MallocChecker.cpp revision 4141e4dcab6b175374710925aa90d547600a5e66 
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 "llvm/ADT/StringExtras.h"
30#include <climits>
31
32using namespace clang;
33using namespace ento;
34
35namespace {
36
37class RefState {
38  enum Kind { // Reference to allocated memory.
39              Allocated,
40              // Reference to released/freed memory.
41              Released,
42              // The responsibility for freeing resources has transfered from
43              // this reference. A relinquished symbol should not be freed.
44              Relinquished } K;
45  const Stmt *S;
46
47public:
48  RefState(Kind k, const Stmt *s) : K(k), S(s) {}
49
50  bool isAllocated() const { return K == Allocated; }
51  bool isReleased() const { return K == Released; }
52  bool isRelinquished() const { return K == Relinquished; }
53
54  const Stmt *getStmt() const { return S; }
55
56  bool operator==(const RefState &X) const {
57    return K == X.K && S == X.S;
58  }
59
60  static RefState getAllocated(const Stmt *s) {
61    return RefState(Allocated, s);
62  }
63  static RefState getReleased(const Stmt *s) { return RefState(Released, s); }
64  static RefState getRelinquished(const Stmt *s) {
65    return RefState(Relinquished, s);
66  }
67
68  void Profile(llvm::FoldingSetNodeID &ID) const {
69    ID.AddInteger(K);
70    ID.AddPointer(S);
71  }
72};
73
74enum ReallocPairKind {
75  RPToBeFreedAfterFailure,
76  // The symbol has been freed when reallocation failed.
77  RPIsFreeOnFailure,
78  // The symbol does not need to be freed after reallocation fails.
79  RPDoNotTrackAfterFailure
80};
81
82/// \class ReallocPair
83/// \brief Stores information about the symbol being reallocated by a call to
84/// 'realloc' to allow modeling failed reallocation later in the path.
85struct ReallocPair {
86  // \brief The symbol which realloc reallocated.
87  SymbolRef ReallocatedSym;
88  ReallocPairKind Kind;
89
90  ReallocPair(SymbolRef S, ReallocPairKind K) :
91    ReallocatedSym(S), Kind(K) {}
92  void Profile(llvm::FoldingSetNodeID &ID) const {
93    ID.AddInteger(Kind);
94    ID.AddPointer(ReallocatedSym);
95  }
96  bool operator==(const ReallocPair &X) const {
97    return ReallocatedSym == X.ReallocatedSym &&
98           Kind == X.Kind;
99  }
100};
101
102typedef std::pair<const Stmt*, const MemRegion*> LeakInfo;
103
104class MallocChecker : public Checker<check::DeadSymbols,
105                                     check::EndPath,
106                                     check::PreStmt<ReturnStmt>,
107                                     check::PreStmt<CallExpr>,
108                                     check::PostStmt<CallExpr>,
109                                     check::PostStmt<BlockExpr>,
110                                     check::PostObjCMessage,
111                                     check::Location,
112                                     check::Bind,
113                                     eval::Assume,
114                                     check::RegionChanges>
115{
116  mutable OwningPtr<BugType> BT_DoubleFree;
117  mutable OwningPtr<BugType> BT_Leak;
118  mutable OwningPtr<BugType> BT_UseFree;
119  mutable OwningPtr<BugType> BT_BadFree;
120  mutable IdentifierInfo *II_malloc, *II_free, *II_realloc, *II_calloc,
121                         *II_valloc, *II_reallocf, *II_strndup, *II_strdup;
122
123public:
124  MallocChecker() : II_malloc(0), II_free(0), II_realloc(0), II_calloc(0),
125                    II_valloc(0), II_reallocf(0), II_strndup(0), II_strdup(0) {}
126
127  /// In pessimistic mode, the checker assumes that it does not know which
128  /// functions might free the memory.
129  struct ChecksFilter {
130    DefaultBool CMallocPessimistic;
131    DefaultBool CMallocOptimistic;
132  };
133
134  ChecksFilter Filter;
135
136  void checkPreStmt(const CallExpr *S, CheckerContext &C) const;
137  void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
138  void checkPostObjCMessage(const ObjCMethodCall &Call, CheckerContext &C) const;
139  void checkPostStmt(const BlockExpr *BE, CheckerContext &C) const;
140  void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
141  void checkEndPath(CheckerContext &C) const;
142  void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
143  ProgramStateRef evalAssume(ProgramStateRef state, SVal Cond,
144                            bool Assumption) const;
145  void checkLocation(SVal l, bool isLoad, const Stmt *S,
146                     CheckerContext &C) const;
147  void checkBind(SVal location, SVal val, const Stmt*S,
148                 CheckerContext &C) const;
149  ProgramStateRef
150  checkRegionChanges(ProgramStateRef state,
151                     const StoreManager::InvalidatedSymbols *invalidated,
152                     ArrayRef<const MemRegion *> ExplicitRegions,
153                     ArrayRef<const MemRegion *> Regions,
154                     const CallEvent *Call) const;
155  bool wantsRegionChangeUpdate(ProgramStateRef state) const {
156    return true;
157  }
158
159  void printState(raw_ostream &Out, ProgramStateRef State,
160                  const char *NL, const char *Sep) const;
161
162private:
163  void initIdentifierInfo(ASTContext &C) const;
164
165  /// Check if this is one of the functions which can allocate/reallocate memory
166  /// pointed to by one of its arguments.
167  bool isMemFunction(const FunctionDecl *FD, ASTContext &C) const;
168  bool isFreeFunction(const FunctionDecl *FD, ASTContext &C) const;
169  bool isAllocationFunction(const FunctionDecl *FD, ASTContext &C) const;
170
171  static ProgramStateRef MallocMemReturnsAttr(CheckerContext &C,
172                                              const CallExpr *CE,
173                                              const OwnershipAttr* Att);
174  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
175                                     const Expr *SizeEx, SVal Init,
176                                     ProgramStateRef state) {
177    return MallocMemAux(C, CE,
178                        state->getSVal(SizeEx, C.getLocationContext()),
179                        Init, state);
180  }
181
182  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
183                                     SVal SizeEx, SVal Init,
184                                     ProgramStateRef state);
185
186  /// Update the RefState to reflect the new memory allocation.
187  static ProgramStateRef MallocUpdateRefState(CheckerContext &C,
188                                              const CallExpr *CE,
189                                              ProgramStateRef state);
190
191  ProgramStateRef FreeMemAttr(CheckerContext &C, const CallExpr *CE,
192                              const OwnershipAttr* Att) const;
193  ProgramStateRef FreeMemAux(CheckerContext &C, const CallExpr *CE,
194                             ProgramStateRef state, unsigned Num,
195                             bool Hold,
196                             bool &ReleasedAllocated,
197                             bool ReturnsNullOnFailure = false) const;
198  ProgramStateRef FreeMemAux(CheckerContext &C, const Expr *Arg,
199                             const Expr *ParentExpr,
200                             ProgramStateRef State,
201                             bool Hold,
202                             bool &ReleasedAllocated,
203                             bool ReturnsNullOnFailure = false) const;
204
205  ProgramStateRef ReallocMem(CheckerContext &C, const CallExpr *CE,
206                             bool FreesMemOnFailure) const;
207  static ProgramStateRef CallocMem(CheckerContext &C, const CallExpr *CE);
208
209  ///\brief Check if the memory associated with this symbol was released.
210  bool isReleased(SymbolRef Sym, CheckerContext &C) const;
211
212  bool checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
213                         const Stmt *S = 0) const;
214
215  /// Check if the function is not known to us. So, for example, we could
216  /// conservatively assume it can free/reallocate it's pointer arguments.
217  bool doesNotFreeMemory(const CallEvent *Call,
218                         ProgramStateRef State) const;
219
220  static bool SummarizeValue(raw_ostream &os, SVal V);
221  static bool SummarizeRegion(raw_ostream &os, const MemRegion *MR);
222  void ReportBadFree(CheckerContext &C, SVal ArgVal, SourceRange range) const;
223
224  /// Find the location of the allocation for Sym on the path leading to the
225  /// exploded node N.
226  LeakInfo getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
227                             CheckerContext &C) const;
228
229  void reportLeak(SymbolRef Sym, ExplodedNode *N, CheckerContext &C) const;
230
231  /// The bug visitor which allows us to print extra diagnostics along the
232  /// BugReport path. For example, showing the allocation site of the leaked
233  /// region.
