CallAndMessageChecker.cpp revision 296417 
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::ObjCMessageNil,
44                    check::PreCall > {
45  mutable std::unique_ptr<BugType> BT_call_null;
46  mutable std::unique_ptr<BugType> BT_call_undef;
47  mutable std::unique_ptr<BugType> BT_cxx_call_null;
48  mutable std::unique_ptr<BugType> BT_cxx_call_undef;
49  mutable std::unique_ptr<BugType> BT_call_arg;
50  mutable std::unique_ptr<BugType> BT_cxx_delete_undef;
51  mutable std::unique_ptr<BugType> BT_msg_undef;
52  mutable std::unique_ptr<BugType> BT_objc_prop_undef;
53  mutable std::unique_ptr<BugType> BT_objc_subscript_undef;
54  mutable std::unique_ptr<BugType> BT_msg_arg;
55  mutable std::unique_ptr<BugType> BT_msg_ret;
56  mutable std::unique_ptr<BugType> BT_call_few_args;
57
58public:
59  ChecksFilter Filter;
60
61  void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
62  void checkPreStmt(const CXXDeleteExpr *DE, CheckerContext &C) const;
63  void checkPreObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const;
64
65  /// Fill in the return value that results from messaging nil based on the
66  /// return type and architecture and diagnose if the return value will be
67  /// garbage.
68  void checkObjCMessageNil(const ObjCMethodCall &msg, CheckerContext &C) const;
69
70  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
71
72private:
73  bool PreVisitProcessArg(CheckerContext &C, SVal V, SourceRange ArgRange,
74                          const Expr *ArgEx, bool IsFirstArgument,
75                          bool CheckUninitFields, const CallEvent &Call,
76                          std::unique_ptr<BugType> &BT,
77                          const ParmVarDecl *ParamDecl) const;
78
79  static void emitBadCall(BugType *BT, CheckerContext &C, const Expr *BadE);
80  void emitNilReceiverBug(CheckerContext &C, const ObjCMethodCall &msg,
81                          ExplodedNode *N) const;
82
83  void HandleNilReceiver(CheckerContext &C,
84                         ProgramStateRef state,
85                         const ObjCMethodCall &msg) const;
86
87  void LazyInit_BT(const char *desc, std::unique_ptr<BugType> &BT) const {
88    if (!BT)
89      BT.reset(new BuiltinBug(this, desc));
90  }
91  bool uninitRefOrPointer(CheckerContext &C, const SVal &V,
92                          SourceRange ArgRange,
93                          const Expr *ArgEx, std::unique_ptr<BugType> &BT,
94                          const ParmVarDecl *ParamDecl, const char *BD) const;
95};
96} // end anonymous namespace
97
98void CallAndMessageChecker::emitBadCall(BugType *BT, CheckerContext &C,
99                                        const Expr *BadE) {
100  ExplodedNode *N = C.generateErrorNode();
101  if (!N)
102    return;
103
104  auto R = llvm::make_unique<BugReport>(*BT, BT->getName(), N);
105  if (BadE) {
106    R->addRange(BadE->getSourceRange());
107    if (BadE->isGLValue())
108      BadE = bugreporter::getDerefExpr(BadE);
109    bugreporter::trackNullOrUndefValue(N, BadE, *R);
110  }
111  C.emitReport(std::move(R));
112}
113
114static StringRef describeUninitializedArgumentInCall(const CallEvent &Call,
115                                                     bool IsFirstArgument) {
116  switch (Call.getKind()) {
117  case CE_ObjCMessage: {
118    const ObjCMethodCall &Msg = cast<ObjCMethodCall>(Call);
119    switch (Msg.getMessageKind()) {
120    case OCM_Message:
121      return "Argument in message expression is an uninitialized value";
122    case OCM_PropertyAccess:
123      assert(Msg.isSetter() && "Getters have no args");
124      return "Argument for property setter is an uninitialized value";
125    case OCM_Subscript:
126      if (Msg.isSetter() && IsFirstArgument)
127        return "Argument for subscript setter is an uninitialized value";
128      return "Subscript index is an uninitialized value";
129    }
130    llvm_unreachable("Unknown message kind.");
131  }
132  case CE_Block:
133    return "Block call argument is an uninitialized value";
134  default:
135    return "Function call argument is an uninitialized value";
136  }
137}
138
139bool CallAndMessageChecker::uninitRefOrPointer(CheckerContext &C,
140                                               const SVal &V,
141                                               SourceRange ArgRange,
142                                               const Expr *ArgEx,
143                                               std::unique_ptr<BugType> &BT,
144                                               const ParmVarDecl *ParamDecl,
145                                               const char *BD) const {
146  if (!Filter.Check_CallAndMessageUnInitRefArg)
147    return false;
148
149  // No parameter declaration available, i.e. variadic function argument.
