MallocChecker.cpp revision 65d4bd60ec6a734b814b7253b1026d35c8e46ce9 
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::PreStmt<ReturnStmt>,
106                                     check::PreStmt<CallExpr>,
107                                     check::PostStmt<CallExpr>,
108                                     check::PostStmt<BlockExpr>,
109                                     check::PostObjCMessage,
110                                     check::Location,
111                                     check::Bind,
112                                     eval::Assume,
113                                     check::RegionChanges>
114{
115  mutable OwningPtr<BugType> BT_DoubleFree;
116  mutable OwningPtr<BugType> BT_Leak;
117  mutable OwningPtr<BugType> BT_UseFree;
118  mutable OwningPtr<BugType> BT_BadFree;
119  mutable IdentifierInfo *II_malloc, *II_free, *II_realloc, *II_calloc,
120                         *II_valloc, *II_reallocf, *II_strndup, *II_strdup;
121
122public:
123  MallocChecker() : II_malloc(0), II_free(0), II_realloc(0), II_calloc(0),
124                    II_valloc(0), II_reallocf(0), II_strndup(0), II_strdup(0) {}
125
126  /// In pessimistic mode, the checker assumes that it does not know which
127  /// functions might free the memory.
128  struct ChecksFilter {
129    DefaultBool CMallocPessimistic;
130    DefaultBool CMallocOptimistic;
131  };
132
133  ChecksFilter Filter;
134
135  void checkPreStmt(const CallExpr *S, CheckerContext &C) const;
136  void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
137  void checkPostObjCMessage(const ObjCMethodCall &Call, CheckerContext &C) const;
138  void checkPostStmt(const BlockExpr *BE, CheckerContext &C) const;
139  void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
140  void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
141  ProgramStateRef evalAssume(ProgramStateRef state, SVal Cond,
142                            bool Assumption) const;
143  void checkLocation(SVal l, bool isLoad, const Stmt *S,
144                     CheckerContext &C) const;
145  void checkBind(SVal location, SVal val, const Stmt*S,
146                 CheckerContext &C) const;
147  ProgramStateRef
148  checkRegionChanges(ProgramStateRef state,
149                     const StoreManager::InvalidatedSymbols *invalidated,
150                     ArrayRef<const MemRegion *> ExplicitRegions,
151                     ArrayRef<const MemRegion *> Regions,
152                     const CallEvent *Call) const;
153  bool wantsRegionChangeUpdate(ProgramStateRef state) const {
154    return true;
155  }
156
157  void printState(raw_ostream &Out, ProgramStateRef State,
158                  const char *NL, const char *Sep) const;
159
160private:
161  void initIdentifierInfo(ASTContext &C) const;
162
163  /// Check if this is one of the functions which can allocate/reallocate memory
164  /// pointed to by one of its arguments.
165  bool isMemFunction(const FunctionDecl *FD, ASTContext &C) const;
166  bool isFreeFunction(const FunctionDecl *FD, ASTContext &C) const;
167  bool isAllocationFunction(const FunctionDecl *FD, ASTContext &C) const;
168
169  static ProgramStateRef MallocMemReturnsAttr(CheckerContext &C,
170                                              const CallExpr *CE,
171                                              const OwnershipAttr* Att);
172  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
173                                     const Expr *SizeEx, SVal Init,
174                                     ProgramStateRef state) {
175    return MallocMemAux(C, CE,
176                        state->getSVal(SizeEx, C.getLocationContext()),
177                        Init, state);
178  }
179
180  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
181                                     SVal SizeEx, SVal Init,
182                                     ProgramStateRef state);
183
184  /// Update the RefState to reflect the new memory allocation.
185  static ProgramStateRef MallocUpdateRefState(CheckerContext &C,
186                                              const CallExpr *CE,
187                                              ProgramStateRef state);
188
189  ProgramStateRef FreeMemAttr(CheckerContext &C, const CallExpr *CE,
190                              const OwnershipAttr* Att) const;
191  ProgramStateRef FreeMemAux(CheckerContext &C, const CallExpr *CE,
192                             ProgramStateRef state, unsigned Num,
193                             bool Hold,
194                             bool &ReleasedAllocated,
195                             bool ReturnsNullOnFailure = false) const;
196  ProgramStateRef FreeMemAux(CheckerContext &C, const Expr *Arg,
197                             const Expr *ParentExpr,
198                             ProgramStateRef State,
199                             bool Hold,
200                             bool &ReleasedAllocated,
201                             bool ReturnsNullOnFailure = false) const;
202
203  ProgramStateRef ReallocMem(CheckerContext &C, const CallExpr *CE,
204                             bool FreesMemOnFailure) const;
205  static ProgramStateRef CallocMem(CheckerContext &C, const CallExpr *CE);
206
207  ///\brief Check if the memory associated with this symbol was released.
208  bool isReleased(SymbolRef Sym, CheckerContext &C) const;
209
210  bool checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
211                         const Stmt *S = 0) const;
212
213  /// Check if the function is not known to us. So, for example, we could
214  /// conservatively assume it can free/reallocate it's pointer arguments.
215  bool doesNotFreeMemory(const CallEvent *Call,
216                         ProgramStateRef State) const;
217
218  static bool SummarizeValue(raw_ostream &os, SVal V);
219  static bool SummarizeRegion(raw_ostream &os, const MemRegion *MR);
220  void ReportBadFree(CheckerContext &C, SVal ArgVal, SourceRange range) const;
221
222  /// Find the location of the allocation for Sym on the path leading to the
223  /// exploded node N.
224  LeakInfo getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
225                             CheckerContext &C) const;
226
227  void reportLeak(SymbolRef Sym, ExplodedNode *N, CheckerContext &C) const;
228
229  /// The bug visitor which allows us to print extra diagnostics along the
230  /// BugReport path. For example, showing the allocation site of the leaked
231  /// region.
232  class MallocBugVisitor : public BugReporterVisitorImpl<MallocBugVisitor> {
233  protected:
234    enum NotificationMode {
235      Normal,
236      ReallocationFailed
237    };
238
239    // The allocated region symbol tracked by the main analysis.
240    SymbolRef Sym;
241
242    // The mode we are in, i.e. what kind of diagnostics will be emitted.
243    NotificationMode Mode;
244
245    // A symbol from when the primary region should have been reallocated.
246    SymbolRef FailedReallocSymbol;
247
248    bool IsLeak;
249
250  public:
251    MallocBugVisitor(SymbolRef S, bool isLeak = false)
252       : Sym(S), Mode(Normal), FailedReallocSymbol(0), IsLeak(isLeak) {}
253
254    virtual ~MallocBugVisitor() {}
255
256    void Profile(llvm::FoldingSetNodeID &ID) const {
257      static int X = 0;
258      ID.AddPointer(&X);
259      ID.AddPointer(Sym);
260    }
261
262    inline bool isAllocated(const RefState *S, const RefState *SPrev,
263                            const Stmt *Stmt) {
264      // Did not track -> allocated. Other state (released) -> allocated.
265      return (Stmt && isa<CallExpr>(Stmt) &&
266              (S && S->isAllocated()) && (!SPrev || !SPrev->isAllocated()));
267    }
268
269    inline bool isReleased(const RefState *S, const RefState *SPrev,
270                           const Stmt *Stmt) {
271      // Did not track -> released. Other state (allocated) -> released.
272      return (Stmt && isa<CallExpr>(Stmt) &&
273              (S && S->isReleased()) && (!SPrev || !SPrev->isReleased()));
274    }
275
276    inline bool isRelinquished(const RefState *S, const RefState *SPrev,
277                               const Stmt *Stmt) {
278      // Did not track -> relinquished. Other state (allocated) -> relinquished.
