| //== ObjCSelfInitChecker.cpp - Checker for 'self' initialization -*- C++ -*--=// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This defines ObjCSelfInitChecker, a builtin check that checks for uses of |
| // 'self' before proper initialization. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| // This checks initialization methods to verify that they assign 'self' to the |
| // result of an initialization call (e.g. [super init], or [self initWith..]) |
| // before using 'self' or any instance variable. |
| // |
| // To perform the required checking, values are tagged with flags that indicate |
| // 1) if the object is the one pointed to by 'self', and 2) if the object |
| // is the result of an initializer (e.g. [super init]). |
| // |
| // Uses of an object that is true for 1) but not 2) trigger a diagnostic. |
| // The uses that are currently checked are: |
| // - Using instance variables. |
| // - Returning the object. |
| // |
| // Note that we don't check for an invalid 'self' that is the receiver of an |
| // obj-c message expression to cut down false positives where logging functions |
| // get information from self (like its class) or doing "invalidation" on self |
| // when the initialization fails. |
| // |
| // Because the object that 'self' points to gets invalidated when a call |
| // receives a reference to 'self', the checker keeps track and passes the flags |
| // for 1) and 2) to the new object that 'self' points to after the call. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h" |
| #include "clang/AST/ParentMap.h" |
| #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" |
| #include "clang/StaticAnalyzer/Core/Checker.h" |
| #include "clang/StaticAnalyzer/Core/CheckerManager.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" |
| #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h" |
| #include "llvm/Support/raw_ostream.h" |
| |
| using namespace clang; |
| using namespace ento; |
| |
| static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND); |
| static bool isInitializationMethod(const ObjCMethodDecl *MD); |
| static bool isInitMessage(const ObjCMethodCall &Msg); |
| static bool isSelfVar(SVal location, CheckerContext &C); |
| |
| namespace { |
| class ObjCSelfInitChecker : public Checker< check::PostObjCMessage, |
| check::PostStmt<ObjCIvarRefExpr>, |
| check::PreStmt<ReturnStmt>, |
| check::PreCall, |
| check::PostCall, |
| check::Location, |
| check::Bind > { |
| mutable std::unique_ptr<BugType> BT; |
| |
| void checkForInvalidSelf(const Expr *E, CheckerContext &C, |
| const char *errorStr) const; |
| |
| public: |
| ObjCSelfInitChecker() {} |
| void checkPostObjCMessage(const ObjCMethodCall &Msg, CheckerContext &C) const; |
| void checkPostStmt(const ObjCIvarRefExpr *E, CheckerContext &C) const; |
| void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const; |
| void checkLocation(SVal location, bool isLoad, const Stmt *S, |
| CheckerContext &C) const; |
| void checkBind(SVal loc, SVal val, const Stmt *S, CheckerContext &C) const; |
| |
| void checkPreCall(const CallEvent &CE, CheckerContext &C) const; |
| void checkPostCall(const CallEvent &CE, CheckerContext &C) const; |
| |
| void printState(raw_ostream &Out, ProgramStateRef State, |
| const char *NL, const char *Sep) const override; |
| }; |
| } // end anonymous namespace |
| |
| namespace { |
| enum SelfFlagEnum { |
| /// No flag set. |
| SelfFlag_None = 0x0, |
| /// Value came from 'self'. |
| SelfFlag_Self = 0x1, |
| /// Value came from the result of an initializer (e.g. [super init]). |
| SelfFlag_InitRes = 0x2 |
| }; |
| } |
| |
| REGISTER_MAP_WITH_PROGRAMSTATE(SelfFlag, SymbolRef, unsigned) |
| REGISTER_TRAIT_WITH_PROGRAMSTATE(CalledInit, bool) |
| |
| /// A call receiving a reference to 'self' invalidates the object that |
| /// 'self' contains. This keeps the "self flags" assigned to the 'self' |
| /// object before the call so we can assign them to the new object that 'self' |
| /// points to after the call. |
