oci_conmon: not make accessible dirs if not needed

do not change the permissions mask for the rundir and the tmpdir when
running a container with a user namespace and the current user is
mapped inside the user namespace.

The change was introduced with
849548f, that dropped the
intermediate mount namespace in favor of allowing root into the user
namespace to access these directories.

Closes: containers#4846

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

libpod/oci_conmon_linux.go

@@ -149,9 +149,23 @@ func (r *ConmonOCIRuntime) Path() string {
 	return r.path
 }
 
+// hasCurrentUserMapped checks whether the current user is mapped inside the container user namespace
+func hasCurrentUserMapped(ctr *Container) bool {
+	if len(ctr.config.IDMappings.UIDMap) == 0 && len(ctr.config.IDMappings.GIDMap) == 0 {
+		return true
+	}
+	uid := os.Geteuid()
+	for _, m := range ctr.config.IDMappings.UIDMap {
+		if uid >= m.HostID && uid < m.HostID + m.Size {
+			return true
+		}
+	}
+	return false
+}
+
 // CreateContainer creates a container.
 func (r *ConmonOCIRuntime) CreateContainer(ctr *Container, restoreOptions *ContainerCheckpointOptions) (err error) {
-	if len(ctr.config.IDMappings.UIDMap) != 0 || len(ctr.config.IDMappings.GIDMap) != 0 {
+	if !hasCurrentUserMapped(ctr) {
 		for _, i := range []string{ctr.state.RunDir, ctr.runtime.config.TmpDir, ctr.config.StaticDir, ctr.state.Mountpoint, ctr.runtime.config.VolumePath} {
 			if err := makeAccessible(i, ctr.RootUID(), ctr.RootGID()); err != nil {
 				return err