279      return (Stmt && (isa<CallExpr>(Stmt) || isa<ObjCMessageExpr>(Stmt) ||
280                                              isa<ObjCPropertyRefExpr>(Stmt)) &&
281              (S && S->isRelinquished()) &&
282              (!SPrev || !SPrev->isRelinquished()));
283    }
284
285    inline bool isReallocFailedCheck(const RefState *S, const RefState *SPrev,
286                                     const Stmt *Stmt) {
287      // If the expression is not a call, and the state change is
288      // released -> allocated, it must be the realloc return value
289      // check. If we have to handle more cases here, it might be cleaner just
290      // to track this extra bit in the state itself.
291      return ((!Stmt || !isa<CallExpr>(Stmt)) &&
292              (S && S->isAllocated()) && (SPrev && !SPrev->isAllocated()));
293    }
294
295    PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
296                                   const ExplodedNode *PrevN,
297                                   BugReporterContext &BRC,
298                                   BugReport &BR);
299
300    PathDiagnosticPiece* getEndPath(BugReporterContext &BRC,
301                                    const ExplodedNode *EndPathNode,
302                                    BugReport &BR) {
303      if (!IsLeak)
304        return 0;
305
306      PathDiagnosticLocation L =
307        PathDiagnosticLocation::createEndOfPath(EndPathNode,
308                                                BRC.getSourceManager());
309      // Do not add the statement itself as a range in case of leak.
310      return new PathDiagnosticEventPiece(L, BR.getDescription(), false);
311    }
312
313  private:
314    class StackHintGeneratorForReallocationFailed
315        : public StackHintGeneratorForSymbol {
316    public:
317      StackHintGeneratorForReallocationFailed(SymbolRef S, StringRef M)
318        : StackHintGeneratorForSymbol(S, M) {}
319
320      virtual std::string getMessageForArg(const Expr *ArgE, unsigned ArgIndex) {
321        // Printed parameters start at 1, not 0.
322        ++ArgIndex;
323
324        SmallString<200> buf;
325        llvm::raw_svector_ostream os(buf);
326
327        os << "Reallocation of " << ArgIndex << llvm::getOrdinalSuffix(ArgIndex)
328           << " parameter failed";
329
330        return os.str();
331      }
332
333      virtual std::string getMessageForReturn(const CallExpr *CallExpr) {
334        return "Reallocation of returned value failed";
335      }
336    };
337  };
338};
339} // end anonymous namespace
340
341REGISTER_MAP_WITH_PROGRAMSTATE(RegionState, SymbolRef, RefState)
342REGISTER_MAP_WITH_PROGRAMSTATE(ReallocPairs, SymbolRef, ReallocPair)
343
344// A map from the freed symbol to the symbol representing the return value of
345// the free function.
346REGISTER_MAP_WITH_PROGRAMSTATE(FreeReturnValue, SymbolRef, SymbolRef)
347
348namespace {
349class StopTrackingCallback : public SymbolVisitor {
350  ProgramStateRef state;
351public:
352  StopTrackingCallback(ProgramStateRef st) : state(st) {}
353  ProgramStateRef getState() const { return state; }
354
355  bool VisitSymbol(SymbolRef sym) {
356    state = state->remove<RegionState>(sym);
357    return true;
358  }
359};
360} // end anonymous namespace
361
362void MallocChecker::initIdentifierInfo(ASTContext &Ctx) const {
363  if (II_malloc)
364    return;
365  II_malloc = &Ctx.Idents.get("malloc");
366  II_free = &Ctx.Idents.get("free");
367  II_realloc = &Ctx.Idents.get("realloc");
368  II_reallocf = &Ctx.Idents.get("reallocf");
369  II_calloc = &Ctx.Idents.get("calloc");
370  II_valloc = &Ctx.Idents.get("valloc");
371  II_strdup = &Ctx.Idents.get("strdup");
372  II_strndup = &Ctx.Idents.get("strndup");
373}
374
375bool MallocChecker::isMemFunction(const FunctionDecl *FD, ASTContext &C) const {
376  if (isFreeFunction(FD, C))
377    return true;
378
379  if (isAllocationFunction(FD, C))
380    return true;
381
382  return false;
383}
384
385bool MallocChecker::isAllocationFunction(const FunctionDecl *FD,
386                                         ASTContext &C) const {
387  if (!FD)
388    return false;
389
390  if (FD->getKind() == Decl::Function) {
391    IdentifierInfo *FunI = FD->getIdentifier();
392    initIdentifierInfo(C);
393
394    if (FunI == II_malloc || FunI == II_realloc ||
395        FunI == II_reallocf || FunI == II_calloc || FunI == II_valloc ||
396        FunI == II_strdup || FunI == II_strndup)
397      return true;
398  }
399
400  if (Filter.CMallocOptimistic && FD->hasAttrs())
401    for (specific_attr_iterator<OwnershipAttr>
402           i = FD->specific_attr_begin<OwnershipAttr>(),
403           e = FD->specific_attr_end<OwnershipAttr>();
404           i != e; ++i)
405      if ((*i)->getOwnKind() == OwnershipAttr::Returns)
406        return true;
407  return false;
408}
409
410bool MallocChecker::isFreeFunction(const FunctionDecl *FD, ASTContext &C) const {
411  if (!FD)
412    return false;
413
414  if (FD->getKind() == Decl::Function) {
415    IdentifierInfo *FunI = FD->getIdentifier();
416    initIdentifierInfo(C);
417
418    if (FunI == II_free || FunI == II_realloc || FunI == II_reallocf)
419      return true;
420  }
421
422  if (Filter.CMallocOptimistic && FD->hasAttrs())
423    for (specific_attr_iterator<OwnershipAttr>
424           i = FD->specific_attr_begin<OwnershipAttr>(),
425           e = FD->specific_attr_end<OwnershipAttr>();
426           i != e; ++i)
427      if ((*i)->getOwnKind() == OwnershipAttr::Takes ||
428          (*i)->getOwnKind() == OwnershipAttr::Holds)
429        return true;
430  return false;
431}
432
433void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const {
434  if (C.wasInlined)
435    return;
436
437  const FunctionDecl *FD = C.getCalleeDecl(CE);
438  if (!FD)
439    return;
440
441  ProgramStateRef State = C.getState();
442  bool ReleasedAllocatedMemory = false;
443
444  if (FD->getKind() == Decl::Function) {
445    initIdentifierInfo(C.getASTContext());
446    IdentifierInfo *FunI = FD->getIdentifier();
447
448    if (FunI == II_malloc || FunI == II_valloc) {
449      if (CE->getNumArgs() < 1)
450        return;
451      State = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(), State);
452    } else if (FunI == II_realloc) {
453      State = ReallocMem(C, CE, false);
454    } else if (FunI == II_reallocf) {
455      State = ReallocMem(C, CE, true);
456    } else if (FunI == II_calloc) {
457      State = CallocMem(C, CE);
458    } else if (FunI == II_free) {
459      State = FreeMemAux(C, CE, State, 0, false, ReleasedAllocatedMemory);
460    } else if (FunI == II_strdup) {
461      State = MallocUpdateRefState(C, CE, State);
462    } else if (FunI == II_strndup) {
463      State = MallocUpdateRefState(C, CE, State);
464    }
465  }
466
467  if (Filter.CMallocOptimistic) {
468    // Check all the attributes, if there are any.
469    // There can be multiple of these attributes.
470    if (FD->hasAttrs())
471      for (specific_attr_iterator<OwnershipAttr>
472          i = FD->specific_attr_begin<OwnershipAttr>(),
473          e = FD->specific_attr_end<OwnershipAttr>();
474          i != e; ++i) {
475        switch ((*i)->getOwnKind()) {
476        case OwnershipAttr::Returns:
477          State = MallocMemReturnsAttr(C, CE, *i);
478          break;
479        case OwnershipAttr::Takes:
480        case OwnershipAttr::Holds:
481          State = FreeMemAttr(C, CE, *i);
482          break;
483        }
484      }
485  }
486  C.addTransition(State);
487}
488
489static bool isFreeWhenDoneSetToZero(const ObjCMethodCall &Call) {
490  Selector S = Call.getSelector();
491  for (unsigned i = 1; i < S.getNumArgs(); ++i)
492    if (S.getNameForSlot(i).equals("freeWhenDone"))
493      if (Call.getArgSVal(i).isConstant(0))
494        return true;
495
496  return false;
497}
498
499void MallocChecker::checkPostObjCMessage(const ObjCMethodCall &Call,
500                                         CheckerContext &C) const {
501  // If the first selector is dataWithBytesNoCopy, assume that the memory will
502  // be released with 'free' by the new object.