| REGISTER_TRAIT_WITH_PROGRAMSTATE(PreCallSelfFlags, unsigned) |
| |
| static SelfFlagEnum getSelfFlags(SVal val, ProgramStateRef state) { |
| if (SymbolRef sym = val.getAsSymbol()) |
| if (const unsigned *attachedFlags = state->get<SelfFlag>(sym)) |
| return (SelfFlagEnum)*attachedFlags; |
| return SelfFlag_None; |
| } |
| |
| static SelfFlagEnum getSelfFlags(SVal val, CheckerContext &C) { |
| return getSelfFlags(val, C.getState()); |
| } |
| |
| static void addSelfFlag(ProgramStateRef state, SVal val, |
| SelfFlagEnum flag, CheckerContext &C) { |
| // We tag the symbol that the SVal wraps. |
| if (SymbolRef sym = val.getAsSymbol()) { |
| state = state->set<SelfFlag>(sym, getSelfFlags(val, state) | flag); |
| C.addTransition(state); |
| } |
| } |
| |
| static bool hasSelfFlag(SVal val, SelfFlagEnum flag, CheckerContext &C) { |
| return getSelfFlags(val, C) & flag; |
| } |
| |
| /// Returns true of the value of the expression is the object that 'self' |
| /// points to and is an object that did not come from the result of calling |
| /// an initializer. |
| static bool isInvalidSelf(const Expr *E, CheckerContext &C) { |
| SVal exprVal = C.getSVal(E); |
| if (!hasSelfFlag(exprVal, SelfFlag_Self, C)) |
| return false; // value did not come from 'self'. |
| if (hasSelfFlag(exprVal, SelfFlag_InitRes, C)) |
| return false; // 'self' is properly initialized. |
| |
| return true; |
| } |
| |
| void ObjCSelfInitChecker::checkForInvalidSelf(const Expr *E, CheckerContext &C, |
| const char *errorStr) const { |
| if (!E) |
| return; |
| |
| if (!C.getState()->get<CalledInit>()) |
| return; |
| |
| if (!isInvalidSelf(E, C)) |
| return; |
| |
| // Generate an error node. |
| ExplodedNode *N = C.generateErrorNode(); |
| if (!N) |
| return; |
| |
| if (!BT) |
| BT.reset(new BugType(this, "Missing \"self = [(super or self) init...]\"", |
| categories::CoreFoundationObjectiveC)); |
| C.emitReport(std::make_unique<PathSensitiveBugReport>(*BT, errorStr, N)); |
| } |
| |
| void ObjCSelfInitChecker::checkPostObjCMessage(const ObjCMethodCall &Msg, |
| CheckerContext &C) const { |
| // When encountering a message that does initialization (init rule), |
| // tag the return value so that we know later on that if self has this value |
| // then it is properly initialized. |
| |
| // FIXME: A callback should disable checkers at the start of functions. |
| if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>( |
| C.getCurrentAnalysisDeclContext()->getDecl()))) |
| return; |
| |
| if (isInitMessage(Msg)) { |
| // Tag the return value as the result of an initializer. |
| ProgramStateRef state = C.getState(); |
| |
| // FIXME this really should be context sensitive, where we record |
| // the current stack frame (for IPA). Also, we need to clean this |
| // value out when we return from this method. |
| state = state->set<CalledInit>(true); |
| |
| SVal V = C.getSVal(Msg.getOriginExpr()); |
| addSelfFlag(state, V, SelfFlag_InitRes, C); |
| return; |
| } |
| |
| // We don't check for an invalid 'self' in an obj-c message expression to cut |
| // down false positives where logging functions get information from self |
| // (like its class) or doing "invalidation" on self when the initialization |
| // fails. |
| } |
| |
| void ObjCSelfInitChecker::checkPostStmt(const ObjCIvarRefExpr *E, |
| CheckerContext &C) const { |
| // FIXME: A callback should disable checkers at the start of functions. |
| if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>( |
| C.getCurrentAnalysisDeclContext()->getDecl()))) |
| return; |
| |
| checkForInvalidSelf( |
| E->getBase(), C, |
| "Instance variable used while 'self' is not set to the result of " |
| "'[(super or self) init...]'"); |
| } |
| |
| void ObjCSelfInitChecker::checkPreStmt(const ReturnStmt *S, |
| CheckerContext &C) const { |
| // FIXME: A callback should disable checkers at the start of functions. |
| if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>( |
| C.getCurrentAnalysisDeclContext()->getDecl()))) |
