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 36 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 (isa<UndefinedVal>(V)) { 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 90 void ento::registerObjCAtSyncChecker(CheckerManager &mgr) { 91 mgr.registerChecker<ObjCAtSyncChecker>(); 92 } 93 94 bool ento::shouldRegisterObjCAtSyncChecker(const CheckerManager &mgr) { 95 const LangOptions &LO = mgr.getLangOpts(); 96 return LO.ObjC; 97 } 98