MallocChecker.cpp revision 47cbd0f3892c7965cf16a58393f9f17a22d4d4d9 
1//=== MallocChecker.cpp - A malloc/free checker -------------------*- 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 file defines malloc/free checker, which checks for potential memory
11// leaks, double free, and use-after-free problems.
12//
13//===----------------------------------------------------------------------===//
14
15#include "ClangSACheckers.h"
16#include "InterCheckerAPI.h"
17#include "clang/StaticAnalyzer/Core/Checker.h"
18#include "clang/StaticAnalyzer/Core/CheckerManager.h"
19#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
21#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
22#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
23#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
24#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
25#include "clang/Basic/SourceManager.h"
26#include "llvm/ADT/ImmutableMap.h"
27#include "llvm/ADT/SmallString.h"
28#include "llvm/ADT/STLExtras.h"
29#include <climits>
30
31using namespace clang;
32using namespace ento;
33
34namespace {
35
36class RefState {
37  enum Kind { // Reference to allocated memory.
38              Allocated,
39              // Reference to released/freed memory.
40              Released,
41              // The responsibility for freeing resources has transfered from
42              // this reference. A relinquished symbol should not be freed.
43              Relinquished } K;
44  const Stmt *S;
45
46public:
47  RefState(Kind k, const Stmt *s) : K(k), S(s) {}
48
49  bool isAllocated() const { return K == Allocated; }
50  bool isReleased() const { return K == Released; }
51  bool isRelinquished() const { return K == Relinquished; }
52
53  const Stmt *getStmt() const { return S; }
54
55  bool operator==(const RefState &X) const {
56    return K == X.K && S == X.S;
57  }
58
59  static RefState getAllocated(const Stmt *s) {
60    return RefState(Allocated, s);
61  }
62  static RefState getReleased(const Stmt *s) { return RefState(Released, s); }
63  static RefState getRelinquished(const Stmt *s) {
64    return RefState(Relinquished, s);
65  }
66
67  void Profile(llvm::FoldingSetNodeID &ID) const {
68    ID.AddInteger(K);
69    ID.AddPointer(S);
70  }
71};
72
73/// \class ReallocPair
74/// \brief Stores information about the symbol being reallocated by a call to
75/// 'realloc' to allow modeling failed reallocation later in the path.
76struct ReallocPair {
77  // \brief The symbol which realloc reallocated.
78  SymbolRef ReallocatedSym;
79  // \brief The flag is true if the symbol does not need to be freed after
80  // reallocation fails.
81  bool IsFreeOnFailure;
82
83  ReallocPair(SymbolRef S, bool F) : ReallocatedSym(S), IsFreeOnFailure(F) {}
84  void Profile(llvm::FoldingSetNodeID &ID) const {
85    ID.AddInteger(IsFreeOnFailure);
86    ID.AddPointer(ReallocatedSym);
87  }
88  bool operator==(const ReallocPair &X) const {
89    return ReallocatedSym == X.ReallocatedSym &&
90           IsFreeOnFailure == X.IsFreeOnFailure;
91  }
92};
93
94typedef std::pair<const Stmt*, const MemRegion*> LeakInfo;
95
96class MallocChecker : public Checker<check::DeadSymbols,
97                                     check::EndPath,
98                                     check::PreStmt<ReturnStmt>,
99                                     check::PreStmt<CallExpr>,
100                                     check::PostStmt<CallExpr>,
101                                     check::PostStmt<BlockExpr>,
102                                     check::PreObjCMessage,
103                                     check::Location,
104                                     check::Bind,
105                                     eval::Assume,
106                                     check::RegionChanges>
107{
108  mutable OwningPtr<BugType> BT_DoubleFree;
109  mutable OwningPtr<BugType> BT_Leak;
110  mutable OwningPtr<BugType> BT_UseFree;
111  mutable OwningPtr<BugType> BT_BadFree;
112  mutable IdentifierInfo *II_malloc, *II_free, *II_realloc, *II_calloc,
113                         *II_valloc, *II_reallocf, *II_strndup, *II_strdup;
114
115public:
116  MallocChecker() : II_malloc(0), II_free(0), II_realloc(0), II_calloc(0),
117                    II_valloc(0), II_reallocf(0), II_strndup(0), II_strdup(0) {}
118
119  /// In pessimistic mode, the checker assumes that it does not know which
120  /// functions might free the memory.
121  struct ChecksFilter {
122    DefaultBool CMallocPessimistic;
123    DefaultBool CMallocOptimistic;
124  };
125
126  ChecksFilter Filter;
127
128  void checkPreStmt(const CallExpr *S, CheckerContext &C) const;
129  void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
130  void checkPreObjCMessage(const ObjCMethodCall &Call, CheckerContext &C) const;
131  void checkPostStmt(const BlockExpr *BE, CheckerContext &C) const;
132  void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
133  void checkEndPath(CheckerContext &C) const;
134  void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
135  ProgramStateRef evalAssume(ProgramStateRef state, SVal Cond,
136                            bool Assumption) const;
137  void checkLocation(SVal l, bool isLoad, const Stmt *S,
138                     CheckerContext &C) const;
139  void checkBind(SVal location, SVal val, const Stmt*S,
140                 CheckerContext &C) const;
141  ProgramStateRef
142  checkRegionChanges(ProgramStateRef state,
143                     const StoreManager::InvalidatedSymbols *invalidated,
144                     ArrayRef<const MemRegion *> ExplicitRegions,
145                     ArrayRef<const MemRegion *> Regions,
146                     const CallEvent *Call) const;
147  bool wantsRegionChangeUpdate(ProgramStateRef state) const {
148    return true;
149  }
150
151  void printState(raw_ostream &Out, ProgramStateRef State,
152                  const char *NL, const char *Sep) const;
153
154private:
155  void initIdentifierInfo(ASTContext &C) const;
156
157  /// Check if this is one of the functions which can allocate/reallocate memory
158  /// pointed to by one of its arguments.
159  bool isMemFunction(const FunctionDecl *FD, ASTContext &C) const;
160  bool isFreeFunction(const FunctionDecl *FD, ASTContext &C) const;
161  bool isAllocationFunction(const FunctionDecl *FD, ASTContext &C) const;
162
163  static ProgramStateRef MallocMemReturnsAttr(CheckerContext &C,
164                                              const CallExpr *CE,
165                                              const OwnershipAttr* Att);
166  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
167                                     const Expr *SizeEx, SVal Init,
168                                     ProgramStateRef state) {
169    return MallocMemAux(C, CE,
170                        state->getSVal(SizeEx, C.getLocationContext()),
171                        Init, state);
172  }
173
174  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
175                                     SVal SizeEx, SVal Init,
176                                     ProgramStateRef state);
177
178  /// Update the RefState to reflect the new memory allocation.
179  static ProgramStateRef MallocUpdateRefState(CheckerContext &C,
180                                              const CallExpr *CE,
181                                              ProgramStateRef state);
182
183  ProgramStateRef FreeMemAttr(CheckerContext &C, const CallExpr *CE,
184                              const OwnershipAttr* Att) const;
185  ProgramStateRef FreeMemAux(CheckerContext &C, const CallExpr *CE,
186                             ProgramStateRef state, unsigned Num,
187                             bool Hold,
188                             bool &ReleasedAllocated) const;
189  ProgramStateRef FreeMemAux(CheckerContext &C, const Expr *Arg,
190                             const Expr *ParentExpr,
191                             ProgramStateRef state,
192                             bool Hold,
193                             bool &ReleasedAllocated) const;
194
195  ProgramStateRef ReallocMem(CheckerContext &C, const CallExpr *CE,
196                             bool FreesMemOnFailure) const;
197  static ProgramStateRef CallocMem(CheckerContext &C, const CallExpr *CE);
198
199  ///\brief Check if the memory associated with this symbol was released.
200  bool isReleased(SymbolRef Sym, CheckerContext &C) const;
201
202  bool checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
203                         const Stmt *S = 0) const;
204
205  /// Check if the function is not known to us. So, for example, we could
206  /// conservatively assume it can free/reallocate it's pointer arguments.
