clang  8.0.0svn
ValistChecker.cpp
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1 //== ValistChecker.cpp - stdarg.h macro usage 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 defines checkers which detect usage of uninitialized va_list values
11 // and va_start calls with no matching va_end.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "ClangSACheckers.h"
21 
22 using namespace clang;
23 using namespace ento;
24 
25 REGISTER_SET_WITH_PROGRAMSTATE(InitializedVALists, const MemRegion *)
26 
27 namespace {
28 typedef SmallVector<const MemRegion *, 2> RegionVector;
29 
30 class ValistChecker : public Checker<check::PreCall, check::PreStmt<VAArgExpr>,
31  check::DeadSymbols> {
32  mutable std::unique_ptr<BugType> BT_leakedvalist, BT_uninitaccess;
33 
34  struct VAListAccepter {
35  CallDescription Func;
36  int VAListPos;
37  };
38  static const SmallVector<VAListAccepter, 15> VAListAccepters;
39  static const CallDescription VaStart, VaEnd, VaCopy;
40 
41 public:
42  enum CheckKind {
43  CK_Uninitialized,
44  CK_Unterminated,
45  CK_CopyToSelf,
46  CK_NumCheckKinds
47  };
48 
49  DefaultBool ChecksEnabled[CK_NumCheckKinds];
50  CheckName CheckNames[CK_NumCheckKinds];
51 
52  void checkPreStmt(const VAArgExpr *VAA, CheckerContext &C) const;
53  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
54  void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const;
55 
56 private:
57  const MemRegion *getVAListAsRegion(SVal SV, const Expr *VAExpr,
58  bool &IsSymbolic, CheckerContext &C) const;
59  const ExplodedNode *getStartCallSite(const ExplodedNode *N,
60  const MemRegion *Reg) const;
61 
62  void reportUninitializedAccess(const MemRegion *VAList, StringRef Msg,
63  CheckerContext &C) const;
64  void reportLeakedVALists(const RegionVector &LeakedVALists, StringRef Msg1,
65  StringRef Msg2, CheckerContext &C, ExplodedNode *N,
66  bool ReportUninit = false) const;
67 
68  void checkVAListStartCall(const CallEvent &Call, CheckerContext &C,
69  bool IsCopy) const;
70  void checkVAListEndCall(const CallEvent &Call, CheckerContext &C) const;
71 
72  class ValistBugVisitor : public BugReporterVisitor {
73  public:
74  ValistBugVisitor(const MemRegion *Reg, bool IsLeak = false)
75  : Reg(Reg), IsLeak(IsLeak) {}
76  void Profile(llvm::FoldingSetNodeID &ID) const override {
77  static int X = 0;
78  ID.AddPointer(&X);
79  ID.AddPointer(Reg);
80  }
81  std::shared_ptr<PathDiagnosticPiece>
82  getEndPath(BugReporterContext &BRC, const ExplodedNode *EndPathNode,
83  BugReport &BR) override {
84  if (!IsLeak)
85  return nullptr;
86 
87  PathDiagnosticLocation L = PathDiagnosticLocation::createEndOfPath(
88  EndPathNode, BRC.getSourceManager());
89  // Do not add the statement itself as a range in case of leak.
90  return std::make_shared<PathDiagnosticEventPiece>(L, BR.getDescription(), false);
91  }
92  std::shared_ptr<PathDiagnosticPiece> VisitNode(const ExplodedNode *N,
93  const ExplodedNode *PrevN,
94  BugReporterContext &BRC,
95  BugReport &BR) override;
96 
97  private:
98  const MemRegion *Reg;
99  bool IsLeak;
100  };
101 };
102 
104  ValistChecker::VAListAccepters = {
105  {{"vfprintf", 3}, 2},
106  {{"vfscanf", 3}, 2},
107  {{"vprintf", 2}, 1},
108  {{"vscanf", 2}, 1},
109  {{"vsnprintf", 4}, 3},
110  {{"vsprintf", 3}, 2},
111  {{"vsscanf", 3}, 2},
112  {{"vfwprintf", 3}, 2},
113  {{"vfwscanf", 3}, 2},
114  {{"vwprintf", 2}, 1},
115  {{"vwscanf", 2}, 1},
116  {{"vswprintf", 4}, 3},
117  // vswprintf is the wide version of vsnprintf,
118  // vsprintf has no wide version
119  {{"vswscanf", 3}, 2}};
120 const CallDescription ValistChecker::VaStart("__builtin_va_start", 2),
121  ValistChecker::VaCopy("__builtin_va_copy", 2),
122  ValistChecker::VaEnd("__builtin_va_end", 1);
123 } // end anonymous namespace
124 
125 void ValistChecker::checkPreCall(const CallEvent &Call,
126  CheckerContext &C) const {
127  if (!Call.isGlobalCFunction())
128  return;
129  if (Call.isCalled(VaStart))
130  checkVAListStartCall(Call, C, false);
131  else if (Call.isCalled(VaCopy))
132  checkVAListStartCall(Call, C, true);
133  else if (Call.isCalled(VaEnd))
134  checkVAListEndCall(Call, C);
135  else {
136  for (auto FuncInfo : VAListAccepters) {
137  if (!Call.isCalled(FuncInfo.Func))
138  continue;
139  bool Symbolic;
140  const MemRegion *VAList =
141  getVAListAsRegion(Call.getArgSVal(FuncInfo.VAListPos),
142  Call.getArgExpr(FuncInfo.VAListPos), Symbolic, C);
143  if (!VAList)
144  return;
145 
146  if (C.getState()->contains<InitializedVALists>(VAList))
147  return;
148 
149  // We did not see va_start call, but the source of the region is unknown.