150  if(!ParamDecl)
151    return false;
152
153  // If parameter is declared as pointer to const in function declaration,
154  // then check if corresponding argument in function call is
155  // pointing to undefined symbol value (uninitialized memory).
156  StringRef Message;
157
158  if (ParamDecl->getType()->isPointerType()) {
159    Message = "Function call argument is a pointer to uninitialized value";
160  } else if (ParamDecl->getType()->isReferenceType()) {
161    Message = "Function call argument is an uninitialized value";
162  } else
163    return false;
164
165  if(!ParamDecl->getType()->getPointeeType().isConstQualified())
166    return false;
167
168  if (const MemRegion *SValMemRegion = V.getAsRegion()) {
169    const ProgramStateRef State = C.getState();
170    const SVal PSV = State->getSVal(SValMemRegion);
171    if (PSV.isUndef()) {
172      if (ExplodedNode *N = C.generateErrorNode()) {
173        LazyInit_BT(BD, BT);
174        auto R = llvm::make_unique<BugReport>(*BT, Message, N);
175        R->addRange(ArgRange);
176        if (ArgEx) {
177          bugreporter::trackNullOrUndefValue(N, ArgEx, *R);
178        }
179        C.emitReport(std::move(R));
180      }
181      return true;
182    }
183  }
184  return false;
185}
186
187bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C,
188                                               SVal V,
189                                               SourceRange ArgRange,
190                                               const Expr *ArgEx,
191                                               bool IsFirstArgument,
192                                               bool CheckUninitFields,
193                                               const CallEvent &Call,
194                                               std::unique_ptr<BugType> &BT,
195                                               const ParmVarDecl *ParamDecl
196                                               ) const {
197  const char *BD = "Uninitialized argument value";
198
199  if (uninitRefOrPointer(C, V, ArgRange, ArgEx, BT, ParamDecl, BD))
200    return true;
201
202  if (V.isUndef()) {
203    if (ExplodedNode *N = C.generateErrorNode()) {
204      LazyInit_BT(BD, BT);
205
206      // Generate a report for this bug.
207      StringRef Desc =
208          describeUninitializedArgumentInCall(Call, IsFirstArgument);
209      auto R = llvm::make_unique<BugReport>(*BT, Desc, N);
210      R->addRange(ArgRange);
211      if (ArgEx)
212        bugreporter::trackNullOrUndefValue(N, ArgEx, *R);
213      C.emitReport(std::move(R));
214    }
215    return true;
216  }
217
218  if (!CheckUninitFields)
219    return false;
220
221  if (Optional<nonloc::LazyCompoundVal> LV =
222          V.getAs<nonloc::LazyCompoundVal>()) {
223
224    class FindUninitializedField {
225    public:
226      SmallVector<const FieldDecl *, 10> FieldChain;
227    private:
228      StoreManager &StoreMgr;
229      MemRegionManager &MrMgr;
230      Store store;
231    public:
232      FindUninitializedField(StoreManager &storeMgr,
233                             MemRegionManager &mrMgr, Store s)
234      : StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {}
235
236      bool Find(const TypedValueRegion *R) {
237        QualType T = R->getValueType();
238        if (const RecordType *RT = T->getAsStructureType()) {
239          const RecordDecl *RD = RT->getDecl()->getDefinition();
240          assert(RD && "Referred record has no definition");
241          for (const auto *I : RD->fields()) {
242            const FieldRegion *FR = MrMgr.getFieldRegion(I, R);
243            FieldChain.push_back(I);
244            T = I->getType();
245            if (T->getAsStructureType()) {
246              if (Find(FR))
247                return true;
248            }
249            else {
250              const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
251              if (V.isUndef())
252                return true;
253            }
254            FieldChain.pop_back();
255          }
256        }
257
258        return false;
259      }
260    };
261
262    const LazyCompoundValData *D = LV->getCVData();
263    FindUninitializedField F(C.getState()->getStateManager().getStoreManager(),
264                             C.getSValBuilder().getRegionManager(),
265                             D->getStore());
266
267    if (F.Find(D->getRegion())) {
268      if (ExplodedNode *N = C.generateErrorNode()) {
269        LazyInit_BT(BD, BT);
270        SmallString<512> Str;
271        llvm::raw_svector_ostream os(Str);
272        os << "Passed-by-value struct argument contains uninitialized data";
273
274        if (F.FieldChain.size() == 1)
275          os << " (e.g., field: '" << *F.FieldChain[0] << "')";
276        else {
277          os << " (e.g., via the field chain: '";
278          bool first = true;
279          for (SmallVectorImpl<const FieldDecl *>::iterator
280               DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){
281            if (first)
282              first = false;
283            else
284              os << '.';
285            os << **DI;
286          }
287          os << "')";
288        }
289
290        // Generate a report for this bug.