207  bool doesNotFreeMemory(const CallEvent *Call,
208                         ProgramStateRef State) const;
209
210  static bool SummarizeValue(raw_ostream &os, SVal V);
211  static bool SummarizeRegion(raw_ostream &os, const MemRegion *MR);
212  void ReportBadFree(CheckerContext &C, SVal ArgVal, SourceRange range) const;
213
214  /// Find the location of the allocation for Sym on the path leading to the
215  /// exploded node N.
216  LeakInfo getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
217                             CheckerContext &C) const;
218
219  void reportLeak(SymbolRef Sym, ExplodedNode *N, CheckerContext &C) const;
220
221  /// The bug visitor which allows us to print extra diagnostics along the
222  /// BugReport path. For example, showing the allocation site of the leaked
223  /// region.
224  class MallocBugVisitor : public BugReporterVisitorImpl<MallocBugVisitor> {
225  protected:
226    enum NotificationMode {
227      Normal,
228      ReallocationFailed
229    };
230
231    // The allocated region symbol tracked by the main analysis.
232    SymbolRef Sym;
233
234    // The mode we are in, i.e. what kind of diagnostics will be emitted.
235    NotificationMode Mode;
236
237    // A symbol from when the primary region should have been reallocated.
238    SymbolRef FailedReallocSymbol;
239
240    bool IsLeak;
241
242  public:
243    MallocBugVisitor(SymbolRef S, bool isLeak = false)
244       : Sym(S), Mode(Normal), FailedReallocSymbol(0), IsLeak(isLeak) {}
245
246    virtual ~MallocBugVisitor() {}
247
248    void Profile(llvm::FoldingSetNodeID &ID) const {
249      static int X = 0;
250      ID.AddPointer(&X);
251      ID.AddPointer(Sym);
252    }
253
254    inline bool isAllocated(const RefState *S, const RefState *SPrev,
255                            const Stmt *Stmt) {
256      // Did not track -> allocated. Other state (released) -> allocated.
257      return (Stmt && isa<CallExpr>(Stmt) &&
258              (S && S->isAllocated()) && (!SPrev || !SPrev->isAllocated()));
259    }
260
261    inline bool isReleased(const RefState *S, const RefState *SPrev,
262                           const Stmt *Stmt) {
263      // Did not track -> released. Other state (allocated) -> released.
264      return (Stmt && isa<CallExpr>(Stmt) &&
265              (S && S->isReleased()) && (!SPrev || !SPrev->isReleased()));
266    }
267
268    inline bool isRelinquished(const RefState *S, const RefState *SPrev,
269                               const Stmt *Stmt) {
270      // Did not track -> relinquished. Other state (allocated) -> relinquished.
271      return (Stmt && (isa<CallExpr>(Stmt) || isa<ObjCMessageExpr>(Stmt) ||
272                                              isa<ObjCPropertyRefExpr>(Stmt)) &&
273              (S && S->isRelinquished()) &&
274              (!SPrev || !SPrev->isRelinquished()));
275    }
276
277    inline bool isReallocFailedCheck(const RefState *S, const RefState *SPrev,
278                                     const Stmt *Stmt) {
279      // If the expression is not a call, and the state change is
280      // released -> allocated, it must be the realloc return value
281      // check. If we have to handle more cases here, it might be cleaner just
282      // to track this extra bit in the state itself.
283      return ((!Stmt || !isa<CallExpr>(Stmt)) &&
284              (S && S->isAllocated()) && (SPrev && !SPrev->isAllocated()));
285    }
286
287    PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
288                                   const ExplodedNode *PrevN,
289                                   BugReporterContext &BRC,
290                                   BugReport &BR);
291
292    PathDiagnosticPiece* getEndPath(BugReporterContext &BRC,
293                                    const ExplodedNode *EndPathNode,
294                                    BugReport &BR) {
295      if (!IsLeak)
296        return 0;
297
298      PathDiagnosticLocation L =
299        PathDiagnosticLocation::createEndOfPath(EndPathNode,
300                                                BRC.getSourceManager());
301      // Do not add the statement itself as a range in case of leak.
302      return new PathDiagnosticEventPiece(L, BR.getDescription(), false);
303    }
304
305  private:
306    class StackHintGeneratorForReallocationFailed
307        : public StackHintGeneratorForSymbol {
308    public:
309      StackHintGeneratorForReallocationFailed(SymbolRef S, StringRef M)
310        : StackHintGeneratorForSymbol(S, M) {}
311
312      virtual std::string getMessageForArg(const Expr *ArgE, unsigned ArgIndex) {
313        SmallString<200> buf;
314        llvm::raw_svector_ostream os(buf);
315
316        os << "Reallocation of ";
317        // Printed parameters start at 1, not 0.
318        printOrdinal(++ArgIndex, os);
319        os << " parameter failed";
320
321        return os.str();
322      }
323
324      virtual std::string getMessageForReturn(const CallExpr *CallExpr) {
325        return "Reallocation of returned value failed";
326      }
327    };
328  };
329};
330} // end anonymous namespace
331
332typedef llvm::ImmutableMap<SymbolRef, RefState> RegionStateTy;
333typedef llvm::ImmutableMap<SymbolRef, ReallocPair > ReallocMap;
334class RegionState {};
335class ReallocPairs {};
336namespace clang {
337namespace ento {
338  template <>
339  struct ProgramStateTrait<RegionState>
340    : public ProgramStatePartialTrait<RegionStateTy> {
341    static void *GDMIndex() { static int x; return &x; }
342  };
343
344  template <>
345  struct ProgramStateTrait<ReallocPairs>
346    : public ProgramStatePartialTrait<ReallocMap> {
347    static void *GDMIndex() { static int x; return &x; }
348  };
349}
350}
351
352namespace {
353class StopTrackingCallback : public SymbolVisitor {
354  ProgramStateRef state;
355public:
356  StopTrackingCallback(ProgramStateRef st) : state(st) {}
357  ProgramStateRef getState() const { return state; }
358
359  bool VisitSymbol(SymbolRef sym) {
360    state = state->remove<RegionState>(sym);
361    return true;
362  }
363};
364} // end anonymous namespace
365
366void MallocChecker::initIdentifierInfo(ASTContext &Ctx) const {
367  if (II_malloc)
368    return;
369  II_malloc = &Ctx.Idents.get("malloc");
370  II_free = &Ctx.Idents.get("free");
371  II_realloc = &Ctx.Idents.get("realloc");
372  II_reallocf = &Ctx.Idents.get("reallocf");
373  II_calloc = &Ctx.Idents.get("calloc");
374  II_valloc = &Ctx.Idents.get("valloc");
375  II_strdup = &Ctx.Idents.get("strdup");
376  II_strndup = &Ctx.Idents.get("strndup");
377}
378
379bool MallocChecker::isMemFunction(const FunctionDecl *FD, ASTContext &C) const {
380  if (isFreeFunction(FD, C))
381    return true;
382
383  if (isAllocationFunction(FD, C))
384    return true;
385
386  return false;
387}
388
389bool MallocChecker::isAllocationFunction(const FunctionDecl *FD,
390                                         ASTContext &C) const {
391  if (!FD)
392    return false;
393
394  if (FD->getKind() == Decl::Function) {
395    IdentifierInfo *FunI = FD->getIdentifier();
396    initIdentifierInfo(C);
397
398    if (FunI == II_malloc || FunI == II_realloc ||
399        FunI == II_reallocf || FunI == II_calloc || FunI == II_valloc ||
400        FunI == II_strdup || FunI == II_strndup)
401      return true;
402  }
403
404  if (Filter.CMallocOptimistic && FD->hasAttrs())
405    for (specific_attr_iterator<OwnershipAttr>
406           i = FD->specific_attr_begin<OwnershipAttr>(),
407           e = FD->specific_attr_end<OwnershipAttr>();
408           i != e; ++i)
409      if ((*i)->getOwnKind() == OwnershipAttr::Returns)
410        return true;
411  return false;
412}
413
414bool MallocChecker::isFreeFunction(const FunctionDecl *FD, ASTContext &C) const {
415  if (!FD)
416    return false;
417
418  if (FD->getKind() == Decl::Function) {
419    IdentifierInfo *FunI = FD->getIdentifier();
420    initIdentifierInfo(C);
421
422    if (FunI == II_free || FunI == II_realloc || FunI == II_reallocf)
423      return true;
424  }
425
426  if (Filter.CMallocOptimistic && FD->hasAttrs())
427    for (specific_attr_iterator<OwnershipAttr>
428           i = FD->specific_attr_begin<OwnershipAttr>(),
429           e = FD->specific_attr_end<OwnershipAttr>();
430           i != e; ++i)
431      if ((*i)->getOwnKind() == OwnershipAttr::Takes ||
432          (*i)->getOwnKind() == OwnershipAttr::Holds)
433        return true;
434  return false;
435}
436
437void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const {
438  const FunctionDecl *FD = C.getCalleeDecl(CE);
439  if (!FD)
440    return;
441
442  ProgramStateRef State = C.getState();
443  bool ReleasedAllocatedMemory = false;
444
445  if (FD->getKind() == Decl::Function) {
446    initIdentifierInfo(C.getASTContext());
447    IdentifierInfo *FunI = FD->getIdentifier();
448
449    if (FunI == II_malloc || FunI == II_valloc) {
450      if (CE->getNumArgs() < 1)
451        return;
452      State = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(), State);
453    } else if (FunI == II_realloc) {
454      State = ReallocMem(C, CE, false);
455    } else if (FunI == II_reallocf) {
456      State = ReallocMem(C, CE, true);
457    } else if (FunI == II_calloc) {
458      State = CallocMem(C, CE);
459    } else if (FunI == II_free) {
460      State = FreeMemAux(C, CE, State, 0, false, ReleasedAllocatedMemory);
461    } else if (FunI == II_strdup) {
462      State = MallocUpdateRefState(C, CE, State);
463    } else if (FunI == II_strndup) {
464      State = MallocUpdateRefState(C, CE, State);
465    }
466  }
467
468  if (Filter.CMallocOptimistic) {
469    // Check all the attributes, if there are any.