503  // Ex:  [NSData dataWithBytesNoCopy:bytes length:10];
504  // Unless 'freeWhenDone' param set to 0.
505  // TODO: Check that the memory was allocated with malloc.
506  bool ReleasedAllocatedMemory = false;
507  Selector S = Call.getSelector();
508  if ((S.getNameForSlot(0) == "dataWithBytesNoCopy" ||
509       S.getNameForSlot(0) == "initWithBytesNoCopy" ||
510       S.getNameForSlot(0) == "initWithCharactersNoCopy") &&
511      !isFreeWhenDoneSetToZero(Call)){
512    unsigned int argIdx  = 0;
513    ProgramStateRef State = FreeMemAux(C, Call.getArgExpr(argIdx),
514                                       Call.getOriginExpr(), C.getState(), true,
515                                       ReleasedAllocatedMemory,
516                                       /* RetNullOnFailure*/ true);
517
518    C.addTransition(State);
519  }
520}
521
522ProgramStateRef MallocChecker::MallocMemReturnsAttr(CheckerContext &C,
523                                                    const CallExpr *CE,
524                                                    const OwnershipAttr* Att) {
525  if (Att->getModule() != "malloc")
526    return 0;
527
528  OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
529  if (I != E) {
530    return MallocMemAux(C, CE, CE->getArg(*I), UndefinedVal(), C.getState());
531  }
532  return MallocMemAux(C, CE, UnknownVal(), UndefinedVal(), C.getState());
533}
534
535ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
536                                           const CallExpr *CE,
537                                           SVal Size, SVal Init,
538                                           ProgramStateRef state) {
539
540  // Bind the return value to the symbolic value from the heap region.
541  // TODO: We could rewrite post visit to eval call; 'malloc' does not have
542  // side effects other than what we model here.
543  unsigned Count = C.blockCount();
544  SValBuilder &svalBuilder = C.getSValBuilder();
545  const LocationContext *LCtx = C.getPredecessor()->getLocationContext();
546  DefinedSVal RetVal =
547    cast<DefinedSVal>(svalBuilder.getConjuredHeapSymbolVal(CE, LCtx, Count));
548  state = state->BindExpr(CE, C.getLocationContext(), RetVal);
549
550  // We expect the malloc functions to return a pointer.
551  if (!isa<Loc>(RetVal))
552    return 0;
553
554  // Fill the region with the initialization value.
555  state = state->bindDefault(RetVal, Init);
556
557  // Set the region's extent equal to the Size parameter.
558  const SymbolicRegion *R =
559      dyn_cast_or_null<SymbolicRegion>(RetVal.getAsRegion());
560  if (!R)
561    return 0;
562  if (isa<DefinedOrUnknownSVal>(Size)) {
563    SValBuilder &svalBuilder = C.getSValBuilder();
564    DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
565    DefinedOrUnknownSVal DefinedSize = cast<DefinedOrUnknownSVal>(Size);
566    DefinedOrUnknownSVal extentMatchesSize =
567        svalBuilder.evalEQ(state, Extent, DefinedSize);
568
569    state = state->assume(extentMatchesSize, true);
570    assert(state);
571  }
572
573  return MallocUpdateRefState(C, CE, state);
574}
575
576ProgramStateRef MallocChecker::MallocUpdateRefState(CheckerContext &C,
577                                                    const CallExpr *CE,
578                                                    ProgramStateRef state) {
579  // Get the return value.
580  SVal retVal = state->getSVal(CE, C.getLocationContext());
581
582  // We expect the malloc functions to return a pointer.
583  if (!isa<Loc>(retVal))
584    return 0;
585
586  SymbolRef Sym = retVal.getAsLocSymbol();
587  assert(Sym);
588
589  // Set the symbol's state to Allocated.
590  return state->set<RegionState>(Sym, RefState::getAllocated(CE));
591
592}
593
594ProgramStateRef MallocChecker::FreeMemAttr(CheckerContext &C,
595                                           const CallExpr *CE,
596                                           const OwnershipAttr* Att) const {
597  if (Att->getModule() != "malloc")
598    return 0;
599
600  ProgramStateRef State = C.getState();
601  bool ReleasedAllocated = false;
602
603  for (OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
604       I != E; ++I) {
605    ProgramStateRef StateI = FreeMemAux(C, CE, State, *I,
606                               Att->getOwnKind() == OwnershipAttr::Holds,
607                               ReleasedAllocated);
608    if (StateI)
609      State = StateI;
610  }
611  return State;
612}
613
614ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
615                                          const CallExpr *CE,
616                                          ProgramStateRef state,
617                                          unsigned Num,
618                                          bool Hold,
619                                          bool &ReleasedAllocated,
620                                          bool ReturnsNullOnFailure) const {
621  if (CE->getNumArgs() < (Num + 1))
622    return 0;
623
624  return FreeMemAux(C, CE->getArg(Num), CE, state, Hold,
625                    ReleasedAllocated, ReturnsNullOnFailure);
626}
627
628/// Checks if the previous call to free on the given symbol failed - if free
629/// failed, returns true. Also, returns the corresponding return value symbol.
630bool didPreviousFreeFail(ProgramStateRef State,
631                         SymbolRef Sym, SymbolRef &RetStatusSymbol) {
632  const SymbolRef *Ret = State->get<FreeReturnValue>(Sym);
633  if (Ret) {
634    assert(*Ret && "We should not store the null return symbol");
635    ConstraintManager &CMgr = State->getConstraintManager();
636    ConditionTruthVal FreeFailed = CMgr.isNull(State, *Ret);
637    RetStatusSymbol = *Ret;
638    return FreeFailed.isConstrainedTrue();
639  }
640  return false;
641}
642
643ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
644                                          const Expr *ArgExpr,
645                                          const Expr *ParentExpr,
646                                          ProgramStateRef State,
647                                          bool Hold,
648                                          bool &ReleasedAllocated,
649                                          bool ReturnsNullOnFailure) const {
650
651  SVal ArgVal = State->getSVal(ArgExpr, C.getLocationContext());
652  if (!isa<DefinedOrUnknownSVal>(ArgVal))
653    return 0;
654  DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(ArgVal);
655
656  // Check for null dereferences.
657  if (!isa<Loc>(location))
658    return 0;
659
660  // The explicit NULL case, no operation is performed.
661  ProgramStateRef notNullState, nullState;
662  llvm::tie(notNullState, nullState) = State->assume(location);
663  if (nullState && !notNullState)
664    return 0;
665
666  // Unknown values could easily be okay
667  // Undefined values are handled elsewhere
668  if (ArgVal.isUnknownOrUndef())
669    return 0;
670
671  const MemRegion *R = ArgVal.getAsRegion();
672
673  // Nonlocs can't be freed, of course.
674  // Non-region locations (labels and fixed addresses) also shouldn't be freed.
675  if (!R) {
676    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
677    return 0;
678  }
679
680  R = R->StripCasts();
681
682  // Blocks might show up as heap data, but should not be free()d
683  if (isa<BlockDataRegion>(R)) {
684    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
685    return 0;
686  }
687
688  const MemSpaceRegion *MS = R->getMemorySpace();
689
690  // Parameters, locals, statics, and globals shouldn't be freed.
691  if (!(isa<UnknownSpaceRegion>(MS) || isa<HeapSpaceRegion>(MS))) {
692    // FIXME: at the time this code was written, malloc() regions were
693    // represented by conjured symbols, which are all in UnknownSpaceRegion.
