->getIndex());
// Zero index is always in bound, this also passes ElementRegions created for
// pointer casts.
if (Idx.isZeroConstant())
return;
const GRState *state = C.getState();
// Get the size of the array.
DefinedOrUnknownSVal NumElements
= C.getStoreManager().getSizeInElements(state, ER->getSuperRegion(),
ER->getValueType());
const GRState *StInBound = state->assumeInBound(Idx, NumElements, true);
const GRState *StOutBound = state->assumeInBound(Idx, NumElements, false);
if (StOutBound && !StInBound) {
ExplodedNode *N = C.generateSink(StOutBound);
if (!N)
return;
if (!BT)
BT.reset(new BuiltinBug("Out-of-bound array access",
"Access out-of-bound array element (buffer overflow)"));
// FIXME: It would be nice to eventually make this diagnostic more clear,
// e.g., by referencing the original declaration or by saying *why* this
// reference is outside the range.
// Generate a report for this bug.
RangedBugReport *report =
new RangedBugReport(*BT, BT->getDescription(), N);
report->addRange(C.getStmt()->getSourceRange());
C.EmitReport(report);
return;
}
// Array bound check succeeded. From this point forward the array bound
// should always succeed.
assert(StInBound);
C.addTransition(StInBound);
}
void ReturnPointerRangeChecker::checkPreStmt(const ReturnStmt *RS,
CheckerContext &C) const {
ProgramStateRef state = C.getState();
const Expr *RetE = RS->getRetValue();
if (!RetE)
return;
SVal V = state->getSVal(RetE, C.getLocationContext());
const MemRegion *R = V.getAsRegion();
const ElementRegion *ER = dyn_cast_or_null<ElementRegion>(R);
if (!ER)
return;
DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>();
// Zero index is always in bound, this also passes ElementRegions created for
// pointer casts.
if (Idx.isZeroConstant())
return;
// FIXME: All of this out-of-bounds checking should eventually be refactored
// into a common place.
DefinedOrUnknownSVal NumElements
= C.getStoreManager().getSizeInElements(state, ER->getSuperRegion(),
ER->getValueType());
ProgramStateRef StInBound = state->assumeInBound(Idx, NumElements, true);
ProgramStateRef StOutBound = state->assumeInBound(Idx, NumElements, false);
if (StOutBound && !StInBound) {
ExplodedNode *N = C.generateSink(StOutBound);
if (!N)
return;
// FIXME: This bug correspond to CWE-466. Eventually we should have bug
// types explicitly reference such exploit categories (when applicable).
if (!BT)
BT.reset(new BuiltinBug(
this, "Return of pointer value outside of expected range",
"Returned pointer value points outside the original object "
"(potential buffer overflow)"));
// FIXME: It would be nice to eventually make this diagnostic more clear,
// e.g., by referencing the original declaration or by saying *why* this
// reference is outside the range.
// Generate a report for this bug.
auto report = llvm::make_unique<BugReport>(*BT, BT->getDescription(), N);
report->addRange(RetE->getSourceRange());
C.emitReport(std::move(report));
}
}
DefinedOrUnknownSVal FieldRegion::getExtent(SValBuilder &svalBuilder) const {
DefinedOrUnknownSVal Extent = DeclRegion::getExtent(svalBuilder);
// A zero-length array at the end of a struct often stands for dynamically-
// allocated extra memory.
if (Extent.isZeroConstant()) {
QualType T = getDesugaredValueType(svalBuilder.getContext());
if (isa<ConstantArrayType>(T))
return UnknownVal();
}
return Extent;
}
ProgramStateRef ProgramState::assumeInBound(DefinedOrUnknownSVal Idx,
DefinedOrUnknownSVal UpperBound,
bool Assumption,
QualType indexTy) const {
if (Idx.isUnknown() || UpperBound.isUnknown())
return this;
// Build an expression for 0 <= Idx < UpperBound.
// This is the same as Idx + MIN < UpperBound + MIN, if overflow is allowed.
// FIXME: This should probably be part of SValBuilder.
ProgramStateManager &SM = getStateManager();
SValBuilder &svalBuilder = SM.getSValBuilder();
ASTContext &Ctx = svalBuilder.getContext();
// Get the offset: the minimum value of the array index type.
BasicValueFactory &BVF = svalBuilder.getBasicValueFactory();
// FIXME: This should be using ValueManager::ArrayindexTy...somehow.
if (indexTy.isNull())
indexTy = Ctx.IntTy;
nonloc::ConcreteInt Min(BVF.getMinValue(indexTy));
// Adjust the index.
SVal newIdx = svalBuilder.evalBinOpNN(this, BO_Add,
cast<NonLoc>(Idx), Min, indexTy);
if (newIdx.isUnknownOrUndef())
return this;
// Adjust the upper bound.
SVal newBound =
svalBuilder.evalBinOpNN(this, BO_Add, cast<NonLoc>(UpperBound),
Min, indexTy);
if (newBound.isUnknownOrUndef())
return this;
// Build the actual comparison.
SVal inBound = svalBuilder.evalBinOpNN(this, BO_LT,
cast<NonLoc>(newIdx), cast<NonLoc>(newBound),
Ctx.IntTy);
if (inBound.isUnknownOrUndef())
return this;
// Finally, let the constraint manager take care of it.
ConstraintManager &CM = SM.getConstraintManager();
return CM.assume(this, cast<DefinedSVal>(inBound), Assumption);
}