470    // There can be multiple of these attributes.
471    if (FD->hasAttrs())
472      for (specific_attr_iterator<OwnershipAttr>
473          i = FD->specific_attr_begin<OwnershipAttr>(),
474          e = FD->specific_attr_end<OwnershipAttr>();
475          i != e; ++i) {
476        switch ((*i)->getOwnKind()) {
477        case OwnershipAttr::Returns:
478          State = MallocMemReturnsAttr(C, CE, *i);
479          break;
480        case OwnershipAttr::Takes:
481        case OwnershipAttr::Holds:
482          State = FreeMemAttr(C, CE, *i);
483          break;
484        }
485      }
486  }
487  C.addTransition(State);
488}
489
490static bool isFreeWhenDoneSetToZero(const ObjCMethodCall &Call) {
491  Selector S = Call.getSelector();
492  for (unsigned i = 1; i < S.getNumArgs(); ++i)
493    if (S.getNameForSlot(i).equals("freeWhenDone"))
494      if (Call.getArgSVal(i).isConstant(0))
495        return true;
496
497  return false;
498}
499
500void MallocChecker::checkPreObjCMessage(const ObjCMethodCall &Call,
501                                        CheckerContext &C) const {
502  // If the first selector is dataWithBytesNoCopy, assume that the memory will
503  // be released with 'free' by the new object.
504  // Ex:  [NSData dataWithBytesNoCopy:bytes length:10];
505  // Unless 'freeWhenDone' param set to 0.
506  // TODO: Check that the memory was allocated with malloc.
507  bool ReleasedAllocatedMemory = false;
508  Selector S = Call.getSelector();
509  if ((S.getNameForSlot(0) == "dataWithBytesNoCopy" ||
510       S.getNameForSlot(0) == "initWithBytesNoCopy" ||
511       S.getNameForSlot(0) == "initWithCharactersNoCopy") &&
512      !isFreeWhenDoneSetToZero(Call)){
513    unsigned int argIdx  = 0;
514    C.addTransition(FreeMemAux(C, Call.getArgExpr(argIdx),
515                    Call.getOriginExpr(), C.getState(), true,
516                    ReleasedAllocatedMemory));
517  }
518}
519
520ProgramStateRef MallocChecker::MallocMemReturnsAttr(CheckerContext &C,
521                                                    const CallExpr *CE,
522                                                    const OwnershipAttr* Att) {
523  if (Att->getModule() != "malloc")
524    return 0;
525
526  OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
527  if (I != E) {
528    return MallocMemAux(C, CE, CE->getArg(*I), UndefinedVal(), C.getState());
529  }
530  return MallocMemAux(C, CE, UnknownVal(), UndefinedVal(), C.getState());
531}
532
533ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
534                                           const CallExpr *CE,
535                                           SVal Size, SVal Init,
536                                           ProgramStateRef state) {
537
538  // Bind the return value to the symbolic value from the heap region.
539  // TODO: We could rewrite post visit to eval call; 'malloc' does not have
540  // side effects other than what we model here.
541  unsigned Count = C.blockCount();
542  SValBuilder &svalBuilder = C.getSValBuilder();
543  const LocationContext *LCtx = C.getPredecessor()->getLocationContext();
544  DefinedSVal RetVal =
545    cast<DefinedSVal>(svalBuilder.getConjuredHeapSymbolVal(CE, LCtx, Count));
546  state = state->BindExpr(CE, C.getLocationContext(), RetVal);
547
548  // We expect the malloc functions to return a pointer.
549  if (!isa<Loc>(RetVal))
550    return 0;
551
552  // Fill the region with the initialization value.
553  state = state->bindDefault(RetVal, Init);
554
555  // Set the region's extent equal to the Size parameter.
556  const SymbolicRegion *R =
557      dyn_cast_or_null<SymbolicRegion>(RetVal.getAsRegion());
558  if (!R)
559    return 0;
560  if (isa<DefinedOrUnknownSVal>(Size)) {
561    SValBuilder &svalBuilder = C.getSValBuilder();
562    DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
563    DefinedOrUnknownSVal DefinedSize = cast<DefinedOrUnknownSVal>(Size);
564    DefinedOrUnknownSVal extentMatchesSize =
565        svalBuilder.evalEQ(state, Extent, DefinedSize);
566
567    state = state->assume(extentMatchesSize, true);
568    assert(state);
569  }
570
571  return MallocUpdateRefState(C, CE, state);
572}
573
574ProgramStateRef MallocChecker::MallocUpdateRefState(CheckerContext &C,
575                                                    const CallExpr *CE,
576                                                    ProgramStateRef state) {
577  // Get the return value.
578  SVal retVal = state->getSVal(CE, C.getLocationContext());
579
580  // We expect the malloc functions to return a pointer.
581  if (!isa<Loc>(retVal))
582    return 0;
583
584  SymbolRef Sym = retVal.getAsLocSymbol();
585  assert(Sym);
586
587  // Set the symbol's state to Allocated.
588  return state->set<RegionState>(Sym, RefState::getAllocated(CE));
589
590}
591
592ProgramStateRef MallocChecker::FreeMemAttr(CheckerContext &C,
593                                           const CallExpr *CE,
594                                           const OwnershipAttr* Att) const {
595  if (Att->getModule() != "malloc")
596    return 0;
597
598  ProgramStateRef State = C.getState();
599  bool ReleasedAllocated = false;
600
601  for (OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
602       I != E; ++I) {
603    ProgramStateRef StateI = FreeMemAux(C, CE, State, *I,
604                               Att->getOwnKind() == OwnershipAttr::Holds,
605                               ReleasedAllocated);
606    if (StateI)
607      State = StateI;
608  }
609  return State;
610}
611
612ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
613                                          const CallExpr *CE,
614                                          ProgramStateRef state,
615                                          unsigned Num,
616                                          bool Hold,
617                                          bool &ReleasedAllocated) const {
618  if (CE->getNumArgs() < (Num + 1))
619    return 0;
620
621  return FreeMemAux(C, CE->getArg(Num), CE, state, Hold, ReleasedAllocated);
622}
623
624ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
625                                          const Expr *ArgExpr,
626                                          const Expr *ParentExpr,
627                                          ProgramStateRef state,
628                                          bool Hold,
629                                          bool &ReleasedAllocated) const {
630
631  SVal ArgVal = state->getSVal(ArgExpr, C.getLocationContext());
632  if (!isa<DefinedOrUnknownSVal>(ArgVal))
633    return 0;
634  DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(ArgVal);
635
636  // Check for null dereferences.
