runtimetest: fix root readonly check

The rootfs might not be readable despite spec.Root.Readonly being false
when the rootfs belong to an unmapped uid. Just skip the test in that
case.

The test will still be executed for
validation/root_readonly_{false,true}.go

Signed-off-by: Alban Crequy <alban@kinvolk.io>

Author: alban

cmd/runtimetest/main.go

@@ -329,6 +329,10 @@ func validateRootFS(spec *rspec.Spec) error {
 			return specerror.NewError(specerror.RootReadonlyImplement, fmt.Errorf("rootfs must be readonly"), rspec.Version)
 		}
 	} else {
+		if spec.Linux != nil && len(spec.Linux.UIDMappings) != 0 {
+			// Skip the test in case of user namespaces
+			return nil
+		}
 		err := testWriteAccess("/")
 		if err != nil {
 			return specerror.NewError(specerror.RootReadonlyImplement, fmt.Errorf("rootfs must not be readonly"), rspec.Version)