234  class MallocBugVisitor : public BugReporterVisitorImpl<MallocBugVisitor> {
235  protected:
236    enum NotificationMode {
237      Normal,
238      ReallocationFailed
239    };
240
241    // The allocated region symbol tracked by the main analysis.
242    SymbolRef Sym;
243
244    // The mode we are in, i.e. what kind of diagnostics will be emitted.
245    NotificationMode Mode;
246
247    // A symbol from when the primary region should have been reallocated.
248    SymbolRef FailedReallocSymbol;
249
250    bool IsLeak;
251
252  public:
253    MallocBugVisitor(SymbolRef S, bool isLeak = false)
254       : Sym(S), Mode(Normal), FailedReallocSymbol(0), IsLeak(isLeak) {}
255
256    virtual ~MallocBugVisitor() {}
257
258    void Profile(llvm::FoldingSetNodeID &ID) const {
259      static int X = 0;
260      ID.AddPointer(&X);
261      ID.AddPointer(Sym);
262    }
263
264    inline bool isAllocated(const RefState *S, const RefState *SPrev,
265                            const Stmt *Stmt) {
266      // Did not track -> allocated. Other state (released) -> allocated.
267      return (Stmt && isa<CallExpr>(Stmt) &&
268              (S && S->isAllocated()) && (!SPrev || !SPrev->isAllocated()));
269    }
270
271    inline bool isReleased(const RefState *S, const RefState *SPrev,
272                           const Stmt *Stmt) {
273      // Did not track -> released. Other state (allocated) -> released.
274      return (Stmt && isa<CallExpr>(Stmt) &&
275              (S && S->isReleased()) && (!SPrev || !SPrev->isReleased()));
276    }
277
278    inline bool isRelinquished(const RefState *S, const RefState *SPrev,
279                               const Stmt *Stmt) {
280      // Did not track -> relinquished. Other state (allocated) -> relinquished.
281      return (Stmt && (isa<CallExpr>(Stmt) || isa<ObjCMessageExpr>(Stmt) ||
282                                              isa<ObjCPropertyRefExpr>(Stmt)) &&
283              (S && S->isRelinquished()) &&
284              (!SPrev || !SPrev->isRelinquished()));
285    }
286
287    inline bool isReallocFailedCheck(const RefState *S, const RefState *SPrev,
288                                     const Stmt *Stmt) {
289      // If the expression is not a call, and the state change is
290      // released -> allocated, it must be the realloc return value
291      // check. If we have to handle more cases here, it might be cleaner just
292      // to track this extra bit in the state itself.
293      return ((!Stmt || !isa<CallExpr>(Stmt)) &&
294              (S && S->isAllocated()) && (SPrev && !SPrev->isAllocated()));
295    }
296
297    PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
298                                   const ExplodedNode *PrevN,
299                                   BugReporterContext &BRC,
300                                   BugReport &BR);
301
302    PathDiagnosticPiece* getEndPath(BugReporterContext &BRC,
303                                    const ExplodedNode *EndPathNode,
304                                    BugReport &BR) {
305      if (!IsLeak)
306        return 0;
307
308      PathDiagnosticLocation L =
309        PathDiagnosticLocation::createEndOfPath(EndPathNode,
310                                                BRC.getSourceManager());
311      // Do not add the statement itself as a range in case of leak.
312      return new PathDiagnosticEventPiece(L, BR.getDescription(), false);
313    }
314
315  private:
316    class StackHintGeneratorForReallocationFailed
317        : public StackHintGeneratorForSymbol {
318    public:
319      StackHintGeneratorForReallocationFailed(SymbolRef S, StringRef M)
320        : StackHintGeneratorForSymbol(S, M) {}
321
322      virtual std::string getMessageForArg(const Expr *ArgE, unsigned ArgIndex) {
323        // Printed parameters start at 1, not 0.
324        ++ArgIndex;
325
326        SmallString<200> buf;
327        llvm::raw_svector_ostream os(buf);
328
329        os << "Reallocation of " << ArgIndex << llvm::getOrdinalSuffix(ArgIndex)
330           << " parameter failed";
331
332        return os.str();
333      }
334
335      virtual std::string getMessageForReturn(const CallExpr *CallExpr) {
336        return "Reallocation of returned value failed";
337      }
338    };
339  };
340};
341} // end anonymous namespace
342
343REGISTER_MAP_WITH_PROGRAMSTATE(RegionState, SymbolRef, RefState)
344REGISTER_MAP_WITH_PROGRAMSTATE(ReallocPairs, SymbolRef, ReallocPair)
345
346// A map from the freed symbol to the symbol representing the return value of
347// the free function.
348REGISTER_MAP_WITH_PROGRAMSTATE(FreeReturnValue, SymbolRef, SymbolRef)
349
350namespace {
351class StopTrackingCallback : public SymbolVisitor {
352  ProgramStateRef state;
353public:
354  StopTrackingCallback(ProgramStateRef st) : state(st) {}
355  ProgramStateRef getState() const { return state; }
356
357  bool VisitSymbol(SymbolRef sym) {
358    state = state->remove<RegionState>(sym);
359    return true;
360  }
361};
362} // end anonymous namespace
363
364void MallocChecker::initIdentifierInfo(ASTContext &Ctx) const {
365  if (II_malloc)
366    return;
367  II_malloc = &Ctx.Idents.get("malloc");
368  II_free = &Ctx.Idents.get("free");
369  II_realloc = &Ctx.Idents.get("realloc");
370  II_reallocf = &Ctx.Idents.get("reallocf");
371  II_calloc = &Ctx.Idents.get("calloc");
372  II_valloc = &Ctx.Idents.get("valloc");
373  II_strdup = &Ctx.Idents.get("strdup");
374  II_strndup = &Ctx.Idents.get("strndup");
375}
376
377bool MallocChecker::isMemFunction(const FunctionDecl *FD, ASTContext &C) const {
378  if (isFreeFunction(FD, C))
379    return true;
380
381  if (isAllocationFunction(FD, C))
382    return true;
383
384  return false;
385}
386
387bool MallocChecker::isAllocationFunction(const FunctionDecl *FD,
388                                         ASTContext &C) const {
389  if (!FD)
390    return false;
391
392  if (FD->getKind() == Decl::Function) {
393    IdentifierInfo *FunI = FD->getIdentifier();
394    initIdentifierInfo(C);
395
396    if (FunI == II_malloc || FunI == II_realloc ||
397        FunI == II_reallocf || FunI == II_calloc || FunI == II_valloc ||
398        FunI == II_strdup || FunI == II_strndup)
399      return true;
400  }
401
402  if (Filter.CMallocOptimistic && FD->hasAttrs())
403    for (specific_attr_iterator<OwnershipAttr>
404           i = FD->specific_attr_begin<OwnershipAttr>(),
405           e = FD->specific_attr_end<OwnershipAttr>();
406           i != e; ++i)
407      if ((*i)->getOwnKind() == OwnershipAttr::Returns)
408        return true;
409  return false;
410}
411
412bool MallocChecker::isFreeFunction(const FunctionDecl *FD, ASTContext &C) const {
413  if (!FD)
414    return false;
415
416  if (FD->getKind() == Decl::Function) {
417    IdentifierInfo *FunI = FD->getIdentifier();
418    initIdentifierInfo(C);
419
420    if (FunI == II_free || FunI == II_realloc || FunI == II_reallocf)
421      return true;
422  }
423
424  if (Filter.CMallocOptimistic && FD->hasAttrs())
425    for (specific_attr_iterator<OwnershipAttr>
426           i = FD->specific_attr_begin<OwnershipAttr>(),
427           e = FD->specific_attr_end<OwnershipAttr>();
428           i != e; ++i)
429      if ((*i)->getOwnKind() == OwnershipAttr::Takes ||
430          (*i)->getOwnKind() == OwnershipAttr::Holds)
431        return true;
432  return false;
433}
434
435void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const {
436  if (C.wasInlined)
437    return;
438
439  const FunctionDecl *FD = C.getCalleeDecl(CE);
440  if (!FD)
441    return;
442
443  ProgramStateRef State = C.getState();
444  bool ReleasedAllocatedMemory = false;
445
446  if (FD->getKind() == Decl::Function) {
447    initIdentifierInfo(C.getASTContext());
448    IdentifierInfo *FunI = FD->getIdentifier();
449
450    if (FunI == II_malloc || FunI == II_valloc) {
451      if (CE->getNumArgs() < 1)
452        return;
453      State = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(), State);
454    } else if (FunI == II_realloc) {
455      State = ReallocMem(C, CE, false);
456    } else if (FunI == II_reallocf) {
457      State = ReallocMem(C, CE, true);
458    } else if (FunI == II_calloc) {
459      State = CallocMem(C, CE);
460    } else if (FunI == II_free) {
461      State = FreeMemAux(C, CE, State, 0, false, ReleasedAllocatedMemory);
462    } else if (FunI == II_strdup) {
463      State = MallocUpdateRefState(C, CE, State);
464    } else if (FunI == II_strndup) {
465      State = MallocUpdateRefState(C, CE, State);
466    }
467  }
468
469  if (Filter.CMallocOptimistic) {
470    // Check all the attributes, if there are any.