637  if (!isa<Loc>(location))
638    return 0;
639
640  // The explicit NULL case, no operation is performed.
641  ProgramStateRef notNullState, nullState;
642  llvm::tie(notNullState, nullState) = state->assume(location);
643  if (nullState && !notNullState)
644    return 0;
645
646  // Unknown values could easily be okay
647  // Undefined values are handled elsewhere
648  if (ArgVal.isUnknownOrUndef())
649    return 0;
650
651  const MemRegion *R = ArgVal.getAsRegion();
652
653  // Nonlocs can't be freed, of course.
654  // Non-region locations (labels and fixed addresses) also shouldn't be freed.
655  if (!R) {
656    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
657    return 0;
658  }
659
660  R = R->StripCasts();
661
662  // Blocks might show up as heap data, but should not be free()d
663  if (isa<BlockDataRegion>(R)) {
664    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
665    return 0;
666  }
667
668  const MemSpaceRegion *MS = R->getMemorySpace();
669
670  // Parameters, locals, statics, and globals shouldn't be freed.
671  if (!(isa<UnknownSpaceRegion>(MS) || isa<HeapSpaceRegion>(MS))) {
672    // FIXME: at the time this code was written, malloc() regions were
673    // represented by conjured symbols, which are all in UnknownSpaceRegion.
674    // This means that there isn't actually anything from HeapSpaceRegion
675    // that should be freed, even though we allow it here.
676    // Of course, free() can work on memory allocated outside the current
677    // function, so UnknownSpaceRegion is always a possibility.
678    // False negatives are better than false positives.
679
680    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
681    return 0;
682  }
683
684  const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
685  // Various cases could lead to non-symbol values here.
686  // For now, ignore them.
687  if (!SR)
688    return 0;
689
690  SymbolRef Sym = SR->getSymbol();
691  const RefState *RS = state->get<RegionState>(Sym);
692
693  // Check double free.
694  if (RS && (RS->isReleased() || RS->isRelinquished())) {
695    if (ExplodedNode *N = C.generateSink()) {
696      if (!BT_DoubleFree)
697        BT_DoubleFree.reset(
698          new BugType("Double free", "Memory Error"));
699      BugReport *R = new BugReport(*BT_DoubleFree,
700        (RS->isReleased() ? "Attempt to free released memory" :
701                            "Attempt to free non-owned memory"), N);
702      R->addRange(ArgExpr->getSourceRange());
703      R->markInteresting(Sym);
704      R->addVisitor(new MallocBugVisitor(Sym));
705      C.EmitReport(R);
706    }
707    return 0;
708  }
709
710  ReleasedAllocated = (RS != 0);
711
712  // Normal free.
713  if (Hold)
714    return state->set<RegionState>(Sym, RefState::getRelinquished(ParentExpr));
715  return state->set<RegionState>(Sym, RefState::getReleased(ParentExpr));
716}
717
718bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) {
719  if (nonloc::ConcreteInt *IntVal = dyn_cast<nonloc::ConcreteInt>(&V))
720    os << "an integer (" << IntVal->getValue() << ")";
721  else if (loc::ConcreteInt *ConstAddr = dyn_cast<loc::ConcreteInt>(&V))
722    os << "a constant address (" << ConstAddr->getValue() << ")";
723  else if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&V))
724    os << "the address of the label '" << Label->getLabel()->getName() << "'";
725  else
726    return false;
727
728  return true;
729}
730
731bool MallocChecker::SummarizeRegion(raw_ostream &os,
732                                    const MemRegion *MR) {
733  switch (MR->getKind()) {
734  case MemRegion::FunctionTextRegionKind: {
735    const FunctionDecl *FD = cast<FunctionTextRegion>(MR)->getDecl();
736    if (FD)
737      os << "the address of the function '" << *FD << '\'';
738    else
739      os << "the address of a function";
740    return true;
741  }
742  case MemRegion::BlockTextRegionKind:
743    os << "block text";
744    return true;
745  case MemRegion::BlockDataRegionKind:
746    // FIXME: where the block came from?
747    os << "a block";
748    return true;
749  default: {
750    const MemSpaceRegion *MS = MR->getMemorySpace();
751
752    if (isa<StackLocalsSpaceRegion>(MS)) {
753      const VarRegion *VR = dyn_cast<VarRegion>(MR);
754      const VarDecl *VD;
755      if (VR)
756        VD = VR->getDecl();
757      else
758        VD = NULL;
759
760      if (VD)
761        os << "the address of the local variable '" << VD->getName() << "'";
762      else
763        os << "the address of a local stack variable";
764      return true;
765    }
766
767    if (isa<StackArgumentsSpaceRegion>(MS)) {
768      const VarRegion *VR = dyn_cast<VarRegion>(MR);
769      const VarDecl *VD;
770      if (VR)
771        VD = VR->getDecl();
772      else
773        VD = NULL;
774
775      if (VD)
776        os << "the address of the parameter '" << VD->getName() << "'";
777      else
778        os << "the address of a parameter";
779      return true;
780    }
781
782    if (isa<GlobalsSpaceRegion>(MS)) {
783      const VarRegion *VR = dyn_cast<VarRegion>(MR);
784      const VarDecl *VD;
785      if (VR)
786        VD = VR->getDecl();
787      else
788        VD = NULL;
789
790      if (VD) {
791        if (VD->isStaticLocal())
792          os << "the address of the static variable '" << VD->getName() << "'";
793        else
794          os << "the address of the global variable '" << VD->getName() << "'";
795      } else
796        os << "the address of a global variable";
797      return true;
798    }
799
800    return false;
801  }
802  }
803}
804
805void MallocChecker::ReportBadFree(CheckerContext &C, SVal ArgVal,
806                                  SourceRange range) const {
807  if (ExplodedNode *N = C.generateSink()) {
808    if (!BT_BadFree)
809      BT_BadFree.reset(new BugType("Bad free", "Memory Error"));
810
811    SmallString<100> buf;
812    llvm::raw_svector_ostream os(buf);
813
814    const MemRegion *MR = ArgVal.getAsRegion();
815    if (MR) {
816      while (const ElementRegion *ER = dyn_cast<ElementRegion>(MR))
817        MR = ER->getSuperRegion();
818
819      // Special case for alloca()
820      if (isa<AllocaRegion>(MR))
821        os << "Argument to free() was allocated by alloca(), not malloc()";
822      else {
823        os << "Argument to free() is ";
824        if (SummarizeRegion(os, MR))
825          os << ", which is not memory allocated by malloc()";
826        else
827          os << "not memory allocated by malloc()";
828      }
829    } else {
830      os << "Argument to free() is ";
831      if (SummarizeValue(os, ArgVal))
832        os << ", which is not memory allocated by malloc()";
833      else
834        os << "not memory allocated by malloc()";
835    }
836
837    BugReport *R = new BugReport(*BT_BadFree, os.str(), N);
838    R->markInteresting(MR);
839    R->addRange(range);
840    C.EmitReport(R);
841  }
842}
843
844ProgramStateRef MallocChecker::ReallocMem(CheckerContext &C,
845                                          const CallExpr *CE,
846                                          bool FreesOnFail) const {
847  if (CE->getNumArgs() < 2)
848    return 0;
849
850  ProgramStateRef state = C.getState();
851  const Expr *arg0Expr = CE->getArg(0);
852  const LocationContext *LCtx = C.getLocationContext();
853  SVal Arg0Val = state->getSVal(arg0Expr, LCtx);
854  if (!isa<DefinedOrUnknownSVal>(Arg0Val))
855    return 0;
856  DefinedOrUnknownSVal arg0Val = cast<DefinedOrUnknownSVal>(Arg0Val);
857
858  SValBuilder &svalBuilder = C.getSValBuilder();
859
860  DefinedOrUnknownSVal PtrEQ =
861    svalBuilder.evalEQ(state, arg0Val, svalBuilder.makeNull());
862
863  // Get the size argument. If there is no size arg then give up.