150  // Be conservative and assume the best.
151  if (Symbolic)
152  return;
153 
154  SmallString<80> Errmsg("Function '");
155  Errmsg += FuncInfo.Func.getFunctionName();
156  Errmsg += "' is called with an uninitialized va_list argument";
157  reportUninitializedAccess(VAList, Errmsg.c_str(), C);
158  break;
159  }
160  }
161 }
162 
163 const MemRegion *ValistChecker::getVAListAsRegion(SVal SV, const Expr *E,
164  bool &IsSymbolic,
165  CheckerContext &C) const {
166  const MemRegion *Reg = SV.getAsRegion();
167  if (!Reg)
168  return nullptr;
169  // TODO: In the future this should be abstracted away by the analyzer.
170  bool VaListModelledAsArray = false;
171  if (const auto *Cast = dyn_cast<CastExpr>(E)) {
172  QualType Ty = Cast->getType();
173  VaListModelledAsArray =
174  Ty->isPointerType() && Ty->getPointeeType()->isRecordType();
175  }
176  if (const auto *DeclReg = Reg->getAs<DeclRegion>()) {
177  if (isa<ParmVarDecl>(DeclReg->getDecl()))
178  Reg = C.getState()->getSVal(SV.castAs<Loc>()).getAsRegion();
179  }
180  IsSymbolic = Reg && Reg->getAs<SymbolicRegion>();
181  // Some VarRegion based VA lists reach here as ElementRegions.
182  const auto *EReg = dyn_cast_or_null<ElementRegion>(Reg);
183  return (EReg && VaListModelledAsArray) ? EReg->getSuperRegion() : Reg;
184 }
185 
186 void ValistChecker::checkPreStmt(const VAArgExpr *VAA,
187  CheckerContext &C) const {
188  ProgramStateRef State = C.getState();
189  const Expr *VASubExpr = VAA->getSubExpr();
190  SVal VAListSVal = C.getSVal(VASubExpr);
191  bool Symbolic;
192  const MemRegion *VAList =
193  getVAListAsRegion(VAListSVal, VASubExpr, Symbolic, C);
194  if (!VAList)
195  return;
196  if (Symbolic)
197  return;
198  if (!State->contains<InitializedVALists>(VAList))
199  reportUninitializedAccess(
200  VAList, "va_arg() is called on an uninitialized va_list", C);
201 }
202 
203 void ValistChecker::checkDeadSymbols(SymbolReaper &SR,
204  CheckerContext &C) const {
205  ProgramStateRef State = C.getState();
206  InitializedVAListsTy TrackedVALists = State->get<InitializedVALists>();
207  RegionVector LeakedVALists;
208  for (auto Reg : TrackedVALists) {
209  if (SR.isLiveRegion(Reg))
210  continue;
211  LeakedVALists.push_back(Reg);
212  State = State->remove<InitializedVALists>(Reg);
213  }
214  if (ExplodedNode *N = C.addTransition(State))
215  reportLeakedVALists(LeakedVALists, "Initialized va_list", " is leaked", C,
216  N);
217 }
218 
219 // This function traverses the exploded graph backwards and finds the node where
220 // the va_list is initialized. That node is used for uniquing the bug paths.
221 // It is not likely that there are several different va_lists that belongs to
222 // different stack frames, so that case is not yet handled.
