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//= UnixAPIChecker.h - Checks preconditions for various Unix APIs --*- C++ -*-//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This defines UnixAPIChecker, which is an assortment of checks on calls
// to various, widely used UNIX/Posix functions.
//
//===----------------------------------------------------------------------===//
#include "GRExprEngineInternalChecks.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Checker/BugReporter/BugType.h"
#include "clang/Checker/PathSensitive/CheckerVisitor.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/StringSwitch.h"
#include <fcntl.h>
using namespace clang;
using llvm::Optional;
namespace {
class UnixAPIChecker : public CheckerVisitor<UnixAPIChecker> {
enum SubChecks {
OpenFn = 0,
PthreadOnceFn = 1,
NumChecks
};
BugType *BTypes[NumChecks];
public:
Optional<uint64_t> Val_O_CREAT;
public:
UnixAPIChecker() { memset(BTypes, 0, sizeof(*BTypes) * NumChecks); }
static void *getTag() { static unsigned tag = 0; return &tag; }
void PreVisitCallExpr(CheckerContext &C, const CallExpr *CE);
};
} //end anonymous namespace
void clang::RegisterUnixAPIChecker(GRExprEngine &Eng) {
Eng.registerCheck(new UnixAPIChecker());
}
//===----------------------------------------------------------------------===//
// Utility functions.
//===----------------------------------------------------------------------===//
static inline void LazyInitialize(BugType *&BT, const char *name) {
if (BT)
return;
BT = new BugType(name, "Unix API");
}
//===----------------------------------------------------------------------===//
// "open" (man 2 open)
//===----------------------------------------------------------------------===//
static void CheckOpen(CheckerContext &C, UnixAPIChecker &UC,
const CallExpr *CE, BugType *&BT) {
// The definition of O_CREAT is platform specific. We need a better way
// of querying this information from the checking environment.
if (!UC.Val_O_CREAT.hasValue()) {
if (C.getASTContext().Target.getTriple().getVendor() == llvm::Triple::Apple)
UC.Val_O_CREAT = 0x0200;
else {
// FIXME: We need a more general way of getting the O_CREAT value.
// We could possibly grovel through the preprocessor state, but
// that would require passing the Preprocessor object to the GRExprEngine.
return;
}
}
LazyInitialize(BT, "Improper use of 'open'");
// Look at the 'oflags' argument for the O_CREAT flag.
const GRState *state = C.getState();
if (CE->getNumArgs() < 2) {
// The frontend should issue a warning for this case, so this is a sanity
// check.
return;
}
// Now check if oflags has O_CREAT set.
const Expr *oflagsEx = CE->getArg(1);
const SVal V = state->getSVal(oflagsEx);
if (!isa<NonLoc>(V)) {
// The case where 'V' can be a location can only be due to a bad header,
// so in this case bail out.
return;
}
NonLoc oflags = cast<NonLoc>(V);
NonLoc ocreateFlag =
cast<NonLoc>(C.getValueManager().makeIntVal(UC.Val_O_CREAT.getValue(),
oflagsEx->getType()));
SVal maskedFlagsUC = C.getSValuator().EvalBinOpNN(state, BinaryOperator::And,
oflags, ocreateFlag,
oflagsEx->getType());
if (maskedFlagsUC.isUnknownOrUndef())
return;
DefinedSVal maskedFlags = cast<DefinedSVal>(maskedFlagsUC);
// Check if maskedFlags is non-zero.
const GRState *trueState, *falseState;
llvm::tie(trueState, falseState) = state->Assume(maskedFlags);
// Only emit an error if the value of 'maskedFlags' is properly
// constrained;
if (!(trueState && !falseState))
return;
if (CE->getNumArgs() < 3) {
ExplodedNode *N = C.GenerateSink(trueState);
if (!N)
return;
EnhancedBugReport *report =
new EnhancedBugReport(*BT,
"Call to 'open' requires a third argument when "
"the 'O_CREAT' flag is set", N);
report->addRange(oflagsEx->getSourceRange());
C.EmitReport(report);
}
}
//===----------------------------------------------------------------------===//
// pthread_once
//===----------------------------------------------------------------------===//
static void CheckPthreadOnce(CheckerContext &C, UnixAPIChecker &,
const CallExpr *CE, BugType *&BT) {
// This is similar to 'CheckDispatchOnce' in the MacOSXAPIChecker.
// They can possibly be refactored.
LazyInitialize(BT, "Improper use of 'pthread_once'");
if (CE->getNumArgs() < 1)
return;
// Check if the first argument is stack allocated. If so, issue a warning
// because that's likely to be bad news.
const GRState *state = C.getState();
const MemRegion *R = state->getSVal(CE->getArg(0)).getAsRegion();
if (!R || !isa<StackSpaceRegion>(R->getMemorySpace()))
return;
ExplodedNode *N = C.GenerateSink(state);
if (!N)
return;
llvm::SmallString<256> S;
llvm::raw_svector_ostream os(S);
os << "Call to 'pthread_once' uses";
if (const VarRegion *VR = dyn_cast<VarRegion>(R))
os << " the local variable '" << VR->getDecl()->getName() << '\'';
else
os << " stack allocated memory";
os << " for the \"control\" value. Using such transient memory for "
"the control value is potentially dangerous.";
if (isa<VarRegion>(R) && isa<StackLocalsSpaceRegion>(R->getMemorySpace()))
os << " Perhaps you intended to declare the variable as 'static'?";
EnhancedBugReport *report = new EnhancedBugReport(*BT, os.str(), N);
report->addRange(CE->getArg(0)->getSourceRange());
C.EmitReport(report);
}
//===----------------------------------------------------------------------===//
// Central dispatch function.
//===----------------------------------------------------------------------===//
typedef void (*SubChecker)(CheckerContext &C, UnixAPIChecker &UC,
const CallExpr *CE, BugType *&BT);
namespace {
class SubCheck {
SubChecker SC;
UnixAPIChecker *UC;
BugType **BT;
public:
SubCheck(SubChecker sc, UnixAPIChecker *uc, BugType *& bt) : SC(sc), UC(uc),
BT(&bt) {}
SubCheck() : SC(NULL), UC(NULL), BT(NULL) {}
void run(CheckerContext &C, const CallExpr *CE) const {
if (SC)
SC(C, *UC, CE, *BT);
}
};
} // end anonymous namespace
void UnixAPIChecker::PreVisitCallExpr(CheckerContext &C, const CallExpr *CE) {
// Get the callee. All the functions we care about are C functions
// with simple identifiers.
const GRState *state = C.getState();
const Expr *Callee = CE->getCallee();
const FunctionTextRegion *Fn =
dyn_cast_or_null<FunctionTextRegion>(state->getSVal(Callee).getAsRegion());
if (!Fn)
return;
const IdentifierInfo *FI = Fn->getDecl()->getIdentifier();
if (!FI)
return;
const SubCheck &SC =
llvm::StringSwitch<SubCheck>(FI->getName())
.Case("open", SubCheck(CheckOpen, this, BTypes[OpenFn]))
.Case("pthread_once", SubCheck(CheckPthreadOnce, this,
BTypes[PthreadOnceFn]))
.Default(SubCheck());
SC.run(C, CE);
}
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