clang  7.0.0svn
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 BugReporterVisitorImpl<ValistBugVisitor> {
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::unique_ptr<PathDiagnosticPiece>
82  getEndPath(BugReporterContext &BRC, const ExplodedNode *EndPathNode,
83  BugReport &BR) override {
84  if (!IsLeak)
85  return nullptr;
86 
88  EndPathNode, BRC.getSourceManager());
89  // Do not add the statement itself as a range in case of leak.
90  return llvm::make_unique<PathDiagnosticEventPiece>(L, BR.getDescription(),
91  false);
92  }
93  std::shared_ptr<PathDiagnosticPiece> VisitNode(const ExplodedNode *N,
94  const ExplodedNode *PrevN,
95  BugReporterContext &BRC,
96  BugReport &BR) override;
97 
98  private:
99  const MemRegion *Reg;
100  bool IsLeak;
101  };
102 };
103 
105  ValistChecker::VAListAccepters = {
106  {{"vfprintf", 3}, 2},
107  {{"vfscanf", 3}, 2},
108  {{"vprintf", 2}, 1},
109  {{"vscanf", 2}, 1},
110  {{"vsnprintf", 4}, 3},
111  {{"vsprintf", 3}, 2},
112  {{"vsscanf", 3}, 2},
113  {{"vfwprintf", 3}, 2},
114  {{"vfwscanf", 3}, 2},
115  {{"vwprintf", 2}, 1},
116  {{"vwscanf", 2}, 1},
117  {{"vswprintf", 4}, 3},
118  // vswprintf is the wide version of vsnprintf,
119  // vsprintf has no wide version
120  {{"vswscanf", 3}, 2}};
121 const CallDescription ValistChecker::VaStart("__builtin_va_start", 2),
122  ValistChecker::VaCopy("__builtin_va_copy", 2),
123  ValistChecker::VaEnd("__builtin_va_end", 1);
124 } // end anonymous namespace
125 
126 void ValistChecker::checkPreCall(const CallEvent &Call,
127  CheckerContext &C) const {
128  if (!Call.isGlobalCFunction())
129  return;
130  if (Call.isCalled(VaStart))
131  checkVAListStartCall(Call, C, false);
132  else if (Call.isCalled(VaCopy))
133  checkVAListStartCall(Call, C, true);
134  else if (Call.isCalled(VaEnd))
135  checkVAListEndCall(Call, C);
136  else {
137  for (auto FuncInfo : VAListAccepters) {
138  if (!Call.isCalled(FuncInfo.Func))
139  continue;
140  bool Symbolic;
141  const MemRegion *VAList =
142  getVAListAsRegion(Call.getArgSVal(FuncInfo.VAListPos),
143  Call.getArgExpr(FuncInfo.VAListPos), Symbolic, C);
144  if (!VAList)
145  return;
146 
147  if (C.getState()->contains<InitializedVALists>(VAList))
148  return;
149 
150  // We did not see va_start call, but the source of the region is unknown.
151  // Be conservative and assume the best.
152  if (Symbolic)
153  return;
154 
155  SmallString<80> Errmsg("Function '");
156  Errmsg += FuncInfo.Func.getFunctionName();
157  Errmsg += "' is called with an uninitialized va_list argument";
158  reportUninitializedAccess(VAList, Errmsg.c_str(), C);
159  break;
160  }
161  }
162 }
163 
164 const MemRegion *ValistChecker::getVAListAsRegion(SVal SV, const Expr *E,
165  bool &IsSymbolic,
166  CheckerContext &C) const {
167  const MemRegion *Reg = SV.getAsRegion();
168  if (!Reg)
169  return nullptr;
170  // TODO: In the future this should be abstracted away by the analyzer.
171  bool VaListModelledAsArray = false;
172  if (const auto *Cast = dyn_cast<CastExpr>(E)) {
173  QualType Ty = Cast->getType();
174  VaListModelledAsArray =
175  Ty->isPointerType() && Ty->getPointeeType()->isRecordType();
176  }
177  if (const auto *DeclReg = Reg->getAs<DeclRegion>()) {
178  if (isa<ParmVarDecl>(DeclReg->getDecl()))
179  Reg = C.getState()->getSVal(SV.castAs<Loc>()).getAsRegion();
180  }
181  IsSymbolic = Reg && Reg->getAs<SymbolicRegion>();
182  // Some VarRegion based VA lists reach here as ElementRegions.