471    // There can be multiple of these attributes.
472    if (FD->hasAttrs())
473      for (specific_attr_iterator<OwnershipAttr>
474          i = FD->specific_attr_begin<OwnershipAttr>(),
475          e = FD->specific_attr_end<OwnershipAttr>();
476          i != e; ++i) {
477        switch ((*i)->getOwnKind()) {
478        case OwnershipAttr::Returns:
479          State = MallocMemReturnsAttr(C, CE, *i);
480          break;
481        case OwnershipAttr::Takes:
482        case OwnershipAttr::Holds:
483          State = FreeMemAttr(C, CE, *i);
484          break;
485        }
486      }
487  }
488  C.addTransition(State);
489}
490
491static bool isFreeWhenDoneSetToZero(const ObjCMethodCall &Call) {
492  Selector S = Call.getSelector();
493  for (unsigned i = 1; i < S.getNumArgs(); ++i)
494    if (S.getNameForSlot(i).equals("freeWhenDone"))
495      if (Call.getArgSVal(i).isConstant(0))
496        return true;
497
498  return false;
499}
500
501void MallocChecker::checkPostObjCMessage(const ObjCMethodCall &Call,
502                                         CheckerContext &C) const {
503  // If the first selector is dataWithBytesNoCopy, assume that the memory will
504  // be released with 'free' by the new object.
505  // Ex:  [NSData dataWithBytesNoCopy:bytes length:10];
506  // Unless 'freeWhenDone' param set to 0.
507  // TODO: Check that the memory was allocated with malloc.
508  bool ReleasedAllocatedMemory = false;
509  Selector S = Call.getSelector();
510  if ((S.getNameForSlot(0) == "dataWithBytesNoCopy" ||
511       S.getNameForSlot(0) == "initWithBytesNoCopy" ||
512       S.getNameForSlot(0) == "initWithCharactersNoCopy") &&
513      !isFreeWhenDoneSetToZero(Call)){
514    unsigned int argIdx  = 0;
515    ProgramStateRef State = FreeMemAux(C, Call.getArgExpr(argIdx),
516                                       Call.getOriginExpr(), C.getState(), true,
517                                       ReleasedAllocatedMemory,
518                                       /* RetNullOnFailure*/ true);
519
520    C.addTransition(State);
521  }
522}
523
524ProgramStateRef MallocChecker::MallocMemReturnsAttr(CheckerContext &C,
525                                                    const CallExpr *CE,
526                                                    const OwnershipAttr* Att) {
527  if (Att->getModule() != "malloc")
528    return 0;
529
530  OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
531  if (I != E) {
532    return MallocMemAux(C, CE, CE->getArg(*I), UndefinedVal(), C.getState());
533  }
534  return MallocMemAux(C, CE, UnknownVal(), UndefinedVal(), C.getState());
535}
536
537ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
538                                           const CallExpr *CE,
539                                           SVal Size, SVal Init,
540                                           ProgramStateRef state) {
541
542  // Bind the return value to the symbolic value from the heap region.
543  // TODO: We could rewrite post visit to eval call; 'malloc' does not have
544  // side effects other than what we model here.
545  unsigned Count = C.blockCount();
546  SValBuilder &svalBuilder = C.getSValBuilder();
547  const LocationContext *LCtx = C.getPredecessor()->getLocationContext();
548  DefinedSVal RetVal =
549    cast<DefinedSVal>(svalBuilder.getConjuredHeapSymbolVal(CE, LCtx, Count));
550  state = state->BindExpr(CE, C.getLocationContext(), RetVal);
551
552  // We expect the malloc functions to return a pointer.
553  if (!isa<Loc>(RetVal))
554    return 0;
555
556  // Fill the region with the initialization value.
557  state = state->bindDefault(RetVal, Init);
558
559  // Set the region's extent equal to the Size parameter.
560  const SymbolicRegion *R =
561      dyn_cast_or_null<SymbolicRegion>(RetVal.getAsRegion());
562  if (!R)
563    return 0;
564  if (isa<DefinedOrUnknownSVal>(Size)) {
565    SValBuilder &svalBuilder = C.getSValBuilder();
566    DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
567    DefinedOrUnknownSVal DefinedSize = cast<DefinedOrUnknownSVal>(Size);
568    DefinedOrUnknownSVal extentMatchesSize =
569        svalBuilder.evalEQ(state, Extent, DefinedSize);
570
571    state = state->assume(extentMatchesSize, true);
572    assert(state);
573  }
574
575  return MallocUpdateRefState(C, CE, state);
576}
577
578ProgramStateRef MallocChecker::MallocUpdateRefState(CheckerContext &C,
579                                                    const CallExpr *CE,
580                                                    ProgramStateRef state) {
581  // Get the return value.
582  SVal retVal = state->getSVal(CE, C.getLocationContext());
583
584  // We expect the malloc functions to return a pointer.
585  if (!isa<Loc>(retVal))
586    return 0;
587
588  SymbolRef Sym = retVal.getAsLocSymbol();
589  assert(Sym);
590
591  // Set the symbol's state to Allocated.
592  return state->set<RegionState>(Sym, RefState::getAllocated(CE));
593
594}
595
596ProgramStateRef MallocChecker::FreeMemAttr(CheckerContext &C,
597                                           const CallExpr *CE,
598                                           const OwnershipAttr* Att) const {
599  if (Att->getModule() != "malloc")
600    return 0;
601
602  ProgramStateRef State = C.getState();
603  bool ReleasedAllocated = false;
604
605  for (OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
606       I != E; ++I) {
607    ProgramStateRef StateI = FreeMemAux(C, CE, State, *I,
608                               Att->getOwnKind() == OwnershipAttr::Holds,
609                               ReleasedAllocated);
610    if (StateI)
611      State = StateI;
612  }
613  return State;
614}
615
616ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
617                                          const CallExpr *CE,
618                                          ProgramStateRef state,
619                                          unsigned Num,
620                                          bool Hold,
621                                          bool &ReleasedAllocated,
622                                          bool ReturnsNullOnFailure) const {
623  if (CE->getNumArgs() < (Num + 1))
624    return 0;
625
626  return FreeMemAux(C, CE->getArg(Num), CE, state, Hold,
627                    ReleasedAllocated, ReturnsNullOnFailure);
628}
629
630/// Check if the previous call to free on the given symbol failed.
631///
632/// For example, if free failed, returns true. In addition, cleans out the
633/// state from the corresponding failure info. Retuns the cleaned out state
634/// and the corresponding return value symbol.
635static std::pair<bool, ProgramStateRef>
636checkAndCleanFreeFailedInfo(ProgramStateRef State,
637                            SymbolRef Sym, const SymbolRef *Ret) {
638  Ret = State->get<FreeReturnValue>(Sym);
639  if (Ret) {
640    assert(*Ret && "We should not store the null return symbol");
641    ConstraintManager &CMgr = State->getConstraintManager();
642    ConditionTruthVal FreeFailed = CMgr.isNull(State, *Ret);
643    State = State->remove<FreeReturnValue>(Sym);
644    return std::pair<bool, ProgramStateRef>(FreeFailed.isConstrainedTrue(),
645                                            State);
646  }
647  return std::pair<bool, ProgramStateRef>(false, State);
648}
649
650ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
651                                          const Expr *ArgExpr,
652                                          const Expr *ParentExpr,
653                                          ProgramStateRef State,
654                                          bool Hold,
655                                          bool &ReleasedAllocated,
656                                          bool ReturnsNullOnFailure) const {
657
658  SVal ArgVal = State->getSVal(ArgExpr, C.getLocationContext());
659  if (!isa<DefinedOrUnknownSVal>(ArgVal))
660    return 0;
661  DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(ArgVal);
662
663  // Check for null dereferences.
