Add option to skip restore spec validation

runsc/boot/restore.go

@@ -132,7 +132,7 @@ func (r *restorer) restoreContainerInfo(l *Loader, info *containerInfo) error {
 
 	if len(r.containers) == r.totalContainers {
 		// Trigger the restore if this is the last container.
-		return r.restore(l)
+		return r.restore(l, info.conf.SkipRestoreSpecValidationUnsafe)
 	}
 	return nil
 }
@@ -544,7 +544,7 @@ func validateSpecs(oldSpecs, newSpecs map[string]*specs.Spec) error {
 	return nil
 }
 
-func (r *restorer) restore(l *Loader) error {
+func (r *restorer) restore(l *Loader, unsafeSkipRestoreSpecValidation bool) error {
 	log.Infof("Starting to restore %d containers", len(r.containers))
 
 	// Create a new root network namespace with the network stack of the
@@ -650,8 +650,10 @@ func (r *restorer) restore(l *Loader) error {
 	if err != nil {
 		return fmt.Errorf("failed to pop container specs from checkpoint: %w", err)
 	}
-	if err := validateSpecs(oldSpecs, l.containerSpecs); err != nil {
-		return fmt.Errorf("failed to validate restore spec: %w", err)
+	if !unsafeSkipRestoreSpecValidation {
+		if err := validateSpecs(oldSpecs, l.containerSpecs); err != nil {
+			return fmt.Errorf("failed to validate restore spec: %w", err)
+		}
 	}
 
 	// Since we have a new kernel we also must make a new watchdog.

runsc/config/config.go

@@ -384,6 +384,10 @@ type Config struct {
 
 	// TestOnlySaveRestoreNetstack indicates netstack should be saved and restored.
 	TestOnlySaveRestoreNetstack bool `flag:"TESTONLY-save-restore-netstack"`
+
+	// UnsafeSkipRestoreSpecValidation optionally skips validation of the container spec for restored
+	// containers.
+	UnsafeSkipRestoreSpecValidation bool `flag:"unsafe-skip-restore-spec-validation"`
 }
 
 func (c *Config) validate() error {

runsc/config/flags.go

@@ -105,6 +105,7 @@ func RegisterFlags(flagSet *flag.FlagSet) {
 	flagSet.Bool("enable-core-tags", false, "enables core tagging. Requires host linux kernel >= 5.14.")
 	flagSet.String("pod-init-config", "", "path to configuration file with additional steps to take during pod creation.")
 	flagSet.Var(HostSettingsCheck.Ptr(), "host-settings", "how to handle non-optimal host kernel settings: check (default, advisory-only), ignore (do not check), adjust (best-effort auto-adjustment), or enforce (auto-adjustment must succeed).")
+	flagSet.Bool("unsafe-skip-restore-spec-validation", false, "Enables skipping validation of the restore-time container spec when restoring checkpoints.")
 
 	// Flags that control sandbox runtime behavior: MM related.
 	flagSet.Bool("app-huge-pages", true, "enable use of huge pages for application memory; requires /sys/kernel/mm/transparent_hugepage/shmem_enabled = advise")