694    // This means that there isn't actually anything from HeapSpaceRegion
695    // that should be freed, even though we allow it here.
696    // Of course, free() can work on memory allocated outside the current
697    // function, so UnknownSpaceRegion is always a possibility.
698    // False negatives are better than false positives.
699
700    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
701    return 0;
702  }
703
704  const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
705  // Various cases could lead to non-symbol values here.
706  // For now, ignore them.
707  if (!SR)
708    return 0;
709
710  SymbolRef Sym = SR->getSymbol();
711  const RefState *RS = State->get<RegionState>(Sym);
712  SymbolRef PreviousRetStatusSymbol = 0;
713
714  // Check double free.
715  if (RS &&
716      (RS->isReleased() || RS->isRelinquished()) &&
717      !didPreviousFreeFail(State, Sym, PreviousRetStatusSymbol)) {
718
719    if (ExplodedNode *N = C.generateSink()) {
720      if (!BT_DoubleFree)
721        BT_DoubleFree.reset(
722          new BugType("Double free", "Memory Error"));
723      BugReport *R = new BugReport(*BT_DoubleFree,
724        (RS->isReleased() ? "Attempt to free released memory" :
725                            "Attempt to free non-owned memory"), N);
726      R->addRange(ArgExpr->getSourceRange());
727      R->markInteresting(Sym);
728      if (PreviousRetStatusSymbol)
729        R->markInteresting(PreviousRetStatusSymbol);
730      R->addVisitor(new MallocBugVisitor(Sym));
731      C.emitReport(R);
732    }
733    return 0;
734  }
735
736  ReleasedAllocated = (RS != 0);
737
738  // Clean out the info on previous call to free return info.
739  State = State->remove<FreeReturnValue>(Sym);
740
741  // Keep track of the return value. If it is NULL, we will know that free
742  // failed.
743  if (ReturnsNullOnFailure) {
744    SVal RetVal = C.getSVal(ParentExpr);
745    SymbolRef RetStatusSymbol = RetVal.getAsSymbol();
746    if (RetStatusSymbol) {
747      C.getSymbolManager().addSymbolDependency(Sym, RetStatusSymbol);
748      State = State->set<FreeReturnValue>(Sym, RetStatusSymbol);
749    }
750  }
751
752  // Normal free.
753  if (Hold)
754    return State->set<RegionState>(Sym, RefState::getRelinquished(ParentExpr));
755  return State->set<RegionState>(Sym, RefState::getReleased(ParentExpr));
756}
757
758bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) {
759  if (nonloc::ConcreteInt *IntVal = dyn_cast<nonloc::ConcreteInt>(&V))
760    os << "an integer (" << IntVal->getValue() << ")";
761  else if (loc::ConcreteInt *ConstAddr = dyn_cast<loc::ConcreteInt>(&V))
762    os << "a constant address (" << ConstAddr->getValue() << ")";
763  else if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&V))
764    os << "the address of the label '" << Label->getLabel()->getName() << "'";
765  else
766    return false;
767
768  return true;
769}
770
771bool MallocChecker::SummarizeRegion(raw_ostream &os,
772                                    const MemRegion *MR) {
773  switch (MR->getKind()) {
774  case MemRegion::FunctionTextRegionKind: {
775    const NamedDecl *FD = cast<FunctionTextRegion>(MR)->getDecl();
776    if (FD)
777      os << "the address of the function '" << *FD << '\'';
778    else
779      os << "the address of a function";
780    return true;
781  }
782  case MemRegion::BlockTextRegionKind:
783    os << "block text";
784    return true;
785  case MemRegion::BlockDataRegionKind:
786    // FIXME: where the block came from?
787    os << "a block";
788    return true;
789  default: {
790    const MemSpaceRegion *MS = MR->getMemorySpace();
791
792    if (isa<StackLocalsSpaceRegion>(MS)) {
793      const VarRegion *VR = dyn_cast<VarRegion>(MR);
794      const VarDecl *VD;
795      if (VR)
796        VD = VR->getDecl();
797      else
798        VD = NULL;
799
800      if (VD)
801        os << "the address of the local variable '" << VD->getName() << "'";
802      else
803        os << "the address of a local stack variable";
804      return true;
805    }
806
807    if (isa<StackArgumentsSpaceRegion>(MS)) {
808      const VarRegion *VR = dyn_cast<VarRegion>(MR);
809      const VarDecl *VD;
810      if (VR)
811        VD = VR->getDecl();
812      else
813        VD = NULL;
814
815      if (VD)
816        os << "the address of the parameter '" << VD->getName() << "'";
817      else
818        os << "the address of a parameter";
819      return true;
820    }
821
822    if (isa<GlobalsSpaceRegion>(MS)) {
823      const VarRegion *VR = dyn_cast<VarRegion>(MR);
824      const VarDecl *VD;
825      if (VR)
826        VD = VR->getDecl();
827      else
828        VD = NULL;
829
830      if (VD) {
831        if (VD->isStaticLocal())
832          os << "the address of the static variable '" << VD->getName() << "'";
833        else
834          os << "the address of the global variable '" << VD->getName() << "'";
835      } else
836        os << "the address of a global variable";
837      return true;
838    }
839
840    return false;
841  }
842  }
843}
844
845void MallocChecker::ReportBadFree(CheckerContext &C, SVal ArgVal,
846                                  SourceRange range) const {
847  if (ExplodedNode *N = C.generateSink()) {
848    if (!BT_BadFree)
849      BT_BadFree.reset(new BugType("Bad free", "Memory Error"));
850
851    SmallString<100> buf;
852    llvm::raw_svector_ostream os(buf);
853
854    const MemRegion *MR = ArgVal.getAsRegion();
855    if (MR) {
856      while (const ElementRegion *ER = dyn_cast<ElementRegion>(MR))
857        MR = ER->getSuperRegion();
858
859      // Special case for alloca()
860      if (isa<AllocaRegion>(MR))
861        os << "Argument to free() was allocated by alloca(), not malloc()";
862      else {
863        os << "Argument to free() is ";
864        if (SummarizeRegion(os, MR))
865          os << ", which is not memory allocated by malloc()";
866        else
867          os << "not memory allocated by malloc()";
868      }
869    } else {
870      os << "Argument to free() is ";
871      if (SummarizeValue(os, ArgVal))
872        os << ", which is not memory allocated by malloc()";
873      else
874        os << "not memory allocated by malloc()";
875    }
876
877    BugReport *R = new BugReport(*BT_BadFree, os.str(), N);
878    R->markInteresting(MR);
879    R->addRange(range);
880    C.emitReport(R);
881  }
882}
883
884ProgramStateRef MallocChecker::ReallocMem(CheckerContext &C,
885                                          const CallExpr *CE,
886                                          bool FreesOnFail) const {
887  if (CE->getNumArgs() < 2)
888    return 0;
889
890  ProgramStateRef state = C.getState();
891  const Expr *arg0Expr = CE->getArg(0);
892  const LocationContext *LCtx = C.getLocationContext();
893  SVal Arg0Val = state->getSVal(arg0Expr, LCtx);
894  if (!isa<DefinedOrUnknownSVal>(Arg0Val))
895    return 0;
896  DefinedOrUnknownSVal arg0Val = cast<DefinedOrUnknownSVal>(Arg0Val);
897
898  SValBuilder &svalBuilder = C.getSValBuilder();
899
900  DefinedOrUnknownSVal PtrEQ =
901    svalBuilder.evalEQ(state, arg0Val, svalBuilder.makeNull());
902
903  // Get the size argument. If there is no size arg then give up.
904  const Expr *Arg1 = CE->getArg(1);
905  if (!Arg1)
906    return 0;
907
908  // Get the value of the size argument.
909  SVal Arg1ValG = state->getSVal(Arg1, LCtx);
910  if (!isa<DefinedOrUnknownSVal>(Arg1ValG))
911    return 0;
912  DefinedOrUnknownSVal Arg1Val = cast<DefinedOrUnknownSVal>(Arg1ValG);
913
914  // Compare the size argument to 0.