664  if (!isa<Loc>(location))
665    return 0;
666
667  // The explicit NULL case, no operation is performed.
668  ProgramStateRef notNullState, nullState;
669  llvm::tie(notNullState, nullState) = State->assume(location);
670  if (nullState && !notNullState)
671    return 0;
672
673  // Unknown values could easily be okay
674  // Undefined values are handled elsewhere
675  if (ArgVal.isUnknownOrUndef())
676    return 0;
677
678  const MemRegion *R = ArgVal.getAsRegion();
679
680  // Nonlocs can't be freed, of course.
681  // Non-region locations (labels and fixed addresses) also shouldn't be freed.
682  if (!R) {
683    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
684    return 0;
685  }
686
687  R = R->StripCasts();
688
689  // Blocks might show up as heap data, but should not be free()d
690  if (isa<BlockDataRegion>(R)) {
691    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
692    return 0;
693  }
694
695  const MemSpaceRegion *MS = R->getMemorySpace();
696
697  // Parameters, locals, statics, and globals shouldn't be freed.
698  if (!(isa<UnknownSpaceRegion>(MS) || isa<HeapSpaceRegion>(MS))) {
699    // FIXME: at the time this code was written, malloc() regions were
700    // represented by conjured symbols, which are all in UnknownSpaceRegion.
701    // This means that there isn't actually anything from HeapSpaceRegion
702    // that should be freed, even though we allow it here.
703    // Of course, free() can work on memory allocated outside the current
704    // function, so UnknownSpaceRegion is always a possibility.
705    // False negatives are better than false positives.
706
707    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
708    return 0;
709  }
710
711  const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
712  // Various cases could lead to non-symbol values here.
713  // For now, ignore them.
714  if (!SR)
715    return 0;
716
717  SymbolRef Sym = SR->getSymbol();
718  const RefState *RS = State->get<RegionState>(Sym);
719  bool FailedToFree = false;
720  const SymbolRef *RetStatusSymbolPtr = 0;
721  llvm::tie(FailedToFree, State) =
722      checkAndCleanFreeFailedInfo(State, Sym, RetStatusSymbolPtr);
723
724  // Check double free.
725  if (RS &&
726      (RS->isReleased() || RS->isRelinquished()) &&
727      !FailedToFree) {
728
729    if (ExplodedNode *N = C.generateSink()) {
730      if (!BT_DoubleFree)
731        BT_DoubleFree.reset(
732          new BugType("Double free", "Memory Error"));
733      BugReport *R = new BugReport(*BT_DoubleFree,
734        (RS->isReleased() ? "Attempt to free released memory" :
735                            "Attempt to free non-owned memory"), N);
736      R->addRange(ArgExpr->getSourceRange());
737      R->markInteresting(Sym);
738      if (RetStatusSymbolPtr)
739        R->markInteresting(*RetStatusSymbolPtr);
740      R->addVisitor(new MallocBugVisitor(Sym));
741      C.emitReport(R);
742    }
743    return 0;
744  }
745
746  ReleasedAllocated = (RS != 0);
747
748  // Keep track of the return value. If it is NULL, we will know that free
749  // failed.
750  if (ReturnsNullOnFailure) {
751    SVal RetVal = C.getSVal(ParentExpr);
752    SymbolRef RetStatusSymbol = RetVal.getAsSymbol();
753    if (RetStatusSymbol) {
754      C.getSymbolManager().addSymbolDependency(Sym, RetStatusSymbol);
755      State = State->set<FreeReturnValue>(Sym, RetStatusSymbol);
756    }
757  }
758
759  // Normal free.
760  if (Hold)
761    return State->set<RegionState>(Sym, RefState::getRelinquished(ParentExpr));
762  return State->set<RegionState>(Sym, RefState::getReleased(ParentExpr));
763}
764
765bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) {
766  if (nonloc::ConcreteInt *IntVal = dyn_cast<nonloc::ConcreteInt>(&V))
767    os << "an integer (" << IntVal->getValue() << ")";
768  else if (loc::ConcreteInt *ConstAddr = dyn_cast<loc::ConcreteInt>(&V))
769    os << "a constant address (" << ConstAddr->getValue() << ")";
770  else if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&V))
771    os << "the address of the label '" << Label->getLabel()->getName() << "'";
772  else
773    return false;
774
775  return true;
776}
777
778bool MallocChecker::SummarizeRegion(raw_ostream &os,
779                                    const MemRegion *MR) {
780  switch (MR->getKind()) {
781  case MemRegion::FunctionTextRegionKind: {
782    const NamedDecl *FD = cast<FunctionTextRegion>(MR)->getDecl();
783    if (FD)
784      os << "the address of the function '" << *FD << '\'';
785    else
786      os << "the address of a function";
787    return true;
788  }
789  case MemRegion::BlockTextRegionKind:
790    os << "block text";
791    return true;
792  case MemRegion::BlockDataRegionKind:
793    // FIXME: where the block came from?
794    os << "a block";
795    return true;
796  default: {
797    const MemSpaceRegion *MS = MR->getMemorySpace();
798
799    if (isa<StackLocalsSpaceRegion>(MS)) {
800      const VarRegion *VR = dyn_cast<VarRegion>(MR);
801      const VarDecl *VD;
802      if (VR)
803        VD = VR->getDecl();
804      else
805        VD = NULL;
806
807      if (VD)
808        os << "the address of the local variable '" << VD->getName() << "'";
809      else
810        os << "the address of a local stack variable";
811      return true;
812    }
813
814    if (isa<StackArgumentsSpaceRegion>(MS)) {
815      const VarRegion *VR = dyn_cast<VarRegion>(MR);
816      const VarDecl *VD;
817      if (VR)
818        VD = VR->getDecl();
819      else
820        VD = NULL;
821
822      if (VD)
823        os << "the address of the parameter '" << VD->getName() << "'";
824      else
825        os << "the address of a parameter";
826      return true;
827    }
828
829    if (isa<GlobalsSpaceRegion>(MS)) {
830      const VarRegion *VR = dyn_cast<VarRegion>(MR);
831      const VarDecl *VD;
832      if (VR)
833        VD = VR->getDecl();
834      else
835        VD = NULL;
836
837      if (VD) {
838        if (VD->isStaticLocal())
839          os << "the address of the static variable '" << VD->getName() << "'";
840        else
841          os << "the address of the global variable '" << VD->getName() << "'";
842      } else
843        os << "the address of a global variable";
844      return true;
845    }
846
847    return false;
848  }
849  }
850}
851
852void MallocChecker::ReportBadFree(CheckerContext &C, SVal ArgVal,
853                                  SourceRange range) const {
854  if (ExplodedNode *N = C.generateSink()) {
855    if (!BT_BadFree)
856      BT_BadFree.reset(new BugType("Bad free", "Memory Error"));
857
858    SmallString<100> buf;
859    llvm::raw_svector_ostream os(buf);
860
861    const MemRegion *MR = ArgVal.getAsRegion();
862    if (MR) {
863      while (const ElementRegion *ER = dyn_cast<ElementRegion>(MR))
864        MR = ER->getSuperRegion();
865
866      // Special case for alloca()
867      if (isa<AllocaRegion>(MR))
868        os << "Argument to free() was allocated by alloca(), not malloc()";
869      else {
870        os << "Argument to free() is ";
871        if (SummarizeRegion(os, MR))
872          os << ", which is not memory allocated by malloc()";
873        else
874          os << "not memory allocated by malloc()";
875      }
876    } else {
877      os << "Argument to free() is ";
878      if (SummarizeValue(os, ArgVal))
879        os << ", which is not memory allocated by malloc()";
880      else
881        os << "not memory allocated by malloc()";
882    }
883
884    BugReport *R = new BugReport(*BT_BadFree, os.str(), N);
885    R->markInteresting(MR);
886    R->addRange(range);
887    C.emitReport(R);
888  }
889}
890
891ProgramStateRef MallocChecker::ReallocMem(CheckerContext &C,
892                                          const CallExpr *CE,
893                                          bool FreesOnFail) const {
894  if (CE->getNumArgs() < 2)
895    return 0;
896
897  ProgramStateRef state = C.getState();
898  const Expr *arg0Expr = CE->getArg(0);
899  const LocationContext *LCtx = C.getLocationContext();
900  SVal Arg0Val = state->getSVal(arg0Expr, LCtx);
901  if (!isa<DefinedOrUnknownSVal>(Arg0Val))
902    return 0;
903  DefinedOrUnknownSVal arg0Val = cast<DefinedOrUnknownSVal>(Arg0Val);
904
905  SValBuilder &svalBuilder = C.getSValBuilder();
906
907  DefinedOrUnknownSVal PtrEQ =
908    svalBuilder.evalEQ(state, arg0Val, svalBuilder.makeNull());
909
910  // Get the size argument. If there is no size arg then give up.