864  const Expr *Arg1 = CE->getArg(1);
865  if (!Arg1)
866    return 0;
867
868  // Get the value of the size argument.
869  SVal Arg1ValG = state->getSVal(Arg1, LCtx);
870  if (!isa<DefinedOrUnknownSVal>(Arg1ValG))
871    return 0;
872  DefinedOrUnknownSVal Arg1Val = cast<DefinedOrUnknownSVal>(Arg1ValG);
873
874  // Compare the size argument to 0.
875  DefinedOrUnknownSVal SizeZero =
876    svalBuilder.evalEQ(state, Arg1Val,
877                       svalBuilder.makeIntValWithPtrWidth(0, false));
878
879  ProgramStateRef StatePtrIsNull, StatePtrNotNull;
880  llvm::tie(StatePtrIsNull, StatePtrNotNull) = state->assume(PtrEQ);
881  ProgramStateRef StateSizeIsZero, StateSizeNotZero;
882  llvm::tie(StateSizeIsZero, StateSizeNotZero) = state->assume(SizeZero);
883  // We only assume exceptional states if they are definitely true; if the
884  // state is under-constrained, assume regular realloc behavior.
885  bool PrtIsNull = StatePtrIsNull && !StatePtrNotNull;
886  bool SizeIsZero = StateSizeIsZero && !StateSizeNotZero;
887
888  // If the ptr is NULL and the size is not 0, the call is equivalent to
889  // malloc(size).
890  if ( PrtIsNull && !SizeIsZero) {
891    ProgramStateRef stateMalloc = MallocMemAux(C, CE, CE->getArg(1),
892                                               UndefinedVal(), StatePtrIsNull);
893    return stateMalloc;
894  }
895
896  if (PrtIsNull && SizeIsZero)
897    return 0;
898
899  // Get the from and to pointer symbols as in toPtr = realloc(fromPtr, size).
900  assert(!PrtIsNull);
901  SymbolRef FromPtr = arg0Val.getAsSymbol();
902  SVal RetVal = state->getSVal(CE, LCtx);
903  SymbolRef ToPtr = RetVal.getAsSymbol();
904  if (!FromPtr || !ToPtr)
905    return 0;
906
907  bool ReleasedAllocated = false;
908
909  // If the size is 0, free the memory.
910  if (SizeIsZero)
911    if (ProgramStateRef stateFree = FreeMemAux(C, CE, StateSizeIsZero, 0,
912                                               false, ReleasedAllocated)){
913      // The semantics of the return value are:
914      // If size was equal to 0, either NULL or a pointer suitable to be passed
915      // to free() is returned. We just free the input pointer and do not add
916      // any constrains on the output pointer.
917      return stateFree;
918    }
919
920  // Default behavior.
921  if (ProgramStateRef stateFree =
922        FreeMemAux(C, CE, state, 0, false, ReleasedAllocated)) {
923
924    ProgramStateRef stateRealloc = MallocMemAux(C, CE, CE->getArg(1),
925                                                UnknownVal(), stateFree);
926    if (!stateRealloc)
927      return 0;
928
929    // Record the info about the reallocated symbol so that we could properly
930    // process failed reallocation.
931    stateRealloc = stateRealloc->set<ReallocPairs>(ToPtr,
932                     ReallocPair(FromPtr, FreesOnFail || !ReleasedAllocated));
933    // The reallocated symbol should stay alive for as long as the new symbol.
934    C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
935    return stateRealloc;
936  }
937  return 0;
938}
939
940ProgramStateRef MallocChecker::CallocMem(CheckerContext &C, const CallExpr *CE){
941  if (CE->getNumArgs() < 2)
942    return 0;
943
944  ProgramStateRef state = C.getState();
945  SValBuilder &svalBuilder = C.getSValBuilder();
946  const LocationContext *LCtx = C.getLocationContext();
947  SVal count = state->getSVal(CE->getArg(0), LCtx);
948  SVal elementSize = state->getSVal(CE->getArg(1), LCtx);
949  SVal TotalSize = svalBuilder.evalBinOp(state, BO_Mul, count, elementSize,
950                                        svalBuilder.getContext().getSizeType());
951  SVal zeroVal = svalBuilder.makeZeroVal(svalBuilder.getContext().CharTy);
952
953  return MallocMemAux(C, CE, TotalSize, zeroVal, state);
954}
955
956LeakInfo
957MallocChecker::getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
958                                 CheckerContext &C) const {
959  const LocationContext *LeakContext = N->getLocationContext();
960  // Walk the ExplodedGraph backwards and find the first node that referred to
961  // the tracked symbol.
962  const ExplodedNode *AllocNode = N;
963  const MemRegion *ReferenceRegion = 0;
964
965  while (N) {
966    ProgramStateRef State = N->getState();
967    if (!State->get<RegionState>(Sym))
968      break;
969
970    // Find the most recent expression bound to the symbol in the current
971    // context.
972    if (!ReferenceRegion) {
973      if (const MemRegion *MR = C.getLocationRegionIfPostStore(N)) {
974        SVal Val = State->getSVal(MR);
975        if (Val.getAsLocSymbol() == Sym)
976          ReferenceRegion = MR;
977      }
978    }
979
980    // Allocation node, is the last node in the current context in which the
981    // symbol was tracked.
982    if (N->getLocationContext() == LeakContext)
983      AllocNode = N;
984    N = N->pred_empty() ? NULL : *(N->pred_begin());
985  }
986
987  ProgramPoint P = AllocNode->getLocation();
988  const Stmt *AllocationStmt = 0;
989  if (CallExitEnd *Exit = dyn_cast<CallExitEnd>(&P))
990    AllocationStmt = Exit->getCalleeContext()->getCallSite();
991  else if (StmtPoint *SP = dyn_cast<StmtPoint>(&P))
992    AllocationStmt = SP->getStmt();
993
994  return LeakInfo(AllocationStmt, ReferenceRegion);
995}
996
997void MallocChecker::reportLeak(SymbolRef Sym, ExplodedNode *N,
998                               CheckerContext &C) const {
999  assert(N);
1000  if (!BT_Leak) {
1001    BT_Leak.reset(new BugType("Memory leak", "Memory Error"));
1002    // Leaks should not be reported if they are post-dominated by a sink:
1003    // (1) Sinks are higher importance bugs.
1004    // (2) NoReturnFunctionChecker uses sink nodes to represent paths ending
1005    //     with __noreturn functions such as assert() or exit(). We choose not
1006    //     to report leaks on such paths.
1007    BT_Leak->setSuppressOnSink(true);
1008  }
1009
1010  // Most bug reports are cached at the location where they occurred.
1011  // With leaks, we want to unique them by the location where they were
1012  // allocated, and only report a single path.
