Re: [PATCH v3 10/23] vhost: vhost_virtqueue_start(): fix failure path

[Raphael Norwitz <raphael.s.norwitz@gmail.com>]

Reviewed-by: Raphael Norwitz <raphael.s.norwitz@gmail.com>

On Wed, Oct 15, 2025 at 11:07 AM Vladimir Sementsov-Ogievskiy
<vsementsov@yandex-team.ru> wrote:
>
> We miss call to unmap in cases when vhost_memory_map() returns
> lenght less than requested (still we consider such cases as an
> error). Let's fix it in vhost_memory_map().
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> Reviewed-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
> ---
>  hw/virtio/vhost.c | 35 ++++++++++++++++++++++-------------
>  1 file changed, 22 insertions(+), 13 deletions(-)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 94efa409aa..be2245cc7e 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -453,11 +453,20 @@ static inline void vhost_dev_log_resize(struct vhost_dev *dev, uint64_t size)
>  }
>
>  static void *vhost_memory_map(struct vhost_dev *dev, hwaddr addr,
> -                              hwaddr *plen, bool is_write)
> +                              hwaddr len, bool is_write)
>  {
>      if (!vhost_dev_has_iommu(dev)) {
> -        return address_space_map(dev->vdev->dma_as, addr, plen, is_write,
> -                                 MEMTXATTRS_UNSPECIFIED);
> +        hwaddr mapped_len = len;
> +        void *res = address_space_map(dev->vdev->dma_as, addr, &mapped_len,
> +                                      is_write, MEMTXATTRS_UNSPECIFIED);
> +        if (!res) {
> +            return NULL;
> +        }
> +        if (len != mapped_len) {
> +            address_space_unmap(dev->vdev->dma_as, res, mapped_len, 0, 0);
> +            return NULL;
> +        }
> +        return res;
>      } else {
>          return (void *)(uintptr_t)addr;
>      }
> @@ -1261,7 +1270,7 @@ int vhost_virtqueue_start(struct vhost_dev *dev,
>      BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
>      VirtioBusState *vbus = VIRTIO_BUS(qbus);
>      VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(vbus);
> -    hwaddr s, l, a;
> +    hwaddr l, a;
>      int r;
>      int vhost_vq_index = dev->vhost_ops->vhost_get_vq_index(dev, idx);
>      struct vhost_vring_file file = {
> @@ -1301,24 +1310,24 @@ int vhost_virtqueue_start(struct vhost_dev *dev,
>          }
>      }
>
> -    vq->desc_size = s = l = virtio_queue_get_desc_size(vdev, idx);
> +    vq->desc_size = l = virtio_queue_get_desc_size(vdev, idx);
>      vq->desc_phys = a;
> -    vq->desc = vhost_memory_map(dev, a, &l, false);
> -    if (!vq->desc || l != s) {
> +    vq->desc = vhost_memory_map(dev, a, l, false);
> +    if (!vq->desc) {
>          r = -ENOMEM;
>          goto fail_alloc_desc;
>      }
> -    vq->avail_size = s = l = virtio_queue_get_avail_size(vdev, idx);
> +    vq->avail_size = l = virtio_queue_get_avail_size(vdev, idx);
>      vq->avail_phys = a = virtio_queue_get_avail_addr(vdev, idx);
> -    vq->avail = vhost_memory_map(dev, a, &l, false);
> -    if (!vq->avail || l != s) {
> +    vq->avail = vhost_memory_map(dev, a, l, false);
> +    if (!vq->avail) {
>          r = -ENOMEM;
>          goto fail_alloc_avail;
>      }
> -    vq->used_size = s = l = virtio_queue_get_used_size(vdev, idx);
> +    vq->used_size = l = virtio_queue_get_used_size(vdev, idx);
>      vq->used_phys = a = virtio_queue_get_used_addr(vdev, idx);
> -    vq->used = vhost_memory_map(dev, a, &l, true);
> -    if (!vq->used || l != s) {
> +    vq->used = vhost_memory_map(dev, a, l, true);
> +    if (!vq->used) {
>          r = -ENOMEM;
>          goto fail_alloc_used;
>      }
> --
> 2.48.1
>
>