security: dac: Take parent security label into account

Until now we ignored user-provided backing chains and while detecting
the code inherited labels of the parent device. With user provided
chains we should keep this functionality, so label of the parent image
in the backing chain will be applied if an image-specific label is not
present.

src/security/security_dac.c

@@ -688,12 +688,14 @@ virSecurityDACRestoreFileLabel(virSecurityDACDataPtr priv,
 
 
 static int
-virSecurityDACSetImageLabel(virSecurityManagerPtr mgr,
-                            virDomainDefPtr def,
-                            virStorageSourcePtr src)
+virSecurityDACSetImageLabelInternal(virSecurityManagerPtr mgr,
+                                    virDomainDefPtr def,
+                                    virStorageSourcePtr src,
+                                    virStorageSourcePtr parent)
 {
     virSecurityLabelDefPtr secdef;
     virSecurityDeviceLabelDefPtr disk_seclabel;
+    virSecurityDeviceLabelDefPtr parent_seclabel = NULL;
     virSecurityDACDataPtr priv = virSecurityManagerGetPrivateData(mgr);
     uid_t user;
     gid_t group;
@@ -705,14 +707,24 @@ virSecurityDACSetImageLabel(virSecurityManagerPtr mgr,
     if (secdef && !secdef->relabel)
         return 0;
 
-    disk_seclabel = virStorageSourceGetSecurityLabelDef(src,
-                                                        SECURITY_DAC_NAME);
-    if (disk_seclabel && !disk_seclabel->relabel)
-        return 0;
+    disk_seclabel = virStorageSourceGetSecurityLabelDef(src, SECURITY_DAC_NAME);
+    if (parent)
+        parent_seclabel = virStorageSourceGetSecurityLabelDef(parent,
+                                                              SECURITY_DAC_NAME);
+
+    if (disk_seclabel && (!disk_seclabel->relabel || disk_seclabel->label)) {
+        if (!disk_seclabel->relabel)
+            return 0;
 
-    if (disk_seclabel && disk_seclabel->label) {
         if (virParseOwnershipIds(disk_seclabel->label, &user, &group) < 0)
             return -1;
+    } else if (parent_seclabel &&
+               (!parent_seclabel->relabel || parent_seclabel->label)) {
+        if (!parent_seclabel->relabel)
+            return 0;
+
+        if (virParseOwnershipIds(parent_seclabel->label, &user, &group) < 0)
+            return -1;
     } else {
         if (virSecurityDACGetImageIds(secdef, priv, &user, &group))
             return -1;
@@ -722,6 +734,14 @@ virSecurityDACSetImageLabel(virSecurityManagerPtr mgr,
 }
 
 
+static int
+virSecurityDACSetImageLabel(virSecurityManagerPtr mgr,
+                            virDomainDefPtr def,
+                            virStorageSourcePtr src)
+{
+    return virSecurityDACSetImageLabelInternal(mgr, def, src, NULL);
+}
+
 static int
 virSecurityDACSetDiskLabel(virSecurityManagerPtr mgr,
                            virDomainDefPtr def,
@@ -731,7 +751,7 @@ virSecurityDACSetDiskLabel(virSecurityManagerPtr mgr,
     virStorageSourcePtr next;
 
     for (next = disk->src; virStorageSourceIsBacking(next); next = next->backingStore) {
-        if (virSecurityDACSetImageLabel(mgr, def, next) < 0)
+        if (virSecurityDACSetImageLabelInternal(mgr, def, next, disk->src) < 0)
             return -1;
     }