| return; |
| |
| checkForInvalidSelf(S->getRetValue(), C, |
| "Returning 'self' while it is not set to the result of " |
| "'[(super or self) init...]'"); |
| } |
| |
| // When a call receives a reference to 'self', [Pre/Post]Call pass |
| // the SelfFlags from the object 'self' points to before the call to the new |
| // object after the call. This is to avoid invalidation of 'self' by logging |
| // functions. |
| // Another common pattern in classes with multiple initializers is to put the |
| // subclass's common initialization bits into a static function that receives |
| // the value of 'self', e.g: |
| // @code |
| // if (!(self = [super init])) |
| // return nil; |
| // if (!(self = _commonInit(self))) |
| // return nil; |
| // @endcode |
| // Until we can use inter-procedural analysis, in such a call, transfer the |
| // SelfFlags to the result of the call. |
| |
| void ObjCSelfInitChecker::checkPreCall(const CallEvent &CE, |
| CheckerContext &C) const { |
| // FIXME: A callback should disable checkers at the start of functions. |
| if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>( |
| C.getCurrentAnalysisDeclContext()->getDecl()))) |
| return; |
| |
| ProgramStateRef state = C.getState(); |
| unsigned NumArgs = CE.getNumArgs(); |
| // If we passed 'self' as and argument to the call, record it in the state |
| // to be propagated after the call. |
| // Note, we could have just given up, but try to be more optimistic here and |
| // assume that the functions are going to continue initialization or will not |
| // modify self. |
| for (unsigned i = 0; i < NumArgs; ++i) { |
| SVal argV = CE.getArgSVal(i); |
| if (isSelfVar(argV, C)) { |
| unsigned selfFlags = getSelfFlags(state->getSVal(argV.castAs<Loc>()), C); |
| C.addTransition(state->set<PreCallSelfFlags>(selfFlags)); |
| return; |
| } else if (hasSelfFlag(argV, SelfFlag_Self, C)) { |
| unsigned selfFlags = getSelfFlags(argV, C); |
| C.addTransition(state->set<PreCallSelfFlags>(selfFlags)); |
| return; |
| } |
| } |
| } |
| |
| void ObjCSelfInitChecker::checkPostCall(const CallEvent &CE, |
| CheckerContext &C) const { |
| // FIXME: A callback should disable checkers at the start of functions. |
| if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>( |
| C.getCurrentAnalysisDeclContext()->getDecl()))) |
| return; |
| |
| ProgramStateRef state = C.getState(); |
| SelfFlagEnum prevFlags = (SelfFlagEnum)state->get<PreCallSelfFlags>(); |
| if (!prevFlags) |
| return; |
| state = state->remove<PreCallSelfFlags>(); |
| |
| unsigned NumArgs = CE.getNumArgs(); |
| for (unsigned i = 0; i < NumArgs; ++i) { |
| SVal argV = CE.getArgSVal(i); |
| if (isSelfVar(argV, C)) { |
| // If the address of 'self' is being passed to the call, assume that the |
| // 'self' after the call will have the same flags. |
| // EX: log(&self) |
| addSelfFlag(state, state->getSVal(argV.castAs<Loc>()), prevFlags, C); |
| return; |
| } else if (hasSelfFlag(argV, SelfFlag_Self, C)) { |
| // If 'self' is passed to the call by value, assume that the function |
| // returns 'self'. So assign the flags, which were set on 'self' to the |
| // return value. |
| // EX: self = performMoreInitialization(self) |
| addSelfFlag(state, CE.getReturnValue(), prevFlags, C); |
| return; |
| } |
| } |
| |
| C.addTransition(state); |
| } |
| |
| void ObjCSelfInitChecker::checkLocation(SVal location, bool isLoad, |
| const Stmt *S, |
| CheckerContext &C) const { |
| if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>( |
| C.getCurrentAnalysisDeclContext()->getDecl()))) |
| return; |
| |
| // Tag the result of a load from 'self' so that we can easily know that the |
| // value is the object that 'self' points to. |
| ProgramStateRef state = C.getState(); |
| if (isSelfVar(location, C)) |
| addSelfFlag(state, state->getSVal(location.castAs<Loc>()), SelfFlag_Self, |
| C); |
| } |
| |
| |
| void ObjCSelfInitChecker::checkBind(SVal loc, SVal val, const Stmt *S, |
| CheckerContext &C) const { |