183  const auto *EReg = dyn_cast_or_null<ElementRegion>(Reg);
184  return (EReg && VaListModelledAsArray) ? EReg->getSuperRegion() : Reg;
185 }
186 
187 void ValistChecker::checkPreStmt(const VAArgExpr *VAA,
188  CheckerContext &C) const {
190  const Expr *VASubExpr = VAA->getSubExpr();
191  SVal VAListSVal = C.getSVal(VASubExpr);
192  bool Symbolic;
193  const MemRegion *VAList =
194  getVAListAsRegion(VAListSVal, VASubExpr, Symbolic, C);
195  if (!VAList)
196  return;
197  if (Symbolic)
198  return;
199  if (!State->contains<InitializedVALists>(VAList))
200  reportUninitializedAccess(
201  VAList, "va_arg() is called on an uninitialized va_list", C);
202 }
203 
204 void ValistChecker::checkDeadSymbols(SymbolReaper &SR,
205  CheckerContext &C) const {
206  ProgramStateRef State = C.getState();
207  InitializedVAListsTy TrackedVALists = State->get<InitializedVALists>();
208  RegionVector LeakedVALists;
209  for (auto Reg : TrackedVALists) {
210  if (SR.isLiveRegion(Reg))
211  continue;
212  LeakedVALists.push_back(Reg);
213  State = State->remove<InitializedVALists>(Reg);
214  }
215  if (ExplodedNode *N = C.addTransition(State))
216  reportLeakedVALists(LeakedVALists, "Initialized va_list", " is leaked", C,
217  N);
218 }
219 
220 // This function traverses the exploded graph backwards and finds the node where
221 // the va_list is initialized. That node is used for uniquing the bug paths.
222 // It is not likely that there are several different va_lists that belongs to
223 // different stack frames, so that case is not yet handled.
224 const ExplodedNode *
225 ValistChecker::getStartCallSite(const ExplodedNode *N,
226  const MemRegion *Reg) const {
227  const LocationContext *LeakContext = N->getLocationContext();
228  const ExplodedNode *StartCallNode = N;
229 
230  bool FoundInitializedState = false;
231 
232  while (N) {
233  ProgramStateRef State = N->getState();
234  if (!State->contains<InitializedVALists>(Reg)) {
235  if (FoundInitializedState)
236  break;
237  } else {
238  FoundInitializedState = true;
239  }
240  const LocationContext *NContext = N->getLocationContext();
241  if (NContext == LeakContext || NContext->isParentOf(LeakContext))
242  StartCallNode = N;
243  N = N->pred_empty() ? nullptr : *(N->pred_begin());
244  }
245 
246  return StartCallNode;
247 }
248 
249 void ValistChecker::reportUninitializedAccess(const MemRegion *VAList,
250  StringRef Msg,
251  CheckerContext &C) const {
252  if (!ChecksEnabled[CK_Uninitialized])
253  return;
254  if (ExplodedNode *N = C.generateErrorNode()) {
255  if (!BT_uninitaccess)
256  BT_uninitaccess.reset(new BugType(CheckNames[CK_Uninitialized],
257  "Uninitialized va_list",
259  auto R = llvm::make_unique<BugReport>(*BT_uninitaccess, Msg, N);
260  R->markInteresting(VAList);
261  R->addVisitor(llvm::make_unique<ValistBugVisitor>(VAList));
262  C.emitReport(std::move(R));
263  }
264 }
265 
266 void ValistChecker::reportLeakedVALists(const RegionVector &LeakedVALists,
267  StringRef Msg1, StringRef Msg2,
269  bool ReportUninit) const {
270  if (!(ChecksEnabled[CK_Unterminated] ||
271  (ChecksEnabled[CK_Uninitialized] && ReportUninit)))
272  return;
273  for (auto Reg : LeakedVALists) {
274  if (!BT_leakedvalist) {
275  // FIXME: maybe creating a new check name for this type of bug is a better
276  // solution.