223 const ExplodedNode *
224 ValistChecker::getStartCallSite(const ExplodedNode *N,
225  const MemRegion *Reg) const {
226  const LocationContext *LeakContext = N->getLocationContext();
227  const ExplodedNode *StartCallNode = N;
228 
229  bool FoundInitializedState = false;
230 
231  while (N) {
232  ProgramStateRef State = N->getState();
233  if (!State->contains<InitializedVALists>(Reg)) {
234  if (FoundInitializedState)
235  break;
236  } else {
237  FoundInitializedState = true;
238  }
239  const LocationContext *NContext = N->getLocationContext();
240  if (NContext == LeakContext || NContext->isParentOf(LeakContext))
241  StartCallNode = N;
242  N = N->pred_empty() ? nullptr : *(N->pred_begin());
243  }
244 
245  return StartCallNode;
246 }
247 
248 void ValistChecker::reportUninitializedAccess(const MemRegion *VAList,
249  StringRef Msg,
250  CheckerContext &C) const {
251  if (!ChecksEnabled[CK_Uninitialized])
252  return;
253  if (ExplodedNode *N = C.generateErrorNode()) {
254  if (!BT_uninitaccess)
255  BT_uninitaccess.reset(new BugType(CheckNames[CK_Uninitialized],
256  "Uninitialized va_list",
258  auto R = llvm::make_unique<BugReport>(*BT_uninitaccess, Msg, N);
259  R->markInteresting(VAList);
260  R->addVisitor(llvm::make_unique<ValistBugVisitor>(VAList));
261  C.emitReport(std::move(R));
262  }
263 }
264 
265 void ValistChecker::reportLeakedVALists(const RegionVector &LeakedVALists,
266  StringRef Msg1, StringRef Msg2,
267  CheckerContext &C, ExplodedNode *N,
268  bool ReportUninit) const {
269  if (!(ChecksEnabled[CK_Unterminated] ||
270  (ChecksEnabled[CK_Uninitialized] && ReportUninit)))
271  return;
272  for (auto Reg : LeakedVALists) {
273  if (!BT_leakedvalist) {
274  // FIXME: maybe creating a new check name for this type of bug is a better
275  // solution.
276  BT_leakedvalist.reset(
277  new BugType(CheckNames[CK_Unterminated].getName().empty()
278  ? CheckNames[CK_Uninitialized]
279  : CheckNames[CK_Unterminated],
280  "Leaked va_list", categories::MemoryError));
281  BT_leakedvalist->setSuppressOnSink(true);
282  }
283 
284  const ExplodedNode *StartNode = getStartCallSite(N, Reg);
285  PathDiagnosticLocation LocUsedForUniqueing;
286 
287  if (const Stmt *StartCallStmt = PathDiagnosticLocation::getStmt(StartNode))
288  LocUsedForUniqueing = PathDiagnosticLocation::createBegin(
289  StartCallStmt, C.getSourceManager(), StartNode->getLocationContext());
290 
291  SmallString<100> Buf;
292  llvm::raw_svector_ostream OS(Buf);
293  OS << Msg1;
294  std::string VariableName = Reg->getDescriptiveName();
295  if (!VariableName.empty())
296  OS << " " << VariableName;
297  OS << Msg2;
298 
299  auto R = llvm::make_unique<BugReport>(
300  *BT_leakedvalist, OS.str(), N, LocUsedForUniqueing,
301  StartNode->getLocationContext()->getDecl());
302  R->markInteresting(Reg);
303  R->addVisitor(llvm::make_unique<ValistBugVisitor>(Reg, true));
304  C.emitReport(std::move(R));
305  }
306 }
307 
308 void ValistChecker::checkVAListStartCall(const CallEvent &Call,
309  CheckerContext &C, bool IsCopy) const {
310  bool Symbolic;
311  const MemRegion *VAList =
312  getVAListAsRegion(Call.getArgSVal(0), Call.getArgExpr(0), Symbolic, C);
313  if (!VAList)
314  return;
315 
316  ProgramStateRef State = C.getState();
317 
318  if (IsCopy) {
319  const MemRegion *Arg2 =
320  getVAListAsRegion(Call.getArgSVal(1), Call.getArgExpr(1), Symbolic, C);
321  if (Arg2) {
322  if (ChecksEnabled[CK_CopyToSelf] && VAList == Arg2) {
323  RegionVector LeakedVALists{VAList};
324  if (ExplodedNode *N = C.addTransition(State))
325  reportLeakedVALists(LeakedVALists, "va_list",
326  " is copied onto itself", C, N, true);
327  return;
328  } else if (!State->contains<InitializedVALists>(Arg2) && !Symbolic) {
329  if (State->contains<InitializedVALists>(VAList)) {
330  State = State->remove<InitializedVALists>(VAList);
331  RegionVector LeakedVALists{VAList};
332  if (ExplodedNode *N = C.addTransition(State))
333  reportLeakedVALists(LeakedVALists, "Initialized va_list",
334  " is overwritten by an uninitialized one", C, N,
335  true);
336  } else {
337  reportUninitializedAccess(Arg2, "Uninitialized va_list is copied", C);
338  }
339  return;
340  }
341  }
342  }
343  if (State->contains<InitializedVALists>(VAList)) {
344  RegionVector LeakedVALists{VAList};
345  if (ExplodedNode *N = C.addTransition(State))
346  reportLeakedVALists(LeakedVALists, "Initialized va_list",
347  " is initialized again", C, N);
348  return;
349  }
350 
351  State = State->add<InitializedVALists>(VAList);
352  C.addTransition(State);
353 }
354 
355 void ValistChecker::checkVAListEndCall(const CallEvent &Call,
356  CheckerContext &C) const {
357  bool Symbolic;
358  const MemRegion *VAList =
359  getVAListAsRegion(Call.getArgSVal(0), Call.getArgExpr(0), Symbolic, C);
360  if (!VAList)
361  return;
362 
363  // We did not see va_start call, but the source of the region is unknown.