1013  PathDiagnosticLocation LocUsedForUniqueing;
1014  const Stmt *AllocStmt = 0;
1015  const MemRegion *Region = 0;
1016  llvm::tie(AllocStmt, Region) = getAllocationSite(N, Sym, C);
1017  if (AllocStmt)
1018    LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt,
1019                            C.getSourceManager(), N->getLocationContext());
1020
1021  SmallString<200> buf;
1022  llvm::raw_svector_ostream os(buf);
1023  os << "Memory is never released; potential leak";
1024  if (Region && Region->canPrintPretty()) {
1025    os << " of memory pointed to by '";
1026    Region->printPretty(os);
1027    os << '\'';
1028  }
1029
1030  BugReport *R = new BugReport(*BT_Leak, os.str(), N, LocUsedForUniqueing);
1031  R->markInteresting(Sym);
1032  R->addVisitor(new MallocBugVisitor(Sym, true));
1033  C.EmitReport(R);
1034}
1035
1036void MallocChecker::checkDeadSymbols(SymbolReaper &SymReaper,
1037                                     CheckerContext &C) const
1038{
1039  if (!SymReaper.hasDeadSymbols())
1040    return;
1041
1042  ProgramStateRef state = C.getState();
1043  RegionStateTy RS = state->get<RegionState>();
1044  RegionStateTy::Factory &F = state->get_context<RegionState>();
1045
1046  bool generateReport = false;
1047  llvm::SmallVector<SymbolRef, 2> Errors;
1048  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
1049    if (SymReaper.isDead(I->first)) {
1050      if (I->second.isAllocated()) {
1051        generateReport = true;
1052        Errors.push_back(I->first);
1053      }
1054      // Remove the dead symbol from the map.
1055      RS = F.remove(RS, I->first);
1056
1057    }
1058  }
1059
1060  // Cleanup the Realloc Pairs Map.
1061  ReallocMap RP = state->get<ReallocPairs>();
1062  for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
1063    if (SymReaper.isDead(I->first) ||
1064        SymReaper.isDead(I->second.ReallocatedSym)) {
1065      state = state->remove<ReallocPairs>(I->first);
1066    }
1067  }
1068
1069  // Generate leak node.
1070  static SimpleProgramPointTag Tag("MallocChecker : DeadSymbolsLeak");
1071  ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
1072
1073  if (generateReport) {
1074    for (llvm::SmallVector<SymbolRef, 2>::iterator
1075         I = Errors.begin(), E = Errors.end(); I != E; ++I) {
1076      reportLeak(*I, N, C);
1077    }
1078  }
1079  C.addTransition(state->set<RegionState>(RS), N);
1080}
1081
1082void MallocChecker::checkEndPath(CheckerContext &C) const {
1083  ProgramStateRef state = C.getState();
1084  RegionStateTy M = state->get<RegionState>();
1085
1086  // If inside inlined call, skip it.
1087  if (C.getLocationContext()->getParent() != 0)
1088    return;
1089
1090  for (RegionStateTy::iterator I = M.begin(), E = M.end(); I != E; ++I) {
1091    RefState RS = I->second;
1092    if (RS.isAllocated()) {
1093      ExplodedNode *N = C.addTransition(state);
1094      if (N)
1095        reportLeak(I->first, N, C);
1096    }
1097  }
1098}
1099
1100void MallocChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const {
1101  // We will check for double free in the post visit.
1102  if (isFreeFunction(C.getCalleeDecl(CE), C.getASTContext()))
1103    return;
1104
1105  // Check use after free, when a freed pointer is passed to a call.
1106  ProgramStateRef State = C.getState();
1107  for (CallExpr::const_arg_iterator I = CE->arg_begin(),
1108                                    E = CE->arg_end(); I != E; ++I) {
1109    const Expr *A = *I;
1110    if (A->getType().getTypePtr()->isAnyPointerType()) {
1111      SymbolRef Sym = State->getSVal(A, C.getLocationContext()).getAsSymbol();
1112      if (!Sym)
1113        continue;
1114      if (checkUseAfterFree(Sym, C, A))
1115        return;
1116    }
1117  }
1118}
1119
1120void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const {
1121  const Expr *E = S->getRetValue();
1122  if (!E)
1123    return;
1124
1125  // Check if we are returning a symbol.
1126  ProgramStateRef State = C.getState();
1127  SVal RetVal = State->getSVal(E, C.getLocationContext());
1128  SymbolRef Sym = RetVal.getAsSymbol();
1129  if (!Sym)
1130    // If we are returning a field of the allocated struct or an array element,
1131    // the callee could still free the memory.
1132    // TODO: This logic should be a part of generic symbol escape callback.
1133    if (const MemRegion *MR = RetVal.getAsRegion())
1134      if (isa<FieldRegion>(MR) || isa<ElementRegion>(MR))
1135        if (const SymbolicRegion *BMR =
1136              dyn_cast<SymbolicRegion>(MR->getBaseRegion()))
1137          Sym = BMR->getSymbol();
1138
1139  // Check if we are returning freed memory.
1140  if (Sym)
1141    if (checkUseAfterFree(Sym, C, E))
1142      return;
1143
1144  // If this function body is not inlined, stop tracking any returned symbols.
1145  if (C.getLocationContext()->getParent() == 0) {
1146    State =
1147      State->scanReachableSymbols<StopTrackingCallback>(RetVal).getState();
1148    C.addTransition(State);
1149  }
1150}
1151
1152// TODO: Blocks should be either inlined or should call invalidate regions
1153// upon invocation. After that's in place, special casing here will not be
1154// needed.
1155void MallocChecker::checkPostStmt(const BlockExpr *BE,
1156                                  CheckerContext &C) const {
1157
1158  // Scan the BlockDecRefExprs for any object the retain count checker
1159  // may be tracking.
1160  if (!BE->getBlockDecl()->hasCaptures())
1161    return;
1162
1163  ProgramStateRef state = C.getState();
1164  const BlockDataRegion *R =
1165    cast<BlockDataRegion>(state->getSVal(BE,
1166                                         C.getLocationContext()).getAsRegion());
1167
1168  BlockDataRegion::referenced_vars_iterator I = R->referenced_vars_begin(),
1169                                            E = R->referenced_vars_end();
1170
1171  if (I == E)
1172    return;
1173
1174  SmallVector<const MemRegion*, 10> Regions;
1175  const LocationContext *LC = C.getLocationContext();
1176  MemRegionManager &MemMgr = C.getSValBuilder().getRegionManager();
1177
1178  for ( ; I != E; ++I) {
1179    const VarRegion *VR = *I;
1180    if (VR->getSuperRegion() == R) {
1181      VR = MemMgr.getVarRegion(VR->getDecl(), LC);
1182    }
1183    Regions.push_back(VR);
1184  }
1185
1186  state =
1187    state->scanReachableSymbols<StopTrackingCallback>(Regions.data(),
1188                                    Regions.data() + Regions.size()).getState();
1189  C.addTransition(state);
1190}
1191
1192bool MallocChecker::isReleased(SymbolRef Sym, CheckerContext &C) const {
1193  assert(Sym);
1194  const RefState *RS = C.getState()->get<RegionState>(Sym);
1195  return (RS && RS->isReleased());
1196}
1197
1198bool MallocChecker::checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
1199                                      const Stmt *S) const {
1200  if (isReleased(Sym, C)) {
1201    if (ExplodedNode *N = C.generateSink()) {
1202      if (!BT_UseFree)
1203        BT_UseFree.reset(new BugType("Use-after-free", "Memory Error"));
1204
1205      BugReport *R = new BugReport(*BT_UseFree,
1206                                   "Use of memory after it is freed",N);
1207      if (S)
1208        R->addRange(S->getSourceRange());
1209      R->markInteresting(Sym);
1210      R->addVisitor(new MallocBugVisitor(Sym));
1211      C.EmitReport(R);
1212      return true;
1213    }
1214  }
1215  return false;
1216}
1217
1218// Check if the location is a freed symbolic region.
1219void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S,
1220                                  CheckerContext &C) const {
1221  SymbolRef Sym = l.getLocSymbolInBase();
1222  if (Sym)
1223    checkUseAfterFree(Sym, C, S);
1224}
1225
1226//===----------------------------------------------------------------------===//
1227// Check various ways a symbol can be invalidated.
1228// TODO: This logic (the next 3 functions) is copied/similar to the
1229// RetainRelease checker. We might want to factor this out.
1230//===----------------------------------------------------------------------===//
1231
1232// Stop tracking symbols when a value escapes as a result of checkBind.
1233// A value escapes in three possible cases:
1234// (1) we are binding to something that is not a memory region.
1235// (2) we are binding to a memregion that does not have stack storage
1236// (3) we are binding to a memregion with stack storage that the store
1237//     does not understand.
