security: selinux: Pass parent storage source into image labeling helper

virSecuritySELinuxSetImageLabelInternal assigns different labels to
backing chain members than to the parent image. This was done via the
'first' flag. Convert it to passing in pointer to the parent
virStorageSource. This will allow us to use the parent virStorageSource
in further changes.

src/security/security_selinux.c

@@ -1592,7 +1592,7 @@ static int
 virSecuritySELinuxSetImageLabelInternal(virSecurityManagerPtr mgr,
                                         virDomainDefPtr def,
                                         virStorageSourcePtr src,
-                                        bool first)
+                                        virStorageSourcePtr parent)
 {
     virSecuritySELinuxDataPtr data = virSecurityManagerGetPrivateData(mgr);
     virSecurityLabelDefPtr secdef;
@@ -1614,7 +1614,7 @@ virSecuritySELinuxSetImageLabelInternal(virSecurityManagerPtr mgr,
 
     if (disk_seclabel && disk_seclabel->relabel && disk_seclabel->label) {
         ret = virSecuritySELinuxSetFilecon(mgr, src->path, disk_seclabel->label);
-    } else if (first) {
+    } else if (!parent || parent == src) {
         if (src->shared) {
             ret = virSecuritySELinuxSetFileconOptional(mgr,
                                                        src->path,
@@ -1660,7 +1660,7 @@ virSecuritySELinuxSetImageLabel(virSecurityManagerPtr mgr,
                                 virDomainDefPtr def,
                                 virStorageSourcePtr src)
 {
-    return virSecuritySELinuxSetImageLabelInternal(mgr, def, src, true);
+    return virSecuritySELinuxSetImageLabelInternal(mgr, def, src, NULL);
 }
 
 
@@ -1670,14 +1670,11 @@ virSecuritySELinuxSetDiskLabel(virSecurityManagerPtr mgr,
                                virDomainDiskDefPtr disk)
 
 {
-    bool first = true;
     virStorageSourcePtr next;
 
     for (next = disk->src; virStorageSourceIsBacking(next); next = next->backingStore) {
-        if (virSecuritySELinuxSetImageLabelInternal(mgr, def, next, first) < 0)
+        if (virSecuritySELinuxSetImageLabelInternal(mgr, def, next, disk->src) < 0)
             return -1;
-
-        first = false;
     }
 
     return 0;