2 files changed, 16 insertions, 0 deletions

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 2a451b14b3cc..c4419ea1ab07 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -68,6 +68,12 @@ static void add_early_randomness(struct hwrng *rng)
         unsigned char bytes[16];
         int bytes_read;
 
+        /*
+         * Currently only virtio-rng cannot return data during device
+         * probe, and that's handled in virtio-rng.c itself.  If there
+         * are more such devices, this call to rng_get_data can be
+         * made conditional here instead of doing it per-device.
+         */
         bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
         if (bytes_read > 0)
                 add_device_randomness(bytes, bytes_read);
diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index f3e71501de54..e9b15bc18b4d 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -38,6 +38,8 @@ struct virtrng_info {
         int index;
 };
 
+static bool probe_done;
+
 static void random_recv_done(struct virtqueue *vq)
 {
         struct virtrng_info *vi = vq->vdev->priv;
@@ -67,6 +69,13 @@ static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
         int ret;
         struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
 
+        /*
+         * Don't ask host for data till we're setup.  This call can
+         * happen during hwrng_register(), after commit d9e7972619.
+         */
+        if (unlikely(!probe_done))
+                return 0;
+
         if (!vi->busy) {
                 vi->busy = true;
                 init_completion(&vi->have_data);
@@ -137,6 +146,7 @@ static int probe_common(struct virtio_device *vdev)
                 return err;
         }
 
+        probe_done = true;
         return 0;
 }