libct: don't pass SpecState to init unless needed

SpecState field of initConfig is only needed to run hooks that are
executed inside a container -- namely CreateContainer and
StartContainer.

If these hooks are not configured, there is no need to fill, marshal and
unmarshal SpecState.

While at it, inline updateSpecState as it is trivial and only has one user.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/process_linux.go

@@ -615,9 +615,16 @@ func (p *initProcess) start() (retErr error) {
 	if err := p.createNetworkInterfaces(); err != nil {
 		return fmt.Errorf("error creating network interfaces: %w", err)
 	}
-	if err := p.updateSpecState(); err != nil {
-		return fmt.Errorf("error updating spec state: %w", err)
+
+	// initConfig.SpecState is only needed to run hooks that are executed
+	// inside a container, i.e. CreateContainer and StartContainer.
+	if p.config.Config.HasHook(configs.CreateContainer, configs.StartContainer) {
+		p.config.SpecState, err = p.container.currentOCIState()
+		if err != nil {
+			return fmt.Errorf("error getting current state: %w", err)
+		}
 	}
+
 	if err := utils.WriteJSON(p.comm.initSockParent, p.config); err != nil {
 		return fmt.Errorf("error sending config to init process: %w", err)
 	}
@@ -779,16 +786,6 @@ func (p *initProcess) start() (retErr error) {
 	return nil
 }
 
-func (p *initProcess) updateSpecState() error {
-	s, err := p.container.currentOCIState()
-	if err != nil {
-		return err
-	}
-
-	p.config.SpecState = s
-	return nil
-}
-
 func (p *initProcess) createNetworkInterfaces() error {
 	for _, config := range p.config.Config.Networks {
 		strategy, err := getStrategy(config.Type)

libcontainer/rootfs_linux.go

@@ -195,11 +195,12 @@ func prepareRootfs(pipe *syncSocket, iConfig *initConfig) (err error) {
 		return &os.PathError{Op: "chdir", Path: config.Rootfs, Err: err}
 	}
 
-	s := iConfig.SpecState
-	s.Pid = unix.Getpid()
-	s.Status = specs.StateCreating
-	if err := iConfig.Config.Hooks.Run(configs.CreateContainer, s); err != nil {
-		return err
+	if s := iConfig.SpecState; s != nil {
+		s.Pid = unix.Getpid()
+		s.Status = specs.StateCreating
+		if err := iConfig.Config.Hooks.Run(configs.CreateContainer, s); err != nil {
+			return err
+		}
 	}
 
 	if config.NoPivotRoot {

libcontainer/standard_init_linux.go

@@ -267,11 +267,12 @@ func (l *linuxStandardInit) Init() error {
 	// https://github.com/torvalds/linux/blob/v4.9/fs/exec.c#L1290-L1318
 	_ = l.fifoFile.Close()
 
-	s := l.config.SpecState
-	s.Pid = unix.Getpid()
-	s.Status = specs.StateCreated
-	if err := l.config.Config.Hooks.Run(configs.StartContainer, s); err != nil {
-		return err
+	if s := l.config.SpecState; s != nil {
+		s.Pid = unix.Getpid()
+		s.Status = specs.StateCreated
+		if err := l.config.Config.Hooks.Run(configs.StartContainer, s); err != nil {
+			return err
+		}
 	}
 
 	// Close all file descriptors we are not passing to the container. This is