vm: allow fine-grained control over program exit conditions

Currently we only support canExit flag.
However there are actually 3 separate conditions:
 - program can exit normally
 - program can timeout (e.g. fuzzer test or runtest can't)
 - program can exit with error (e.g. C test can)
Allow to specify these 3 conditions separately.

pkg/instance/instance.go

@@ -265,11 +265,11 @@ func (inst *inst) testInstance() error {
 
 	cmd := FuzzerCmd(fuzzerBin, executorBin, "test", inst.cfg.TargetOS, inst.cfg.TargetArch, fwdAddr,
 		inst.cfg.Sandbox, 0, 0, false, false, true, false)
-	outc, errc, err := inst.vm.Run(5*time.Minute, nil, cmd)
+	outc, errc, err := inst.vm.Run(10*time.Minute, nil, cmd)
 	if err != nil {
 		return fmt.Errorf("failed to run binary in VM: %v", err)
 	}
-	rep := inst.vm.MonitorExecution(outc, errc, inst.reporter, true)
+	rep := inst.vm.MonitorExecution(outc, errc, inst.reporter, vm.ExitNormal)
 	if rep != nil {
 		if err := inst.reporter.Symbolize(rep); err != nil {
 			// TODO(dvyukov): send such errors to dashboard.
@@ -350,7 +350,8 @@ func (inst *inst) testProgram(command string, testTime time.Duration) error {
 	if err != nil {
 		return fmt.Errorf("failed to run binary in VM: %v", err)
 	}
-	rep := inst.vm.MonitorExecution(outc, errc, inst.reporter, true)
+	rep := inst.vm.MonitorExecution(outc, errc, inst.reporter,
+		vm.ExitTimeout|vm.ExitNormal|vm.ExitError)
 	if rep == nil {
 		return nil
 	}

pkg/repro/repro.go

@@ -587,7 +587,8 @@ func (ctx *context) testImpl(inst *vm.Instance, command string, duration time.Du
 	if err != nil {
 		return false, fmt.Errorf("failed to run command in VM: %v", err)
 	}
-	rep := inst.MonitorExecution(outc, errc, ctx.reporter, true)
+	rep := inst.MonitorExecution(outc, errc, ctx.reporter,
+		vm.ExitTimeout|vm.ExitNormal|vm.ExitError)
 	if rep == nil {
 		ctx.reproLog(2, "program did not crash")
 		return false, nil

syz-manager/manager.go

@@ -574,7 +574,7 @@ func (mgr *Manager) runInstance(index int) (*Crash, error) {
 		return nil, fmt.Errorf("failed to run fuzzer: %v", err)
 	}
 
-	rep := inst.MonitorExecution(outc, errc, mgr.reporter, false)
+	rep := inst.MonitorExecution(outc, errc, mgr.reporter, vm.ExitTimeout)
 	if rep == nil {
 		// This is the only "OK" outcome.
 		log.Logf(0, "vm-%v: running for %v, restarting", index, time.Since(start))

tools/syz-crush/crush.go

@@ -107,7 +107,7 @@ func runInstance(cfg *mgrconfig.Config, reporter report.Reporter, vmPool *vm.Poo
 	}
 
 	log.Logf(0, "vm-%v: crushing...", index)
-	rep := inst.MonitorExecution(outc, errc, reporter, false)
+	rep := inst.MonitorExecution(outc, errc, reporter, vm.ExitTimeout)
 	if rep == nil {
 		// This is the only "OK" outcome.
 		log.Logf(0, "vm-%v: running long enough, restarting", index)

tools/syz-runtest/runtest.go

@@ -177,7 +177,7 @@ func (mgr *Manager) boot(name string, index int) (*report.Report, error) {
 	if err != nil {
 		return nil, fmt.Errorf("failed to run fuzzer: %v", err)
 	}
-	rep := inst.MonitorExecution(outc, errc, mgr.reporter, true)
+	rep := inst.MonitorExecution(outc, errc, mgr.reporter, vm.ExitNormal)
 	return rep, nil
 }
 

vm/vm.go

@@ -135,19 +135,30 @@ func (inst *Instance) Close() {
 	os.RemoveAll(inst.workdir)
 }
 