911  const Expr *Arg1 = CE->getArg(1);
912  if (!Arg1)
913    return 0;
914
915  // Get the value of the size argument.
916  SVal Arg1ValG = state->getSVal(Arg1, LCtx);
917  if (!isa<DefinedOrUnknownSVal>(Arg1ValG))
918    return 0;
919  DefinedOrUnknownSVal Arg1Val = cast<DefinedOrUnknownSVal>(Arg1ValG);
920
921  // Compare the size argument to 0.
922  DefinedOrUnknownSVal SizeZero =
923    svalBuilder.evalEQ(state, Arg1Val,
924                       svalBuilder.makeIntValWithPtrWidth(0, false));
925
926  ProgramStateRef StatePtrIsNull, StatePtrNotNull;
927  llvm::tie(StatePtrIsNull, StatePtrNotNull) = state->assume(PtrEQ);
928  ProgramStateRef StateSizeIsZero, StateSizeNotZero;
929  llvm::tie(StateSizeIsZero, StateSizeNotZero) = state->assume(SizeZero);
930  // We only assume exceptional states if they are definitely true; if the
931  // state is under-constrained, assume regular realloc behavior.
932  bool PrtIsNull = StatePtrIsNull && !StatePtrNotNull;
933  bool SizeIsZero = StateSizeIsZero && !StateSizeNotZero;
934
935  // If the ptr is NULL and the size is not 0, the call is equivalent to
936  // malloc(size).
937  if ( PrtIsNull && !SizeIsZero) {
938    ProgramStateRef stateMalloc = MallocMemAux(C, CE, CE->getArg(1),
939                                               UndefinedVal(), StatePtrIsNull);
940    return stateMalloc;
941  }
942
943  if (PrtIsNull && SizeIsZero)
944    return 0;
945
946  // Get the from and to pointer symbols as in toPtr = realloc(fromPtr, size).
947  assert(!PrtIsNull);
948  SymbolRef FromPtr = arg0Val.getAsSymbol();
949  SVal RetVal = state->getSVal(CE, LCtx);
950  SymbolRef ToPtr = RetVal.getAsSymbol();
951  if (!FromPtr || !ToPtr)
952    return 0;
953
954  bool ReleasedAllocated = false;
955
956  // If the size is 0, free the memory.
957  if (SizeIsZero)
958    if (ProgramStateRef stateFree = FreeMemAux(C, CE, StateSizeIsZero, 0,
959                                               false, ReleasedAllocated)){
960      // The semantics of the return value are:
961      // If size was equal to 0, either NULL or a pointer suitable to be passed
962      // to free() is returned. We just free the input pointer and do not add
963      // any constrains on the output pointer.
964      return stateFree;
965    }
966
967  // Default behavior.
968  if (ProgramStateRef stateFree =
969        FreeMemAux(C, CE, state, 0, false, ReleasedAllocated)) {
970
971    ProgramStateRef stateRealloc = MallocMemAux(C, CE, CE->getArg(1),
972                                                UnknownVal(), stateFree);
973    if (!stateRealloc)
974      return 0;
975
976    ReallocPairKind Kind = RPToBeFreedAfterFailure;
977    if (FreesOnFail)
978      Kind = RPIsFreeOnFailure;
979    else if (!ReleasedAllocated)
980      Kind = RPDoNotTrackAfterFailure;
981
982    // Record the info about the reallocated symbol so that we could properly
983    // process failed reallocation.
984    stateRealloc = stateRealloc->set<ReallocPairs>(ToPtr,
985                                                   ReallocPair(FromPtr, Kind));
986    // The reallocated symbol should stay alive for as long as the new symbol.
987    C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
988    return stateRealloc;
989  }
990  return 0;
991}
992
993ProgramStateRef MallocChecker::CallocMem(CheckerContext &C, const CallExpr *CE){
994  if (CE->getNumArgs() < 2)
995    return 0;
996
997  ProgramStateRef state = C.getState();
998  SValBuilder &svalBuilder = C.getSValBuilder();
999  const LocationContext *LCtx = C.getLocationContext();
1000  SVal count = state->getSVal(CE->getArg(0), LCtx);
1001  SVal elementSize = state->getSVal(CE->getArg(1), LCtx);
1002  SVal TotalSize = svalBuilder.evalBinOp(state, BO_Mul, count, elementSize,
1003                                        svalBuilder.getContext().getSizeType());
1004  SVal zeroVal = svalBuilder.makeZeroVal(svalBuilder.getContext().CharTy);
1005
1006  return MallocMemAux(C, CE, TotalSize, zeroVal, state);
1007}
1008
1009LeakInfo
1010MallocChecker::getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
1011                                 CheckerContext &C) const {
1012  const LocationContext *LeakContext = N->getLocationContext();
1013  // Walk the ExplodedGraph backwards and find the first node that referred to
1014  // the tracked symbol.
1015  const ExplodedNode *AllocNode = N;
1016  const MemRegion *ReferenceRegion = 0;
1017
1018  while (N) {
1019    ProgramStateRef State = N->getState();
1020    if (!State->get<RegionState>(Sym))
1021      break;
1022
1023    // Find the most recent expression bound to the symbol in the current
1024    // context.
1025    if (!ReferenceRegion) {
1026      if (const MemRegion *MR = C.getLocationRegionIfPostStore(N)) {
1027        SVal Val = State->getSVal(MR);
1028        if (Val.getAsLocSymbol() == Sym)
1029          ReferenceRegion = MR;
1030      }
1031    }
1032
1033    // Allocation node, is the last node in the current context in which the
1034    // symbol was tracked.
1035    if (N->getLocationContext() == LeakContext)
1036      AllocNode = N;
1037    N = N->pred_empty() ? NULL : *(N->pred_begin());
1038  }
1039
1040  ProgramPoint P = AllocNode->getLocation();
1041  const Stmt *AllocationStmt = 0;
1042  if (CallExitEnd *Exit = dyn_cast<CallExitEnd>(&P))
1043    AllocationStmt = Exit->getCalleeContext()->getCallSite();
1044  else if (StmtPoint *SP = dyn_cast<StmtPoint>(&P))
1045    AllocationStmt = SP->getStmt();
1046
1047  return LeakInfo(AllocationStmt, ReferenceRegion);
1048}
1049
1050void MallocChecker::reportLeak(SymbolRef Sym, ExplodedNode *N,
1051                               CheckerContext &C) const {
1052  assert(N);
1053  if (!BT_Leak) {
1054    BT_Leak.reset(new BugType("Memory leak", "Memory Error"));
1055    // Leaks should not be reported if they are post-dominated by a sink:
1056    // (1) Sinks are higher importance bugs.
1057    // (2) NoReturnFunctionChecker uses sink nodes to represent paths ending
1058    //     with __noreturn functions such as assert() or exit(). We choose not
1059    //     to report leaks on such paths.
1060    BT_Leak->setSuppressOnSink(true);
1061  }
1062
1063  // Most bug reports are cached at the location where they occurred.
1064  // With leaks, we want to unique them by the location where they were
1065  // allocated, and only report a single path.
