exec: Change MountFS to only relabel dirs that didnt exist

This PR introduces a new change to how ignition mounts filesystems,
Now when file systems are being mounted ignition will relabel directories
if they did not exist previously.
Whereas before file systems could be relabelled if they did/didnt exist previously
Fix #1452

docs/release-notes.md

@@ -26,6 +26,7 @@ Starting with this release, ignition-validate binaries are signed with the
 - Clarify documentation of `passwordHash` fields
 - Correctly document Tang `advertisement` field as optional
 - Fix failure disabling nonexistent unit with systemd ≥ 252
+- Don't relabel a mount point that already exists
 
 ### Test changes
 

internal/exec/stages/mount/mount.go

@@ -123,29 +123,25 @@ func (s stage) mountFs(fs types.Filesystem) error {
 		return err
 	}
 
-	var firstMissing string
-	if distro.SelinuxRelabel() {
-		var err error
-		firstMissing, err = util.FindFirstMissingPathComponent(path)
+	if _, err := os.Stat(path); err != nil && os.IsNotExist(err) {
+		firstMissing, err := util.FindFirstMissingPathComponent(path)
 		if err != nil {
 			return err
 		}
-	}
 
-	if _, err := os.Stat(path); err != nil && os.IsNotExist(err) {
 		// Record created directories for use by the files stage.
 		// NotateMkdirAll() is relative to the DestDir.
 		if err := s.NotateMkdirAll(relpath, 0755); err != nil {
 			return err
 		}
-	} else if err != nil {
-		return err
-	}
 
-	if distro.SelinuxRelabel() {
-		if err := s.RelabelFiles([]string{firstMissing}); err != nil {
-			return err
+		if distro.SelinuxRelabel() {
+			if err := s.RelabelFiles([]string{firstMissing}); err != nil {
+				return err
+			}
 		}
+	} else if err != nil {
+		return err
 	}
 
 	args := translateOptionSliceToString(fs.MountOptions, ",")