Fix race conditions in libcontainerd process handling

daemon/kill.go

@@ -4,10 +4,10 @@ import (
 	"context"
 	"fmt"
 	"runtime"
-	"strings"
 	"syscall"
 	"time"
 
+	"github.com/docker/docker/api/errdefs"
 	containerpkg "github.com/docker/docker/container"
 	"github.com/docker/docker/libcontainerd"
 	"github.com/docker/docker/pkg/signal"
@@ -97,15 +97,11 @@ func (daemon *Daemon) killWithSignal(container *containerpkg.Container, sig int)
 	}
 
 	if err := daemon.kill(container, sig); err != nil {
-		err = errors.Wrapf(err, "Cannot kill container %s", container.ID)
-		// if container or process not exists, ignore the error
-		// TODO: we shouldn't have to parse error strings from containerd
-		if strings.Contains(err.Error(), "container not found") ||
-			strings.Contains(err.Error(), "no such process") {
-			logrus.Warnf("container kill failed because of 'container not found' or 'no such process': %s", err.Error())
+		if errdefs.IsNotFound(err) {
 			unpause = false
+			logrus.WithError(err).WithField("container", container.ID).WithField("action", "kill").Debug("container kill failed because of 'container not found' or 'no such process'")
 		} else {
-			return err
+			return errors.Wrapf(err, "Cannot kill container %s", container.ID)
 		}
 	}
 
@@ -171,7 +167,7 @@ func (daemon *Daemon) Kill(container *containerpkg.Container) error {
 // killPossibleDeadProcess is a wrapper around killSig() suppressing "no such process" error.
 func (daemon *Daemon) killPossiblyDeadProcess(container *containerpkg.Container, sig int) error {
 	err := daemon.killWithSignal(container, sig)
-	if err == syscall.ESRCH {
+	if errdefs.IsNotFound(err) {
 		e := errNoSuchProcess{container.GetPID(), sig}
 		logrus.Debug(e)
 		return e

libcontainerd/client_daemon.go

@@ -27,6 +27,7 @@ import (
 	"github.com/containerd/containerd/archive"
 	"github.com/containerd/containerd/cio"
 	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/images"
 	"github.com/containerd/containerd/linux/runctypes"
 	"github.com/containerd/typeurl"
@@ -42,7 +43,7 @@ import (
 const InitProcessName = "init"
 
 type container struct {
-	sync.Mutex
+	mu sync.Mutex
 
 	bundleDir string
 	ctr       containerd.Container
@@ -51,6 +52,54 @@ type container struct {
 	oomKilled bool
 }
 
+func (c *container) setTask(t containerd.Task) {
+	c.mu.Lock()
+	c.task = t
+	c.mu.Unlock()
+}
+
+func (c *container) getTask() containerd.Task {
+	c.mu.Lock()
+	t := c.task
+	c.mu.Unlock()
+	return t
+}
+
+func (c *container) addProcess(id string, p containerd.Process) {
+	c.mu.Lock()
+	if c.execs == nil {
+		c.execs = make(map[string]containerd.Process)
+	}
+	c.execs[id] = p
+	c.mu.Unlock()
+}
+
+func (c *container) deleteProcess(id string) {
+	c.mu.Lock()
+	delete(c.execs, id)
+	c.mu.Unlock()
+}
+
+func (c *container) getProcess(id string) containerd.Process {
+	c.mu.Lock()
+	p := c.execs[id]
+	c.mu.Unlock()
+	return p
+}
+
+func (c *container) setOOMKilled(killed bool) {
+	c.mu.Lock()
+	c.oomKilled = killed
+	c.mu.Unlock()
+}
+
+func (c *container) getOOMKilled() bool {
+	c.mu.Lock()
+	killed := c.oomKilled
+	c.mu.Unlock()
+	return killed
+}
+
 type client struct {
 	sync.RWMutex // protects containers map
 
