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vhost: Track descriptor chain in private at SVQ 

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 <eperezma@redhat.com>
Message-Id: <20220512175747.142058-2-eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Eugenio Pérez 2022-05-12 19:57:42 +02:00 committed by Michael S. Tsirkin
parent aa69abe6e8
commit 495fe3a787
2 changed files with 13 additions and 5 deletions
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12
hw/virtio/vhost-shadow-virtqueue.c
View File

@ -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);

6
hw/virtio/vhost-shadow-virtqueue.h
View File

@ -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;