1//===--- CallAndMessageChecker.cpp ------------------------------*- C++ -*--==//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This defines CallAndMessageChecker, a builtin checker that checks for various
11// errors of call and objc message expressions.
12//
13//===----------------------------------------------------------------------===//
14
15#include "ClangSACheckers.h"
16#include "clang/AST/ParentMap.h"
17#include "clang/Basic/TargetInfo.h"
18#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
19#include "clang/StaticAnalyzer/Core/Checker.h"
20#include "clang/StaticAnalyzer/Core/CheckerManager.h"
21#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
22#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
23#include "llvm/ADT/SmallString.h"
24#include "llvm/Support/raw_ostream.h"
25
26using namespace clang;
27using namespace ento;
28
29namespace {
30
31struct ChecksFilter {
32  DefaultBool Check_CallAndMessageUnInitRefArg;
33  DefaultBool Check_CallAndMessageChecker;
34
35  CheckName CheckName_CallAndMessageUnInitRefArg;
36  CheckName CheckName_CallAndMessageChecker;
37};
38
39class CallAndMessageChecker
40  : public Checker< check::PreStmt<CallExpr>,
41                    check::PreStmt<CXXDeleteExpr>,
42                    check::PreObjCMessage,
43                    check::PreCall > {
44  mutable std::unique_ptr<BugType> BT_call_null;
45  mutable std::unique_ptr<BugType> BT_call_undef;
46  mutable std::unique_ptr<BugType> BT_cxx_call_null;
47  mutable std::unique_ptr<BugType> BT_cxx_call_undef;
48  mutable std::unique_ptr<BugType> BT_call_arg;
49  mutable std::unique_ptr<BugType> BT_cxx_delete_undef;
50  mutable std::unique_ptr<BugType> BT_msg_undef;
51  mutable std::unique_ptr<BugType> BT_objc_prop_undef;
52  mutable std::unique_ptr<BugType> BT_objc_subscript_undef;
53  mutable std::unique_ptr<BugType> BT_msg_arg;
54  mutable std::unique_ptr<BugType> BT_msg_ret;
55  mutable std::unique_ptr<BugType> BT_call_few_args;
56
57public:
58  ChecksFilter Filter;
59
60  void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
61  void checkPreStmt(const CXXDeleteExpr *DE, CheckerContext &C) const;
62  void checkPreObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const;
63  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
64
65private:
66  bool PreVisitProcessArg(CheckerContext &C, SVal V, SourceRange ArgRange,
67                          const Expr *ArgEx, bool IsFirstArgument,
68                          bool CheckUninitFields, const CallEvent &Call,
69                          std::unique_ptr<BugType> &BT,
70                          const ParmVarDecl *ParamDecl) const;
71
72  static void emitBadCall(BugType *BT, CheckerContext &C, const Expr *BadE);
73  void emitNilReceiverBug(CheckerContext &C, const ObjCMethodCall &msg,
74                          ExplodedNode *N) const;
75
76  void HandleNilReceiver(CheckerContext &C,
77                         ProgramStateRef state,
78                         const ObjCMethodCall &msg) const;
79
80  void LazyInit_BT(const char *desc, std::unique_ptr<BugType> &BT) const {
81    if (!BT)
82      BT.reset(new BuiltinBug(this, desc));
83  }
84  bool uninitRefOrPointer(CheckerContext &C, const SVal &V,
85                          const SourceRange &ArgRange,
86                          const Expr *ArgEx, std::unique_ptr<BugType> &BT,
87                          const ParmVarDecl *ParamDecl, const char *BD) const;
88};
89} // end anonymous namespace
90
91void CallAndMessageChecker::emitBadCall(BugType *BT, CheckerContext &C,
92                                        const Expr *BadE) {
93  ExplodedNode *N = C.generateSink();
94  if (!N)
95    return;
96
97  BugReport *R = new BugReport(*BT, BT->getName(), N);
98  if (BadE) {
99    R->addRange(BadE->getSourceRange());
100    if (BadE->isGLValue())
101      BadE = bugreporter::getDerefExpr(BadE);
102    bugreporter::trackNullOrUndefValue(N, BadE, *R);
103  }
104  C.emitReport(R);
105}
106
107static StringRef describeUninitializedArgumentInCall(const CallEvent &Call,
108                                                     bool IsFirstArgument) {
109  switch (Call.getKind()) {
110  case CE_ObjCMessage: {
111    const ObjCMethodCall &Msg = cast<ObjCMethodCall>(Call);
112    switch (Msg.getMessageKind()) {
113    case OCM_Message:
114      return "Argument in message expression is an uninitialized value";
115    case OCM_PropertyAccess:
116      assert(Msg.isSetter() && "Getters have no args");
117      return "Argument for property setter is an uninitialized value";
118    case OCM_Subscript:
119      if (Msg.isSetter() && IsFirstArgument)
120        return "Argument for subscript setter is an uninitialized value";
121      return "Subscript index is an uninitialized value";
122    }
123    llvm_unreachable("Unknown message kind.");
124  }
125  case CE_Block:
126    return "Block call argument is an uninitialized value";
127  default:
128    return "Function call argument is an uninitialized value";
129  }
130}
131
132bool CallAndMessageChecker::uninitRefOrPointer(CheckerContext &C,
133                                               const SVal &V,
134                                               const SourceRange &ArgRange,
135                                               const Expr *ArgEx,
136                                               std::unique_ptr<BugType> &BT,
137                                               const ParmVarDecl *ParamDecl,
138                                               const char *BD) const {
139  if (!Filter.Check_CallAndMessageUnInitRefArg)
140    return false;
141
142  // No parameter declaration available, i.e. variadic function argument.