915  DefinedOrUnknownSVal SizeZero =
916    svalBuilder.evalEQ(state, Arg1Val,
917                       svalBuilder.makeIntValWithPtrWidth(0, false));
918
919  ProgramStateRef StatePtrIsNull, StatePtrNotNull;
920  llvm::tie(StatePtrIsNull, StatePtrNotNull) = state->assume(PtrEQ);
921  ProgramStateRef StateSizeIsZero, StateSizeNotZero;
922  llvm::tie(StateSizeIsZero, StateSizeNotZero) = state->assume(SizeZero);
923  // We only assume exceptional states if they are definitely true; if the
924  // state is under-constrained, assume regular realloc behavior.
925  bool PrtIsNull = StatePtrIsNull && !StatePtrNotNull;
926  bool SizeIsZero = StateSizeIsZero && !StateSizeNotZero;
927
928  // If the ptr is NULL and the size is not 0, the call is equivalent to
929  // malloc(size).
930  if ( PrtIsNull && !SizeIsZero) {
931    ProgramStateRef stateMalloc = MallocMemAux(C, CE, CE->getArg(1),
932                                               UndefinedVal(), StatePtrIsNull);
933    return stateMalloc;
934  }
935
936  if (PrtIsNull && SizeIsZero)
937    return 0;
938
939  // Get the from and to pointer symbols as in toPtr = realloc(fromPtr, size).
940  assert(!PrtIsNull);
941  SymbolRef FromPtr = arg0Val.getAsSymbol();
942  SVal RetVal = state->getSVal(CE, LCtx);
943  SymbolRef ToPtr = RetVal.getAsSymbol();
944  if (!FromPtr || !ToPtr)
945    return 0;
946
947  bool ReleasedAllocated = false;
948
949  // If the size is 0, free the memory.
950  if (SizeIsZero)
951    if (ProgramStateRef stateFree = FreeMemAux(C, CE, StateSizeIsZero, 0,
952                                               false, ReleasedAllocated)){
953      // The semantics of the return value are:
954      // If size was equal to 0, either NULL or a pointer suitable to be passed
955      // to free() is returned. We just free the input pointer and do not add
956      // any constrains on the output pointer.
957      return stateFree;
958    }
959
960  // Default behavior.
961  if (ProgramStateRef stateFree =
962        FreeMemAux(C, CE, state, 0, false, ReleasedAllocated)) {
963
964    ProgramStateRef stateRealloc = MallocMemAux(C, CE, CE->getArg(1),
965                                                UnknownVal(), stateFree);
966    if (!stateRealloc)
967      return 0;
968
969    ReallocPairKind Kind = RPToBeFreedAfterFailure;
970    if (FreesOnFail)
971      Kind = RPIsFreeOnFailure;
972    else if (!ReleasedAllocated)
973      Kind = RPDoNotTrackAfterFailure;
974
975    // Record the info about the reallocated symbol so that we could properly
976    // process failed reallocation.
977    stateRealloc = stateRealloc->set<ReallocPairs>(ToPtr,
978                                                   ReallocPair(FromPtr, Kind));
979    // The reallocated symbol should stay alive for as long as the new symbol.
980    C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
981    return stateRealloc;
982  }
983  return 0;
984}
985
986ProgramStateRef MallocChecker::CallocMem(CheckerContext &C, const CallExpr *CE){
987  if (CE->getNumArgs() < 2)
988    return 0;
989
990  ProgramStateRef state = C.getState();
991  SValBuilder &svalBuilder = C.getSValBuilder();
992  const LocationContext *LCtx = C.getLocationContext();
993  SVal count = state->getSVal(CE->getArg(0), LCtx);
994  SVal elementSize = state->getSVal(CE->getArg(1), LCtx);
995  SVal TotalSize = svalBuilder.evalBinOp(state, BO_Mul, count, elementSize,
996                                        svalBuilder.getContext().getSizeType());
997  SVal zeroVal = svalBuilder.makeZeroVal(svalBuilder.getContext().CharTy);
998
999  return MallocMemAux(C, CE, TotalSize, zeroVal, state);
1000}
1001
1002LeakInfo
1003MallocChecker::getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
1004                                 CheckerContext &C) const {
1005  const LocationContext *LeakContext = N->getLocationContext();
1006  // Walk the ExplodedGraph backwards and find the first node that referred to
1007  // the tracked symbol.
1008  const ExplodedNode *AllocNode = N;
1009  const MemRegion *ReferenceRegion = 0;
1010
1011  while (N) {
1012    ProgramStateRef State = N->getState();
1013    if (!State->get<RegionState>(Sym))
1014      break;
1015
1016    // Find the most recent expression bound to the symbol in the current
1017    // context.
1018    if (!ReferenceRegion) {
1019      if (const MemRegion *MR = C.getLocationRegionIfPostStore(N)) {
1020        SVal Val = State->getSVal(MR);
1021        if (Val.getAsLocSymbol() == Sym)
1022          ReferenceRegion = MR;
1023      }
1024    }
1025
1026    // Allocation node, is the last node in the current context in which the
1027    // symbol was tracked.
1028    if (N->getLocationContext() == LeakContext)
1029      AllocNode = N;
1030    N = N->pred_empty() ? NULL : *(N->pred_begin());
1031  }
1032
1033  ProgramPoint P = AllocNode->getLocation();
1034  const Stmt *AllocationStmt = 0;
1035  if (CallExitEnd *Exit = dyn_cast<CallExitEnd>(&P))
1036    AllocationStmt = Exit->getCalleeContext()->getCallSite();
1037  else if (StmtPoint *SP = dyn_cast<StmtPoint>(&P))
1038    AllocationStmt = SP->getStmt();
1039
1040  return LeakInfo(AllocationStmt, ReferenceRegion);
1041}
1042
1043void MallocChecker::reportLeak(SymbolRef Sym, ExplodedNode *N,
1044                               CheckerContext &C) const {
1045  assert(N);
1046  if (!BT_Leak) {
1047    BT_Leak.reset(new BugType("Memory leak", "Memory Error"));
1048    // Leaks should not be reported if they are post-dominated by a sink:
1049    // (1) Sinks are higher importance bugs.
1050    // (2) NoReturnFunctionChecker uses sink nodes to represent paths ending
1051    //     with __noreturn functions such as assert() or exit(). We choose not
1052    //     to report leaks on such paths.
1053    BT_Leak->setSuppressOnSink(true);
1054  }
1055
1056  // Most bug reports are cached at the location where they occurred.
1057  // With leaks, we want to unique them by the location where they were
1058  // allocated, and only report a single path.
1059  PathDiagnosticLocation LocUsedForUniqueing;
1060  const Stmt *AllocStmt = 0;
1061  const MemRegion *Region = 0;
1062  llvm::tie(AllocStmt, Region) = getAllocationSite(N, Sym, C);
1063  if (AllocStmt)
1064    LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt,
1065                            C.getSourceManager(), N->getLocationContext());
1066
1067  SmallString<200> buf;
1068  llvm::raw_svector_ostream os(buf);
1069  os << "Memory is never released; potential leak";
1070  if (Region && Region->canPrintPretty()) {
1071    os << " of memory pointed to by '";
1072    Region->printPretty(os);
1073    os << '\'';
1074  }
1075
1076  BugReport *R = new BugReport(*BT_Leak, os.str(), N, LocUsedForUniqueing);
1077  R->markInteresting(Sym);
1078  R->addVisitor(new MallocBugVisitor(Sym, true));
1079  C.emitReport(R);
1080}
1081
1082void MallocChecker::checkDeadSymbols(SymbolReaper &SymReaper,
1083                                     CheckerContext &C) const
1084{
1085  if (!SymReaper.hasDeadSymbols())
1086    return;
1087
1088  ProgramStateRef state = C.getState();
1089  RegionStateTy RS = state->get<RegionState>();
1090  RegionStateTy::Factory &F = state->get_context<RegionState>();
1091
1092  llvm::SmallVector<SymbolRef, 2> Errors;
1093  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
1094    if (SymReaper.isDead(I->first)) {
1095      if (I->second.isAllocated())
1096        Errors.push_back(I->first);
1097      // Remove the dead symbol from the map.