291        auto R = llvm::make_unique<BugReport>(*BT, os.str(), N);
292        R->addRange(ArgRange);
293
294        // FIXME: enhance track back for uninitialized value for arbitrary
295        // memregions
296        C.emitReport(std::move(R));
297      }
298      return true;
299    }
300  }
301
302  return false;
303}
304
305void CallAndMessageChecker::checkPreStmt(const CallExpr *CE,
306                                         CheckerContext &C) const{
307
308  const Expr *Callee = CE->getCallee()->IgnoreParens();
309  ProgramStateRef State = C.getState();
310  const LocationContext *LCtx = C.getLocationContext();
311  SVal L = State->getSVal(Callee, LCtx);
312
313  if (L.isUndef()) {
314    if (!BT_call_undef)
315      BT_call_undef.reset(new BuiltinBug(
316          this, "Called function pointer is an uninitalized pointer value"));
317    emitBadCall(BT_call_undef.get(), C, Callee);
318    return;
319  }
320
321  ProgramStateRef StNonNull, StNull;
322  std::tie(StNonNull, StNull) = State->assume(L.castAs<DefinedOrUnknownSVal>());
323
324  if (StNull && !StNonNull) {
325    if (!BT_call_null)
326      BT_call_null.reset(new BuiltinBug(
327          this, "Called function pointer is null (null dereference)"));
328    emitBadCall(BT_call_null.get(), C, Callee);
329    return;
330  }
331
332  C.addTransition(StNonNull);
333}
334
335void CallAndMessageChecker::checkPreStmt(const CXXDeleteExpr *DE,
336                                         CheckerContext &C) const {
337
338  SVal Arg = C.getSVal(DE->getArgument());
339  if (Arg.isUndef()) {
340    StringRef Desc;
341    ExplodedNode *N = C.generateErrorNode();
342    if (!N)
343      return;
344    if (!BT_cxx_delete_undef)
345      BT_cxx_delete_undef.reset(
346          new BuiltinBug(this, "Uninitialized argument value"));
347    if (DE->isArrayFormAsWritten())
348      Desc = "Argument to 'delete[]' is uninitialized";
349    else
350      Desc = "Argument to 'delete' is uninitialized";
351    BugType *BT = BT_cxx_delete_undef.get();
352    auto R = llvm::make_unique<BugReport>(*BT, Desc, N);
353    bugreporter::trackNullOrUndefValue(N, DE, *R);
354    C.emitReport(std::move(R));
355    return;
356  }
357}
358
359
360void CallAndMessageChecker::checkPreCall(const CallEvent &Call,
361                                         CheckerContext &C) const {
362  ProgramStateRef State = C.getState();
363
364  // If this is a call to a C++ method, check if the callee is null or
365  // undefined.
366  if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) {
367    SVal V = CC->getCXXThisVal();
368    if (V.isUndef()) {
369      if (!BT_cxx_call_undef)
370        BT_cxx_call_undef.reset(
371            new BuiltinBug(this, "Called C++ object pointer is uninitialized"));
372      emitBadCall(BT_cxx_call_undef.get(), C, CC->getCXXThisExpr());
373      return;
374    }
375
376    ProgramStateRef StNonNull, StNull;
377    std::tie(StNonNull, StNull) =
378        State->assume(V.castAs<DefinedOrUnknownSVal>());
379
380    if (StNull && !StNonNull) {
381      if (!BT_cxx_call_null)
382        BT_cxx_call_null.reset(
383            new BuiltinBug(this, "Called C++ object pointer is null"));
384      emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr());
385      return;
386    }
387
388    State = StNonNull;
389  }
390
391  const Decl *D = Call.getDecl();
392  const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D);
393  if (FD) {
394    // If we have a declaration, we can make sure we pass enough parameters to
395    // the function.
396    unsigned Params = FD->getNumParams();
397    if (Call.getNumArgs() < Params) {
398      ExplodedNode *N = C.generateErrorNode();
399      if (!N)
400        return;
401
402      LazyInit_BT("Function call with too few arguments", BT_call_few_args);
403
404      SmallString<512> Str;
405      llvm::raw_svector_ostream os(Str);
406      os << "Function taking " << Params << " argument"
407         << (Params == 1 ? "" : "s") << " is called with less ("
408         << Call.getNumArgs() << ")";
409
410      C.emitReport(
411          llvm::make_unique<BugReport>(*BT_call_few_args, os.str(), N));
412    }
413  }
414
415  // Don't check for uninitialized field values in arguments if the
416  // caller has a body that is available and we have the chance to inline it.
