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/*
 * Bytecode Analysis Framework
 * Copyright (C) 2005,2008 University of Maryland
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package edu.umd.cs.findbugs.detect;

import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import javax.annotation.Nonnull;

import org.apache.bcel.Const;
import org.apache.bcel.classfile.Constant;
import org.apache.bcel.classfile.ConstantClass;
import org.apache.bcel.classfile.ConstantNameAndType;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.INVOKEDYNAMIC;
import org.apache.bcel.generic.Instruction;
import org.apache.bcel.generic.InstructionHandle;
import org.apache.bcel.generic.InvokeInstruction;
import org.apache.bcel.generic.ObjectType;
import org.apache.bcel.generic.Type;

import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.IntAnnotation;
import edu.umd.cs.findbugs.SourceLineAnnotation;
import edu.umd.cs.findbugs.StringAnnotation;
import edu.umd.cs.findbugs.SystemProperties;
import edu.umd.cs.findbugs.ba.AnalysisContext;
import edu.umd.cs.findbugs.ba.BasicBlock;
import edu.umd.cs.findbugs.ba.CFG;
import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
import edu.umd.cs.findbugs.ba.Edge;
import edu.umd.cs.findbugs.ba.Location;
import edu.umd.cs.findbugs.ba.Path;
import edu.umd.cs.findbugs.ba.PathVisitor;
import edu.umd.cs.findbugs.ba.XFactory;
import edu.umd.cs.findbugs.ba.XMethod;
import edu.umd.cs.findbugs.ba.ch.Subtypes2;
import edu.umd.cs.findbugs.ba.obl.Obligation;
import edu.umd.cs.findbugs.ba.obl.ObligationAcquiredOrReleasedInLoopException;
import edu.umd.cs.findbugs.ba.obl.ObligationDataflow;
import edu.umd.cs.findbugs.ba.obl.ObligationFactory;
import edu.umd.cs.findbugs.ba.obl.ObligationPolicyDatabase;
import edu.umd.cs.findbugs.ba.obl.State;
import edu.umd.cs.findbugs.ba.obl.StateSet;
import edu.umd.cs.findbugs.ba.type.TypeDataflow;
import edu.umd.cs.findbugs.ba.type.TypeFrame;
import edu.umd.cs.findbugs.bcel.CFGDetector;
import edu.umd.cs.findbugs.classfile.CheckedAnalysisException;
import edu.umd.cs.findbugs.classfile.ClassDescriptor;
import edu.umd.cs.findbugs.classfile.DescriptorFactory;
import edu.umd.cs.findbugs.classfile.Global;
import edu.umd.cs.findbugs.classfile.IAnalysisCache;
import edu.umd.cs.findbugs.classfile.MethodDescriptor;

/**
 * Find unsatisfied obligations in Java methods. Examples: open streams, open
 * database connections, etc.