1098      RS = F.remove(RS, I->first);
1099
1100    }
1101  }
1102
1103  // Cleanup the Realloc Pairs Map.
1104  ReallocPairsTy RP = state->get<ReallocPairs>();
1105  for (ReallocPairsTy::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
1106    if (SymReaper.isDead(I->first) ||
1107        SymReaper.isDead(I->second.ReallocatedSym)) {
1108      state = state->remove<ReallocPairs>(I->first);
1109    }
1110  }
1111
1112  // Cleanup the FreeReturnValue Map.
1113  FreeReturnValueTy FR = state->get<FreeReturnValue>();
1114  for (FreeReturnValueTy::iterator I = FR.begin(), E = FR.end(); I != E; ++I) {
1115    if (SymReaper.isDead(I->first) ||
1116        SymReaper.isDead(I->second)) {
1117      state = state->remove<FreeReturnValue>(I->first);
1118    }
1119  }
1120
1121  // Generate leak node.
1122  ExplodedNode *N = C.getPredecessor();
1123  if (!Errors.empty()) {
1124    static SimpleProgramPointTag Tag("MallocChecker : DeadSymbolsLeak");
1125    N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
1126    for (llvm::SmallVector<SymbolRef, 2>::iterator
1127        I = Errors.begin(), E = Errors.end(); I != E; ++I) {
1128      reportLeak(*I, N, C);
1129    }
1130  }
1131
1132  C.addTransition(state->set<RegionState>(RS), N);
1133}
1134
1135void MallocChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const {
1136  // We will check for double free in the post visit.
1137  if (isFreeFunction(C.getCalleeDecl(CE), C.getASTContext()))
1138    return;
1139
1140  // Check use after free, when a freed pointer is passed to a call.
1141  ProgramStateRef State = C.getState();
1142  for (CallExpr::const_arg_iterator I = CE->arg_begin(),
1143                                    E = CE->arg_end(); I != E; ++I) {
1144    const Expr *A = *I;
1145    if (A->getType().getTypePtr()->isAnyPointerType()) {
1146      SymbolRef Sym = State->getSVal(A, C.getLocationContext()).getAsSymbol();
1147      if (!Sym)
1148        continue;
1149      if (checkUseAfterFree(Sym, C, A))
1150        return;
1151    }
1152  }
1153}
1154
1155void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const {
1156  const Expr *E = S->getRetValue();
1157  if (!E)
1158    return;
1159
1160  // Check if we are returning a symbol.
1161  ProgramStateRef State = C.getState();
1162  SVal RetVal = State->getSVal(E, C.getLocationContext());
1163  SymbolRef Sym = RetVal.getAsSymbol();
1164  if (!Sym)
1165    // If we are returning a field of the allocated struct or an array element,
1166    // the callee could still free the memory.
1167    // TODO: This logic should be a part of generic symbol escape callback.
1168    if (const MemRegion *MR = RetVal.getAsRegion())
1169      if (isa<FieldRegion>(MR) || isa<ElementRegion>(MR))
1170        if (const SymbolicRegion *BMR =
1171              dyn_cast<SymbolicRegion>(MR->getBaseRegion()))
1172          Sym = BMR->getSymbol();
1173
1174  // Check if we are returning freed memory.
1175  if (Sym)
1176    checkUseAfterFree(Sym, C, E);
1177}
1178
1179// TODO: Blocks should be either inlined or should call invalidate regions
1180// upon invocation. After that's in place, special casing here will not be
1181// needed.
1182void MallocChecker::checkPostStmt(const BlockExpr *BE,
1183                                  CheckerContext &C) const {
1184
1185  // Scan the BlockDecRefExprs for any object the retain count checker
1186  // may be tracking.
1187  if (!BE->getBlockDecl()->hasCaptures())
1188    return;
1189
1190  ProgramStateRef state = C.getState();
1191  const BlockDataRegion *R =
1192    cast<BlockDataRegion>(state->getSVal(BE,
1193                                         C.getLocationContext()).getAsRegion());
1194
1195  BlockDataRegion::referenced_vars_iterator I = R->referenced_vars_begin(),
1196                                            E = R->referenced_vars_end();
1197
1198  if (I == E)
1199    return;
1200
1201  SmallVector<const MemRegion*, 10> Regions;
1202  const LocationContext *LC = C.getLocationContext();
1203  MemRegionManager &MemMgr = C.getSValBuilder().getRegionManager();
1204
1205  for ( ; I != E; ++I) {
1206    const VarRegion *VR = *I;
1207    if (VR->getSuperRegion() == R) {
1208      VR = MemMgr.getVarRegion(VR->getDecl(), LC);
1209    }
1210    Regions.push_back(VR);
1211  }
1212
1213  state =
1214    state->scanReachableSymbols<StopTrackingCallback>(Regions.data(),
1215                                    Regions.data() + Regions.size()).getState();
1216  C.addTransition(state);
1217}
1218
1219bool MallocChecker::isReleased(SymbolRef Sym, CheckerContext &C) const {
1220  assert(Sym);
1221  const RefState *RS = C.getState()->get<RegionState>(Sym);
1222  return (RS && RS->isReleased());
1223}
1224
1225bool MallocChecker::checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
1226                                      const Stmt *S) const {
1227  if (isReleased(Sym, C)) {
1228    if (ExplodedNode *N = C.generateSink()) {
1229      if (!BT_UseFree)
1230        BT_UseFree.reset(new BugType("Use-after-free", "Memory Error"));
1231
1232      BugReport *R = new BugReport(*BT_UseFree,
1233                                   "Use of memory after it is freed",N);
1234      if (S)
1235        R->addRange(S->getSourceRange());
1236      R->markInteresting(Sym);
1237      R->addVisitor(new MallocBugVisitor(Sym));
1238      C.emitReport(R);
1239      return true;
1240    }
1241  }
1242  return false;
1243}
1244
1245// Check if the location is a freed symbolic region.
1246void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S,
1247                                  CheckerContext &C) const {
1248  SymbolRef Sym = l.getLocSymbolInBase();
1249  if (Sym)
1250    checkUseAfterFree(Sym, C, S);
1251}
1252
1253//===----------------------------------------------------------------------===//
1254// Check various ways a symbol can be invalidated.
1255// TODO: This logic (the next 3 functions) is copied/similar to the
1256// RetainRelease checker. We might want to factor this out.
1257//===----------------------------------------------------------------------===//
1258
1259// Stop tracking symbols when a value escapes as a result of checkBind.
1260// A value escapes in three possible cases:
1261// (1) we are binding to something that is not a memory region.
1262// (2) we are binding to a memregion that does not have stack storage
1263// (3) we are binding to a memregion with stack storage that the store
1264//     does not understand.
1265void MallocChecker::checkBind(SVal loc, SVal val, const Stmt *S,
1266                              CheckerContext &C) const {
1267  // Are we storing to something that causes the value to "escape"?
1268  bool escapes = true;
1269  ProgramStateRef state = C.getState();
1270
1271  if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) {
1272    escapes = !regionLoc->getRegion()->hasStackStorage();
1273
1274    if (!escapes) {
1275      // To test (3), generate a new state with the binding added.  If it is
1276      // the same state, then it escapes (since the store cannot represent
1277      // the binding).
1278      // Do this only if we know that the store is not supposed to generate the
1279      // same state.
1280      SVal StoredVal = state->getSVal(regionLoc->getRegion());
1281      if (StoredVal != val)
1282        escapes = (state == (state->bindLoc(*regionLoc, val)));
1283    }
1284  }
1285
1286  // If our store can represent the binding and we aren't storing to something
1287  // that doesn't have local storage then just return and have the simulation
1288  // state continue as is.
