*: allow to not use pivot_root

runc has a `--no-pivot` flag, that uses MS_MOVE instead.

This patch set bubbles up a runtime config to enable using no-pivot
globally.

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

cmd/crio/config.go

@@ -77,6 +77,9 @@ runtime_untrusted_workload = "{{ .RuntimeUntrustedWorkload }}"
 # container runtime for all containers.
 default_workload_trust = "{{ .DefaultWorkloadTrust }}"
 
+# no_pivot instructs the runtime to not use pivot_root, but instead use MS_MOVE
+no_pivot = {{ .NoPivot }}
+
 # conmon is the path to conmon binary, used for managing the runtime.
 conmon = "{{ .Conmon }}"
 

conmon/conmon.c

@@ -104,6 +104,7 @@ static char *opt_runtime_path = NULL;
 static char *opt_bundle_path = NULL;
 static char *opt_pid_file = NULL;
 static bool opt_systemd_cgroup = false;
+static bool opt_no_pivot = false;
 static char *opt_exec_process_spec = NULL;
 static bool opt_exec = false;
 static char *opt_log_path = NULL;
@@ -117,6 +118,7 @@ static GOptionEntry opt_entries[] =
   { "cid", 'c', 0, G_OPTION_ARG_STRING, &opt_cid, "Container ID", NULL },
   { "cuuid", 'u', 0, G_OPTION_ARG_STRING, &opt_cuuid, "Container UUID", NULL },
   { "runtime", 'r', 0, G_OPTION_ARG_STRING, &opt_runtime_path, "Runtime path", NULL },
+  { "no-pivot", 0, 0, G_OPTION_ARG_NONE, &opt_no_pivot, "do not use pivot_root", NULL },
   { "bundle", 'b', 0, G_OPTION_ARG_STRING, &opt_bundle_path, "Bundle path", NULL },
   { "pidfile", 'p', 0, G_OPTION_ARG_STRING, &opt_pid_file, "PID file", NULL },
   { "systemd-cgroup", 's', 0, G_OPTION_ARG_NONE, &opt_systemd_cgroup, "Enable systemd cgroup manager", NULL },
@@ -1265,6 +1267,12 @@ int main(int argc, char *argv[])
 			 NULL);
 	}
 
+	if (!opt_exec && opt_no_pivot) {
+		add_argv(runtime_argv,
+			"--no-pivot",
+			NULL);
+	}
+
 	if (csname != NULL) {
 		add_argv(runtime_argv,
 			 "--console-socket", csname,

libkpod/config.go

@@ -118,6 +118,9 @@ type RuntimeConfig struct {
 	// container runtime for all containers.
 	DefaultWorkloadTrust string `toml:"default_workload_trust"`
 
+	// NoPivot instructs the runtime to not use `pivot_root`, but instead use `MS_MOVE`
+	NoPivot bool `toml:"no_pivot"`
+
 	// Conmon is the path to conmon binary, used for managing the runtime.
 	Conmon string `toml:"conmon"`
 

libkpod/container_server.go

@@ -121,7 +121,7 @@ func New(config *Config) (*ContainerServer, error) {
 		return nil, err
 	}
 
-	runtime, err := oci.New(config.Runtime, config.RuntimeUntrustedWorkload, config.DefaultWorkloadTrust, config.Conmon, config.ConmonEnv, config.CgroupManager, config.ContainerExitsDir, config.LogSizeMax)
+	runtime, err := oci.New(config.Runtime, config.RuntimeUntrustedWorkload, config.DefaultWorkloadTrust, config.Conmon, config.ConmonEnv, config.CgroupManager, config.ContainerExitsDir, config.LogSizeMax, config.NoPivot)
 	if err != nil {
 		return nil, err
 	}

oci/oci.go

@@ -38,7 +38,15 @@ const (
 )
 
 // New creates a new Runtime with options provided
-func New(runtimeTrustedPath string, runtimeUntrustedPath string, trustLevel string, conmonPath string, conmonEnv []string, cgroupManager string, containerExitsDir string, logSizeMax int64) (*Runtime, error) {
+func New(runtimeTrustedPath string,
+	runtimeUntrustedPath string,
+	trustLevel string,
+	conmonPath string,
+	conmonEnv []string,
+	cgroupManager string,
+	containerExitsDir string,
+	logSizeMax int64,
+	noPivot bool) (*Runtime, error) {
 	r := &Runtime{
 		name:              filepath.Base(runtimeTrustedPath),
 		trustedPath:       runtimeTrustedPath,
@@ -49,6 +57,7 @@ func New(runtimeTrustedPath string, runtimeUntrustedPath string, trustLevel stri
 		cgroupManager:     cgroupManager,
 		containerExitsDir: containerExitsDir,
 		logSizeMax:        logSizeMax,
+		noPivot:           noPivot,
 	}
 	return r, nil
 }
@@ -64,6 +73,7 @@ type Runtime struct {
 	cgroupManager     string
 	containerExitsDir string
 	logSizeMax        int64
+	noPivot           bool
 }
 
 // syncInfo is used to return data from monitor process to daemon
@@ -161,6 +171,9 @@ func (r *Runtime) CreateContainer(c *Container, cgroupParent string) error {
 	if r.logSizeMax >= 0 {
 		args = append(args, "--log-size-max", fmt.Sprintf("%v", r.logSizeMax))
 	}
+	if r.noPivot {
+		args = append(args, "--no-pivot")
+	}
 	if c.terminal {
 		args = append(args, "-t")
 	} else if c.stdin {