 *
 * 

* See Weimer and Necula, Finding and preventing run-time error handling mistakes, OOPSLA 2004. *

* * @author David Hovemeyer */ public class FindUnsatisfiedObligation extends CFGDetector { private static final boolean DEBUG = SystemProperties.getBoolean("oa.debug"); private static final String DEBUG_METHOD = SystemProperties.getProperty("oa.method"); private static final boolean DEBUG_FP = SystemProperties.getBoolean("oa.debug.fp"); /** * Compute possible obligation transfers as a way of suppressing false * positives due to "wrapper" objects. Not quite ready for prime time. */ private static final boolean COMPUTE_TRANSFERS = SystemProperties.getBoolean("oa.transfers", true); /** * Report path information from point of resource creation to CFG exit. This * makes the reported warning a lot easier to understand. */ private static final boolean REPORT_PATH = SystemProperties.getBoolean("oa.reportpath", true); private static final boolean REPORT_PATH_DEBUG = SystemProperties.getBoolean("oa.reportpath.debug"); /** * Report the final obligation set as part of the BugInstance. */ private static final boolean REPORT_OBLIGATION_SET = SystemProperties.getBoolean("oa.report.obligationset", true); private final BugReporter bugReporter; private final ObligationPolicyDatabase database; public FindUnsatisfiedObligation(BugReporter bugReporter) { this.bugReporter = bugReporter; IAnalysisCache analysisCache = Global.getAnalysisCache(); database = analysisCache.getDatabase(ObligationPolicyDatabase.class); } @Override public void visitClass(ClassDescriptor classDescriptor) throws CheckedAnalysisException { IAnalysisCache analysisCache = Global.getAnalysisCache(); ObligationFactory factory = database.getFactory(); JavaClass jclass = analysisCache.getClassAnalysis(JavaClass.class, classDescriptor); for (Constant c : jclass.getConstantPool().getConstantPool()) { if (c instanceof ConstantNameAndType) { ConstantNameAndType cnt = (ConstantNameAndType) c; String signature = cnt.getSignature(jclass.getConstantPool()); if (factory.signatureInvolvesObligations(signature)) { super.visitClass(classDescriptor); return; } } else if (c instanceof ConstantClass) { String className = ((ConstantClass) c).getBytes(jclass.getConstantPool()); if (factory.signatureInvolvesObligations(className)) { super.visitClass(classDescriptor); return; } } } if (DEBUG) { System.out.println(classDescriptor + " isn't interesting for obligation analysis"); } } @Override protected void visitMethodCFG(MethodDescriptor methodDescriptor, CFG cfg) throws CheckedAnalysisException { MethodChecker methodChecker = new MethodChecker(methodDescriptor, cfg); methodChecker.analyzeMethod(); } /** * Helper class to keep track of possible obligation transfers observed * along paths where an obligation appears to be leaked. */ private static class PossibleObligationTransfer { Obligation consumed, produced; public PossibleObligationTransfer(@Nonnull Obligation consumed, @Nonnull Obligation produced) { this.consumed = consumed; this.produced = produced; } /** * Determine whether the state has "balanced" obligation counts for the * consumed and produced Obligation types. * * @param state * a State * @return true if the obligation counts are balanced, false otherwise */ private boolean balanced(State state) { int consumedCount = state.getObligationSet().getCount(consumed.getId()); int producedCount = state.getObligationSet().getCount(produced.getId()); return (consumedCount + producedCount == 0) && (consumedCount == 1 || producedCount == 1); } private boolean matches(Obligation possiblyLeakedObligation) { return consumed.equals(possiblyLeakedObligation) || produced.equals(possiblyLeakedObligation); } @Override public String toString() { return consumed + " -> " + produced; } } /** * A helper class to check a single method for unsatisfied obligations. * Avoids having to pass millions of parameters to each method (type * dataflow, null value dataflow, etc.). */ private class MethodChecker { MethodDescriptor methodDescriptor; CFG cfg; IAnalysisCache