virtio: handle short buffers in virtio_rng.
If the device fills less than 4 bytes of our random buffer, we'll
BUG_ON. It's nicer to handle the case where it partially fills the
buffer (the protocol doesn't explicitly bad that).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index f2041fe..32216b6 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -35,13 +35,13 @@
static void random_recv_done(struct virtqueue *vq)
{
- int len;
+ unsigned int len;
/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
if (!vq->vq_ops->get_buf(vq, &len))
return;
- data_left = len / sizeof(random_data[0]);
+ data_left += len;
complete(&have_data);
}
@@ -49,7 +49,7 @@
{
struct scatterlist sg;
- sg_init_one(&sg, random_data, RANDOM_DATA_SIZE);
+ sg_init_one(&sg, random_data+data_left, RANDOM_DATA_SIZE-data_left);
/* There should always be room for one buffer. */
if (vq->vq_ops->add_buf(vq, &sg, 0, 1, random_data) != 0)
BUG();
@@ -59,24 +59,32 @@
/* At least we don't udelay() in a loop like some other drivers. */
static int virtio_data_present(struct hwrng *rng, int wait)
{
- if (data_left)
+ if (data_left >= sizeof(u32))
return 1;
+again:
if (!wait)
return 0;
wait_for_completion(&have_data);
+
+ /* Not enough? Re-register. */
+ if (unlikely(data_left < sizeof(u32))) {
+ register_buffer();
+ goto again;
+ }
+
return 1;
}
/* virtio_data_present() must have succeeded before this is called. */
static int virtio_data_read(struct hwrng *rng, u32 *data)
{
- BUG_ON(!data_left);
+ BUG_ON(data_left < sizeof(u32));
+ data_left -= sizeof(u32);
+ *data = random_data[data_left / 4];
- *data = random_data[--data_left];
-
- if (!data_left) {
+ if (data_left < sizeof(u32)) {
init_completion(&have_data);
register_buffer();
}