virtio: order used ring after used index read (2d61ba95) · Commits · 戴 / test

On SMP guests, reads from the ring might bypass used index reads. This causes guest crashes because host writes to used index to signal ring data readiness. Fix this by inserting rmb before used ring reads. Signed-off-by:

Michael S. Tsirkin <mst@redhat.com> Signed-off-by:

Rusty Russell <rusty@rustcorp.com.au> Cc: stable@kernel.org

drivers/virtio/virtio_ring.c

+3 −0

Original line number	Original line	Diff line number	Diff line
	@@ -285,6 +285,9 @@ static void vring_get_buf(struct virtqueue _vq, unsigned int *len)
	return NULL;		return NULL;
	}		}

			/* Only get used array entries after they have been exposed by host. */
			rmb();

	i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;		i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
	*len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;		*len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;

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