1289  if (!escapes)
1290      return;
1291
1292  // Otherwise, find all symbols referenced by 'val' that we are tracking
1293  // and stop tracking them.
1294  state = state->scanReachableSymbols<StopTrackingCallback>(val).getState();
1295  C.addTransition(state);
1296}
1297
1298// If a symbolic region is assumed to NULL (or another constant), stop tracking
1299// it - assuming that allocation failed on this path.
1300ProgramStateRef MallocChecker::evalAssume(ProgramStateRef state,
1301                                              SVal Cond,
1302                                              bool Assumption) const {
1303  RegionStateTy RS = state->get<RegionState>();
1304  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
1305    // If the symbol is assumed to be NULL, remove it from consideration.
1306    ConstraintManager &CMgr = state->getConstraintManager();
1307    ConditionTruthVal AllocFailed = CMgr.isNull(state, I.getKey());
1308    if (AllocFailed.isConstrainedTrue())
1309      state = state->remove<RegionState>(I.getKey());
1310  }
1311
1312  // Realloc returns 0 when reallocation fails, which means that we should
1313  // restore the state of the pointer being reallocated.
1314  ReallocPairsTy RP = state->get<ReallocPairs>();
1315  for (ReallocPairsTy::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
1316    // If the symbol is assumed to be NULL, remove it from consideration.
1317    ConstraintManager &CMgr = state->getConstraintManager();
1318    ConditionTruthVal AllocFailed = CMgr.isNull(state, I.getKey());
1319    if (!AllocFailed.isConstrainedTrue())
1320      continue;
1321
1322    SymbolRef ReallocSym = I.getData().ReallocatedSym;
1323    if (const RefState *RS = state->get<RegionState>(ReallocSym)) {
1324      if (RS->isReleased()) {
1325        if (I.getData().Kind == RPToBeFreedAfterFailure)
1326          state = state->set<RegionState>(ReallocSym,
1327              RefState::getAllocated(RS->getStmt()));
1328        else if (I.getData().Kind == RPDoNotTrackAfterFailure)
1329          state = state->remove<RegionState>(ReallocSym);
1330        else
1331          assert(I.getData().Kind == RPIsFreeOnFailure);
1332      }
1333    }
1334    state = state->remove<ReallocPairs>(I.getKey());
1335  }
1336
1337  return state;
1338}
1339
1340// Check if the function is known to us. So, for example, we could
1341// conservatively assume it can free/reallocate its pointer arguments.
1342// (We assume that the pointers cannot escape through calls to system
1343// functions not handled by this checker.)
1344bool MallocChecker::doesNotFreeMemory(const CallEvent *Call,
1345                                      ProgramStateRef State) const {
1346  assert(Call);
1347
1348  // For now, assume that any C++ call can free memory.
1349  // TODO: If we want to be more optimistic here, we'll need to make sure that
1350  // regions escape to C++ containers. They seem to do that even now, but for
1351  // mysterious reasons.
1352  if (!(isa<FunctionCall>(Call) || isa<ObjCMethodCall>(Call)))
1353    return false;
1354
1355  // Check Objective-C messages by selector name.
1356  if (const ObjCMethodCall *Msg = dyn_cast<ObjCMethodCall>(Call)) {
1357    // If it's not a framework call, or if it takes a callback, assume it
1358    // can free memory.
1359    if (!Call->isInSystemHeader() || Call->hasNonZeroCallbackArg())
1360      return false;
1361
1362    Selector S = Msg->getSelector();
1363
1364    // Whitelist the ObjC methods which do free memory.
1365    // - Anything containing 'freeWhenDone' param set to 1.
1366    //   Ex: dataWithBytesNoCopy:length:freeWhenDone.
1367    for (unsigned i = 1; i < S.getNumArgs(); ++i) {
1368      if (S.getNameForSlot(i).equals("freeWhenDone")) {
1369        if (Call->getArgSVal(i).isConstant(1))
1370          return false;
1371        else
1372          return true;
1373      }
1374    }
1375
1376    // If the first selector ends with NoCopy, assume that the ownership is
1377    // transferred as well.
1378    // Ex:  [NSData dataWithBytesNoCopy:bytes length:10];
1379    StringRef FirstSlot = S.getNameForSlot(0);
1380    if (FirstSlot.endswith("NoCopy"))
1381      return false;
1382
1383    // If the first selector starts with addPointer, insertPointer,
1384    // or replacePointer, assume we are dealing with NSPointerArray or similar.
1385    // This is similar to C++ containers (vector); we still might want to check
1386    // that the pointers get freed by following the container itself.
1387    if (FirstSlot.startswith("addPointer") ||
1388        FirstSlot.startswith("insertPointer") ||
1389        FirstSlot.startswith("replacePointer")) {
1390      return false;
1391    }
1392
1393    // Otherwise, assume that the method does not free memory.
1394    // Most framework methods do not free memory.
1395    return true;
1396  }
1397
1398  // At this point the only thing left to handle is straight function calls.
1399  const FunctionDecl *FD = cast<FunctionCall>(Call)->getDecl();
1400  if (!FD)
1401    return false;
1402
1403  ASTContext &ASTC = State->getStateManager().getContext();
1404
1405  // If it's one of the allocation functions we can reason about, we model
1406  // its behavior explicitly.
1407  if (isMemFunction(FD, ASTC))
1408    return true;
1409
1410  // If it's not a system call, assume it frees memory.
1411  if (!Call->isInSystemHeader())
1412    return false;
1413
1414  // White list the system functions whose arguments escape.
1415  const IdentifierInfo *II = FD->getIdentifier();
1416  if (!II)
1417    return false;
1418  StringRef FName = II->getName();
1419
1420  // White list the 'XXXNoCopy' CoreFoundation functions.
1421  // We specifically check these before
1422  if (FName.endswith("NoCopy")) {
1423    // Look for the deallocator argument. We know that the memory ownership
1424    // is not transferred only if the deallocator argument is
1425    // 'kCFAllocatorNull'.
1426    for (unsigned i = 1; i < Call->getNumArgs(); ++i) {
1427      const Expr *ArgE = Call->getArgExpr(i)->IgnoreParenCasts();
1428      if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(ArgE)) {
1429        StringRef DeallocatorName = DE->getFoundDecl()->getName();
1430        if (DeallocatorName == "kCFAllocatorNull")
1431          return true;
1432      }
1433    }
1434    return false;
1435  }
1436
1437  // Associating streams with malloced buffers. The pointer can escape if
1438  // 'closefn' is specified (and if that function does free memory),
1439  // but it will not if closefn is not specified.
1440  // Currently, we do not inspect the 'closefn' function (PR12101).
1441  if (FName == "funopen")
1442    if (Call->getNumArgs() >= 4 && Call->getArgSVal(4).isConstant(0))
1443      return true;
1444
1445  // Do not warn on pointers passed to 'setbuf' when used with std streams,
1446  // these leaks might be intentional when setting the buffer for stdio.
1447  // http://stackoverflow.com/questions/2671151/who-frees-setvbuf-buffer
1448  if (FName == "setbuf" || FName =="setbuffer" ||
1449      FName == "setlinebuf" || FName == "setvbuf") {
1450    if (Call->getNumArgs() >= 1) {
1451      const Expr *ArgE = Call->getArgExpr(0)->IgnoreParenCasts();
1452      if (const DeclRefExpr *ArgDRE = dyn_cast<DeclRefExpr>(ArgE))
1453        if (const VarDecl *D = dyn_cast<VarDecl>(ArgDRE->getDecl()))
1454          if (D->getCanonicalDecl()->getName().find("std") != StringRef::npos)
1455            return false;
1456    }
1457  }
1458
1459  // A bunch of other functions which either take ownership of a pointer or
1460  // wrap the result up in a struct or object, meaning it can be freed later.
