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 const BugType BT_null{this, "Nil value used as mutex for @synchronized() " 29 "(no synchronization will occur)"}; 30 const BugType BT_undef{this, "Uninitialized value used as mutex " 31 "for @synchronized"}; 32 33 public: 34 void checkPreStmt(const ObjCAtSynchronizedStmt *S, CheckerContext &C) const; 35 }; 36 } // end anonymous namespace 37 38 void ObjCAtSyncChecker::checkPreStmt(const ObjCAtSynchronizedStmt *S, 39 CheckerContext &C) const { 40 41 const Expr *Ex = S->getSynchExpr(); 42 ProgramStateRef state = C.getState(); 43 SVal V = C.getSVal(Ex); 44 45 // Uninitialized value used for the mutex? 46 if (isa<UndefinedVal>(V)) { 47 if (ExplodedNode *N = C.generateErrorNode()) { 48 auto report = std::make_unique<PathSensitiveBugReport>( 49 BT_undef, BT_undef.getDescription(), N); 50 bugreporter::trackExpressionValue(N, Ex, *report); 51 C.emitReport(std::move(report)); 52 } 53 return; 54 } 55 56 if (V.isUnknown()) 57 return; 58 59 // Check for null mutexes. 60 ProgramStateRef notNullState, nullState; 61 std::tie(notNullState, nullState) = state->assume(V.castAs<DefinedSVal>()); 62 63 if (nullState) { 64 if (!notNullState) { 65 // Generate an error node. This isn't a sink since 66 // a null mutex just means no synchronization occurs. 67 if (ExplodedNode *N = C.generateNonFatalErrorNode(nullState)) { 68 auto report = std::make_unique<PathSensitiveBugReport>( 69 BT_null, BT_null.getDescription(), N); 70 bugreporter::trackExpressionValue(N, Ex, *report); 71 72 C.emitReport(std::move(report)); 73 return; 74 } 75 } 76 // Don't add a transition for 'nullState'. If the value is 77 // under-constrained to be null or non-null, assume it is non-null 78 // afterwards. 79 } 80 81 if (notNullState) 82 C.addTransition(notNullState); 83 } 84 85 void ento::registerObjCAtSyncChecker(CheckerManager &mgr) { 86 mgr.registerChecker<ObjCAtSyncChecker>(); 87 } 88 89 bool ento::shouldRegisterObjCAtSyncChecker(const CheckerManager &mgr) { 90 const LangOptions &LO = mgr.getLangOpts(); 91 return LO.ObjC; 92 } 93