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>
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@ -35,13 +35,13 @@ static DECLARE_COMPLETION(have_data);
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static void random_recv_done(struct virtqueue *vq)
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{
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int len;
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unsigned int len;
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/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
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if (!vq->vq_ops->get_buf(vq, &len))
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return;
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data_left = len / sizeof(random_data[0]);
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data_left += len;
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complete(&have_data);
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}
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@ -49,7 +49,7 @@ static void register_buffer(void)
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{
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struct scatterlist sg;
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sg_init_one(&sg, random_data, RANDOM_DATA_SIZE);
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sg_init_one(&sg, random_data+data_left, RANDOM_DATA_SIZE-data_left);
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/* There should always be room for one buffer. */
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if (vq->vq_ops->add_buf(vq, &sg, 0, 1, random_data) != 0)
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BUG();
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@ -59,24 +59,32 @@ static void register_buffer(void)
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/* At least we don't udelay() in a loop like some other drivers. */
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static int virtio_data_present(struct hwrng *rng, int wait)
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{
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if (data_left)
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if (data_left >= sizeof(u32))
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return 1;
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again:
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if (!wait)
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return 0;
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wait_for_completion(&have_data);
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/* Not enough? Re-register. */
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if (unlikely(data_left < sizeof(u32))) {
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register_buffer();
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goto again;
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}
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return 1;
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}
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/* virtio_data_present() must have succeeded before this is called. */
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static int virtio_data_read(struct hwrng *rng, u32 *data)
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{
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BUG_ON(!data_left);
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BUG_ON(data_left < sizeof(u32));
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data_left -= sizeof(u32);
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*data = random_data[data_left / 4];
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*data = random_data[--data_left];
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if (!data_left) {
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if (data_left < sizeof(u32)) {
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init_completion(&have_data);
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register_buffer();
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}
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