| // Allow assignment of anything to self. Self is a local variable in the |
| // initializer, so it is legal to assign anything to it, like results of |
| // static functions/method calls. After self is assigned something we cannot |
| // reason about, stop enforcing the rules. |
| // (Only continue checking if the assigned value should be treated as self.) |
| if ((isSelfVar(loc, C)) && |
| !hasSelfFlag(val, SelfFlag_InitRes, C) && |
| !hasSelfFlag(val, SelfFlag_Self, C) && |
| !isSelfVar(val, C)) { |
| |
| // Stop tracking the checker-specific state in the state. |
| ProgramStateRef State = C.getState(); |
| State = State->remove<CalledInit>(); |
| if (SymbolRef sym = loc.getAsSymbol()) |
| State = State->remove<SelfFlag>(sym); |
| C.addTransition(State); |
| } |
| } |
| |
| void ObjCSelfInitChecker::printState(raw_ostream &Out, ProgramStateRef State, |
| const char *NL, const char *Sep) const { |
| SelfFlagTy FlagMap = State->get<SelfFlag>(); |
| bool DidCallInit = State->get<CalledInit>(); |
| SelfFlagEnum PreCallFlags = (SelfFlagEnum)State->get<PreCallSelfFlags>(); |
| |
| if (FlagMap.isEmpty() && !DidCallInit && !PreCallFlags) |
| return; |
| |
| Out << Sep << NL << *this << " :" << NL; |
| |
| if (DidCallInit) |
| Out << " An init method has been called." << NL; |
| |
| if (PreCallFlags != SelfFlag_None) { |
| if (PreCallFlags & SelfFlag_Self) { |
| Out << " An argument of the current call came from the 'self' variable." |
| << NL; |
| } |
| if (PreCallFlags & SelfFlag_InitRes) { |
| Out << " An argument of the current call came from an init method." |
| << NL; |
| } |
| } |
| |
| Out << NL; |
| for (SelfFlagTy::iterator I = FlagMap.begin(), E = FlagMap.end(); |
| I != E; ++I) { |
| Out << I->first << " : "; |
| |
| if (I->second == SelfFlag_None) |
| Out << "none"; |
| |
| if (I->second & SelfFlag_Self) |
| Out << "self variable"; |
| |
| if (I->second & SelfFlag_InitRes) { |
| if (I->second != SelfFlag_InitRes) |
| Out << " | "; |
| Out << "result of init method"; |
| } |
| |
| Out << NL; |
| } |
| } |
| |
| |
| // FIXME: A callback should disable checkers at the start of functions. |
| static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND) { |
| if (!ND) |
| return false; |
| |
| const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(ND); |
| if (!MD) |
| return false; |
| if (!isInitializationMethod(MD)) |
| return false; |
| |
| // self = [super init] applies only to NSObject subclasses. |
| // For instance, NSProxy doesn't implement -init. |
| ASTContext &Ctx = MD->getASTContext(); |
| IdentifierInfo* NSObjectII = &Ctx.Idents.get("NSObject"); |
| ObjCInterfaceDecl *ID = MD->getClassInterface()->getSuperClass(); |
| for ( ; ID ; ID = ID->getSuperClass()) { |
| IdentifierInfo *II = ID->getIdentifier(); |
| |
| if (II == NSObjectII) |
| break; |
| } |
| return ID != nullptr; |
| } |
| |
| /// Returns true if the location is 'self'. |
| static bool isSelfVar(SVal location, CheckerContext &C) { |
| AnalysisDeclContext *analCtx = C.getCurrentAnalysisDeclContext(); |
| if (!analCtx->getSelfDecl()) |
| return false; |
| if (!location.getAs<loc::MemRegionVal>()) |
| return false; |
| |
| loc::MemRegionVal MRV = location.castAs<loc::MemRegionVal>(); |
| if (const DeclRegion *DR = dyn_cast<DeclRegion>(MRV.stripCasts())) |
| return (DR->getDecl() == analCtx->getSelfDecl()); |
| |
| return false; |
| } |
| |
| static bool isInitializationMethod(const ObjCMethodDecl *MD) { |
| return MD->getMethodFamily() == OMF_init; |
| } |
| |
| static bool isInitMessage(const ObjCMethodCall &Call) { |
| return Call.getMethodFamily() == OMF_init; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Registration. |
| //===----------------------------------------------------------------------===// |
| |
| void ento::registerObjCSelfInitChecker(CheckerManager &mgr) { |
| mgr.registerChecker<ObjCSelfInitChecker>(); |
| } |
| |
| bool ento::shouldRegisterObjCSelfInitChecker(const LangOptions &LO) { |
| return true; |
| } |