364  // Be conservative and assume the best.
365  if (Symbolic)
366  return;
367 
368  if (!C.getState()->contains<InitializedVALists>(VAList)) {
369  reportUninitializedAccess(
370  VAList, "va_end() is called on an uninitialized va_list", C);
371  return;
372  }
373  ProgramStateRef State = C.getState();
374  State = State->remove<InitializedVALists>(VAList);
375  C.addTransition(State);
376 }
377 
378 std::shared_ptr<PathDiagnosticPiece> ValistChecker::ValistBugVisitor::VisitNode(
379  const ExplodedNode *N, const ExplodedNode *PrevN, BugReporterContext &BRC,
380  BugReport &) {
381  ProgramStateRef State = N->getState();
382  ProgramStateRef StatePrev = PrevN->getState();
383 
385  if (!S)
386  return nullptr;
387 
388  StringRef Msg;
389  if (State->contains<InitializedVALists>(Reg) &&
390  !StatePrev->contains<InitializedVALists>(Reg))
391  Msg = "Initialized va_list";
392  else if (!State->contains<InitializedVALists>(Reg) &&
393  StatePrev->contains<InitializedVALists>(Reg))
394  Msg = "Ended va_list";
395 
396  if (Msg.empty())
397  return nullptr;
398 
399  PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
400  N->getLocationContext());
401  return std::make_shared<PathDiagnosticEventPiece>(Pos, Msg, true);
402 }
403 
404 #define REGISTER_CHECKER(name) \
405  void ento::register##name##Checker(CheckerManager &mgr) { \
406  ValistChecker *checker = mgr.registerChecker<ValistChecker>(); \
407  checker->ChecksEnabled[ValistChecker::CK_##name] = true; \
408  checker->CheckNames[ValistChecker::CK_##name] = mgr.getCurrentCheckName(); \
409  }
410 
412 REGISTER_CHECKER(Unterminated)
413 REGISTER_CHECKER(CopyToSelf)
A (possibly-)qualified type.
Definition: Type.h:642
Stmt - This represents one statement.
Definition: Stmt.h:66
QualType getPointeeType() const
If this is a pointer, ObjC object pointer, or block pointer, this returns the respective pointee...
Definition: Type.cpp:497
bool isRecordType() const
Definition: Type.h:6250
IntrusiveRefCntPtr< const ProgramState > ProgramStateRef
const Expr * getSubExpr() const
Definition: Expr.h:3919
std::string getName(ArrayRef< StringRef > Parts) const
Get the platform-specific name separator.
#define REGISTER_SET_WITH_PROGRAMSTATE(Name, Elem)
Declares an immutable set of type NameTy, suitable for placement into the ProgramState.
bool isParentOf(const LocationContext *LC) const
LineState State
Represents a call to the builtin function __builtin_va_arg.
Definition: Expr.h:3901
This represents one expression.
Definition: Expr.h:105
static const Stmt * getStmt(const ExplodedNode *N)
Given an exploded node, retrieve the statement that should be used for the diagnostic location...
static PathDiagnosticLocation createBegin(const Decl *D, const SourceManager &SM)
Create a location for the beginning of the declaration.
Dataflow Directional Tag Classes.
#define REGISTER_CHECKER(name)
X
Add a minimal nested name specifier fixit hint to allow lookup of a tag name from an outer enclosing ...
Definition: SemaDecl.cpp:13824
static PathDiagnosticLocation createEndOfPath(const ExplodedNode *N, const SourceManager &SM)
Create a location corresponding to the next valid ExplodedNode as end of path location.
bool isPointerType() const
Definition: Type.h:6177