1238void MallocChecker::checkBind(SVal loc, SVal val, const Stmt *S,
1239                              CheckerContext &C) const {
1240  // Are we storing to something that causes the value to "escape"?
1241  bool escapes = true;
1242  ProgramStateRef state = C.getState();
1243
1244  if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) {
1245    escapes = !regionLoc->getRegion()->hasStackStorage();
1246
1247    if (!escapes) {
1248      // To test (3), generate a new state with the binding added.  If it is
1249      // the same state, then it escapes (since the store cannot represent
1250      // the binding).
1251      // Do this only if we know that the store is not supposed to generate the
1252      // same state.
1253      SVal StoredVal = state->getSVal(regionLoc->getRegion());
1254      if (StoredVal != val)
1255        escapes = (state == (state->bindLoc(*regionLoc, val)));
1256    }
1257  }
1258
1259  // If our store can represent the binding and we aren't storing to something
1260  // that doesn't have local storage then just return and have the simulation
1261  // state continue as is.
1262  if (!escapes)
1263      return;
1264
1265  // Otherwise, find all symbols referenced by 'val' that we are tracking
1266  // and stop tracking them.
1267  state = state->scanReachableSymbols<StopTrackingCallback>(val).getState();
1268  C.addTransition(state);
1269}
1270
1271// If a symbolic region is assumed to NULL (or another constant), stop tracking
1272// it - assuming that allocation failed on this path.
1273ProgramStateRef MallocChecker::evalAssume(ProgramStateRef state,
1274                                              SVal Cond,
1275                                              bool Assumption) const {
1276  RegionStateTy RS = state->get<RegionState>();
1277  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
1278    // If the symbol is assumed to be NULL, remove it from consideration.
1279    if (state->getConstraintManager().isNull(state, I.getKey()).isTrue())
1280      state = state->remove<RegionState>(I.getKey());
1281  }
1282
1283  // Realloc returns 0 when reallocation fails, which means that we should
1284  // restore the state of the pointer being reallocated.
1285  ReallocMap RP = state->get<ReallocPairs>();
1286  for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
1287    // If the symbol is assumed to be NULL, remove it from consideration.
1288    if (state->getConstraintManager().isNull(state, I.getKey()).isTrue()) {
1289      SymbolRef ReallocSym = I.getData().ReallocatedSym;
1290      if (const RefState *RS = state->get<RegionState>(ReallocSym)) {
1291        if (RS->isReleased() && ! I.getData().IsFreeOnFailure)
1292          state = state->set<RegionState>(ReallocSym,
1293                             RefState::getAllocated(RS->getStmt()));
1294      }
1295      state = state->remove<ReallocPairs>(I.getKey());
1296    }
1297  }
1298
1299  return state;
1300}
1301
1302// Check if the function is known to us. So, for example, we could
1303// conservatively assume it can free/reallocate its pointer arguments.
1304// (We assume that the pointers cannot escape through calls to system
1305// functions not handled by this checker.)
1306bool MallocChecker::doesNotFreeMemory(const CallEvent *Call,
1307                                      ProgramStateRef State) const {
1308  assert(Call);
1309
1310  // For now, assume that any C++ call can free memory.
1311  // TODO: If we want to be more optimistic here, we'll need to make sure that
1312  // regions escape to C++ containers. They seem to do that even now, but for
1313  // mysterious reasons.
1314  if (!(isa<FunctionCall>(Call) || isa<ObjCMethodCall>(Call)))
1315    return false;
1316
1317  // Check Objective-C messages by selector name.
1318  if (const ObjCMethodCall *Msg = dyn_cast<ObjCMethodCall>(Call)) {
1319    // If it's not a framework call, or if it takes a callback, assume it
1320    // can free memory.
1321    if (!Call->isInSystemHeader() || Call->hasNonZeroCallbackArg())
1322      return false;
1323
1324    Selector S = Msg->getSelector();
1325
1326    // Whitelist the ObjC methods which do free memory.
1327    // - Anything containing 'freeWhenDone' param set to 1.
1328    //   Ex: dataWithBytesNoCopy:length:freeWhenDone.
1329    for (unsigned i = 1; i < S.getNumArgs(); ++i) {
1330      if (S.getNameForSlot(i).equals("freeWhenDone")) {
1331        if (Call->getArgSVal(i).isConstant(1))
1332          return false;
1333        else
1334          return true;
1335      }
1336    }
1337
1338    // If the first selector ends with NoCopy, assume that the ownership is
1339    // transferred as well.
1340    // Ex:  [NSData dataWithBytesNoCopy:bytes length:10];
1341    StringRef FirstSlot = S.getNameForSlot(0);
1342    if (FirstSlot.endswith("NoCopy"))
1343      return false;
1344
1345    // If the first selector starts with addPointer, insertPointer,
1346    // or replacePointer, assume we are dealing with NSPointerArray or similar.
1347    // This is similar to C++ containers (vector); we still might want to check
1348    // that the pointers get freed by following the container itself.
1349    if (FirstSlot.startswith("addPointer") ||
1350        FirstSlot.startswith("insertPointer") ||
1351        FirstSlot.startswith("replacePointer")) {
1352      return false;
1353    }
1354
1355    // Otherwise, assume that the method does not free memory.
1356    // Most framework methods do not free memory.
1357    return true;
1358  }
1359
1360  // At this point the only thing left to handle is straight function calls.
1361  const FunctionDecl *FD = cast<FunctionCall>(Call)->getDecl();
1362  if (!FD)
1363    return false;
1364
1365  ASTContext &ASTC = State->getStateManager().getContext();
1366
1367  // If it's one of the allocation functions we can reason about, we model
1368  // its behavior explicitly.
1369  if (isMemFunction(FD, ASTC))
1370    return true;
1371
1372  // If it's not a system call, assume it frees memory.
1373  if (!Call->isInSystemHeader())
1374    return false;
1375
1376  // White list the system functions whose arguments escape.
1377  const IdentifierInfo *II = FD->getIdentifier();
1378  if (!II)
1379    return false;
1380  StringRef FName = II->getName();
1381
1382  // White list the 'XXXNoCopy' CoreFoundation functions.
1383  // We specifically check these before
1384  if (FName.endswith("NoCopy")) {
1385    // Look for the deallocator argument. We know that the memory ownership
1386    // is not transferred only if the deallocator argument is
1387    // 'kCFAllocatorNull'.
1388    for (unsigned i = 1; i < Call->getNumArgs(); ++i) {
1389      const Expr *ArgE = Call->getArgExpr(i)->IgnoreParenCasts();
1390      if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(ArgE)) {
1391        StringRef DeallocatorName = DE->getFoundDecl()->getName();
1392        if (DeallocatorName == "kCFAllocatorNull")
1393          return true;
1394      }
1395    }
1396    return false;
1397  }
1398
1399  // Associating streams with malloced buffers. The pointer can escape if
1400  // 'closefn' is specified (and if that function does free memory),
1401  // but it will not if closefn is not specified.
1402  // Currently, we do not inspect the 'closefn' function (PR12101).
1403  if (FName == "funopen")
1404    if (Call->getNumArgs() >= 4 && Call->getArgSVal(4).isConstant(0))
1405      return true;
1406
1407  // Do not warn on pointers passed to 'setbuf' when used with std streams,
1408  // these leaks might be intentional when setting the buffer for stdio.
1409  // http://stackoverflow.com/questions/2671151/who-frees-setvbuf-buffer
1410  if (FName == "setbuf" || FName =="setbuffer" ||
1411      FName == "setlinebuf" || FName == "setvbuf") {
1412    if (Call->getNumArgs() >= 1) {
1413      const Expr *ArgE = Call->getArgExpr(0)->IgnoreParenCasts();
1414      if (const DeclRefExpr *ArgDRE = dyn_cast<DeclRefExpr>(ArgE))
1415        if (const VarDecl *D = dyn_cast<VarDecl>(ArgDRE->getDecl()))
1416          if (D->getCanonicalDecl()->getName().find("std") != StringRef::npos)
1417            return false;
1418    }
1419  }
1420
1421  // A bunch of other functions which either take ownership of a pointer or
1422  // wrap the result up in a struct or object, meaning it can be freed later.