143  if(!ParamDecl)
144    return false;
145
146  // If parameter is declared as pointer to const in function declaration,
147  // then check if corresponding argument in function call is
148  // pointing to undefined symbol value (uninitialized memory).
149  StringRef Message;
150
151  if (ParamDecl->getType()->isPointerType()) {
152    Message = "Function call argument is a pointer to uninitialized value";
153  } else if (ParamDecl->getType()->isReferenceType()) {
154    Message = "Function call argument is an uninitialized value";
155  } else
156    return false;
157
158  if(!ParamDecl->getType()->getPointeeType().isConstQualified())
159    return false;
160
161  if (const MemRegion *SValMemRegion = V.getAsRegion()) {
162    const ProgramStateRef State = C.getState();
163    const SVal PSV = State->getSVal(SValMemRegion);
164    if (PSV.isUndef()) {
165      if (ExplodedNode *N = C.generateSink()) {
166        LazyInit_BT(BD, BT);
167        BugReport *R = new BugReport(*BT, Message, N);
168        R->addRange(ArgRange);
169        if (ArgEx) {
170          bugreporter::trackNullOrUndefValue(N, ArgEx, *R);
171        }
172        C.emitReport(R);
173      }
174      return true;
175    }
176  }
177  return false;
178}
179
180bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C,
181                                               SVal V,
182                                               SourceRange ArgRange,
183                                               const Expr *ArgEx,
184                                               bool IsFirstArgument,
185                                               bool CheckUninitFields,
186                                               const CallEvent &Call,
187                                               std::unique_ptr<BugType> &BT,
188                                               const ParmVarDecl *ParamDecl
189                                               ) const {
190  const char *BD = "Uninitialized argument value";
191
192  if (uninitRefOrPointer(C, V, ArgRange, ArgEx, BT, ParamDecl, BD))
193    return true;
194
195  if (V.isUndef()) {
196    if (ExplodedNode *N = C.generateSink()) {
197      LazyInit_BT(BD, BT);
198
199      // Generate a report for this bug.
