xref: /freebsd/contrib/llvm-project/clang/lib/StaticAnalyzer/Checkers/InnerPointerChecker.cpp (revision cfd6422a5217410fbd66f7a7a8a64d9d85e61229)
1 //=== InnerPointerChecker.cpp -------------------------------------*- C++ -*--//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file defines a check that marks a raw pointer to a C++ container's
10 // inner buffer released when the object is destroyed. This information can
11 // be used by MallocChecker to detect use-after-free problems.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "AllocationState.h"
16 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
17 #include "InterCheckerAPI.h"
18 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
19 #include "clang/StaticAnalyzer/Core/BugReporter/CommonBugCategories.h"
20 #include "clang/StaticAnalyzer/Core/Checker.h"
21 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
22 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
23 
24 using namespace clang;
25 using namespace ento;
26 
27 // Associate container objects with a set of raw pointer symbols.
28 REGISTER_SET_FACTORY_WITH_PROGRAMSTATE(PtrSet, SymbolRef)
29 REGISTER_MAP_WITH_PROGRAMSTATE(RawPtrMap, const MemRegion *, PtrSet)
30 
31 
32 namespace {
33 
34 class InnerPointerChecker
35     : public Checker<check::DeadSymbols, check::PostCall> {
36 
37   CallDescription AppendFn, AssignFn, ClearFn, CStrFn, DataFn, EraseFn,
38       InsertFn, PopBackFn, PushBackFn, ReplaceFn, ReserveFn, ResizeFn,
39       ShrinkToFitFn, SwapFn;
40 
41 public:
42   class InnerPointerBRVisitor : public BugReporterVisitor {
43     SymbolRef PtrToBuf;
44 
45   public:
46     InnerPointerBRVisitor(SymbolRef Sym) : PtrToBuf(Sym) {}
47 
48     static void *getTag() {
49       static int Tag = 0;
50       return &Tag;
51     }
52 
53     void Profile(llvm::FoldingSetNodeID &ID) const override {
54       ID.AddPointer(getTag());
55     }
56 
57     virtual PathDiagnosticPieceRef
58     VisitNode(const ExplodedNode *N, BugReporterContext &BRC,
59               PathSensitiveBugReport &BR) override;
60 
61     // FIXME: Scan the map once in the visitor's constructor and do a direct
62     // lookup by region.
63     bool isSymbolTracked(ProgramStateRef State, SymbolRef Sym) {
64       RawPtrMapTy Map = State->get<RawPtrMap>();
65       for (const auto &Entry : Map) {
66         if (Entry.second.contains(Sym))
67           return true;
68       }
69       return false;
70     }
71   };
72 
73   InnerPointerChecker()
74       : AppendFn({"std", "basic_string", "append"}),
75         AssignFn({"std", "basic_string", "assign"}),
76         ClearFn({"std", "basic_string", "clear"}),
77         CStrFn({"std", "basic_string", "c_str"}),
78         DataFn({"std", "basic_string", "data"}),
79         EraseFn({"std", "basic_string", "erase"}),
80         InsertFn({"std", "basic_string", "insert"}),
81         PopBackFn({"std", "basic_string", "pop_back"}),
82         PushBackFn({"std", "basic_string", "push_back"}),
83         ReplaceFn({"std", "basic_string", "replace"}),
84         ReserveFn({"std", "basic_string", "reserve"}),
85         ResizeFn({"std", "basic_string", "resize"}),
86         ShrinkToFitFn({"std", "basic_string", "shrink_to_fit"}),
87         SwapFn({"std", "basic_string", "swap"}) {}
88 
89   /// Check whether the called member function potentially invalidates
90   /// pointers referring to the container object's inner buffer.
91   bool isInvalidatingMemberFunction(const CallEvent &Call) const;
92 
93   /// Mark pointer symbols associated with the given memory region released
94   /// in the program state.
95   void markPtrSymbolsReleased(const CallEvent &Call, ProgramStateRef State,
96                               const MemRegion *ObjRegion,
97                               CheckerContext &C) const;
98 
99   /// Standard library functions that take a non-const `basic_string` argument by
100   /// reference may invalidate its inner pointers. Check for these cases and
101   /// mark the pointers released.
102   void checkFunctionArguments(const CallEvent &Call, ProgramStateRef State,
103                               CheckerContext &C) const;
104 
105   /// Record the connection between raw pointers referring to a container
106   /// object's inner buffer and the object's memory region in the program state.
107   /// Mark potentially invalidated pointers released.
