diff --git a/arch/um/drivers/random.c b/arch/um/drivers/random.c
index 4949044773ba78b93797d43701ab751b0a1bce23..6eabb7022a2d6c1c45a7f62327a50c4b1c88d734 100644
--- a/arch/um/drivers/random.c
+++ b/arch/um/drivers/random.c
@@ -7,6 +7,7 @@
  * of the GNU General Public License, incorporated herein by reference.
  */
 #include <linux/sched.h>
+#include <linux/smp_lock.h>
 #include <linux/module.h>
 #include <linux/fs.h>
 #include <linux/interrupt.h>
@@ -33,6 +34,8 @@ static DECLARE_WAIT_QUEUE_HEAD(host_read_wait);
 
 static int rng_dev_open (struct inode *inode, struct file *filp)
 {
+	cycle_kernel_lock();
+
 	/* enforce read-only access to this chrdev */
 	if ((filp->f_mode & FMODE_READ) == 0)
 		return -EINVAL;