analysisCache; ObligationDataflow dataflow; ConstantPoolGen cpg; TypeDataflow typeDataflow; Subtypes2 subtypes2; XMethod xmethod; MethodChecker(MethodDescriptor methodDescriptor, CFG cfg) { this.methodDescriptor = methodDescriptor; this.cfg = cfg; } public void analyzeMethod() throws CheckedAnalysisException { if (DEBUG_METHOD != null && !methodDescriptor.getName().equals(DEBUG_METHOD)) { return; } if (DEBUG) { System.out.println("*** Analyzing method " + methodDescriptor); } xmethod = XFactory.createXMethod(methodDescriptor); analysisCache = Global.getAnalysisCache(); // // Execute the obligation dataflow analysis // try { dataflow = analysisCache.getMethodAnalysis(ObligationDataflow.class, methodDescriptor); } catch (ObligationAcquiredOrReleasedInLoopException e) { // It is not possible to analyze this method. if (DEBUG) { System.out.println("FindUnsatisifedObligation: " + methodDescriptor + ": " + e.getMessage()); } return; } // // Additional analyses // needed these to apply the false-positive // suppression heuristics. // cpg = analysisCache.getClassAnalysis(ConstantPoolGen.class, methodDescriptor.getClassDescriptor()); typeDataflow = analysisCache.getMethodAnalysis(TypeDataflow.class, methodDescriptor); subtypes2 = Global.getAnalysisCache().getDatabase(Subtypes2.class); // // Main loop: looking at the StateSet at the exit block of the CFG, // see if there are any states with nonempty obligation sets. // Map leakedObligationMap = new HashMap<>(); StateSet factAtExit = dataflow.getResultFact(cfg.getExit()); for (Iterator i = factAtExit.stateIterator(); i.hasNext();) { State state = i.next(); checkStateForLeakedObligations(state, leakedObligationMap); } // // Report a separate BugInstance for each Obligation,State pair. // (Two different obligations may be leaked in the same state.) // for (Map.Entry entry : leakedObligationMap.entrySet()) { Obligation obligation = entry.getKey(); State state = entry.getValue(); reportWarning(obligation, state, factAtExit); } // TODO: closing of nonexistent resources } private void checkStateForLeakedObligations(State state, Map leakedObligationMap) throws IllegalStateException { if (DEBUG) { Path path = state.getPath(); if (path.getLength() > 0 && path.getBlockIdAt(path.getLength() - 1) != cfg.getExit().getLabel()) { throw new IllegalStateException("path " + path + " at cfg exit has no label for exit block"); } } for (int id = 0; id < database.getFactory().getMaxObligationTypes(); ++id) { Obligation obligation = database.getFactory().getObligationById(id); // If the raw count produced by the analysis // for this obligation type is 0, // assume everything is ok on this state's path. int rawLeakCount = state.getObligationSet().getCount(id); if (rawLeakCount == 0) { continue; } // Apply the false-positive suppression heuristics int leakCount = getAdjustedLeakCount(state, id); if (leakCount > 0) { leakedObligationMap.put(obligation, state); } // TODO: if the leak count is less than 0, then a nonexistent // resource was closed } } private void reportWarning(Obligation obligation, State state, StateSet factAtExit) { String className = obligation.getClassName(); if (methodDescriptor.isStatic() && "main".equals(methodDescriptor.getName()) && "([Ljava/lang/String;)V".equals(methodDescriptor.getSignature()) && (className.contains("InputStream") || className.contains("Reader") || factAtExit.isOnExceptionPath())) { // Don't report unclosed input streams and readers in main() // methods return; } if (methodDescriptor.getName().equals(Const.CONSTRUCTOR_NAME)) { try { if (subtypes2.isSubtype(methodDescriptor.getClassDescriptor(), DescriptorFactory.createClassDescriptorFromDottedClassName( obligation.getClassName()))) { return; } } catch (Exception e) { AnalysisContext.logError("huh", e); } } String bugPattern = factAtExit.isOnExceptionPath() ? "OBL_UNSATISFIED_OBLIGATION_EXCEPTION_EDGE" : "OBL_UNSATISFIED_OBLIGATION"; BugInstance bugInstance = new BugInstance(FindUnsatisfiedObligation.this, bugPattern, NORMAL_PRIORITY).addClassAndMethod(methodDescriptor).addClass(className).describe("CLASS_REFTYPE"); // Report