diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index da992a3..1bcd208 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -33,6 +33,7 @@
 #include "linux/mm.h"
 #include "linux/slab.h"
 #include "linux/vmalloc.h"
+#include "linux/smp_lock.h"
 #include "linux/blkpg.h"
 #include "linux/genhd.h"
 #include "linux/spinlock.h"
@@ -1098,6 +1099,7 @@
 	struct ubd *ubd_dev = disk->private_data;
 	int err = 0;
 
+	lock_kernel();
 	if(ubd_dev->count == 0){
 		err = ubd_open_dev(ubd_dev);
 		if(err){
@@ -1115,7 +1117,8 @@
 	        if(--ubd_dev->count == 0) ubd_close_dev(ubd_dev);
 	        err = -EROFS;
 	}*/
- out:
+out:
+	unlock_kernel();
 	return err;
 }
 
@@ -1123,8 +1126,10 @@
 {
 	struct ubd *ubd_dev = disk->private_data;
 
+	lock_kernel();
 	if(--ubd_dev->count == 0)
 		ubd_close_dev(ubd_dev);
+	unlock_kernel();
 	return 0;
 }