108   void checkPostCall(const CallEvent &Call, CheckerContext &C) const;
109 
110   /// Clean up the program state map.
111   void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
112 };
113 
114 } // end anonymous namespace
115 
116 bool InnerPointerChecker::isInvalidatingMemberFunction(
117         const CallEvent &Call) const {
118   if (const auto *MemOpCall = dyn_cast<CXXMemberOperatorCall>(&Call)) {
119     OverloadedOperatorKind Opc = MemOpCall->getOriginExpr()->getOperator();
120     if (Opc == OO_Equal || Opc == OO_PlusEqual)
121       return true;
122     return false;
123   }
124   return (isa<CXXDestructorCall>(Call) || Call.isCalled(AppendFn) ||
125           Call.isCalled(AssignFn) || Call.isCalled(ClearFn) ||
126           Call.isCalled(EraseFn) || Call.isCalled(InsertFn) ||
127           Call.isCalled(PopBackFn) || Call.isCalled(PushBackFn) ||
128           Call.isCalled(ReplaceFn) || Call.isCalled(ReserveFn) ||
129           Call.isCalled(ResizeFn) || Call.isCalled(ShrinkToFitFn) ||
130           Call.isCalled(SwapFn));
131 }
132 
133 void InnerPointerChecker::markPtrSymbolsReleased(const CallEvent &Call,
134                                                  ProgramStateRef State,
135                                                  const MemRegion *MR,
136                                                  CheckerContext &C) const {
137   if (const PtrSet *PS = State->get<RawPtrMap>(MR)) {
138     const Expr *Origin = Call.getOriginExpr();
139     for (const auto Symbol : *PS) {
140       // NOTE: `Origin` may be null, and will be stored so in the symbol's
141       // `RefState` in MallocChecker's `RegionState` program state map.
142       State = allocation_state::markReleased(State, Symbol, Origin);
143     }
144     State = State->remove<RawPtrMap>(MR);
145     C.addTransition(State);
146     return;
147   }
148 }
149 
150 void InnerPointerChecker::checkFunctionArguments(const CallEvent &Call,
151                                                  ProgramStateRef State,
152                                                  CheckerContext &C) const {
153   if (const auto *FC = dyn_cast<AnyFunctionCall>(&Call)) {
154     const FunctionDecl *FD = FC->getDecl();
155     if (!FD || !FD->isInStdNamespace())
156       return;
157 
158     for (unsigned I = 0, E = FD->getNumParams(); I != E; ++I) {
159       QualType ParamTy = FD->getParamDecl(I)->getType();
160       if (!ParamTy->isReferenceType() ||
161           ParamTy->getPointeeType().isConstQualified())
162         continue;
163 
164       // In case of member operator calls, `this` is counted as an
165       // argument but not as a parameter.
166       bool isaMemberOpCall = isa<CXXMemberOperatorCall>(FC);
167       unsigned ArgI = isaMemberOpCall ? I+1 : I;
168 
169       SVal Arg = FC->getArgSVal(ArgI);
170       const auto *ArgRegion =
171           dyn_cast_or_null<TypedValueRegion>(Arg.getAsRegion());
172       if (!ArgRegion)
173         continue;
174 
175       markPtrSymbolsReleased(Call, State, ArgRegion, C);
176     }
177   }
178 }
179 
180 // [string.require]
181 //
182 // "References, pointers, and iterators referring to the elements of a
183 // basic_string sequence may be invalidated by the following uses of that
184 // basic_string object:
185 //
186 // -- As an argument to any standard library function taking a reference
187 // to non-const basic_string as an argument. For example, as an argument to
188 // non-member functions swap(), operator>>(), and getline(), or as an argument
189 // to basic_string::swap().
190 //
191 // -- Calling non-const member functions, except operator[], at, front, back,
192 // begin, rbegin, end, and rend."
193 
194 void InnerPointerChecker::checkPostCall(const CallEvent &Call,
195                                         CheckerContext &C) const {
196   ProgramStateRef State = C.getState();
197 
198   if (const auto *ICall = dyn_cast<CXXInstanceCall>(&Call)) {
199     // TODO: Do we need these to be typed?
200     const auto *ObjRegion = dyn_cast_or_null<TypedValueRegion>(
201         ICall->getCXXThisVal().getAsRegion());
202     if (!ObjRegion)
203       return;
204 
205     if (Call.isCalled(CStrFn) || Call.isCalled(DataFn)) {
206       SVal RawPtr = Call.getReturnValue();
207       if (SymbolRef Sym = RawPtr.getAsSymbol(/*IncludeBaseRegions=*/true)) {
208         // Start tracking this raw pointer by adding it to the set of symbols
209         // associated with this container object in the program state map.