200      StringRef Desc =
201          describeUninitializedArgumentInCall(Call, IsFirstArgument);
202      BugReport *R = new BugReport(*BT, Desc, N);
203      R->addRange(ArgRange);
204      if (ArgEx)
205        bugreporter::trackNullOrUndefValue(N, ArgEx, *R);
206      C.emitReport(R);
207    }
208    return true;
209  }
210
211  if (!CheckUninitFields)
212    return false;
213
214  if (Optional<nonloc::LazyCompoundVal> LV =
215          V.getAs<nonloc::LazyCompoundVal>()) {
216
217    class FindUninitializedField {
218    public:
219      SmallVector<const FieldDecl *, 10> FieldChain;
220    private:
221      StoreManager &StoreMgr;
222      MemRegionManager &MrMgr;
223      Store store;
224    public:
225      FindUninitializedField(StoreManager &storeMgr,
226                             MemRegionManager &mrMgr, Store s)
227      : StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {}
228
229      bool Find(const TypedValueRegion *R) {
230        QualType T = R->getValueType();
231        if (const RecordType *RT = T->getAsStructureType()) {
232          const RecordDecl *RD = RT->getDecl()->getDefinition();
233          assert(RD && "Referred record has no definition");
234          for (const auto *I : RD->fields()) {
235            const FieldRegion *FR = MrMgr.getFieldRegion(I, R);
236            FieldChain.push_back(I);
237            T = I->getType();
238            if (T->getAsStructureType()) {
239              if (Find(FR))
240                return true;
241            }
242            else {
243              const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
244              if (V.isUndef())
245                return true;
246            }
247            FieldChain.pop_back();
248          }
249        }
250
251        return false;
252      }
253    };
254
255    const LazyCompoundValData *D = LV->getCVData();
256    FindUninitializedField F(C.getState()->getStateManager().getStoreManager(),
257                             C.getSValBuilder().getRegionManager(),
258                             D->getStore());
259
260    if (F.Find(D->getRegion())) {
261      if (ExplodedNode *N = C.generateSink()) {
262        LazyInit_BT(BD, BT);
263        SmallString<512> Str;
264        llvm::raw_svector_ostream os(Str);
265        os << "Passed-by-value struct argument contains uninitialized data";
266
267        if (F.FieldChain.size() == 1)
268          os << " (e.g., field: '" << *F.FieldChain[0] << "')";
269        else {
270          os << " (e.g., via the field chain: '";
271          bool first = true;
272          for (SmallVectorImpl<const FieldDecl *>::iterator
273               DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){
274            if (first)
275              first = false;
276            else
277              os << '.';
278            os << **DI;
279          }
280          os << "')";
281        }
282
283        // Generate a report for this bug.
284        BugReport *R = new BugReport(*BT, os.str(), N);
285        R->addRange(ArgRange);
286
287        // FIXME: enhance track back for uninitialized value for arbitrary
288        // memregions
289        C.emitReport(R);
290      }
291      return true;
292    }
293  }
294
295  return false;
296}
297
298void CallAndMessageChecker::checkPreStmt(const CallExpr *CE,
299                                         CheckerContext &C) const{
300
301  const Expr *Callee = CE->getCallee()->IgnoreParens();
302  ProgramStateRef State = C.getState();
303  const LocationContext *LCtx = C.getLocationContext();
304  SVal L = State->getSVal(Callee, LCtx);
305
306  if (L.isUndef()) {
307    if (!BT_call_undef)
308      BT_call_undef.reset(new BuiltinBug(
309          this, "Called function pointer is an uninitalized pointer value"));
310    emitBadCall(BT_call_undef.get(), C, Callee);
311    return;
312  }
313
314  ProgramStateRef StNonNull, StNull;
315  std::tie(StNonNull, StNull) = State->assume(L.castAs<DefinedOrUnknownSVal>());
316
317  if (StNull && !StNonNull) {
318    if (!BT_call_null)
319      BT_call_null.reset(new BuiltinBug(
320          this, "Called function pointer is null (null dereference)"));
321    emitBadCall(BT_call_null.get(), C, Callee);
322    return;
323  }
324
325  C.addTransition(StNonNull);
326}
327
328void CallAndMessageChecker::checkPreStmt(const CXXDeleteExpr *DE,
329                                         CheckerContext &C) const {
330
331  SVal Arg = C.getSVal(DE->getArgument());
332  if (Arg.isUndef()) {
333    StringRef Desc;
334    ExplodedNode *N = C.generateSink();
335    if (!N)
336      return;
337    if (!BT_cxx_delete_undef)
338      BT_cxx_delete_undef.reset(
339          new BuiltinBug(this, "Uninitialized argument value"));
340    if (DE->isArrayFormAsWritten())
341      Desc = "Argument to 'delete[]' is uninitialized";
342    else
343      Desc = "Argument to 'delete' is uninitialized";
344    BugType *BT = BT_cxx_delete_undef.get();
345    BugReport *R = new BugReport(*BT, Desc, N);
346    bugreporter::trackNullOrUndefValue(N, DE, *R);
347    C.emitReport(R);
348    return;
349  }
350}
351
352
353void CallAndMessageChecker::checkPreCall(const CallEvent &Call,
354                                         CheckerContext &C) const {
355  ProgramStateRef State = C.getState();
356
357  // If this is a call to a C++ method, check if the callee is null or
358  // undefined.