277  BT_leakedvalist.reset(
278  new BugType(CheckNames[CK_Unterminated].getName().empty()
279  ? CheckNames[CK_Uninitialized]
280  : CheckNames[CK_Unterminated],
281  "Leaked va_list", categories::MemoryError));
282  BT_leakedvalist->setSuppressOnSink(true);
283  }
284 
285  const ExplodedNode *StartNode = getStartCallSite(N, Reg);
286  PathDiagnosticLocation LocUsedForUniqueing;
287 
288  if (const Stmt *StartCallStmt = PathDiagnosticLocation::getStmt(StartNode))
289  LocUsedForUniqueing = PathDiagnosticLocation::createBegin(
290  StartCallStmt, C.getSourceManager(), StartNode->getLocationContext());
291 
292  SmallString<100> Buf;
293  llvm::raw_svector_ostream OS(Buf);
294  OS << Msg1;
295  std::string VariableName = Reg->getDescriptiveName();
296  if (!VariableName.empty())
297  OS << " " << VariableName;
298  OS << Msg2;
299 
300  auto R = llvm::make_unique<BugReport>(
301  *BT_leakedvalist, OS.str(), N, LocUsedForUniqueing,
302  StartNode->getLocationContext()->getDecl());
303  R->markInteresting(Reg);
304  R->addVisitor(llvm::make_unique<ValistBugVisitor>(Reg, true));
305  C.emitReport(std::move(R));
306  }
307 }
308 
309 void ValistChecker::checkVAListStartCall(const CallEvent &Call,
310  CheckerContext &C, bool IsCopy) const {
311  bool Symbolic;
312  const MemRegion *VAList =
313  getVAListAsRegion(Call.getArgSVal(0), Call.getArgExpr(0), Symbolic, C);
314  if (!VAList)
315  return;
316 
317  ProgramStateRef State = C.getState();
318 
319  if (IsCopy) {
320  const MemRegion *Arg2 =
321  getVAListAsRegion(Call.getArgSVal(1), Call.getArgExpr(1), Symbolic, C);
322  if (Arg2) {
323  if (ChecksEnabled[CK_CopyToSelf] && VAList == Arg2) {
324  RegionVector LeakedVALists{VAList};
325  if (ExplodedNode *N = C.addTransition(State))
326  reportLeakedVALists(LeakedVALists, "va_list",
327  " is copied onto itself", C, N, true);
328  return;
329  } else if (!State->contains<InitializedVALists>(Arg2) && !Symbolic) {
330  if (State->contains<InitializedVALists>(VAList)) {
331  State = State->remove<InitializedVALists>(VAList);
332  RegionVector LeakedVALists{VAList};
333  if (ExplodedNode *N = C.addTransition(State))
334  reportLeakedVALists(LeakedVALists, "Initialized va_list",
335  " is overwritten by an uninitialized one", C, N,
336  true);
337  } else {
338  reportUninitializedAccess(Arg2, "Uninitialized va_list is copied", C);
339  }
340  return;
341  }
342  }
343  }
344  if (State->contains<InitializedVALists>(VAList)) {
345  RegionVector LeakedVALists{VAList};
346  if (ExplodedNode *N = C.addTransition(State))
347  reportLeakedVALists(LeakedVALists, "Initialized va_list",
348  " is initialized again", C, N);
349  return;
350  }
351 
352  State = State->add<InitializedVALists>(VAList);
353  C.addTransition(State);
354 }
355 
356 void ValistChecker::checkVAListEndCall(const CallEvent &Call,
357  CheckerContext &C) const {
358  bool Symbolic;
359  const MemRegion *VAList =
360  getVAListAsRegion(Call.getArgSVal(0), Call.getArgExpr(0), Symbolic, C);
361  if (!VAList)
362  return;
363 
364  // We did not see va_start call, but the source of the region is unknown.
365  // Be conservative and assume the best.
