Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit b2add016 authored by Laurent Vivier's avatar Laurent Vivier Committed by Greg Kroah-Hartman
Browse files

hwrng: virtio - don't waste entropy 



[ Upstream commit 5c8e933050044d6dd2a000f9a5756ae73cbe7c44 ]

if we don't use all the entropy available in the buffer, keep it
and use it later.

Signed-off-by: default avatarLaurent Vivier <lvivier@redhat.com>
Link: https://lore.kernel.org/r/20211028101111.128049-4-lvivier@redhat.com


Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Stable-dep-of: ac52578d6e8d ("hwrng: virtio - Fix race on data_avail and actual data")
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent eaf91a80

drivers/char/hw_random/virtio-rng.c

+35 −17
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ struct virtrng_info { 
	/* data transfer */

	struct completion have_data;

	unsigned int data_avail;

	unsigned int data_idx;

	/* minimal size returned by rng_buffer_size() */

#if SMP_CACHE_BYTES < 32

	u8 data[32];
@@ -54,6 +55,9 @@ static void random_recv_done(struct virtqueue *vq) 
	if (!virtqueue_get_buf(vi->vq, &vi->data_avail))

		return;



	vi->data_idx = 0;

	vi->busy = false;



	complete(&vi->have_data);

}
@@ -70,6 +74,16 @@ static void register_buffer(struct virtrng_info *vi) 
	virtqueue_kick(vi->vq);

}



static unsigned int copy_data(struct virtrng_info *vi, void *buf,

			      unsigned int size)

{

	size = min_t(unsigned int, size, vi->data_avail);

	memcpy(buf, vi->data + vi->data_idx, size);

	vi->data_idx += size;

	vi->data_avail -= size;

	return size;

}



static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)

{

	int ret;
@@ -80,17 +94,29 @@ static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) 
	if (vi->hwrng_removed)

		return -ENODEV;



	if (!vi->busy) {

		vi->busy = true;

		reinit_completion(&vi->have_data);

		register_buffer(vi);

	read = 0;



	/* copy available data */

	if (vi->data_avail) {

		chunk = copy_data(vi, buf, size);

		size -= chunk;

		read += chunk;

	}



	if (!wait)

		return 0;

		return read;



	read = 0;

	/* We have already copied available entropy,

	 * so either size is 0 or data_avail is 0

	 */

	while (size != 0) {

		/* data_avail is 0 */

		if (!vi->busy) {

			/* no pending request, ask for more */

			vi->busy = true;

			reinit_completion(&vi->have_data);

			register_buffer(vi);

		}

		ret = wait_for_completion_killable(&vi->have_data);

		if (ret < 0)

			return ret;
@@ -100,20 +126,11 @@ static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) 
		if (vi->data_avail == 0)

			return read;



		chunk = min_t(unsigned int, size, vi->data_avail);

		memcpy(buf + read, vi->data, chunk);

		read += chunk;

		chunk = copy_data(vi, buf + read, size);

		size -= chunk;

		vi->data_avail = 0;



		if (size != 0) {

			reinit_completion(&vi->have_data);

			register_buffer(vi);

		}

		read += chunk;

	}



	vi->busy = false;



	return read;

}
@@ -173,6 +190,7 @@ static void remove_common(struct virtio_device *vdev) 


	vi->hwrng_removed = true;

	vi->data_avail = 0;

	vi->data_idx = 0;

	complete(&vi->have_data);

	vdev->config->reset(vdev);

	vi->busy = false;