1//===- ObjCSuperDeallocChecker.cpp - Check correct use of [super dealloc] -===//
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 defines ObjCSuperDeallocChecker, a builtin check that warns when
10// self is used after a call to [super dealloc] in MRR mode.
11//
12//===----------------------------------------------------------------------===//
13
14#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
15#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
16#include "clang/StaticAnalyzer/Core/Checker.h"
17#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
18#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
19#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
20#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
21
22using namespace clang;
23using namespace ento;
24
25namespace {
26class ObjCSuperDeallocChecker
27 : public Checker<check::PostObjCMessage, check::PreObjCMessage,
28 check::PreCall, check::Location> {
29 mutable const IdentifierInfo *IIdealloc = nullptr;
30 mutable const IdentifierInfo *IINSObject = nullptr;
31 mutable Selector SELdealloc;
32
33 const BugType DoubleSuperDeallocBugType{
34 this, "[super dealloc] should not be called more than once",
35 categories::CoreFoundationObjectiveC};
36
37 void initIdentifierInfoAndSelectors(const ASTContext &Ctx) const;
38
39 bool isSuperDeallocMessage(const ObjCMethodCall &M) const;
40
41public:
42 void checkPostObjCMessage(const ObjCMethodCall &M, CheckerContext &C) const;
43 void checkPreObjCMessage(const ObjCMethodCall &M, CheckerContext &C) const;
44
45 void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
46
47 void checkLocation(SVal l, bool isLoad, const Stmt *S,
48 CheckerContext &C) const;
49
50private:
51
52 void diagnoseCallArguments(const CallEvent &CE, CheckerContext &C) const;
53
54 void reportUseAfterDealloc(SymbolRef Sym, StringRef Desc, const Stmt *S,
55 CheckerContext &C) const;
56};
57
58} // End anonymous namespace.
59
60// Remember whether [super dealloc] has previously been called on the
61// SymbolRef for the receiver.
62REGISTER_SET_WITH_PROGRAMSTATE(CalledSuperDealloc, SymbolRef)
63
64namespace {
65class SuperDeallocBRVisitor final : public BugReporterVisitor {
66 SymbolRef ReceiverSymbol;
67 bool Satisfied;
68
69public:
70 SuperDeallocBRVisitor(SymbolRef ReceiverSymbol)
71 : ReceiverSymbol(ReceiverSymbol), Satisfied(false) {}
72
73 PathDiagnosticPieceRef VisitNode(const ExplodedNode *Succ,
74 BugReporterContext &BRC,
75 PathSensitiveBugReport &BR) override;
76
77 void Profile(llvm::FoldingSetNodeID &ID) const override {
78 ID.Add(x: ReceiverSymbol);
79 }
80};
81} // End anonymous namespace.
82
83void ObjCSuperDeallocChecker::checkPreObjCMessage(const ObjCMethodCall &M,
84 CheckerContext &C) const {
85
86 ProgramStateRef State = C.getState();
87 SymbolRef ReceiverSymbol = M.getReceiverSVal().getAsSymbol();
88 if (!ReceiverSymbol) {
89 diagnoseCallArguments(CE: M, C);
90 return;
91 }
92
93 bool AlreadyCalled = State->contains<CalledSuperDealloc>(key: ReceiverSymbol);
94 if (!AlreadyCalled)
95 return;
96
97 StringRef Desc;
98
99 if (isSuperDeallocMessage(M)) {
100 Desc = "[super dealloc] should not be called multiple times";
101 } else {
102 Desc = StringRef();
103 }
104
105 reportUseAfterDealloc(Sym: ReceiverSymbol, Desc, S: M.getOriginExpr(), C);
106}
107
108void ObjCSuperDeallocChecker::checkPreCall(const CallEvent &Call,
109 CheckerContext &C) const {
110 diagnoseCallArguments(CE: Call, C);
111}
112
113void ObjCSuperDeallocChecker::checkPostObjCMessage(const ObjCMethodCall &M,
114 CheckerContext &C) const {
115 // Check for [super dealloc] method call.
116 if (!isSuperDeallocMessage(M))
117 return;
118
119 ProgramStateRef State = C.getState();
120 SymbolRef SelfSymbol = State->getSelfSVal(SF: C.getStackFrame()).getAsSymbol();
121 assert(SelfSymbol && "No receiver symbol at call to [super dealloc]?");
122
123 // We add this transition in checkPostObjCMessage to avoid warning when
124 // we inline a call to [super dealloc] where the inlined call itself
125 // calls [super dealloc].
126 State = State->add<CalledSuperDealloc>(K: SelfSymbol);
127 C.addTransition(State);
128}
129
130void ObjCSuperDeallocChecker::checkLocation(SVal L, bool IsLoad, const Stmt *S,
131 CheckerContext &C) const {
132 SymbolRef BaseSym = L.getLocSymbolInBase();
133 if (!BaseSym)
134 return;
135
136 ProgramStateRef State = C.getState();
137
138 if (!State->contains<CalledSuperDealloc>(key: BaseSym))
139 return;
140
141 const MemRegion *R = L.getAsRegion();
142 if (!R)
143 return;
144
145 // Climb the super regions to find the base symbol while recording
146 // the second-to-last region for error reporting.