@@ -160,10 +209,10 @@ func (c *client) Create(ctx context.Context, id string, ociSpec *specs.Spec, run
 // Start create and start a task for the specified containerd id
 func (c *client) Start(ctx context.Context, id, checkpointDir string, withStdin bool, attachStdio StdioCallback) (int, error) {
 	ctr := c.getContainer(id)
-	switch {
-	case ctr == nil:
+	if ctr == nil {
 		return -1, errors.WithStack(newNotFoundError("no such container"))
-	case ctr.task != nil:
+	}
+	if t := ctr.getTask(); t != nil {
 		return -1, errors.WithStack(newConflictError("container already started"))
 	}
 
@@ -227,9 +276,7 @@ func (c *client) Start(ctx context.Context, id, checkpointDir string, withStdin
 		return -1, err
 	}
 
-	c.Lock()
-	c.containers[id].task = t
-	c.Unlock()
+	ctr.setTask(t)
 
 	// Signal c.createIO that it can call CloseIO
 	close(stdinCloseSync)
@@ -239,9 +286,7 @@ func (c *client) Start(ctx context.Context, id, checkpointDir string, withStdin
 			c.logger.WithError(err).WithField("container", id).
 				Error("failed to delete task after fail start")
 		}
-		c.Lock()
-		c.containers[id].task = nil
-		c.Unlock()
+		ctr.setTask(nil)
 		return -1, err
 	}
 
@@ -250,12 +295,15 @@ func (c *client) Start(ctx context.Context, id, checkpointDir string, withStdin
 
 func (c *client) Exec(ctx context.Context, containerID, processID string, spec *specs.Process, withStdin bool, attachStdio StdioCallback) (int, error) {
 	ctr := c.getContainer(containerID)
-	switch {
-	case ctr == nil:
+	if ctr == nil {
 		return -1, errors.WithStack(newNotFoundError("no such container"))
-	case ctr.task == nil:
+	}
+	t := ctr.getTask()
+	if t == nil {
 		return -1, errors.WithStack(newInvalidParameterError("container is not running"))
-	case ctr.execs != nil && ctr.execs[processID] != nil:
+	}
+
+	if p := ctr.getProcess(processID); p != nil {
 		return -1, errors.WithStack(newConflictError("id already in use"))
 	}
 
@@ -278,7 +326,7 @@ func (c *client) Exec(ctx context.Context, containerID, processID string, spec *
 		}
 	}()
 
-	p, err = ctr.task.Exec(ctx, processID, spec, func(id string) (cio.IO, error) {
+	p, err = t.Exec(ctx, processID, spec, func(id string) (cio.IO, error) {
 		rio, err = c.createIO(fifos, containerID, processID, stdinCloseSync, attachStdio)
 		return rio, err
 	})
@@ -291,21 +339,14 @@ func (c *client) Exec(ctx context.Context, containerID, processID string, spec *
 		return -1, err
 	}
 
-	ctr.Lock()
-	if ctr.execs == nil {
-		ctr.execs = make(map[string]containerd.Process)
-	}
-	ctr.execs[processID] = p
-	ctr.Unlock()
+	ctr.addProcess(processID, p)
 
 	// Signal c.createIO that it can call CloseIO
 	close(stdinCloseSync)
 
 	if err = p.Start(ctx); err != nil {
 		p.Delete(context.Background())
-		ctr.Lock()
-		delete(ctr.execs, processID)
-		ctr.Unlock()
+		ctr.deleteProcess(processID)
 		return -1, err
 	}
 
@@ -317,7 +358,7 @@ func (c *client) SignalProcess(ctx context.Context, containerID, processID strin
 	if err != nil {
 		return err
 	}
-	return p.Kill(ctx, syscall.Signal(signal))
+	return wrapError(p.Kill(ctx, syscall.Signal(signal)))
 }
 
 func (c *client) ResizeTerminal(ctx context.Context, containerID, processID string, width, height int) error {
@@ -431,12 +472,9 @@ func (c *client) DeleteTask(ctx context.Context, containerID string) (uint32, ti
 		return 255, time.Now(), nil
 	}
 