417  // This is a hack, but is a reasonable compromise betweens sometimes warning
418  // and sometimes not depending on if we decide to inline a function.
419  const bool checkUninitFields =
420    !(C.getAnalysisManager().shouldInlineCall() && (D && D->getBody()));
421
422  std::unique_ptr<BugType> *BT;
423  if (isa<ObjCMethodCall>(Call))
424    BT = &BT_msg_arg;
425  else
426    BT = &BT_call_arg;
427
428  for (unsigned i = 0, e = Call.getNumArgs(); i != e; ++i) {
429    const ParmVarDecl *ParamDecl = nullptr;
430    if(FD && i < FD->getNumParams())
431      ParamDecl = FD->getParamDecl(i);
432    if (PreVisitProcessArg(C, Call.getArgSVal(i), Call.getArgSourceRange(i),
433                           Call.getArgExpr(i), /*IsFirstArgument=*/i == 0,
434                           checkUninitFields, Call, *BT, ParamDecl))
435      return;
436  }
437
438  // If we make it here, record our assumptions about the callee.
439  C.addTransition(State);
440}
441
442void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg,
443                                                CheckerContext &C) const {
444  SVal recVal = msg.getReceiverSVal();
445  if (recVal.isUndef()) {
446    if (ExplodedNode *N = C.generateErrorNode()) {
447      BugType *BT = nullptr;
448      switch (msg.getMessageKind()) {
449      case OCM_Message:
450        if (!BT_msg_undef)
451          BT_msg_undef.reset(new BuiltinBug(this,
452                                            "Receiver in message expression "
453                                            "is an uninitialized value"));
454        BT = BT_msg_undef.get();
455        break;
456      case OCM_PropertyAccess:
457        if (!BT_objc_prop_undef)
458          BT_objc_prop_undef.reset(new BuiltinBug(
459              this, "Property access on an uninitialized object pointer"));
460        BT = BT_objc_prop_undef.get();
461        break;
462      case OCM_Subscript:
463        if (!BT_objc_subscript_undef)
464          BT_objc_subscript_undef.reset(new BuiltinBug(
465              this, "Subscript access on an uninitialized object pointer"));
466        BT = BT_objc_subscript_undef.get();
467        break;
468      }
469      assert(BT && "Unknown message kind.");
470
471      auto R = llvm::make_unique<BugReport>(*BT, BT->getName(), N);
472      const ObjCMessageExpr *ME = msg.getOriginExpr();
473      R->addRange(ME->getReceiverRange());
474
475      // FIXME: getTrackNullOrUndefValueVisitor can't handle "super" yet.
476      if (const Expr *ReceiverE = ME->getInstanceReceiver())
477        bugreporter::trackNullOrUndefValue(N, ReceiverE, *R);
478      C.emitReport(std::move(R));
479    }
480    return;
481  }
482}
483
484void CallAndMessageChecker::checkObjCMessageNil(const ObjCMethodCall &msg,
485                                                CheckerContext &C) const {
486  HandleNilReceiver(C, C.getState(), msg);
487}
488
489void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C,
490                                               const ObjCMethodCall &msg,
491                                               ExplodedNode *N) const {
492
493  if (!BT_msg_ret)
494    BT_msg_ret.reset(
495        new BuiltinBug(this, "Receiver in message expression is 'nil'"));
496
497  const ObjCMessageExpr *ME = msg.getOriginExpr();
498
499  QualType ResTy = msg.getResultType();
500
501  SmallString<200> buf;
502  llvm::raw_svector_ostream os(buf);
503  os << "The receiver of message '";
504  ME->getSelector().print(os);
505  os << "' is nil";
506  if (ResTy->isReferenceType()) {
507    os << ", which results in forming a null reference";
508  } else {
509    os << " and returns a value of type '";
510    msg.getResultType().print(os, C.getLangOpts());
511    os << "' that will be garbage";
512  }
513
514  auto report = llvm::make_unique<BugReport>(*BT_msg_ret, os.str(), N);
515  report->addRange(ME->getReceiverRange());
516  // FIXME: This won't track "self" in messages to super.
517  if (const Expr *receiver = ME->getInstanceReceiver()) {
518    bugreporter::trackNullOrUndefValue(N, receiver, *report);
519  }
520  C.emitReport(std::move(report));
521}
522
523static bool supportsNilWithFloatRet(const llvm::Triple &triple) {
524  return (triple.getVendor() == llvm::Triple::Apple &&
525          (triple.isiOS() || triple.isWatchOS() ||
526           !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.generateErrorNode(state, &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