+type ExitCondition int
+
+const (
+	// The program is allowed to exit after timeout.
+	ExitTimeout = ExitCondition(1 << iota)
+	// The program is allowed to exit with no errors.
+	ExitNormal
+	// The program is allowed to exit with errors.
+	ExitError
+)
+
 // MonitorExecution monitors execution of a program running inside of a VM.
 // It detects kernel oopses in output, lost connections, hangs, etc.
 // outc/errc is what vm.Instance.Run returns, reporter parses kernel output for oopses.
-// If canExit is false and the program exits, it is treated as an error.
+// Exit says which exit modes should be considered as errors/OK.
 // Returns a non-symbolized crash report, or nil if no error happens.
 func (inst *Instance) MonitorExecution(outc <-chan []byte, errc <-chan error,
-	reporter report.Reporter, canExit bool) (rep *report.Report) {
+	reporter report.Reporter, exit ExitCondition) (rep *report.Report) {
 	mon := &monitor{
 		inst:     inst,
 		outc:     outc,
 		errc:     errc,
 		reporter: reporter,
-		canExit:  canExit,
+		exit:     exit,
 	}
 	lastExecuteTime := time.Now()
 	ticker := time.NewTicker(tickerPeriod)
@@ -159,13 +170,24 @@ func (inst *Instance) MonitorExecution(outc <-chan []byte, errc <-chan error,
 			case nil:
 				// The program has exited without errors,
 				// but wait for kernel output in case there is some delayed oops.
-				return mon.extractError("")
+				crash := ""
+				if mon.exit&ExitNormal == 0 {
+					crash = lostConnectionCrash
+				}
+				return mon.extractError(crash)
 			case ErrTimeout:
+				if mon.exit&ExitTimeout == 0 {
+					return mon.extractError(timeoutCrash)
+				}
 				return nil
 			default:
 				// Note: connection lost can race with a kernel oops message.
 				// In such case we want to return the kernel oops.
-				return mon.extractError(lostConnectionCrash)
+				crash := ""
+				if mon.exit&ExitError == 0 {
+					crash = lostConnectionCrash
+				}
+				return mon.extractError(crash)
 			}
 		case out, ok := <-outc:
 			if !ok {
@@ -229,14 +251,13 @@ type monitor struct {
 	outc     <-chan []byte
 	errc     <-chan error
 	reporter report.Reporter
-	canExit  bool
+	exit     ExitCondition
 	output   []byte
 	matchPos int
 }
 
 func (mon *monitor) extractError(defaultError string) *report.Report {
-	crashed := defaultError != "" || !mon.canExit
-	if crashed {
+	if defaultError != "" {
 		// N.B. we always wait below for other errors.
 		diag, _ := mon.inst.Diagnose()
 		if len(diag) > 0 {
@@ -251,10 +272,7 @@ func (mon *monitor) extractError(defaultError string) *report.Report {
 	}
 	if !mon.reporter.ContainsCrash(mon.output[mon.matchPos:]) {
 		if defaultError == "" {
-			if mon.canExit {
-				return nil
-			}
-			defaultError = lostConnectionCrash
+			return nil
 		}
 		rep := &report.Report{
 			Title:      defaultError,
@@ -263,7 +281,7 @@ func (mon *monitor) extractError(defaultError string) *report.Report {
 		}
 		return rep
 	}
-	if !crashed {
+	if defaultError == "" {
 		diag, wait := mon.inst.Diagnose()
 		if len(diag) > 0 {
 			mon.output = append(mon.output, "DIAGNOSIS:\n"...)
@@ -314,6 +332,7 @@ const (
 
 	lostConnectionCrash  = "lost connection to test machine"
 	noOutputCrash        = "no output from test machine"
+	timeoutCrash         = "timed out"
 	executingProgramStr1 = "executing program"  // syz-fuzzer output
 	executingProgramStr2 = "executed programs:" // syz-execprog output
 	fuzzerPreemptedStr   = "SYZ-FUZZER: PREEMPTED"

vm/vm_test.go

@@ -83,7 +83,7 @@ func init() {
 
 type Test struct {
 	Name           string
-	CanExit        bool // if the program is allowed to exit normally
+	Exit           ExitCondition
 	DiagnoseBug    bool // Diagnose produces output that is detected as kernel crash
 	DiagnoseNoWait bool // Diagnose returns output directly rather than to console
 	Body           func(outc chan []byte, errc chan error)
@@ -92,8 +92,8 @@ type Test struct {
 