1066  PathDiagnosticLocation LocUsedForUniqueing;
1067  const Stmt *AllocStmt = 0;
1068  const MemRegion *Region = 0;
1069  llvm::tie(AllocStmt, Region) = getAllocationSite(N, Sym, C);
1070  if (AllocStmt)
1071    LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt,
1072                            C.getSourceManager(), N->getLocationContext());
1073
1074  SmallString<200> buf;
1075  llvm::raw_svector_ostream os(buf);
1076  os << "Memory is never released; potential leak";
1077  if (Region && Region->canPrintPretty()) {
1078    os << " of memory pointed to by '";
1079    Region->printPretty(os);
1080    os << '\'';
1081  }
1082
1083  BugReport *R = new BugReport(*BT_Leak, os.str(), N, LocUsedForUniqueing);
1084  R->markInteresting(Sym);
1085  R->addVisitor(new MallocBugVisitor(Sym, true));
1086  C.emitReport(R);
1087}
1088
1089void MallocChecker::checkDeadSymbols(SymbolReaper &SymReaper,
1090                                     CheckerContext &C) const
1091{
1092  if (!SymReaper.hasDeadSymbols())
1093    return;
1094
1095  ProgramStateRef state = C.getState();
1096  RegionStateTy RS = state->get<RegionState>();
1097  RegionStateTy::Factory &F = state->get_context<RegionState>();
1098
1099  llvm::SmallVector<SymbolRef, 2> Errors;
1100  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
1101    if (SymReaper.isDead(I->first)) {
1102      if (I->second.isAllocated())
1103        Errors.push_back(I->first);
1104      // Remove the dead symbol from the map.
1105      RS = F.remove(RS, I->first);
1106
1107    }
1108  }
1109
1110  // Cleanup the Realloc Pairs Map.
1111  ReallocPairsTy RP = state->get<ReallocPairs>();
1112  for (ReallocPairsTy::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
1113    if (SymReaper.isDead(I->first) ||
1114        SymReaper.isDead(I->second.ReallocatedSym)) {
1115      state = state->remove<ReallocPairs>(I->first);
1116    }
1117  }
1118
1119  // Cleanup the FreeReturnValue Map.
1120  FreeReturnValueTy FR = state->get<FreeReturnValue>();
1121  for (FreeReturnValueTy::iterator I = FR.begin(), E = FR.end(); I != E; ++I) {
1122    if (SymReaper.isDead(I->first) ||
1123        SymReaper.isDead(I->second)) {
1124      state = state->remove<FreeReturnValue>(I->first);
1125    }
1126  }
1127
1128  // Generate leak node.
1129  ExplodedNode *N = C.getPredecessor();
1130  if (!Errors.empty()) {
1131    static SimpleProgramPointTag Tag("MallocChecker : DeadSymbolsLeak");
1132    N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
1133    for (llvm::SmallVector<SymbolRef, 2>::iterator
1134        I = Errors.begin(), E = Errors.end(); I != E; ++I) {
1135      reportLeak(*I, N, C);
1136    }
1137  }
1138
1139  C.addTransition(state->set<RegionState>(RS), N);
1140}
1141
1142void MallocChecker::checkEndPath(CheckerContext &C) const {
1143  ProgramStateRef state = C.getState();
1144  RegionStateTy M = state->get<RegionState>();
1145
1146  // If inside inlined call, skip it.
1147  if (C.getLocationContext()->getParent() != 0)
1148    return;
1149
1150  for (RegionStateTy::iterator I = M.begin(), E = M.end(); I != E; ++I) {
1151    RefState RS = I->second;
1152    if (RS.isAllocated()) {
1153      ExplodedNode *N = C.addTransition(state);
1154      if (N)
1155        reportLeak(I->first, N, C);
1156    }
1157  }
1158}
1159
1160void MallocChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const {
1161  // We will check for double free in the post visit.
1162  if (isFreeFunction(C.getCalleeDecl(CE), C.getASTContext()))
1163    return;
1164
1165  // Check use after free, when a freed pointer is passed to a call.
1166  ProgramStateRef State = C.getState();
1167  for (CallExpr::const_arg_iterator I = CE->arg_begin(),
1168                                    E = CE->arg_end(); I != E; ++I) {
1169    const Expr *A = *I;
1170    if (A->getType().getTypePtr()->isAnyPointerType()) {
1171      SymbolRef Sym = State->getSVal(A, C.getLocationContext()).getAsSymbol();
1172      if (!Sym)
1173        continue;
1174      if (checkUseAfterFree(Sym, C, A))
1175        return;
1176    }
1177  }
1178}
1179
1180void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const {
1181  const Expr *E = S->getRetValue();
1182  if (!E)
1183    return;
1184
1185  // Check if we are returning a symbol.
1186  ProgramStateRef State = C.getState();
1187  SVal RetVal = State->getSVal(E, C.getLocationContext());
1188  SymbolRef Sym = RetVal.getAsSymbol();
1189  if (!Sym)
1190    // If we are returning a field of the allocated struct or an array element,
1191    // the callee could still free the memory.
1192    // TODO: This logic should be a part of generic symbol escape callback.
1193    if (const MemRegion *MR = RetVal.getAsRegion())
1194      if (isa<FieldRegion>(MR) || isa<ElementRegion>(MR))
1195        if (const SymbolicRegion *BMR =
1196              dyn_cast<SymbolicRegion>(MR->getBaseRegion()))
1197          Sym = BMR->getSymbol();
1198
1199  // Check if we are returning freed memory.
1200  if (Sym)
1201    if (checkUseAfterFree(Sym, C, E))
1202      return;
1203
1204  // If this function body is not inlined, stop tracking any returned symbols.
1205  if (C.getLocationContext()->getParent() == 0) {
1206    State =
1207      State->scanReachableSymbols<StopTrackingCallback>(RetVal).getState();
1208    C.addTransition(State);
1209  }
1210}
1211
1212// TODO: Blocks should be either inlined or should call invalidate regions
1213// upon invocation. After that's in place, special casing here will not be
1214// needed.
1215void MallocChecker::checkPostStmt(const BlockExpr *BE,
1216                                  CheckerContext &C) const {
1217
1218  // Scan the BlockDecRefExprs for any object the retain count checker
1219  // may be tracking.
1220  if (!BE->getBlockDecl()->hasCaptures())
1221    return;
1222
1223  ProgramStateRef state = C.getState();
1224  const BlockDataRegion *R =
1225    cast<BlockDataRegion>(state->getSVal(BE,
1226                                         C.getLocationContext()).getAsRegion());
1227
1228  BlockDataRegion::referenced_vars_iterator I = R->referenced_vars_begin(),
1229                                            E = R->referenced_vars_end();
1230
1231  if (I == E)
1232    return;
1233
1234  SmallVector<const MemRegion*, 10> Regions;
1235  const LocationContext *LC = C.getLocationContext();
1236  MemRegionManager &MemMgr = C.getSValBuilder().getRegionManager();
1237
1238  for ( ; I != E; ++I) {
1239    const VarRegion *VR = *I;
1240    if (VR->getSuperRegion() == R) {
1241      VR = MemMgr.getVarRegion(VR->getDecl(), LC);
1242    }
1243    Regions.push_back(VR);
1244  }
1245
1246  state =
1247    state->scanReachableSymbols<StopTrackingCallback>(Regions.data(),
1248                                    Regions.data() + Regions.size()).getState();
1249  C.addTransition(state);
1250}
1251
1252bool MallocChecker::isReleased(SymbolRef Sym, CheckerContext &C) const {
1253  assert(Sym);
1254  const RefState *RS = C.getState()->get<RegionState>(Sym);
1255  return (RS && RS->isReleased());
1256}
1257
1258bool MallocChecker::checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
1259                                      const Stmt *S) const {
1260  if (isReleased(Sym, C)) {
1261    if (ExplodedNode *N = C.generateSink()) {
1262      if (!BT_UseFree)
1263        BT_UseFree.reset(new BugType("Use-after-free", "Memory Error"));
1264
1265      BugReport *R = new BugReport(*BT_UseFree,
1266                                   "Use of memory after it is freed",N);
1267      if (S)
1268        R->addRange(S->getSourceRange());
1269      R->markInteresting(Sym);
1270      R->addVisitor(new MallocBugVisitor(Sym));
1271      C.emitReport(R);
1272      return true;
1273    }
1274  }
1275  return false;
1276}
1277
1278// Check if the location is a freed symbolic region.
1279void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S,
1280                                  CheckerContext &C) const {
1281  SymbolRef Sym = l.getLocSymbolInBase();
1282  if (Sym)
1283    checkUseAfterFree(Sym, C, S);
1284}
1285
1286//===----------------------------------------------------------------------===//
1287// Check various ways a symbol can be invalidated.
1288// TODO: This logic (the next 3 functions) is copied/similar to the
1289// RetainRelease checker. We might want to factor this out.
1290//===----------------------------------------------------------------------===//
1291
1292// Stop tracking symbols when a value escapes as a result of checkBind.
1293// A value escapes in three possible cases:
1294// (1) we are binding to something that is not a memory region.
1295// (2) we are binding to a memregion that does not have stack storage
1296// (3) we are binding to a memregion with stack storage that the store
1297//     does not understand.