359  if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) {
360    SVal V = CC->getCXXThisVal();
361    if (V.isUndef()) {
362      if (!BT_cxx_call_undef)
363        BT_cxx_call_undef.reset(
364            new BuiltinBug(this, "Called C++ object pointer is uninitialized"));
365      emitBadCall(BT_cxx_call_undef.get(), C, CC->getCXXThisExpr());
366      return;
367    }
368
369    ProgramStateRef StNonNull, StNull;
370    std::tie(StNonNull, StNull) =
371        State->assume(V.castAs<DefinedOrUnknownSVal>());
372
373    if (StNull && !StNonNull) {
374      if (!BT_cxx_call_null)
375        BT_cxx_call_null.reset(
376            new BuiltinBug(this, "Called C++ object pointer is null"));
377      emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr());
378      return;
379    }
380
381    State = StNonNull;
382  }
383
384  const Decl *D = Call.getDecl();
385  const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D);
386  if (FD) {
387    // If we have a declaration, we can make sure we pass enough parameters to
388    // the function.
389    unsigned Params = FD->getNumParams();
390    if (Call.getNumArgs() < Params) {
391      ExplodedNode *N = C.generateSink();
392      if (!N)
393        return;
394
395      LazyInit_BT("Function call with too few arguments", BT_call_few_args);
396
397      SmallString<512> Str;
398      llvm::raw_svector_ostream os(Str);
399      os << "Function taking " << Params << " argument"
400         << (Params == 1 ? "" : "s") << " is called with less ("
401         << Call.getNumArgs() << ")";
402
403      BugReport *R = new BugReport(*BT_call_few_args, os.str(), N);
404      C.emitReport(R);
405    }
406  }
407
408  // Don't check for uninitialized field values in arguments if the
409  // caller has a body that is available and we have the chance to inline it.
410  // This is a hack, but is a reasonable compromise betweens sometimes warning
411  // and sometimes not depending on if we decide to inline a function.
412  const bool checkUninitFields =
413    !(C.getAnalysisManager().shouldInlineCall() && (D && D->getBody()));
414
415  std::unique_ptr<BugType> *BT;
416  if (isa<ObjCMethodCall>(Call))
417    BT = &BT_msg_arg;
418  else
419    BT = &BT_call_arg;
420
421  for (unsigned i = 0, e = Call.getNumArgs(); i != e; ++i) {
422    const ParmVarDecl *ParamDecl = nullptr;
423    if(FD && i < FD->getNumParams())
424      ParamDecl = FD->getParamDecl(i);
425    if (PreVisitProcessArg(C, Call.getArgSVal(i), Call.getArgSourceRange(i),
426                           Call.getArgExpr(i), /*IsFirstArgument=*/i == 0,
427                           checkUninitFields, Call, *BT, ParamDecl))
428      return;
429  }
430
431  // If we make it here, record our assumptions about the callee.
432  C.addTransition(State);
433}
434
435void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg,
436                                                CheckerContext &C) const {
437  SVal recVal = msg.getReceiverSVal();
438  if (recVal.isUndef()) {
439    if (ExplodedNode *N = C.generateSink()) {
440      BugType *BT = nullptr;
441      switch (msg.getMessageKind()) {
442      case OCM_Message:
443        if (!BT_msg_undef)
444          BT_msg_undef.reset(new BuiltinBug(this,
445                                            "Receiver in message expression "
446                                            "is an uninitialized value"));
447        BT = BT_msg_undef.get();
448        break;
449      case OCM_PropertyAccess:
450        if (!BT_objc_prop_undef)
451          BT_objc_prop_undef.reset(new BuiltinBug(
452              this, "Property access on an uninitialized object pointer"));
453        BT = BT_objc_prop_undef.get();
454        break;
455      case OCM_Subscript:
456        if (!BT_objc_subscript_undef)
457          BT_objc_subscript_undef.reset(new BuiltinBug(
458              this, "Subscript access on an uninitialized object pointer"));
459        BT = BT_objc_subscript_undef.get();
460        break;
461      }
462      assert(BT && "Unknown message kind.");
463
464      BugReport *R = new BugReport(*BT, BT->getName(), N);
465      const ObjCMessageExpr *ME = msg.getOriginExpr();
466      R->addRange(ME->getReceiverRange());
467
468      // FIXME: getTrackNullOrUndefValueVisitor can't handle "super" yet.
469      if (const Expr *ReceiverE = ME->getInstanceReceiver())
470        bugreporter::trackNullOrUndefValue(N, ReceiverE, *R);
471      C.emitReport(R);
472    }
473    return;
474  } else {
475    // Bifurcate the state into nil and non-nil ones.
476    DefinedOrUnknownSVal receiverVal = recVal.castAs<DefinedOrUnknownSVal>();
477
478    ProgramStateRef state = C.getState();
479    ProgramStateRef notNilState, nilState;
480    std::tie(notNilState, nilState) = state->assume(receiverVal);
481
482    // Handle receiver must be nil.