366  if (Symbolic)
367  return;
368 
369  if (!C.getState()->contains<InitializedVALists>(VAList)) {
370  reportUninitializedAccess(
371  VAList, "va_end() is called on an uninitialized va_list", C);
372  return;
373  }
374  ProgramStateRef State = C.getState();
375  State = State->remove<InitializedVALists>(VAList);
376  C.addTransition(State);
377 }
378 
379 std::shared_ptr<PathDiagnosticPiece> ValistChecker::ValistBugVisitor::VisitNode(
380  const ExplodedNode *N, const ExplodedNode *PrevN, BugReporterContext &BRC,
381  BugReport &) {
382  ProgramStateRef State = N->getState();
383  ProgramStateRef StatePrev = PrevN->getState();
384 
386  if (!S)
387  return nullptr;
388 
389  StringRef Msg;
390  if (State->contains<InitializedVALists>(Reg) &&
391  !StatePrev->contains<InitializedVALists>(Reg))
392  Msg = "Initialized va_list";
393  else if (!State->contains<InitializedVALists>(Reg) &&
394  StatePrev->contains<InitializedVALists>(Reg))
395  Msg = "Ended va_list";
396 
397  if (Msg.empty())
398  return nullptr;
399 
401  N->getLocationContext());
402  return std::make_shared<PathDiagnosticEventPiece>(Pos, Msg, true);
403 }
404 
405 #define REGISTER_CHECKER(name) \
406  void ento::register##name##Checker(CheckerManager &mgr) { \
407  ValistChecker *checker = mgr.registerChecker<ValistChecker>(); \
408  checker->ChecksEnabled[ValistChecker::CK_##name] = true; \
409  checker->CheckNames[ValistChecker::CK_##name] = mgr.getCurrentCheckName(); \
410  }
411 
413 REGISTER_CHECKER(Unterminated)
414 REGISTER_CHECKER(CopyToSelf)
A (possibly-)qualified type.
Definition: Type.h:654
MemRegion - The root abstract class for all memory regions.
Definition: MemRegion.h:94
ExplodedNode * generateErrorNode(ProgramStateRef State=nullptr, const ProgramPointTag *Tag=nullptr)
Generate a transition to a node that will be used to report an error.
Stmt - This represents one statement.
Definition: Stmt.h:66
A helper class which wraps a boolean value set to false by default.
Definition: Checker.h:567
QualType getPointeeType() const
If this is a pointer, ObjC object pointer, or block pointer, this returns the respective pointee...
Definition: Type.cpp:460
bool isRecordType() const
Definition: Type.h:6101
ExplodedNode * addTransition(ProgramStateRef State=nullptr, const ProgramPointTag *Tag=nullptr)
Generates a new transition in the program state graph (ExplodedGraph).
StringRef getDescription() const
Definition: BugReporter.h:207
const Expr * getSubExpr() const
Definition: Expr.h:3835
const ProgramStateRef & getState() const
SVal getSVal(const Stmt *S) const
Get the value of arbitrary expressions at this point in the path.
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
const MemRegion * getSuperRegion() const
Definition: MemRegion.h:443
LineState State
This class provides a convenience implementation for clone() using the Curiously-Recurring Template P...
virtual const Expr * getArgExpr(unsigned Index) const
Returns the expression associated with a given argument.
Definition: CallEvent.h:298
bool isLiveRegion(const MemRegion *region)
const LocationContext * getLocationContext() const
Represents a call to the builtin function __builtin_va_arg.
Definition: Expr.h:3817
const RegionTy * getAs() const
Definition: MemRegion.h:1180
SymbolicRegion - A special, "non-concrete" region.
Definition: MemRegion.h:759
Expr - This represents one expression.
Definition: Expr.h:106
void emitReport(std::unique_ptr< BugReport > R)
Emit the diagnostics report.
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.
This class represents a description of a function call using the number of arguments and the name of ...
Definition: CallEvent.h:77
const MemRegion * getAsRegion() const
Definition: SVals.cpp:151
SVal - This represents a symbolic expression, which can be either an L-value or an R-value...
Definition: SVals.h:76
A class responsible for cleaning up unused symbols.
std::string getDescriptiveName(bool UseQuotes=true) const
Get descriptive name for memory region.
Definition: MemRegion.cpp:632
Dataflow Directional Tag Classes.
Represents an abstract call to a function or method along a particular path.
Definition: CallEvent.h:164
const Decl * getDecl() const
T castAs() const
Convert to the specified SVal type, asserting that this SVal is of the desired type.
Definition: SVals.h:104
const ProgramStateRef & getState() const
bool isGlobalCFunction(StringRef SpecificName=StringRef()) const
Returns true if the callee is an externally-visible function in the top-level namespace, such as malloc.
Definition: CallEvent.cpp:161
#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:13503
bool isCalled(const CallDescription &CD) const
Returns true if the CallEvent is a call to a function that matches the CallDescription.
Definition: CallEvent.cpp:253
pred_iterator pred_begin()
SourceManager & getSourceManager()
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:6028
virtual SVal getArgSVal(unsigned Index) const
Returns the value of a given argument at the time of the call.
Definition: CallEvent.cpp:268
This class provides an interface through which checkers can create individual bug reports...
Definition: BugReporter.h:70
SourceManager & getSourceManager()
Definition: BugReporter.h:581