Index: sys/dev/hyperv/vmbus/vmbus.c
===================================================================
--- sys/dev/hyperv/vmbus/vmbus.c        (revision 318252)
+++ sys/dev/hyperv/vmbus/vmbus.c        (working copy)
@@ -1307,11 +1307,14 @@
 {
        struct sysctl_oid_list *child;
        struct sysctl_ctx_list *ctx;
+        struct root_hold_token *root_mount_token = NULL;
        int ret;

        if (sc->vmbus_flags & VMBUS_FLAG_ATTACHED)
                return (0);

+       root_mount_token = root_mount_hold("vmbus");
+
 #ifdef NEW_PCIB
        vmbus_get_mmio_res(sc->vmbus_dev);
 #endif
@@ -1383,9 +1386,11 @@
            CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, sc, 0,
            vmbus_sysctl_version, "A", "vmbus version");

+       root_mount_rel(root_mount_token);
        return (ret);

 cleanup:
+       root_mount_rel(root_mount_token);
        vmbus_scan_teardown(sc);
        vmbus_intr_teardown(sc);
        vmbus_dma_free(sc);