1298void MallocChecker::checkBind(SVal loc, SVal val, const Stmt *S,
1299                              CheckerContext &C) const {
1300  // Are we storing to something that causes the value to "escape"?
1301  bool escapes = true;
1302  ProgramStateRef state = C.getState();
1303
1304  if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) {
1305    escapes = !regionLoc->getRegion()->hasStackStorage();
1306
1307    if (!escapes) {
1308      // To test (3), generate a new state with the binding added.  If it is
1309      // the same state, then it escapes (since the store cannot represent
1310      // the binding).
1311      // Do this only if we know that the store is not supposed to generate the
1312      // same state.
1313      SVal StoredVal = state->getSVal(regionLoc->getRegion());
1314      if (StoredVal != val)
1315        escapes = (state == (state->bindLoc(*regionLoc, val)));
1316    }
1317  }
1318
1319  // If our store can represent the binding and we aren't storing to something
1320  // that doesn't have local storage then just return and have the simulation
1321  // state continue as is.
1322  if (!escapes)
1323      return;
1324
1325  // Otherwise, find all symbols referenced by 'val' that we are tracking
1326  // and stop tracking them.
1327  state = state->scanReachableSymbols<StopTrackingCallback>(val).getState();
1328  C.addTransition(state);
1329}
1330
1331// If a symbolic region is assumed to NULL (or another constant), stop tracking
1332// it - assuming that allocation failed on this path.
1333ProgramStateRef MallocChecker::evalAssume(ProgramStateRef state,
1334                                              SVal Cond,
1335                                              bool Assumption) const {
1336  RegionStateTy RS = state->get<RegionState>();
1337  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
1338    // If the symbol is assumed to be NULL, remove it from consideration.
1339    ConstraintManager &CMgr = state->getConstraintManager();
1340    ConditionTruthVal AllocFailed = CMgr.isNull(state, I.getKey());
1341    if (AllocFailed.isConstrainedTrue())
1342      state = state->remove<RegionState>(I.getKey());
1343  }
1344
1345  // Realloc returns 0 when reallocation fails, which means that we should
1346  // restore the state of the pointer being reallocated.
1347  ReallocPairsTy RP = state->get<ReallocPairs>();
1348  for (ReallocPairsTy::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
1349    // If the symbol is assumed to be NULL, remove it from consideration.
1350    ConstraintManager &CMgr = state->getConstraintManager();
1351    ConditionTruthVal AllocFailed = CMgr.isNull(state, I.getKey());
1352    if (!AllocFailed.isConstrainedTrue())
1353      continue;
1354
1355    SymbolRef ReallocSym = I.getData().ReallocatedSym;
1356    if (const RefState *RS = state->get<RegionState>(ReallocSym)) {
1357      if (RS->isReleased()) {
1358        if (I.getData().Kind == RPToBeFreedAfterFailure)
1359          state = state->set<RegionState>(ReallocSym,
1360              RefState::getAllocated(RS->getStmt()));
1361        else if (I.getData().Kind == RPDoNotTrackAfterFailure)
1362          state = state->remove<RegionState>(ReallocSym);
1363        else
1364          assert(I.getData().Kind == RPIsFreeOnFailure);
1365      }
1366    }
1367    state = state->remove<ReallocPairs>(I.getKey());
1368  }
1369
1370  return state;
1371}
1372
1373// Check if the function is known to us. So, for example, we could
1374// conservatively assume it can free/reallocate its pointer arguments.
1375// (We assume that the pointers cannot escape through calls to system
1376// functions not handled by this checker.)
1377bool MallocChecker::doesNotFreeMemory(const CallEvent *Call,
1378                                      ProgramStateRef State) const {
1379  assert(Call);
1380
1381  // For now, assume that any C++ call can free memory.
1382  // TODO: If we want to be more optimistic here, we'll need to make sure that
1383  // regions escape to C++ containers. They seem to do that even now, but for
1384  // mysterious reasons.
1385  if (!(isa<FunctionCall>(Call) || isa<ObjCMethodCall>(Call)))
1386    return false;
1387
1388  // Check Objective-C messages by selector name.
1389  if (const ObjCMethodCall *Msg = dyn_cast<ObjCMethodCall>(Call)) {
1390    // If it's not a framework call, or if it takes a callback, assume it
1391    // can free memory.
1392    if (!Call->isInSystemHeader() || Call->hasNonZeroCallbackArg())
1393      return false;
1394
1395    Selector S = Msg->getSelector();
1396
1397    // Whitelist the ObjC methods which do free memory.
1398    // - Anything containing 'freeWhenDone' param set to 1.
1399    //   Ex: dataWithBytesNoCopy:length:freeWhenDone.
1400    for (unsigned i = 1; i < S.getNumArgs(); ++i) {
1401      if (S.getNameForSlot(i).equals("freeWhenDone")) {
1402        if (Call->getArgSVal(i).isConstant(1))
1403          return false;
1404        else
1405          return true;
1406      }
1407    }
1408
1409    // If the first selector ends with NoCopy, assume that the ownership is
1410    // transferred as well.
1411    // Ex:  [NSData dataWithBytesNoCopy:bytes length:10];
1412    StringRef FirstSlot = S.getNameForSlot(0);
1413    if (FirstSlot.endswith("NoCopy"))
1414      return false;
1415
1416    // If the first selector starts with addPointer, insertPointer,
1417    // or replacePointer, assume we are dealing with NSPointerArray or similar.
1418    // This is similar to C++ containers (vector); we still might want to check
1419    // that the pointers get freed by following the container itself.
1420    if (FirstSlot.startswith("addPointer") ||
1421        FirstSlot.startswith("insertPointer") ||
1422        FirstSlot.startswith("replacePointer")) {
1423      return false;
1424    }
1425
1426    // Otherwise, assume that the method does not free memory.
1427    // Most framework methods do not free memory.
1428    return true;
1429  }
1430
1431  // At this point the only thing left to handle is straight function calls.
1432  const FunctionDecl *FD = cast<FunctionCall>(Call)->getDecl();
1433  if (!FD)
1434    return false;
1435
1436  ASTContext &ASTC = State->getStateManager().getContext();
1437
1438  // If it's one of the allocation functions we can reason about, we model
1439  // its behavior explicitly.
1440  if (isMemFunction(FD, ASTC))
1441    return true;
1442
1443  // If it's not a system call, assume it frees memory.
1444  if (!Call->isInSystemHeader())
1445    return false;
1446
1447  // White list the system functions whose arguments escape.
1448  const IdentifierInfo *II = FD->getIdentifier();
1449  if (!II)
1450    return false;
1451  StringRef FName = II->getName();
1452
1453  // White list the 'XXXNoCopy' CoreFoundation functions.
1454  // We specifically check these before
1455  if (FName.endswith("NoCopy")) {
1456    // Look for the deallocator argument. We know that the memory ownership
1457    // is not transferred only if the deallocator argument is
1458    // 'kCFAllocatorNull'.
1459    for (unsigned i = 1; i < Call->getNumArgs(); ++i) {
1460      const Expr *ArgE = Call->getArgExpr(i)->IgnoreParenCasts();
1461      if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(ArgE)) {
1462        StringRef DeallocatorName = DE->getFoundDecl()->getName();
1463        if (DeallocatorName == "kCFAllocatorNull")
1464          return true;
1465      }
1466    }
1467    return false;
1468  }
1469
1470  // Associating streams with malloced buffers. The pointer can escape if
1471  // 'closefn' is specified (and if that function does free memory),
1472  // but it will not if closefn is not specified.
1473  // Currently, we do not inspect the 'closefn' function (PR12101).
1474  if (FName == "funopen")
1475    if (Call->getNumArgs() >= 4 && Call->getArgSVal(4).isConstant(0))
1476      return true;
1477
1478  // Do not warn on pointers passed to 'setbuf' when used with std streams,
1479  // these leaks might be intentional when setting the buffer for stdio.
1480  // http://stackoverflow.com/questions/2671151/who-frees-setvbuf-buffer
1481  if (FName == "setbuf" || FName =="setbuffer" ||
1482      FName == "setlinebuf" || FName == "setvbuf") {
1483    if (Call->getNumArgs() >= 1) {
1484      const Expr *ArgE = Call->getArgExpr(0)->IgnoreParenCasts();
1485      if (const DeclRefExpr *ArgDRE = dyn_cast<DeclRefExpr>(ArgE))
1486        if (const VarDecl *D = dyn_cast<VarDecl>(ArgDRE->getDecl()))
1487          if (D->getCanonicalDecl()->getName().find("std") != StringRef::npos)
1488            return false;
1489    }
1490  }
1491
1492  // A bunch of other functions which either take ownership of a pointer or
1493  // wrap the result up in a struct or object, meaning it can be freed later.