1423  // (See RetainCountChecker.) Not all the parameters here are invalidated,
1424  // but the Malloc checker cannot differentiate between them. The right way
1425  // of doing this would be to implement a pointer escapes callback.
1426  if (FName == "CGBitmapContextCreate" ||
1427      FName == "CGBitmapContextCreateWithData" ||
1428      FName == "CVPixelBufferCreateWithBytes" ||
1429      FName == "CVPixelBufferCreateWithPlanarBytes" ||
1430      FName == "OSAtomicEnqueue") {
1431    return false;
1432  }
1433
1434  // Handle cases where we know a buffer's /address/ can escape.
1435  // Note that the above checks handle some special cases where we know that
1436  // even though the address escapes, it's still our responsibility to free the
1437  // buffer.
1438  if (Call->argumentsMayEscape())
1439    return false;
1440
1441  // Otherwise, assume that the function does not free memory.
1442  // Most system calls do not free the memory.
1443  return true;
1444}
1445
1446// If the symbol we are tracking is invalidated, but not explicitly (ex: the &p
1447// escapes, when we are tracking p), do not track the symbol as we cannot reason
1448// about it anymore.
1449ProgramStateRef
1450MallocChecker::checkRegionChanges(ProgramStateRef State,
1451                            const StoreManager::InvalidatedSymbols *invalidated,
1452                                    ArrayRef<const MemRegion *> ExplicitRegions,
1453                                    ArrayRef<const MemRegion *> Regions,
1454                                    const CallEvent *Call) const {
1455  if (!invalidated || invalidated->empty())
1456    return State;
1457  llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols;
1458
1459  // If it's a call which might free or reallocate memory, we assume that all
1460  // regions (explicit and implicit) escaped.
1461
1462  // Otherwise, whitelist explicit pointers; we still can track them.
1463  if (!Call || doesNotFreeMemory(Call, State)) {
1464    for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(),
1465        E = ExplicitRegions.end(); I != E; ++I) {
1466      if (const SymbolicRegion *R = (*I)->StripCasts()->getAs<SymbolicRegion>())
1467        WhitelistedSymbols.insert(R->getSymbol());
1468    }
1469  }
1470
1471  for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(),
1472       E = invalidated->end(); I!=E; ++I) {
1473    SymbolRef sym = *I;
1474    if (WhitelistedSymbols.count(sym))
1475      continue;
1476    // The symbol escaped. Note, we assume that if the symbol is released,
1477    // passing it out will result in a use after free. We also keep tracking
1478    // relinquished symbols.
1479    if (const RefState *RS = State->get<RegionState>(sym)) {
1480      if (RS->isAllocated())
1481        State = State->remove<RegionState>(sym);
1482    }
1483  }
1484  return State;
1485}
1486
1487static SymbolRef findFailedReallocSymbol(ProgramStateRef currState,
1488                                         ProgramStateRef prevState) {
1489  ReallocMap currMap = currState->get<ReallocPairs>();
1490  ReallocMap prevMap = prevState->get<ReallocPairs>();
1491
1492  for (ReallocMap::iterator I = prevMap.begin(), E = prevMap.end();
1493       I != E; ++I) {
1494    SymbolRef sym = I.getKey();
1495    if (!currMap.lookup(sym))
1496      return sym;
1497  }
1498
1499  return NULL;
1500}
1501
1502PathDiagnosticPiece *
1503MallocChecker::MallocBugVisitor::VisitNode(const ExplodedNode *N,
1504                                           const ExplodedNode *PrevN,
1505                                           BugReporterContext &BRC,
1506                                           BugReport &BR) {
1507  ProgramStateRef state = N->getState();
1508  ProgramStateRef statePrev = PrevN->getState();
1509
1510  const RefState *RS = state->get<RegionState>(Sym);
1511  const RefState *RSPrev = statePrev->get<RegionState>(Sym);
1512  if (!RS)
1513    return 0;
1514
1515  const Stmt *S = 0;
1516  const char *Msg = 0;
1517  StackHintGeneratorForSymbol *StackHint = 0;
1518
1519  // Retrieve the associated statement.
1520  ProgramPoint ProgLoc = N->getLocation();
1521  if (StmtPoint *SP = dyn_cast<StmtPoint>(&ProgLoc))
1522    S = SP->getStmt();
1523  else if (CallExitEnd *Exit = dyn_cast<CallExitEnd>(&ProgLoc))
1524    S = Exit->getCalleeContext()->getCallSite();
1525  // If an assumption was made on a branch, it should be caught
1526  // here by looking at the state transition.
1527  else if (BlockEdge *Edge = dyn_cast<BlockEdge>(&ProgLoc)) {
1528    const CFGBlock *srcBlk = Edge->getSrc();
1529    S = srcBlk->getTerminator();
1530  }
1531  if (!S)
1532    return 0;
1533
1534  // FIXME: We will eventually need to handle non-statement-based events
1535  // (__attribute__((cleanup))).
1536
1537  // Find out if this is an interesting point and what is the kind.
1538  if (Mode == Normal) {
1539    if (isAllocated(RS, RSPrev, S)) {
1540      Msg = "Memory is allocated";
1541      StackHint = new StackHintGeneratorForSymbol(Sym,
1542                                                  "Returned allocated memory");
1543    } else if (isReleased(RS, RSPrev, S)) {
1544      Msg = "Memory is released";
1545      StackHint = new StackHintGeneratorForSymbol(Sym,
1546                                                  "Returned released memory");
1547    } else if (isRelinquished(RS, RSPrev, S)) {
1548      Msg = "Memory ownership is transfered";
1549      StackHint = new StackHintGeneratorForSymbol(Sym, "");
1550    } else if (isReallocFailedCheck(RS, RSPrev, S)) {
1551      Mode = ReallocationFailed;
1552      Msg = "Reallocation failed";
1553      StackHint = new StackHintGeneratorForReallocationFailed(Sym,
1554                                                       "Reallocation failed");
1555
1556      if (SymbolRef sym = findFailedReallocSymbol(state, statePrev)) {
1557        // Is it possible to fail two reallocs WITHOUT testing in between?
1558        assert((!FailedReallocSymbol || FailedReallocSymbol == sym) &&
1559          "We only support one failed realloc at a time.");
1560        BR.markInteresting(sym);
1561        FailedReallocSymbol = sym;
1562      }
1563    }
1564
1565  // We are in a special mode if a reallocation failed later in the path.
1566  } else if (Mode == ReallocationFailed) {
1567    assert(FailedReallocSymbol && "No symbol to look for.");
1568
1569    // Is this is the first appearance of the reallocated symbol?
1570    if (!statePrev->get<RegionState>(FailedReallocSymbol)) {
1571      // We're at the reallocation point.
1572      Msg = "Attempt to reallocate memory";
1573      StackHint = new StackHintGeneratorForSymbol(Sym,
1574                                                 "Returned reallocated memory");
1575      FailedReallocSymbol = NULL;
1576      Mode = Normal;
1577    }
1578  }
1579
1580  if (!Msg)
1581    return 0;
1582  assert(StackHint);
1583
1584  // Generate the extra diagnostic.
1585  PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
1586                             N->getLocationContext());
1587  return new PathDiagnosticEventPiece(Pos, Msg, true, StackHint);
1588}
1589
1590void MallocChecker::printState(raw_ostream &Out, ProgramStateRef State,
1591                               const char *NL, const char *Sep) const {
1592
1593  RegionStateTy RS = State->get<RegionState>();
1594
1595  if (!RS.isEmpty())
1596    Out << "Has Malloc data" << NL;
1597}
1598
1599#define REGISTER_CHECKER(name) \
1600void ento::register##name(CheckerManager &mgr) {\
1601  registerCStringCheckerBasic(mgr); \
1602  mgr.registerChecker<MallocChecker>()->Filter.C##name = true;\
1603}
1604
1605REGISTER_CHECKER(MallocPessimistic)
1606REGISTER_CHECKER(MallocOptimistic)
1607