-	c.Lock()
-	if ctr, ok := c.containers[containerID]; ok {
-		ctr.task = nil
+	if ctr := c.getContainer(containerID); ctr != nil {
+		ctr.setTask(nil)
 	}
-	c.Unlock()
-
 	return status.ExitCode(), status.ExitTime(), nil
 }
 
@@ -470,7 +508,12 @@ func (c *client) Status(ctx context.Context, containerID string) (Status, error)
 		return StatusUnknown, errors.WithStack(newNotFoundError("no such container"))
 	}
 
-	s, err := ctr.task.Status(ctx)
+	t := ctr.getTask()
+	if t == nil {
+		return StatusUnknown, errors.WithStack(newNotFoundError("no such task"))
+	}
+
+	s, err := t.Status(ctx)
 	if err != nil {
 		return StatusUnknown, err
 	}
@@ -546,26 +589,22 @@ func (c *client) removeContainer(id string) {
 
 func (c *client) getProcess(containerID, processID string) (containerd.Process, error) {
 	ctr := c.getContainer(containerID)
-	switch {
-	case ctr == nil:
+	if ctr == nil {
 		return nil, errors.WithStack(newNotFoundError("no such container"))
-	case ctr.task == nil:
+	}
+
+	t := ctr.getTask()
+	if t == nil {
 		return nil, errors.WithStack(newNotFoundError("container is not running"))
-	case processID == InitProcessName:
-		return ctr.task, nil
-	default:
-		ctr.Lock()
-		defer ctr.Unlock()
-		if ctr.execs == nil {
-			return nil, errors.WithStack(newNotFoundError("no execs"))
-		}
+	}
+	if processID == InitProcessName {
+		return t, nil
 	}
 
-	p := ctr.execs[processID]
+	p := ctr.getProcess(processID)
 	if p == nil {
 		return nil, errors.WithStack(newNotFoundError("no such exec"))
 	}
-
 	return p, nil
 }
 
@@ -623,12 +662,7 @@ func (c *client) processEvent(ctr *container, et EventType, ei EventInfo) {
 		}
 
 		if et == EventExit && ei.ProcessID != ei.ContainerID {
-			var p containerd.Process
-			ctr.Lock()
-			if ctr.execs != nil {
-				p = ctr.execs[ei.ProcessID]
-			}
-			ctr.Unlock()
+			p := ctr.getProcess(ei.ProcessID)
 			if p == nil {
 				c.logger.WithError(errors.New("no such process")).
 					WithFields(logrus.Fields{
@@ -644,9 +678,8 @@ func (c *client) processEvent(ctr *container, et EventType, ei EventInfo) {
 					"process":   ei.ProcessID,
 				}).Warn("failed to delete process")
 			}
-			c.Lock()
-			delete(ctr.execs, ei.ProcessID)
-			c.Unlock()
+			ctr.deleteProcess(ei.ProcessID)
+
 			ctr := c.getContainer(ei.ContainerID)
 			if ctr == nil {
 				c.logger.WithFields(logrus.Fields{
@@ -783,10 +816,10 @@ func (c *client) processEventStream(ctx context.Context) {
 		}
 
 		if oomKilled {
-			ctr.oomKilled = true
+			ctr.setOOMKilled(true)
 			oomKilled = false
 		}
-		ei.OOMKilled = ctr.oomKilled
+		ei.OOMKilled = ctr.getOOMKilled()
 
 		c.processEvent(ctr, et, ei)
 	}
@@ -816,12 +849,19 @@ func (c *client) writeContent(ctx context.Context, mediaType, ref string, r io.R
 }
 
 func wrapError(err error) error {
-	if err != nil {
-		msg := err.Error()
-		for _, s := range []string{"container does not exist", "not found", "no such container"} {
-			if strings.Contains(msg, s) {
-				return wrapNotFoundError(err)
-			}
+	if err == nil {
+		return nil
+	}
+
+	switch {
+	case errdefs.IsNotFound(err):
+		return wrapNotFoundError(err)
+	}
+
+	msg := err.Error()
+	for _, s := range []string{"container does not exist", "not found", "no such container"} {
+		if strings.Contains(msg, s) {
+			return wrapNotFoundError(err)
 		}
 	}
 	return err