1 //== ObjCAtSyncChecker.cpp - nil mutex checker for @synchronized -*- 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 defines ObjCAtSyncChecker, a builtin check that checks for null pointers
10 // used as mutexes for @synchronized.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
15 #include "clang/AST/StmtObjC.h"
16 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.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/PathSensitive/ExprEngine.h"
21
22 using namespace clang;
23 using namespace ento;
24
25 namespace {
26 class ObjCAtSyncChecker
27 : public Checker< check::PreStmt<ObjCAtSynchronizedStmt> > {
28 mutable std::unique_ptr<BuiltinBug> BT_null;
29 mutable std::unique_ptr<BuiltinBug> BT_undef;
30
31 public:
32 void checkPreStmt(const ObjCAtSynchronizedStmt *S, CheckerContext &C) const;
33 };
34 } // end anonymous namespace
35
checkPreStmt(const ObjCAtSynchronizedStmt * S,CheckerContext & C) const36 void ObjCAtSyncChecker::checkPreStmt(const ObjCAtSynchronizedStmt *S,
37 CheckerContext &C) const {
38
39 const Expr *Ex = S->getSynchExpr();
40 ProgramStateRef state = C.getState();
41 SVal V = C.getSVal(Ex);
42
43 // Uninitialized value used for the mutex?
44 if (V.getAs<UndefinedVal>()) {
45 if (ExplodedNode *N = C.generateErrorNode()) {
46 if (!BT_undef)
47 BT_undef.reset(new BuiltinBug(this, "Uninitialized value used as mutex "
48 "for @synchronized"));
49 auto report = std::make_unique<PathSensitiveBugReport>(
50 *BT_undef, BT_undef->getDescription(), N);
51 bugreporter::trackExpressionValue(N, Ex, *report);
52 C.emitReport(std::move(report));
53 }
54 return;
55 }
56
57 if (V.isUnknown())
58 return;
59
60 // Check for null mutexes.
61 ProgramStateRef notNullState, nullState;
62 std::tie(notNullState, nullState) = state->assume(V.castAs<DefinedSVal>());
63
64 if (nullState) {
65 if (!notNullState) {
66 // Generate an error node. This isn't a sink since
67 // a null mutex just means no synchronization occurs.
68 if (ExplodedNode *N = C.generateNonFatalErrorNode(nullState)) {
69 if (!BT_null)
70 BT_null.reset(new BuiltinBug(
71 this, "Nil value used as mutex for @synchronized() "
72 "(no synchronization will occur)"));
73 auto report = std::make_unique<PathSensitiveBugReport>(
74 *BT_null, BT_null->getDescription(), N);
75 bugreporter::trackExpressionValue(N, Ex, *report);
76
77 C.emitReport(std::move(report));
78 return;
79 }
80 }
81 // Don't add a transition for 'nullState'. If the value is
82 // under-constrained to be null or non-null, assume it is non-null
83 // afterwards.
84 }
85
86 if (notNullState)
87 C.addTransition(notNullState);
88 }
89
registerObjCAtSyncChecker(CheckerManager & mgr)90 void ento::registerObjCAtSyncChecker(CheckerManager &mgr) {
91 mgr.registerChecker<ObjCAtSyncChecker>();
92 }
93
shouldRegisterObjCAtSyncChecker(const CheckerManager & mgr)94 bool ento::shouldRegisterObjCAtSyncChecker(const CheckerManager &mgr) {
95 const LangOptions &LO = mgr.getLangOpts();
96 return LO.ObjC;
97 }
98