 var tests = []*Test{
 	{
-		Name:    "program-exits-normally",
-		CanExit: true,
+		Name: "program-exits-normally",
+		Exit: ExitNormal,
 		Body: func(outc chan []byte, errc chan error) {
 			time.Sleep(time.Second)
 			errc <- nil
@@ -111,7 +111,7 @@ var tests = []*Test{
 	},
 	{
 		Name:        "#875-diagnose-bugs",
-		CanExit:     true,
+		Exit:        ExitNormal,
 		DiagnoseBug: true,
 		Body: func(outc chan []byte, errc chan error) {
 			errc <- nil
@@ -166,8 +166,8 @@ var tests = []*Test{
 		},
 	},
 	{
-		Name:    "program-exits-but-kernel-crashes-afterwards",
-		CanExit: true,
+		Name: "program-exits-but-kernel-crashes-afterwards",
+		Exit: ExitNormal,
 		Body: func(outc chan []byte, errc chan error) {
 			errc <- nil
 			time.Sleep(time.Second)
@@ -183,10 +183,20 @@ var tests = []*Test{
 	},
 	{
 		Name: "timeout",
+		Exit: ExitTimeout,
 		Body: func(outc chan []byte, errc chan error) {
 			errc <- vmimpl.ErrTimeout
 		},
 	},
+	{
+		Name: "bad-timeout",
+		Body: func(outc chan []byte, errc chan error) {
+			errc <- vmimpl.ErrTimeout
+		},
+		Report: &report.Report{
+			Title: timeoutCrash,
+		},
+	},
 	{
 		Name: "program-crashes",
 		Body: func(outc chan []byte, errc chan error) {
@@ -196,6 +206,13 @@ var tests = []*Test{
 			Title: lostConnectionCrash,
 		},
 	},
+	{
+		Name: "program-crashes-expected",
+		Exit: ExitError,
+		Body: func(outc chan []byte, errc chan error) {
+			errc <- fmt.Errorf("error")
+		},
+	},
 	{
 		Name: "no-output-1",
 		Body: func(outc chan []byte, errc chan error) {
@@ -217,8 +234,8 @@ var tests = []*Test{
 		},
 	},
 	{
-		Name:    "no-no-output-1",
-		CanExit: true,
+		Name: "no-no-output-1",
+		Exit: ExitNormal,
 		Body: func(outc chan []byte, errc chan error) {
 			for i := 0; i < 5; i++ {
 				time.Sleep(time.Second)
@@ -228,8 +245,8 @@ var tests = []*Test{
 		},
 	},
 	{
-		Name:    "no-no-output-2",
-		CanExit: true,
+		Name: "no-no-output-2",
+		Exit: ExitNormal,
 		Body: func(outc chan []byte, errc chan error) {
 			for i := 0; i < 5; i++ {
 				time.Sleep(time.Second)
@@ -239,17 +256,17 @@ var tests = []*Test{
 		},
 	},
 	{
-		Name:    "outc-closed",
-		CanExit: true,
+		Name: "outc-closed",
+		Exit: ExitTimeout,
 		Body: func(outc chan []byte, errc chan error) {
 			close(outc)
 			time.Sleep(time.Second)
 			errc <- vmimpl.ErrTimeout
 		},
 	},
 	{
-		Name:    "lots-of-output",
-		CanExit: true,
+		Name: "lots-of-output",
+		Exit: ExitTimeout,
 		Body: func(outc chan []byte, errc chan error) {
 			for i := 0; i < 100; i++ {
 				outc <- []byte("something\n")
@@ -308,7 +325,7 @@ func testMonitorExecution(t *testing.T, test *Test) {
 		test.Body(testInst.outc, testInst.errc)
 		done <- true
 	}()
-	rep := inst.MonitorExecution(outc, errc, reporter, test.CanExit)
+	rep := inst.MonitorExecution(outc, errc, reporter, test.Exit)
 	<-done
 	if test.Report != nil && rep == nil {
 		t.Fatalf("got no report")