1 //== ObjCAtSyncChecker.cpp - nil mutex checker for @synchronized -*- 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 ObjCAtSyncChecker, a builtin check that checks for null pointers
11 // used as mutexes for @synchronized.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "ClangSACheckers.h"
16 #include "clang/AST/StmtObjC.h"
17 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
18 #include "clang/StaticAnalyzer/Core/Checker.h"
19 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
20 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
21 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
22
23 using namespace clang;
24 using namespace ento;
25
26 namespace {
27 class ObjCAtSyncChecker
28 : public Checker< check::PreStmt<ObjCAtSynchronizedStmt> > {
29 mutable std::unique_ptr<BuiltinBug> BT_null;
30 mutable std::unique_ptr<BuiltinBug> BT_undef;
31
32 public:
33 void checkPreStmt(const ObjCAtSynchronizedStmt *S, CheckerContext &C) const;
34 };
35 } // end anonymous namespace
36
checkPreStmt(const ObjCAtSynchronizedStmt * S,CheckerContext & C) const37 void ObjCAtSyncChecker::checkPreStmt(const ObjCAtSynchronizedStmt *S,
38 CheckerContext &C) const {
39
40 const Expr *Ex = S->getSynchExpr();
41 ProgramStateRef state = C.getState();
42 SVal V = state->getSVal(Ex, C.getLocationContext());
43
44 // Uninitialized value used for the mutex?
45 if (V.getAs<UndefinedVal>()) {
46 if (ExplodedNode *N = C.generateErrorNode()) {
47 if (!BT_undef)
48 BT_undef.reset(new BuiltinBug(this, "Uninitialized value used as mutex "
49 "for @synchronized"));
50 auto report =
51 llvm::make_unique<BugReport>(*BT_undef, BT_undef->getDescription(), N);
52 bugreporter::trackNullOrUndefValue(N, Ex, *report);
53 C.emitReport(std::move(report));
54 }
55 return;
56 }
57
58 if (V.isUnknown())
59 return;
60
61 // Check for null mutexes.
62 ProgramStateRef notNullState, nullState;
63 std::tie(notNullState, nullState) = state->assume(V.castAs<DefinedSVal>());
64
65 if (nullState) {
66 if (!notNullState) {
67 // Generate an error node. This isn't a sink since
68 // a null mutex just means no synchronization occurs.
69 if (ExplodedNode *N = C.generateNonFatalErrorNode(nullState)) {
70 if (!BT_null)
71 BT_null.reset(new BuiltinBug(
72 this, "Nil value used as mutex for @synchronized() "
73 "(no synchronization will occur)"));
74 auto report =
75 llvm::make_unique<BugReport>(*BT_null, BT_null->getDescription(), N);
76 bugreporter::trackNullOrUndefValue(N, Ex, *report);
77
78 C.emitReport(std::move(report));
79 return;
80 }
81 }
82 // Don't add a transition for 'nullState'. If the value is
83 // under-constrained to be null or non-null, assume it is non-null
84 // afterwards.
85 }
86
87 if (notNullState)
88 C.addTransition(notNullState);
89 }
90
registerObjCAtSyncChecker(CheckerManager & mgr)91 void ento::registerObjCAtSyncChecker(CheckerManager &mgr) {
92 if (mgr.getLangOpts().ObjC2)
93 mgr.registerChecker<ObjCAtSyncChecker>();
94 }
95