storage: Disallow wiping an extended disk partition

https://bugzilla.redhat.com/show_bug.cgi?id=1225694

Check if the disk partition to be wiped is the extended partition, if
so then disallow it. Do this via changing the wipeVol backend to check
the volume before passing to the common virStorageBackendVolWipeLocal

src/storage/storage_backend_disk.c

@@ -851,6 +851,24 @@ virStorageBackendDiskBuildVolFrom(virConnectPtr conn,
 }
 
 
+static int
+virStorageBackendDiskVolWipe(virConnectPtr conn,
+                             virStoragePoolObjPtr pool,
+                             virStorageVolDefPtr vol,
+                             unsigned int algorithm,
+                             unsigned int flags)
+{
+    if (vol->source.partType != VIR_STORAGE_VOL_DISK_TYPE_EXTENDED)
+        return virStorageBackendVolWipeLocal(conn, pool, vol, algorithm, flags);
+
+    /* Wiping an extended partition is not support */
+    virReportError(VIR_ERR_NO_SUPPORT,
+                   _("cannot wipe extended partition '%s'"),
+                   vol->target.path);
+    return -1;
+}
+
+
 virStorageBackend virStorageBackendDisk = {
     .type = VIR_STORAGE_POOL_DISK,
 
@@ -862,5 +880,5 @@ virStorageBackend virStorageBackendDisk = {
     .buildVolFrom = virStorageBackendDiskBuildVolFrom,
     .uploadVol = virStorageBackendVolUploadLocal,
     .downloadVol = virStorageBackendVolDownloadLocal,
-    .wipeVol = virStorageBackendVolWipeLocal,
+    .wipeVol = virStorageBackendDiskVolWipe,
 };