1494  // (See RetainCountChecker.) Not all the parameters here are invalidated,
1495  // but the Malloc checker cannot differentiate between them. The right way
1496  // of doing this would be to implement a pointer escapes callback.
1497  if (FName == "CGBitmapContextCreate" ||
1498      FName == "CGBitmapContextCreateWithData" ||
1499      FName == "CVPixelBufferCreateWithBytes" ||
1500      FName == "CVPixelBufferCreateWithPlanarBytes" ||
1501      FName == "OSAtomicEnqueue") {
1502    return false;
1503  }
1504
1505  // Handle cases where we know a buffer's /address/ can escape.
1506  // Note that the above checks handle some special cases where we know that
1507  // even though the address escapes, it's still our responsibility to free the
1508  // buffer.
1509  if (Call->argumentsMayEscape())
1510    return false;
1511
1512  // Otherwise, assume that the function does not free memory.
1513  // Most system calls do not free the memory.
1514  return true;
1515}
1516
1517// If the symbol we are tracking is invalidated, but not explicitly (ex: the &p
1518// escapes, when we are tracking p), do not track the symbol as we cannot reason
1519// about it anymore.
1520ProgramStateRef
1521MallocChecker::checkRegionChanges(ProgramStateRef State,
1522                            const StoreManager::InvalidatedSymbols *invalidated,
1523                                    ArrayRef<const MemRegion *> ExplicitRegions,
1524                                    ArrayRef<const MemRegion *> Regions,
1525                                    const CallEvent *Call) const {
1526  if (!invalidated || invalidated->empty())
1527    return State;
1528  llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols;
1529
1530  // If it's a call which might free or reallocate memory, we assume that all
1531  // regions (explicit and implicit) escaped.
1532
1533  // Otherwise, whitelist explicit pointers; we still can track them.
1534  if (!Call || doesNotFreeMemory(Call, State)) {
1535    for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(),
1536        E = ExplicitRegions.end(); I != E; ++I) {
1537      if (const SymbolicRegion *R = (*I)->StripCasts()->getAs<SymbolicRegion>())
1538        WhitelistedSymbols.insert(R->getSymbol());
1539    }
1540  }
1541
1542  for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(),
1543       E = invalidated->end(); I!=E; ++I) {
1544    SymbolRef sym = *I;
1545    if (WhitelistedSymbols.count(sym))
1546      continue;
1547    // The symbol escaped. Note, we assume that if the symbol is released,
1548    // passing it out will result in a use after free. We also keep tracking
1549    // relinquished symbols.
1550    if (const RefState *RS = State->get<RegionState>(sym)) {
1551      if (RS->isAllocated())
1552        State = State->remove<RegionState>(sym);
1553    }
1554  }
1555  return State;
1556}
1557
1558static SymbolRef findFailedReallocSymbol(ProgramStateRef currState,
1559                                         ProgramStateRef prevState) {
1560  ReallocPairsTy currMap = currState->get<ReallocPairs>();
1561  ReallocPairsTy prevMap = prevState->get<ReallocPairs>();
1562
1563  for (ReallocPairsTy::iterator I = prevMap.begin(), E = prevMap.end();
1564       I != E; ++I) {
1565    SymbolRef sym = I.getKey();
1566    if (!currMap.lookup(sym))
1567      return sym;
1568  }
1569
1570  return NULL;
1571}
1572
1573PathDiagnosticPiece *
1574MallocChecker::MallocBugVisitor::VisitNode(const ExplodedNode *N,
1575                                           const ExplodedNode *PrevN,
1576                                           BugReporterContext &BRC,
1577                                           BugReport &BR) {
1578  ProgramStateRef state = N->getState();
1579  ProgramStateRef statePrev = PrevN->getState();
1580
1581  const RefState *RS = state->get<RegionState>(Sym);
1582  const RefState *RSPrev = statePrev->get<RegionState>(Sym);
1583  if (!RS)
1584    return 0;
1585
1586  const Stmt *S = 0;
1587  const char *Msg = 0;
1588  StackHintGeneratorForSymbol *StackHint = 0;
1589
1590  // Retrieve the associated statement.
1591  ProgramPoint ProgLoc = N->getLocation();
1592  if (StmtPoint *SP = dyn_cast<StmtPoint>(&ProgLoc))
1593    S = SP->getStmt();
1594  else if (CallExitEnd *Exit = dyn_cast<CallExitEnd>(&ProgLoc))
1595    S = Exit->getCalleeContext()->getCallSite();
1596  // If an assumption was made on a branch, it should be caught
1597  // here by looking at the state transition.
1598  else if (BlockEdge *Edge = dyn_cast<BlockEdge>(&ProgLoc)) {
1599    const CFGBlock *srcBlk = Edge->getSrc();
1600    S = srcBlk->getTerminator();
1601  }
1602  if (!S)
1603    return 0;
1604
1605  // FIXME: We will eventually need to handle non-statement-based events
1606  // (__attribute__((cleanup))).
1607
1608  // Find out if this is an interesting point and what is the kind.
1609  if (Mode == Normal) {
1610    if (isAllocated(RS, RSPrev, S)) {
1611      Msg = "Memory is allocated";
1612      StackHint = new StackHintGeneratorForSymbol(Sym,
1613                                                  "Returned allocated memory");
1614    } else if (isReleased(RS, RSPrev, S)) {
1615      Msg = "Memory is released";
1616      StackHint = new StackHintGeneratorForSymbol(Sym,
1617                                                  "Returned released memory");
1618    } else if (isRelinquished(RS, RSPrev, S)) {
1619      Msg = "Memory ownership is transfered";
1620      StackHint = new StackHintGeneratorForSymbol(Sym, "");
1621    } else if (isReallocFailedCheck(RS, RSPrev, S)) {
1622      Mode = ReallocationFailed;
1623      Msg = "Reallocation failed";
1624      StackHint = new StackHintGeneratorForReallocationFailed(Sym,
1625                                                       "Reallocation failed");
1626
1627      if (SymbolRef sym = findFailedReallocSymbol(state, statePrev)) {
1628        // Is it possible to fail two reallocs WITHOUT testing in between?
1629        assert((!FailedReallocSymbol || FailedReallocSymbol == sym) &&
1630          "We only support one failed realloc at a time.");
1631        BR.markInteresting(sym);
1632        FailedReallocSymbol = sym;
1633      }
1634    }
1635
1636  // We are in a special mode if a reallocation failed later in the path.
1637  } else if (Mode == ReallocationFailed) {
1638    assert(FailedReallocSymbol && "No symbol to look for.");
1639
1640    // Is this is the first appearance of the reallocated symbol?
1641    if (!statePrev->get<RegionState>(FailedReallocSymbol)) {
1642      // We're at the reallocation point.
1643      Msg = "Attempt to reallocate memory";
1644      StackHint = new StackHintGeneratorForSymbol(Sym,
1645                                                 "Returned reallocated memory");
1646      FailedReallocSymbol = NULL;
1647      Mode = Normal;
1648    }
1649  }
1650
1651  if (!Msg)
1652    return 0;
1653  assert(StackHint);
1654
1655  // Generate the extra diagnostic.
1656  PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
1657                             N->getLocationContext());
1658  return new PathDiagnosticEventPiece(Pos, Msg, true, StackHint);
1659}
1660
1661void MallocChecker::printState(raw_ostream &Out, ProgramStateRef State,
1662                               const char *NL, const char *Sep) const {
1663
1664  RegionStateTy RS = State->get<RegionState>();
1665
1666  if (!RS.isEmpty())
1667    Out << "Has Malloc data" << NL;
1668}
1669
1670#define REGISTER_CHECKER(name) \
1671void ento::register##name(CheckerManager &mgr) {\
1672  registerCStringCheckerBasic(mgr); \
1673  mgr.registerChecker<MallocChecker>()->Filter.C##name = true;\
1674}
1675
1676REGISTER_CHECKER(MallocPessimistic)
1677REGISTER_CHECKER(MallocOptimistic)
1678