Fixes bug with fifo files

This commit addresses an issue with the fifo paths specified in the
machine config not being relative to the jailer's root path. This change
fixes this by making the path relative and running chown on those fifo
files

Signed-off-by: xibz <[email protected]>

Author: xibz

runtime/runc_jailer.go

@@ -245,17 +245,23 @@ func (j *runcJailer) BuildLinkFifoHandler() firecracker.Handler {
 			contentsPath := j.RootPath()
 			fifoFileName := filepath.Base(m.Cfg.LogFifo)
 			newFifoPath := filepath.Join(contentsPath, fifoFileName)
-			if err := os.Link(m.Cfg.LogFifo, newFifoPath); err != nil {
+			// Since Firecracker is unaware that we are in a jailed environment and
+			// what owner/group to set this as when creating, we will manually have
+			// to adjust the permission bits ourselves
+			if err := linkAndChown(m.Cfg.LogFifo, newFifoPath, j.Config.UID, j.Config.GID); err != nil {
 				return err
 			}
-			m.Cfg.LogFifo = newFifoPath
+			// this path needs to be relative to the root path, and since we are
+			// placing the file in the root path the LogFifo value should just be the
+			// file name.
+			m.Cfg.LogFifo = fifoFileName
 
 			metricFifoFileName := filepath.Base(m.Cfg.MetricsFifo)
 			newMetricFifoPath := filepath.Join(contentsPath, metricFifoFileName)
-			if err := os.Link(m.Cfg.MetricsFifo, newMetricFifoPath); err != nil {
+			if err := linkAndChown(m.Cfg.MetricsFifo, newMetricFifoPath, j.Config.UID, j.Config.GID); err != nil {
 				return err
 			}
-			m.Cfg.MetricsFifo = newMetricFifoPath
+			m.Cfg.MetricsFifo = metricFifoFileName
 
 			return nil
 		},
@@ -493,6 +499,18 @@ func mkdirAllWithPermissions(path string, mode os.FileMode, uid, gid uint32) err
 	return nil
 }
 
+func linkAndChown(src, dst string, uid, gid uint32) error {
+	if err := os.Link(src, dst); err != nil {
+		return err
+	}
+
+	if err := os.Chown(dst, int(uid), int(gid)); err != nil {
+		return err
+	}
+
+	return nil
+}
+
 func getNetNS(spec specs.Spec) string {
 	for _, ns := range spec.Linux.Namespaces {
 		if ns.Type == networkNamespaceRuncName {