210 
211         PtrSet::Factory &F = State->getStateManager().get_context<PtrSet>();
212         const PtrSet *SetPtr = State->get<RawPtrMap>(ObjRegion);
213         PtrSet Set = SetPtr ? *SetPtr : F.getEmptySet();
214         assert(C.wasInlined || !Set.contains(Sym));
215         Set = F.add(Set, Sym);
216 
217         State = State->set<RawPtrMap>(ObjRegion, Set);
218         C.addTransition(State);
219       }
220       return;
221     }
222 
223     // Check [string.require] / second point.
224     if (isInvalidatingMemberFunction(Call)) {
225       markPtrSymbolsReleased(Call, State, ObjRegion, C);
226       return;
227     }
228   }
229 
230   // Check [string.require] / first point.
231   checkFunctionArguments(Call, State, C);
232 }
233 
234 void InnerPointerChecker::checkDeadSymbols(SymbolReaper &SymReaper,
235                                            CheckerContext &C) const {
236   ProgramStateRef State = C.getState();
237   PtrSet::Factory &F = State->getStateManager().get_context<PtrSet>();
238   RawPtrMapTy RPM = State->get<RawPtrMap>();
239   for (const auto &Entry : RPM) {
240     if (!SymReaper.isLiveRegion(Entry.first)) {
241       // Due to incomplete destructor support, some dead regions might
242       // remain in the program state map. Clean them up.
243       State = State->remove<RawPtrMap>(Entry.first);
244     }
245     if (const PtrSet *OldSet = State->get<RawPtrMap>(Entry.first)) {
246       PtrSet CleanedUpSet = *OldSet;
247       for (const auto Symbol : Entry.second) {
248         if (!SymReaper.isLive(Symbol))
249           CleanedUpSet = F.remove(CleanedUpSet, Symbol);
250       }
251       State = CleanedUpSet.isEmpty()
252                   ? State->remove<RawPtrMap>(Entry.first)
253                   : State->set<RawPtrMap>(Entry.first, CleanedUpSet);
254     }
255   }
256   C.addTransition(State);
257 }
258 
259 namespace clang {
260 namespace ento {
261 namespace allocation_state {
262 
263 std::unique_ptr<BugReporterVisitor> getInnerPointerBRVisitor(SymbolRef Sym) {
264   return std::make_unique<InnerPointerChecker::InnerPointerBRVisitor>(Sym);
265 }
266 
267 const MemRegion *getContainerObjRegion(ProgramStateRef State, SymbolRef Sym) {
268   RawPtrMapTy Map = State->get<RawPtrMap>();
269   for (const auto &Entry : Map) {
270     if (Entry.second.contains(Sym)) {
271       return Entry.first;
272     }
273   }
274   return nullptr;
275 }
276 
277 } // end namespace allocation_state
278 } // end namespace ento
279 } // end namespace clang
280 
281 PathDiagnosticPieceRef InnerPointerChecker::InnerPointerBRVisitor::VisitNode(
282     const ExplodedNode *N, BugReporterContext &BRC, PathSensitiveBugReport &) {
283   if (!isSymbolTracked(N->getState(), PtrToBuf) ||
284       isSymbolTracked(N->getFirstPred()->getState(), PtrToBuf))
285     return nullptr;
286 
287   const Stmt *S = N->getStmtForDiagnostics();
288   if (!S)
289     return nullptr;
290 
291   const MemRegion *ObjRegion =
292       allocation_state::getContainerObjRegion(N->getState(), PtrToBuf);
293   const auto *TypedRegion = cast<TypedValueRegion>(ObjRegion);
294   QualType ObjTy = TypedRegion->getValueType();
295 
296   SmallString<256> Buf;
297   llvm::raw_svector_ostream OS(Buf);
298   OS << "Pointer to inner buffer of '" << ObjTy.getAsString()
299      << "' obtained here";
300   PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
301                              N->getLocationContext());
302   return std::make_shared<PathDiagnosticEventPiece>(Pos, OS.str(), true);
303 }
304 
305 void ento::registerInnerPointerChecker(CheckerManager &Mgr) {
306   registerInnerPointerCheckerAux(Mgr);
307   Mgr.registerChecker<InnerPointerChecker>();
308 }
309 
310 bool ento::shouldRegisterInnerPointerChecker(const CheckerManager &mgr) {
311   return true;
312 }
313