147 const MemRegion *PriorSubRegion = nullptr;
148 while (const SubRegion *SR = dyn_cast<SubRegion>(Val: R)) {
149 if (const SymbolicRegion *SymR = dyn_cast<SymbolicRegion>(Val: SR)) {
150 BaseSym = SymR->getSymbol();
151 break;
152 } else {
153 R = SR->getSuperRegion();
154 PriorSubRegion = SR;
155 }
156 }
157
158 StringRef Desc = StringRef();
159 auto *IvarRegion = dyn_cast_or_null<ObjCIvarRegion>(Val: PriorSubRegion);
160
161 std::string Buf;
162 llvm::raw_string_ostream OS(Buf);
163 if (IvarRegion) {
164 OS << "Use of instance variable '" << *IvarRegion->getDecl() <<
165 "' after 'self' has been deallocated";
166 Desc = Buf;
167 }
168
169 reportUseAfterDealloc(Sym: BaseSym, Desc, S, C);
170}
171
172/// Report a use-after-dealloc on Sym. If not empty,
173/// Desc will be used to describe the error; otherwise,
174/// a default warning will be used.
175void ObjCSuperDeallocChecker::reportUseAfterDealloc(SymbolRef Sym,
176 StringRef Desc,
177 const Stmt *S,
178 CheckerContext &C) const {
179 // We have a use of self after free.
180 // This likely causes a crash, so stop exploring the
181 // path by generating a sink.
182 ExplodedNode *ErrNode = C.generateErrorNode();
183 // If we've already reached this node on another path, return.
184 if (!ErrNode)
185 return;
186
187 if (Desc.empty())
188 Desc = "Use of 'self' after it has been deallocated";
189
190 // Generate the report.
191 auto BR = std::make_unique<PathSensitiveBugReport>(args: DoubleSuperDeallocBugType,
192 args&: Desc, args&: ErrNode);
193 BR->addRange(R: S->getSourceRange());
194 BR->addVisitor(visitor: std::make_unique<SuperDeallocBRVisitor>(args&: Sym));
195 C.emitReport(R: std::move(BR));
196}
197
198/// Diagnose if any of the arguments to CE have already been
199/// dealloc'd.
200void ObjCSuperDeallocChecker::diagnoseCallArguments(const CallEvent &CE,
201 CheckerContext &C) const {
202 ProgramStateRef State = C.getState();
203 unsigned ArgCount = CE.getNumArgs();
204 for (unsigned I = 0; I < ArgCount; I++) {
205 SymbolRef Sym = CE.getArgSVal(Index: I).getAsSymbol();
206 if (!Sym)
207 continue;
208
209 if (State->contains<CalledSuperDealloc>(key: Sym)) {
210 reportUseAfterDealloc(Sym, Desc: StringRef(), S: CE.getArgExpr(Index: I), C);
211 return;
212 }
213 }
214}
215
216void ObjCSuperDeallocChecker::initIdentifierInfoAndSelectors(
217 const ASTContext &Ctx) const {
218 if (IIdealloc)
219 return;
220
221 IIdealloc = &Ctx.Idents.get(Name: "dealloc");
222 IINSObject = &Ctx.Idents.get(Name: "NSObject");
223
224 SELdealloc = Ctx.Selectors.getSelector(NumArgs: 0, IIV: &IIdealloc);
225}
226
227bool
228ObjCSuperDeallocChecker::isSuperDeallocMessage(const ObjCMethodCall &M) const {
229 if (M.getOriginExpr()->getReceiverKind() != ObjCMessageExpr::SuperInstance)
230 return false;
231
232 const ASTContext &Ctx = M.getASTContext();
233 initIdentifierInfoAndSelectors(Ctx);
234
235 return M.getSelector() == SELdealloc;
236}
237
238PathDiagnosticPieceRef
239SuperDeallocBRVisitor::VisitNode(const ExplodedNode *Succ,
240 BugReporterContext &BRC,
241 PathSensitiveBugReport &) {
242 if (Satisfied)
243 return nullptr;
244
245 ProgramStateRef State = Succ->getState();
246
247 bool CalledNow =
248 Succ->getState()->contains<CalledSuperDealloc>(key: ReceiverSymbol);
249 bool CalledBefore =
250 Succ->getFirstPred()->getState()->contains<CalledSuperDealloc>(
251 key: ReceiverSymbol);
252
253 // Is Succ the node on which the analyzer noted that [super dealloc] was
254 // called on ReceiverSymbol?
255 if (CalledNow && !CalledBefore) {
256 Satisfied = true;
257
258 ProgramPoint P = Succ->getLocation();
259 PathDiagnosticLocation L =
260 PathDiagnosticLocation::create(P, SMng: BRC.getSourceManager());
261
262 if (!L.isValid() || !L.asLocation().isValid())
263 return nullptr;
264
265 return std::make_shared<PathDiagnosticEventPiece>(
266 args&: L, args: "[super dealloc] called here");
267 }
268
269 return nullptr;
270}
271
272//===----------------------------------------------------------------------===//
273// Checker Registration.
274//===----------------------------------------------------------------------===//
275
276void ento::registerObjCSuperDeallocChecker(CheckerManager &Mgr) {
277 Mgr.registerChecker<ObjCSuperDeallocChecker>();
278}
279
280bool ento::shouldRegisterObjCSuperDeallocChecker(const CheckerManager &mgr) {
281 return true;
282}
283