1461  // (See RetainCountChecker.) Not all the parameters here are invalidated,
1462  // but the Malloc checker cannot differentiate between them. The right way
1463  // of doing this would be to implement a pointer escapes callback.
1464  if (FName == "CGBitmapContextCreate" ||
1465      FName == "CGBitmapContextCreateWithData" ||
1466      FName == "CVPixelBufferCreateWithBytes" ||
1467      FName == "CVPixelBufferCreateWithPlanarBytes" ||
1468      FName == "OSAtomicEnqueue") {
1469    return false;
1470  }
1471
1472  // Handle cases where we know a buffer's /address/ can escape.
1473  // Note that the above checks handle some special cases where we know that
1474  // even though the address escapes, it's still our responsibility to free the
1475  // buffer.
1476  if (Call->argumentsMayEscape())
1477    return false;
1478
1479  // Otherwise, assume that the function does not free memory.
1480  // Most system calls do not free the memory.
1481  return true;
1482}
1483
1484// If the symbol we are tracking is invalidated, but not explicitly (ex: the &p
1485// escapes, when we are tracking p), do not track the symbol as we cannot reason
1486// about it anymore.
1487ProgramStateRef
1488MallocChecker::checkRegionChanges(ProgramStateRef State,
1489                            const StoreManager::InvalidatedSymbols *invalidated,
1490                                    ArrayRef<const MemRegion *> ExplicitRegions,
1491                                    ArrayRef<const MemRegion *> Regions,
1492                                    const CallEvent *Call) const {
1493  if (!invalidated || invalidated->empty())
1494    return State;
1495  llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols;
1496
1497  // If it's a call which might free or reallocate memory, we assume that all
1498  // regions (explicit and implicit) escaped.
1499
1500  // Otherwise, whitelist explicit pointers; we still can track them.
1501  if (!Call || doesNotFreeMemory(Call, State)) {
1502    for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(),
1503        E = ExplicitRegions.end(); I != E; ++I) {
1504      if (const SymbolicRegion *R = (*I)->StripCasts()->getAs<SymbolicRegion>())
1505        WhitelistedSymbols.insert(R->getSymbol());
1506    }
1507  }
1508
1509  for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(),
1510       E = invalidated->end(); I!=E; ++I) {
1511    SymbolRef sym = *I;
1512    if (WhitelistedSymbols.count(sym))
1513      continue;
1514    // The symbol escaped. Note, we assume that if the symbol is released,
1515    // passing it out will result in a use after free. We also keep tracking
1516    // relinquished symbols.
1517    if (const RefState *RS = State->get<RegionState>(sym)) {
1518      if (RS->isAllocated())
1519        State = State->remove<RegionState>(sym);
1520    }
1521  }
1522  return State;
1523}
1524
1525static SymbolRef findFailedReallocSymbol(ProgramStateRef currState,
1526                                         ProgramStateRef prevState) {
1527  ReallocPairsTy currMap = currState->get<ReallocPairs>();
1528  ReallocPairsTy prevMap = prevState->get<ReallocPairs>();
1529
1530  for (ReallocPairsTy::iterator I = prevMap.begin(), E = prevMap.end();
1531       I != E; ++I) {
1532    SymbolRef sym = I.getKey();
1533    if (!currMap.lookup(sym))
1534      return sym;
1535  }
1536
1537  return NULL;
1538}
1539
1540PathDiagnosticPiece *
1541MallocChecker::MallocBugVisitor::VisitNode(const ExplodedNode *N,
1542                                           const ExplodedNode *PrevN,
1543                                           BugReporterContext &BRC,
1544                                           BugReport &BR) {
1545  ProgramStateRef state = N->getState();
1546  ProgramStateRef statePrev = PrevN->getState();
1547
1548  const RefState *RS = state->get<RegionState>(Sym);
1549  const RefState *RSPrev = statePrev->get<RegionState>(Sym);
1550  if (!RS)
1551    return 0;
1552
1553  const Stmt *S = 0;
1554  const char *Msg = 0;
1555  StackHintGeneratorForSymbol *StackHint = 0;
1556
1557  // Retrieve the associated statement.
1558  ProgramPoint ProgLoc = N->getLocation();
1559  if (StmtPoint *SP = dyn_cast<StmtPoint>(&ProgLoc))
1560    S = SP->getStmt();
1561  else if (CallExitEnd *Exit = dyn_cast<CallExitEnd>(&ProgLoc))
1562    S = Exit->getCalleeContext()->getCallSite();
1563  // If an assumption was made on a branch, it should be caught
1564  // here by looking at the state transition.
1565  else if (BlockEdge *Edge = dyn_cast<BlockEdge>(&ProgLoc)) {
1566    const CFGBlock *srcBlk = Edge->getSrc();
1567    S = srcBlk->getTerminator();
1568  }
1569  if (!S)
1570    return 0;
1571
1572  // FIXME: We will eventually need to handle non-statement-based events
1573  // (__attribute__((cleanup))).
1574
1575  // Find out if this is an interesting point and what is the kind.
1576  if (Mode == Normal) {
1577    if (isAllocated(RS, RSPrev, S)) {
1578      Msg = "Memory is allocated";
1579      StackHint = new StackHintGeneratorForSymbol(Sym,
1580                                                  "Returned allocated memory");
1581    } else if (isReleased(RS, RSPrev, S)) {
1582      Msg = "Memory is released";
1583      StackHint = new StackHintGeneratorForSymbol(Sym,
1584                                                  "Returned released memory");
1585    } else if (isRelinquished(RS, RSPrev, S)) {
1586      Msg = "Memory ownership is transfered";
1587      StackHint = new StackHintGeneratorForSymbol(Sym, "");
1588    } else if (isReallocFailedCheck(RS, RSPrev, S)) {
1589      Mode = ReallocationFailed;
1590      Msg = "Reallocation failed";
1591      StackHint = new StackHintGeneratorForReallocationFailed(Sym,
1592                                                       "Reallocation failed");
1593
1594      if (SymbolRef sym = findFailedReallocSymbol(state, statePrev)) {
1595        // Is it possible to fail two reallocs WITHOUT testing in between?
1596        assert((!FailedReallocSymbol || FailedReallocSymbol == sym) &&
1597          "We only support one failed realloc at a time.");
1598        BR.markInteresting(sym);
1599        FailedReallocSymbol = sym;
1600      }
1601    }
1602
1603  // We are in a special mode if a reallocation failed later in the path.
1604  } else if (Mode == ReallocationFailed) {
1605    assert(FailedReallocSymbol && "No symbol to look for.");
1606
1607    // Is this is the first appearance of the reallocated symbol?
1608    if (!statePrev->get<RegionState>(FailedReallocSymbol)) {
1609      // We're at the reallocation point.
1610      Msg = "Attempt to reallocate memory";
1611      StackHint = new StackHintGeneratorForSymbol(Sym,
1612                                                 "Returned reallocated memory");
1613      FailedReallocSymbol = NULL;
1614      Mode = Normal;
1615    }
1616  }
1617
1618  if (!Msg)
1619    return 0;
1620  assert(StackHint);
1621
1622  // Generate the extra diagnostic.
1623  PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
1624                             N->getLocationContext());
1625  return new PathDiagnosticEventPiece(Pos, Msg, true, StackHint);
1626}
1627
1628void MallocChecker::printState(raw_ostream &Out, ProgramStateRef State,
1629                               const char *NL, const char *Sep) const {
1630
1631  RegionStateTy RS = State->get<RegionState>();
1632
1633  if (!RS.isEmpty())
1634    Out << "Has Malloc data" << NL;
1635}
1636
1637#define REGISTER_CHECKER(name) \
1638void ento::register##name(CheckerManager &mgr) {\
1639  registerCStringCheckerBasic(mgr); \
1640  mgr.registerChecker<MallocChecker>()->Filter.C##name = true;\
1641}
1642
1643REGISTER_CHECKER(MallocPessimistic)
1644REGISTER_CHECKER(MallocOptimistic)
1645