how many instances of the obligation are remaining bugInstance.addInt(state.getObligationSet().getCount(obligation.getId())).describe( IntAnnotation.INT_OBLIGATIONS_REMAINING); // Add source line information annotateWarningWithSourceLineInformation(state, obligation, bugInstance); if (REPORT_OBLIGATION_SET) { bugInstance.addString(state.getObligationSet().toString()).describe(StringAnnotation.REMAINING_OBLIGATIONS_ROLE); } bugReporter.reportBug(bugInstance); } private void annotateWarningWithSourceLineInformation(State state, Obligation obligation, BugInstance bugInstance) { // The reportPath() method currently does all reporting // of source line information. if (REPORT_PATH) { reportPath(bugInstance, obligation, state); } } /** * Helper class to apply the false-positive suppression heuristics along * a Path where an obligation leak might have occurred. */ private class PostProcessingPathVisitor implements PathVisitor { Obligation possiblyLeakedObligation; State state; int adjustedLeakCount; BasicBlock curBlock; boolean couldNotAnalyze; List transferList; public PostProcessingPathVisitor(Obligation possiblyLeakedObligation/* * , * int * initialLeakCount */, State state) { this.possiblyLeakedObligation = possiblyLeakedObligation; this.state = state; this.adjustedLeakCount = state.getObligationSet().getCount(possiblyLeakedObligation.getId()); if (COMPUTE_TRANSFERS) { this.transferList = new LinkedList<>(); } } public int getAdjustedLeakCount() { return adjustedLeakCount; } public boolean couldNotAnalyze() { return couldNotAnalyze; } @Override public void visitBasicBlock(BasicBlock basicBlock) { curBlock = basicBlock; if (COMPUTE_TRANSFERS && basicBlock == cfg.getExit()) { // We're at the CFG exit. if (adjustedLeakCount == 1) { applyPossibleObligationTransfers(); } } } @Override public void visitInstructionHandle(InstructionHandle handle) { try { Instruction ins = handle.getInstruction(); short opcode = ins.getOpcode(); if (DEBUG) { System.out.printf("%3d %s%n", handle.getPosition(), Const.getOpcodeName(opcode)); } if (opcode == Const.PUTFIELD || opcode == Const.PUTSTATIC || opcode == Const.ARETURN) { // // A value is being assigned to a field or returned from // the method. // Location loc = new Location(handle, curBlock); TypeFrame typeFrame = typeDataflow.getFactAtLocation(loc); if (!typeFrame.isValid()) { // dead code? couldNotAnalyze = true; } Type tosType = typeFrame.getTopValue(); if (tosType instanceof ObjectType && isPossibleInstanceOfObligationType(subtypes2, (ObjectType) tosType, possiblyLeakedObligation.getType())) { // Remove one obligation of this type adjustedLeakCount--; if (DEBUG) { System.out.println("removing obligation to close " + tosType + " at " + handle.getPosition()); } } } if (COMPUTE_TRANSFERS && ins instanceof InvokeInstruction) { checkForPossibleObligationTransfer((InvokeInstruction) ins, handle); } } catch (ClassNotFoundException e) { bugReporter.reportMissingClass(e); couldNotAnalyze = true; } catch (DataflowAnalysisException e) { couldNotAnalyze = true; } } private void applyPossibleObligationTransfers() { // // See if we recorded any possible obligation transfers // that might have created a "wrapper" object. // In many cases, it is correct to close either // the "wrapped" or "wrapper" object. // So, if we see a possible transfer, and we see // a +1/-1 obligation count for the pair // (consumed and produced obligation types), // rather than 0/0, // then we will assume that which resource was closed // (wrapper or wrapped) was the opposite of what // we expected. // for (PossibleObligationTransfer transfer : transferList) { if (DEBUG_FP) { System.out.println("Checking possible transfer " + transfer + "..."); } boolean matches = transfer.matches(possiblyLeakedObligation); if (DEBUG_FP) { System.out.println(" matches: " + possiblyLeakedObligation); } if (matches) { boolean balanced = transfer.balanced(state); if (DEBUG_FP) { System.out.println(" balanced: " + balanced + " in " + state.getObligationSet()); } if (balanced) { if (DEBUG_FP) { System.out.println(" Suppressing path because " + "a transfer appears to result in balanced " + "outstanding obligations"); } adjustedLeakCount = 0; break; } } } } private void checkForPossibleObligationTransfer(InvokeInstruction inv, InstructionHandle handle) throws ClassNotFoundException { // // We will assume that a method invocation might transfer // an obligation from one type to another if // 1. either // - it's a constructor where the constructed // type and exactly one param type // are obligation types, or // - it's a method where the return type and // exactly one param type are obligation types // 2. at least one instance of the resource "consumed" // by the transfer exists at the point of the transfer. // E.g., if we see a transfer of InputStream->Reader, // there must be an instance of InputStream at // the transfer point. // if (inv instanceof INVOKEDYNAMIC) { return; } if (DEBUG_FP) { System.out.println("Checking " + handle + " as possible obligation transfer...:"); } // Find the State which is a prefix of the error state // at the location of this (possible) transfer. State transferState = getTransferState(handle); if (transferState == null) { if (DEBUG_FP) { System.out.println("No transfer state???"); } return; } String methodName = inv.getMethodName(cpg); Type producedType = Const.CONSTRUCTOR_NAME.equals(methodName) ? inv.getReferenceType(cpg) : inv.getReturnType(cpg); if (DEBUG_FP && !(producedType instanceof ObjectType)) { System.out.println("Produced type " + producedType + " not an ObjectType"); } if (producedType instanceof ObjectType) { Obligation produced = database.getFactory().getObligationByType((ObjectType) producedType); if (DEBUG_FP && produced == null) { System.out.println("Produced type " + producedType + " not an obligation type"); } if (produced != null) { XMethod calledMethod = XFactory.createXMethod(inv, cpg); Obligation[] params = database.getFactory().getParameterObligationTypes(calledMethod); for (int i = 0; i < params.length; i++) { Obligation consumed = params[i]; if (DEBUG_FP && consumed == null) { System.out.println("Param " + i + " not an obligation type"); } if (DEBUG_FP && consumed != null && consumed.equals(produced)) { System.out.println("Consumed type is the same as produced type"); } if (consumed != null && !consumed.equals(produced)) { // See if an instance of the consumed obligation // type // exists here. if (transferState.getObligationSet().getCount(consumed.getId()) > 0) { transferList.add(new PossibleObligationTransfer(consumed, produced)); if (DEBUG_FP) { System.out.println("===> Possible transfer of " + consumed + " to " + produced + " at " + handle); } } else if (DEBUG_FP) { System.out.println(handle + " not a transfer " + "of " + consumed + "->" + produced + " because no instances of " + consumed); System.out.println("I see " + transferState.getObligationSet()); } } } } } } @Override public void visitEdge(Edge edge) { if (DEBUG_FP) { System.out.println("visit edge " + edge); } } private State getTransferState(InstructionHandle handle) { StateSet stateSet; try { stateSet = dataflow.getFactAtLocation(new Location(handle, curBlock)); } catch (DataflowAnalysisException e) { bugReporter.logError("Error checking obligation state at " + handle, e); return null; } List prefixes = stateSet.getPrefixStates(state.getPath()); if (prefixes.size() != 1) { // Could this happen? if (DEBUG_FP) { System.out.println("at " + handle + " in " + xmethod + " found " + prefixes.size() + " states which are prefixes of error state"); } return null; } return prefixes.get(0); } } /** * Get the adjusted leak count for the given State and obligation type. * Use heuristics to account for: *
    *
  • null checks (count the number of times the supposedly leaked * obligation is compared to null, and subtract those from the leak * count)
  • *
  • field assignments (count number of times obligation type is * assigned to a field, and subtract those from the leak count)
  • *
