From 495fe3a78749c39c0e772c4e1a55d6cb8a7e5292 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= Date: Thu, 12 May 2022 19:57:42 +0200 Subject: [PATCH] vhost: Track descriptor chain in private at SVQ MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The device could have access to modify them, and it definitely have access when we implement packed vq. Harden SVQ maintaining a private copy of the descriptor chain. Other fields like buffer addresses are already maintained sepparatedly. Signed-off-by: Eugenio Pérez Message-Id: <20220512175747.142058-2-eperezma@redhat.com> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- hw/virtio/vhost-shadow-virtqueue.c | 12 +++++++----- hw/virtio/vhost-shadow-virtqueue.h | 6 ++++++ 2 files changed, 13 insertions(+), 5 deletions(-) diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c index 1e5cfe2af6..1d6552b0fe 100644 --- a/hw/virtio/vhost-shadow-virtqueue.c +++ b/hw/virtio/vhost-shadow-virtqueue.c @@ -138,6 +138,7 @@ static void vhost_vring_write_descs(VhostShadowVirtqueue *svq, hwaddr *sg, for (n = 0; n < num; n++) { if (more_descs || (n + 1 < num)) { descs[i].flags = flags | cpu_to_le16(VRING_DESC_F_NEXT); + descs[i].next = cpu_to_le16(svq->desc_next[i]); } else { descs[i].flags = flags; } @@ -145,10 +146,10 @@ static void vhost_vring_write_descs(VhostShadowVirtqueue *svq, hwaddr *sg, descs[i].len = cpu_to_le32(iovec[n].iov_len); last = i; - i = cpu_to_le16(descs[i].next); + i = cpu_to_le16(svq->desc_next[i]); } - svq->free_head = le16_to_cpu(descs[last].next); + svq->free_head = le16_to_cpu(svq->desc_next[last]); } static bool vhost_svq_add_split(VhostShadowVirtqueue *svq, @@ -336,7 +337,6 @@ static void vhost_svq_disable_notification(VhostShadowVirtqueue *svq) static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq, uint32_t *len) { - vring_desc_t *descs = svq->vring.desc; const vring_used_t *used = svq->vring.used; vring_used_elem_t used_elem; uint16_t last_used; @@ -365,7 +365,7 @@ static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq, return NULL; } - descs[used_elem.id].next = svq->free_head; + svq->desc_next[used_elem.id] = svq->free_head; svq->free_head = used_elem.id; *len = used_elem.len; @@ -540,8 +540,9 @@ void vhost_svq_start(VhostShadowVirtqueue *svq, VirtIODevice *vdev, svq->vring.used = qemu_memalign(qemu_real_host_page_size(), device_size); memset(svq->vring.used, 0, device_size); svq->ring_id_maps = g_new0(VirtQueueElement *, svq->vring.num); + svq->desc_next = g_new0(uint16_t, svq->vring.num); for (unsigned i = 0; i < svq->vring.num - 1; i++) { - svq->vring.desc[i].next = cpu_to_le16(i + 1); + svq->desc_next[i] = cpu_to_le16(i + 1); } } @@ -574,6 +575,7 @@ void vhost_svq_stop(VhostShadowVirtqueue *svq) virtqueue_detach_element(svq->vq, next_avail_elem, 0); } svq->vq = NULL; + g_free(svq->desc_next); g_free(svq->ring_id_maps); qemu_vfree(svq->vring.desc); qemu_vfree(svq->vring.used); diff --git a/hw/virtio/vhost-shadow-virtqueue.h b/hw/virtio/vhost-shadow-virtqueue.h index e5e24c536d..c132c994e9 100644 --- a/hw/virtio/vhost-shadow-virtqueue.h +++ b/hw/virtio/vhost-shadow-virtqueue.h @@ -53,6 +53,12 @@ typedef struct VhostShadowVirtqueue { /* Next VirtQueue element that guest made available */ VirtQueueElement *next_guest_avail_elem; + /* + * Backup next field for each descriptor so we can recover securely, not + * needing to trust the device access. + */ + uint16_t *desc_next; + /* Next head to expose to the device */ uint16_t shadow_avail_idx;