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Diffstat (limited to 'lib/StaticAnalyzer/Checkers/SimpleStreamChecker.cpp')
| -rw-r--r-- | lib/StaticAnalyzer/Checkers/SimpleStreamChecker.cpp | 348 |
1 files changed, 348 insertions, 0 deletions
diff --git a/lib/StaticAnalyzer/Checkers/SimpleStreamChecker.cpp b/lib/StaticAnalyzer/Checkers/SimpleStreamChecker.cpp new file mode 100644 index 0000000..ee055ad --- /dev/null +++ b/lib/StaticAnalyzer/Checkers/SimpleStreamChecker.cpp @@ -0,0 +1,348 @@ +//===-- 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 "ClangSACheckers.h" +#include "clang/StaticAnalyzer/Core/Checker.h" +#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" +#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h" +#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" + +using namespace clang; +using namespace ento; + +namespace { +typedef llvm::SmallVector<SymbolRef, 2> 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<check::PostCall, + check::PreCall, + check::DeadSymbols, + check::Bind, + check::RegionChanges> { + + mutable IdentifierInfo *IIfopen, *IIfclose; + + OwningPtr<BugType> DoubleCloseBugType; + OwningPtr<BugType> LeakBugType; + + void initIdentifierInfo(ASTContext &Ctx) const; + + void reportDoubleClose(SymbolRef FileDescSym, + const CallEvent &Call, + CheckerContext &C) const; + + void reportLeaks(SymbolVector 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; + + /// Deal with symbol escape as a byproduct of a bind. + void checkBind(SVal location, SVal val, const Stmt*S, + CheckerContext &C) const; + + /// Deal with symbol escape as a byproduct of a region change. + ProgramStateRef + checkRegionChanges(ProgramStateRef state, + const StoreManager::InvalidatedSymbols *invalidated, + ArrayRef<const MemRegion *> ExplicitRegions, + ArrayRef<const MemRegion *> Regions, + const CallEvent *Call) const; + bool wantsRegionChangeUpdate(ProgramStateRef state) const { + return true; + } +}; + +} // 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 : public SymbolVisitor { + ProgramStateRef state; +public: + StopTrackingCallback(ProgramStateRef st) : state(st) {} + ProgramStateRef getState() const { return state; } + + bool VisitSymbol(SymbolRef sym) { + state = state->remove<StreamMap>(sym); + return true; + } +}; +} // end anonymous namespace + + +SimpleStreamChecker::SimpleStreamChecker() : IIfopen(0), IIfclose(0) { + // Initialize the bug types. + DoubleCloseBugType.reset(new BugType("Double fclose", + "Unix Stream API Error")); + + LeakBugType.reset(new BugType("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 { + initIdentifierInfo(C.getASTContext()); + + if (!Call.isGlobalCFunction()) + return; + + if (Call.getCalleeIdentifier() != IIfopen) + 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<StreamMap>(FileDesc, StreamState::getOpened()); + C.addTransition(State); +} + +void SimpleStreamChecker::checkPreCall(const CallEvent &Call, + CheckerContext &C) const { + initIdentifierInfo(C.getASTContext()); + + if (!Call.isGlobalCFunction()) + return; + + if (Call.getCalleeIdentifier() != IIfclose) + return; + + if (Call.getNumArgs() != 1) + 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<StreamMap>(FileDesc); + if (SS && SS->isClosed()) { + reportDoubleClose(FileDesc, Call, C); + return; + } + + // Generate the next transition, in which the stream is closed. + State = State->set<StreamMap>(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<StreamMap>(); + 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<StreamMap>(Sym); + } + + ExplodedNode *N = C.addTransition(State); + 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.generateSink(); + // If we've already reached this node on another path, return. + if (!ErrNode) + return; + + // Generate the report. + BugReport *R = new BugReport(*DoubleCloseBugType, + "Closing a previously closed file stream", ErrNode); + R->addRange(Call.getSourceRange()); + R->markInteresting(FileDescSym); + C.emitReport(R); +} + +void SimpleStreamChecker::reportLeaks(SymbolVector LeakedStreams, + CheckerContext &C, + ExplodedNode *ErrNode) const { + // Attach bug reports to the leak node. + // TODO: Identify the leaked file descriptor. + for (llvm::SmallVector<SymbolRef, 2>::iterator + I = LeakedStreams.begin(), E = LeakedStreams.end(); I != E; ++I) { + BugReport *R = new BugReport(*LeakBugType, + "Opened file is never closed; potential resource leak", ErrNode); + R->markInteresting(*I); + C.emitReport(R); + } +} + +// Check various ways a symbol can be invalidated. +// Stop tracking symbols when a value escapes as a result of checkBind. +// A value escapes in three possible cases: +// (1) We are binding to something that is not a memory region. +// (2) We are binding to a MemRegion that does not have stack storage +// (3) We are binding to a MemRegion with stack storage that the store +// does not understand. +void SimpleStreamChecker::checkBind(SVal loc, SVal val, const Stmt *S, + CheckerContext &C) const { + // Are we storing to something that causes the value to "escape"? + bool escapes = true; + ProgramStateRef state = C.getState(); + + if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) { + escapes = !regionLoc->getRegion()->hasStackStorage(); + + if (!escapes) { + // To test (3), generate a new state with the binding added. If it is + // the same state, then it escapes (since the store cannot represent + // the binding). Do this only if we know that the store is not supposed + // to generate the same state. + SVal StoredVal = state->getSVal(regionLoc->getRegion()); + if (StoredVal != val) + escapes = (state == (state->bindLoc(*regionLoc, val))); + } + } + + // If our store can represent the binding and we aren't storing to something + // that doesn't have local storage then just return the state and + // continue as is. + if (!escapes) + return; + + // Otherwise, find all symbols referenced by 'val' that we are tracking + // and stop tracking them. + state = state->scanReachableSymbols<StopTrackingCallback>(val).getState(); + C.addTransition(state); +} + +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 symbol we are tracking is invalidated, do not track the symbol as +// we cannot reason about it anymore. +ProgramStateRef +SimpleStreamChecker::checkRegionChanges(ProgramStateRef State, + const StoreManager::InvalidatedSymbols *invalidated, + ArrayRef<const MemRegion *> ExplicitRegions, + ArrayRef<const MemRegion *> Regions, + const CallEvent *Call) const { + + if (!invalidated || invalidated->empty()) + return State; + + // If it's a call which might close the file, we assume that all regions + // (explicit and implicit) escaped. Otherwise, whitelist explicit pointers + // (the parameters to the call); we still can track them. + llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols; + if (!Call || guaranteedNotToCloseFile(*Call)) { + for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(), + E = ExplicitRegions.end(); I != E; ++I) { + if (const SymbolicRegion *R = (*I)->StripCasts()->getAs<SymbolicRegion>()) + WhitelistedSymbols.insert(R->getSymbol()); + } + } + + for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(), + E = invalidated->end(); I!=E; ++I) { + SymbolRef sym = *I; + if (WhitelistedSymbols.count(sym)) + continue; + // The symbol escaped. Optimistically, assume that the corresponding file + // handle will be closed somewhere else. + State = State->remove<StreamMap>(sym); + } + return State; +} + +void SimpleStreamChecker::initIdentifierInfo(ASTContext &Ctx) const { + if (IIfopen) + return; + IIfopen = &Ctx.Idents.get("fopen"); + IIfclose = &Ctx.Idents.get("fclose"); +} + +void ento::registerSimpleStreamChecker(CheckerManager &mgr) { + mgr.registerChecker<SimpleStreamChecker>(); +} |