  • return statements (if an instance of the obligation type is * returned from the method, subtract one from leak count)
  • *
* * @return the adjusted leak count (positive if leaked obligation, * negative if attempt to release an un-acquired obligation) */ private int getAdjustedLeakCount(State state, int obligationId) { final Obligation obligation = database.getFactory().getObligationById(obligationId); Path path = state.getPath(); PostProcessingPathVisitor visitor = new PostProcessingPathVisitor(obligation, state); path.acceptVisitor(cfg, visitor); if (visitor.couldNotAnalyze()) { return 0; } else { return visitor.getAdjustedLeakCount(); } } private boolean isPossibleInstanceOfObligationType(Subtypes2 subtypes2, ObjectType type, ObjectType obligationType) throws ClassNotFoundException { // // If we're tracking, e.g., InputStream obligations, // and we see a FileInputStream reference being assigned // to a field (or returned from a method), // then the false-positive supressions heuristic should apply. // return subtypes2.isSubtype(type, obligationType); } private void reportPath(final BugInstance bugInstance, final Obligation obligation, final State state) { Path path = state.getPath(); // This PathVisitor will traverse the Path and add appropriate // SourceLineAnnotations to the BugInstance. PathVisitor visitor = new PathVisitor() { boolean sawFirstCreation; SourceLineAnnotation lastSourceLine;// = creationSourceLine; BasicBlock curBlock; @Override public void visitBasicBlock(BasicBlock basicBlock) { curBlock = basicBlock; // See if the initial instance of the leaked resource // is in the entry fact due to a @WillClose annotation. if (curBlock == cfg.getEntry()) { // Get the entry fact - it should have precisely one // state StateSet entryFact = dataflow.getResultFact(curBlock); Iterator i = entryFact.stateIterator(); if (i.hasNext()) { State entryState = i.next(); if (entryState.getObligationSet().getCount(obligation.getId()) > 0) { lastSourceLine = SourceLineAnnotation.forFirstLineOfMethod(methodDescriptor); lastSourceLine .setDescription(SourceLineAnnotation.ROLE_OBLIGATION_CREATED_BY_WILLCLOSE_PARAMETER); bugInstance.add(lastSourceLine); sawFirstCreation = true; if (REPORT_PATH_DEBUG) { System.out.println(" " + obligation + " created by @WillClose parameter at " + lastSourceLine); } } } } } @Override public void visitInstructionHandle(InstructionHandle handle) { boolean isCreation = (dataflow.getAnalysis().getActionCache().addsObligation(curBlock, handle, obligation)); if (!sawFirstCreation && !isCreation) { return; } SourceLineAnnotation sourceLine = SourceLineAnnotation.fromVisitedInstruction(methodDescriptor, new Location( handle, curBlock)); sourceLine.setDescription(isCreation ? SourceLineAnnotation.ROLE_OBLIGATION_CREATED : SourceLineAnnotation.ROLE_PATH_CONTINUES); boolean isInteresting = (sourceLine.getStartLine() > 0) && (lastSourceLine == null || isCreation || sourceLine.getStartLine() != lastSourceLine.getStartLine()); if (REPORT_PATH_DEBUG) { System.out.println(" " + handle.getPosition() + " --> " + sourceLine + (isInteresting ? " **" : "")); } if (isInteresting) { bugInstance.add(sourceLine); lastSourceLine = sourceLine; if (isCreation) { sawFirstCreation = true; } } } @Override public void visitEdge(Edge edge) { if (REPORT_PATH_DEBUG) { System.out.println("Edge of type " + Edge.edgeTypeToString(edge.getType()) + " to " + edge.getTarget().getLabel()); if (edge.getTarget().getFirstInstruction() != null) { System.out.println(" First instruction in target: " + edge.getTarget().getFirstInstruction()); } if (edge.getTarget().isExceptionThrower()) { System.out.println(" exception thrower for " + edge.getTarget().getExceptionThrower()); } if (edge.isExceptionEdge()) { System.out.println(" exceptions thrown: " + typeDataflow.getEdgeExceptionSet(edge)); } } } }; // Visit the Path path.acceptVisitor(cfg, visitor); } } /* * (non-Javadoc) * * @see edu.umd.cs.findbugs.Detector#report() */ public void report() { // Nothing to do here } }




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