syzkaller/vm/vm.go

// Copyright 2015 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.

package vm

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"os"
	"regexp"
	"syscall"
	"time"

	"github.com/google/syzkaller/report"
)

// Instance represents a Linux VM or a remote physical machine.
type Instance interface {
	// Copy copies a hostSrc file into vm and returns file name in vm.
	Copy(hostSrc string) (string, error)

	// Forward setups forwarding from within VM to host port port
	// and returns address to use in VM.
	Forward(port int) (string, error)

	// Run runs cmd inside of the VM (think of ssh cmd).
	// outc receives combined cmd and kernel console output.
	// errc receives either command Wait return error or vm.TimeoutErr.
	// Command is terminated after timeout. Send on the stop chan can be used to terminate it earlier.
	Run(timeout time.Duration, stop <-chan bool, command string) (outc <-chan []byte, errc <-chan error, err error)

	// Close stops and destroys the VM.
	Close()
}

type Config struct {
	Name        string
	Index       int
	Workdir     string
	Bin         string
	BinArgs     string
	Initrd      string
	Kernel      string
	Cmdline     string
	Image       string
	Sshkey      string
	Executor    string
	Device      string
	MachineType string
	Cpu         int
	Mem         int
	Debug       bool
}

type ctorFunc func(cfg *Config) (Instance, error)

var ctors = make(map[string]ctorFunc)

func Register(typ string, ctor ctorFunc) {
	ctors[typ] = ctor
}

// Close to interrupt all pending operations.
var Shutdown = make(chan struct{})

// Create creates and boots a new VM instance.
func Create(typ string, cfg *Config) (Instance, error) {
	ctor := ctors[typ]
	if ctor == nil {
		return nil, fmt.Errorf("unknown instance type '%v'", typ)
	}
	return ctor(cfg)
}

func LongPipe() (io.ReadCloser, io.WriteCloser, error) {
	r, w, err := os.Pipe()
	if err != nil {
		return nil, nil, fmt.Errorf("failed to create pipe: %v", err)
	}
	for sz := 128 << 10; sz <= 2<<20; sz *= 2 {
		syscall.Syscall(syscall.SYS_FCNTL, w.Fd(), syscall.F_SETPIPE_SZ, uintptr(sz))
	}
	return r, w, err
}

var TimeoutErr = errors.New("timeout")

func MonitorExecution(outc <-chan []byte, errc <-chan error, local, needOutput bool, ignores []*regexp.Regexp) (desc string, text, output []byte, crashed, timedout bool) {
	waitForOutput := func() {
		dur := time.Second
		if needOutput {
			dur = 10 * time.Second
		}
		timer := time.NewTimer(dur).C
		for {
			select {
			case out, ok := <-outc:
				if !ok {
					return
				}
				output = append(output, out...)
			case <-timer:
				return
			}
		}
	}

	matchPos := 0
	const (
		beforeContext = 256 << 10
		afterContext  = 128 << 10
	)
	extractError := func(defaultError string) (string, []byte, []byte, bool, bool) {
		// Give it some time to finish writing the error message.
		waitForOutput()
		if bytes.Contains(output, []byte("SYZ-FUZZER: PREEMPTED")) {
			return "preempted", nil, nil, false, true
		}
		if !report.ContainsCrash(output[matchPos:], ignores) {
			return defaultError, nil, output, true, false
		}
		desc, text, start, end := report.Parse(output[matchPos:], ignores)
		start = start + matchPos - beforeContext
		if start < 0 {
			start = 0
		}
		end = end + matchPos + afterContext
		if end > len(output) {
			end = len(output)
		}
		return desc, text, output[start:end], true, false
	}

	lastExecuteTime := time.Now()
	ticker := time.NewTimer(3 * time.Minute)
	tickerFired := false
	for {
		if !tickerFired && !ticker.Stop() {
			<-ticker.C
		}
		tickerFired = false
		ticker.Reset(3 * time.Minute)
		select {
		case err := <-errc:
			switch err {
			case nil:
				waitForOutput()
				return "", nil, output, false, false
			case TimeoutErr:
				return err.Error(), nil, nil, false, true
			default:
				// Note: connection lost can race with a kernel oops message.
				// In such case we want to return the kernel oops.
				return extractError("lost connection to test machine")
			}
		case out := <-outc:
			output = append(output, out...)
			if bytes.Index(output[matchPos:], []byte("executing program")) != -1 { // syz-fuzzer output
				lastExecuteTime = time.Now()
			}
			if bytes.Index(output[matchPos:], []byte("executed programs:")) != -1 { // syz-execprog output
				lastExecuteTime = time.Now()
			}
			if report.ContainsCrash(output[matchPos:], ignores) {
				return extractError("")
			}
			if len(output) > 2*beforeContext {
				copy(output, output[len(output)-beforeContext:])
				output = output[:beforeContext]
			}
			matchPos = len(output) - 128
			if matchPos < 0 {
				matchPos = 0
			}
			// In some cases kernel constantly prints something to console,
			// but fuzzer is not actually executing programs.
			if !local && time.Since(lastExecuteTime) > 3*time.Minute {
				return "test machine is not executing programs", nil, output, true, false
			}
		case <-ticker.C:
			tickerFired = true
			if !local {
				return "no output from test machine", nil, output, true, false
			}
		case <-Shutdown:
			return "", nil, nil, false, false
		}
	}
}

// Sleep for d.
// If shutdown is in progress, return false prematurely.
func SleepInterruptible(d time.Duration) bool {
	select {
	case <-time.After(d):
		return true
	case <-Shutdown:
		return false
	}
}