483    if (nilState && !notNilState) {
484      HandleNilReceiver(C, state, msg);
485      return;
486    }
487  }
488}
489
490void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C,
491                                               const ObjCMethodCall &msg,
492                                               ExplodedNode *N) const {
493
494  if (!BT_msg_ret)
495    BT_msg_ret.reset(
496        new BuiltinBug(this, "Receiver in message expression is 'nil'"));
497
498  const ObjCMessageExpr *ME = msg.getOriginExpr();
499
500  QualType ResTy = msg.getResultType();
501
502  SmallString<200> buf;
503  llvm::raw_svector_ostream os(buf);
504  os << "The receiver of message '";
505  ME->getSelector().print(os);
506  os << "' is nil";
507  if (ResTy->isReferenceType()) {
508    os << ", which results in forming a null reference";
509  } else {
510    os << " and returns a value of type '";
511    msg.getResultType().print(os, C.getLangOpts());
512    os << "' that will be garbage";
513  }
514
515  BugReport *report = new BugReport(*BT_msg_ret, os.str(), N);
516  report->addRange(ME->getReceiverRange());
517  // FIXME: This won't track "self" in messages to super.
518  if (const Expr *receiver = ME->getInstanceReceiver()) {
519    bugreporter::trackNullOrUndefValue(N, receiver, *report);
520  }
521  C.emitReport(report);
522}
523
524static bool supportsNilWithFloatRet(const llvm::Triple &triple) {
525  return (triple.getVendor() == llvm::Triple::Apple &&
526          (triple.isiOS() || !triple.isMacOSXVersionLT(10,5)));
527}
528
529void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C,
530                                              ProgramStateRef state,
531                                              const ObjCMethodCall &Msg) const {
532  ASTContext &Ctx = C.getASTContext();
533  static CheckerProgramPointTag Tag(this, "NilReceiver");
534
535  // Check the return type of the message expression.  A message to nil will
536  // return different values depending on the return type and the architecture.
537  QualType RetTy = Msg.getResultType();
538  CanQualType CanRetTy = Ctx.getCanonicalType(RetTy);
539  const LocationContext *LCtx = C.getLocationContext();
540
541  if (CanRetTy->isStructureOrClassType()) {
542    // Structure returns are safe since the compiler zeroes them out.
543    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
544    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
545    return;
546  }
547
548  // Other cases: check if sizeof(return type) > sizeof(void*)
549  if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap()
550                                  .isConsumedExpr(Msg.getOriginExpr())) {
551    // Compute: sizeof(void *) and sizeof(return type)
552    const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy);
553    const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy);
554
555    if (CanRetTy.getTypePtr()->isReferenceType()||
556        (voidPtrSize < returnTypeSize &&
557         !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) &&
558           (Ctx.FloatTy == CanRetTy ||
559            Ctx.DoubleTy == CanRetTy ||
560            Ctx.LongDoubleTy == CanRetTy ||
561            Ctx.LongLongTy == CanRetTy ||
562            Ctx.UnsignedLongLongTy == CanRetTy)))) {
563      if (ExplodedNode *N = C.generateSink(state, nullptr, &Tag))
564        emitNilReceiverBug(C, Msg, N);
565      return;
566    }
567
568    // Handle the safe cases where the return value is 0 if the
569    // receiver is nil.
570    //
571    // FIXME: For now take the conservative approach that we only
572    // return null values if we *know* that the receiver is nil.
573    // This is because we can have surprises like:
574    //
575    //   ... = [[NSScreens screens] objectAtIndex:0];
576    //
577    // What can happen is that [... screens] could return nil, but
578    // it most likely isn't nil.  We should assume the semantics
579    // of this case unless we have *a lot* more knowledge.
580    //
581    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
582    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
583    return;
584  }
585
586  C.addTransition(state);
587}
588
589#define REGISTER_CHECKER(name)                                                 \
590  void ento::register##name(CheckerManager &mgr) {                             \
591    CallAndMessageChecker *Checker =                                           \
592        mgr.registerChecker<CallAndMessageChecker>();                          \
593    Checker->Filter.Check_##name = true;                                       \
594    Checker->Filter.CheckName_##name = mgr.getCurrentCheckName();              \
595  }
596
597REGISTER_CHECKER(CallAndMessageUnInitRefArg)
598REGISTER_CHECKER(CallAndMessageChecker)
599