//===-- SimpleStreamChecker.cpp -----------------------------------------*- C++ -*--// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // Defines a checker for proper use of fopen/fclose APIs. // - If a file has been closed with fclose, it should not be accessed again. // Accessing a closed file results in undefined behavior. // - If a file was opened with fopen, it must be closed with fclose before // the execution ends. Failing to do so results in a resource leak. // //===----------------------------------------------------------------------===// #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h" #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" #include "clang/StaticAnalyzer/Core/Checker.h" #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h" #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" #include using namespace clang; using namespace ento; namespace { typedef SmallVector SymbolVector; struct StreamState { private: enum Kind { Opened, Closed } K; StreamState(Kind InK) : K(InK) { } public: bool isOpened() const { return K == Opened; } bool isClosed() const { return K == Closed; } static StreamState getOpened() { return StreamState(Opened); } static StreamState getClosed() { return StreamState(Closed); } bool operator==(const StreamState &X) const { return K == X.K; } void Profile(llvm::FoldingSetNodeID &ID) const { ID.AddInteger(K); } }; class SimpleStreamChecker : public Checker { CallDescription OpenFn, CloseFn; std::unique_ptr DoubleCloseBugType; std::unique_ptr LeakBugType; void reportDoubleClose(SymbolRef FileDescSym, const CallEvent &Call, CheckerContext &C) const; void reportLeaks(ArrayRef LeakedStreams, CheckerContext &C, ExplodedNode *ErrNode) const; bool guaranteedNotToCloseFile(const CallEvent &Call) const; public: SimpleStreamChecker(); /// Process fopen. void checkPostCall(const CallEvent &Call, CheckerContext &C) const; /// Process fclose. void checkPreCall(const CallEvent &Call, CheckerContext &C) const; void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const; /// Stop tracking addresses which escape. ProgramStateRef checkPointerEscape(ProgramStateRef State, const InvalidatedSymbols &Escaped, const CallEvent *Call, PointerEscapeKind Kind) const; }; } // end anonymous namespace /// The state of the checker is a map from tracked stream symbols to their /// state. Let's store it in the ProgramState. REGISTER_MAP_WITH_PROGRAMSTATE(StreamMap, SymbolRef, StreamState) namespace { class StopTrackingCallback final : public SymbolVisitor { ProgramStateRef state; public: StopTrackingCallback(ProgramStateRef st) : state(std::move(st)) {} ProgramStateRef getState() const { return state; } bool VisitSymbol(SymbolRef sym) override { state = state->remove(sym); return true; } }; } // end anonymous namespace SimpleStreamChecker::SimpleStreamChecker() : OpenFn("fopen"), CloseFn("fclose", 1) { // Initialize the bug types. DoubleCloseBugType.reset( new BugType(this, "Double fclose", "Unix Stream API Error")); LeakBugType.reset( new BugType(this, "Resource Leak", "Unix Stream API Error")); // Sinks are higher importance bugs as well as calls to assert() or exit(0). LeakBugType->setSuppressOnSink(true); } void SimpleStreamChecker::checkPostCall(const CallEvent &Call, CheckerContext &C) const { if (!Call.isGlobalCFunction()) return; if (!Call.isCalled(OpenFn)) return; // Get the symbolic value corresponding to the file handle. SymbolRef FileDesc = Call.getReturnValue().getAsSymbol(); if (!FileDesc) return; // Generate the next transition (an edge in the exploded graph). ProgramStateRef State = C.getState(); State = State->set(FileDesc, StreamState::getOpened()); C.addTransition(State); } void SimpleStreamChecker::checkPreCall(const CallEvent &Call, CheckerContext &C) const { if (!Call.isGlobalCFunction()) return; if (!Call.isCalled(CloseFn)) return; // Get the symbolic value corresponding to the file handle. SymbolRef FileDesc = Call.getArgSVal(0).getAsSymbol(); if (!FileDesc) return; // Check if the stream has already been closed. ProgramStateRef State = C.getState(); const StreamState *SS = State->get(FileDesc); if (SS && SS->isClosed()) { reportDoubleClose(FileDesc, Call, C); return; } // Generate the next transition, in which the stream is closed. State = State->set(FileDesc, StreamState::getClosed()); C.addTransition(State); } static bool isLeaked(SymbolRef Sym, const StreamState &SS, bool IsSymDead, ProgramStateRef State) { if (IsSymDead && SS.isOpened()) { // If a symbol is NULL, assume that fopen failed on this path. // A symbol should only be considered leaked if it is non-null. ConstraintManager &CMgr = State->getConstraintManager(); ConditionTruthVal OpenFailed = CMgr.isNull(State, Sym); return !OpenFailed.isConstrainedTrue(); } return false; } void SimpleStreamChecker::checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const { ProgramStateRef State = C.getState(); SymbolVector LeakedStreams; StreamMapTy TrackedStreams = State->get(); for (StreamMapTy::iterator I = TrackedStreams.begin(), E = TrackedStreams.end(); I != E; ++I) { SymbolRef Sym = I->first; bool IsSymDead = SymReaper.isDead(Sym); // Collect leaked symbols. if (isLeaked(Sym, I->second, IsSymDead, State)) LeakedStreams.push_back(Sym); // Remove the dead symbol from the streams map. if (IsSymDead) State = State->remove(Sym); } ExplodedNode *N = C.generateNonFatalErrorNode(State); if (!N) return; reportLeaks(LeakedStreams, C, N); } void SimpleStreamChecker::reportDoubleClose(SymbolRef FileDescSym, const CallEvent &Call, CheckerContext &C) const { // We reached a bug, stop exploring the path here by generating a sink. ExplodedNode *ErrNode = C.generateErrorNode(); // If we've already reached this node on another path, return. if (!ErrNode) return; // Generate the report. auto R = llvm::make_unique(*DoubleCloseBugType, "Closing a previously closed file stream", ErrNode); R->addRange(Call.getSourceRange()); R->markInteresting(FileDescSym); C.emitReport(std::move(R)); } void SimpleStreamChecker::reportLeaks(ArrayRef LeakedStreams, CheckerContext &C, ExplodedNode *ErrNode) const { // Attach bug reports to the leak node. // TODO: Identify the leaked file descriptor. for (SymbolRef LeakedStream : LeakedStreams) { auto R = llvm::make_unique(*LeakBugType, "Opened file is never closed; potential resource leak", ErrNode); R->markInteresting(LeakedStream); C.emitReport(std::move(R)); } } bool SimpleStreamChecker::guaranteedNotToCloseFile(const CallEvent &Call) const{ // If it's not in a system header, assume it might close a file. if (!Call.isInSystemHeader()) return false; // Handle cases where we know a buffer's /address/ can escape. if (Call.argumentsMayEscape()) return false; // Note, even though fclose closes the file, we do not list it here // since the checker is modeling the call. return true; } // If the pointer we are tracking escaped, do not track the symbol as // we cannot reason about it anymore. ProgramStateRef SimpleStreamChecker::checkPointerEscape(ProgramStateRef State, const InvalidatedSymbols &Escaped, const CallEvent *Call, PointerEscapeKind Kind) const { // If we know that the call cannot close a file, there is nothing to do. if (Kind == PSK_DirectEscapeOnCall && guaranteedNotToCloseFile(*Call)) { return State; } for (InvalidatedSymbols::const_iterator I = Escaped.begin(), E = Escaped.end(); I != E; ++I) { SymbolRef Sym = *I; // The symbol escaped. Optimistically, assume that the corresponding file // handle will be closed somewhere else. State = State->remove(Sym); } return State; } void ento::registerSimpleStreamChecker(CheckerManager &mgr) { mgr.registerChecker(); }