Re: [PATCH] vhost-vdpa: reject zero-size unmap

On Thu, Jul 16, 2026 at 5:02 AM Weimin Xiong <[email protected]> wrote:
>
> From: xiongweimin <[email protected]>
>
> Reject unmap requests with size == 0 to prevent iova + size - 1
> from underflowing to U64_MAX, which would incorrectly unmap the
> entire IOTLB range.
>
> This fix also covers the error rollback path in vhost_vdpa_va_map:
> when the first VMA lookup fails, map_iova equals iova, resulting
> in a zero-size unmap that would otherwise clear the whole IOTLB.
>
> Signed-off-by: xiongweimin <[email protected]>

Acked-by: Eugenio Pérez <[email protected]>

Thanks!

> ---
>  drivers/vhost/vdpa.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index bb96b1aa5..f49bf1cfb 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -1035,6 +1035,9 @@ static void vhost_vdpa_unmap(struct vhost_vdpa *v,
>         const struct vdpa_config_ops *ops = vdpa->config;
>         u32 asid = iotlb_to_asid(iotlb);
>
> +       if (!size)
> +               return;
> +
>         vhost_vdpa_iotlb_unmap(v, iotlb, iova, iova + size - 1, asid);
>
>         if (ops->set_map) {
> --
> 2.39.3
>