[PATCH v2] vringh: Fix loop descriptors check in the indirect cases

Jason Wang
2022-05-10T07:43:57Z

On Thu, May 5, 2022 at 6:08 PM Xie Yongji <xieyongji at bytedance.com>
wrote:
>
> We should use size of descriptor chain to test loop condition
> in the indirect case. And another statistical count is also introduced
> for indirect descriptors to avoid conflict with the statistical count
> of direct descriptors.
>
> Fixes: f87d0fbb5798 ("vringh: host-side implementation of virtio
rings.")
> Signed-off-by: Xie Yongji <xieyongji at bytedance.com>
> Signed-off-by: Fam Zheng <fam.zheng at bytedance.com>
> ---
>  drivers/vhost/vringh.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
> index 14e2043d7685..eab55accf381 100644
> --- a/drivers/vhost/vringh.c
> +++ b/drivers/vhost/vringh.c
> @@ -292,7 +292,7 @@ __vringh_iov(struct vringh *vrh, u16 i,
>              int (*copy)(const struct vringh *vrh,
>                          void *dst, const void *src, size_t len))
>  {
> -       int err, count = 0, up_next, desc_max;
> +       int err, count = 0, indirect_count = 0, up_next, desc_max;
>         struct vring_desc desc, *descs;
>         struct vringh_range range = { -1ULL, 0 }, slowrange;
>         bool slow = false;
> @@ -349,7 +349,12 @@ __vringh_iov(struct vringh *vrh, u16 i,
>                         continue;
>                 }
>
> -               if (count++ == vrh->vring.num) {
> +               if (up_next == -1)
> +                       count++;
> +               else
> +                       indirect_count++;
> +
> +               if (count > vrh->vring.num || indirect_count >
desc_max) {
>                         vringh_bad("Descriptor loop in %p",
descs);
>                         err = -ELOOP;
>                         goto fail;
> @@ -411,6 +416,7 @@ __vringh_iov(struct vringh *vrh, u16 i,
>                                 i = return_from_indirect(vrh, &up_next,
>                                                          &descs,
&desc_max);
>                                 slow = false;
> +                               indirect_count = 0;

Do we need to reset up_next to -1 here?

Thanks

>                         } else
>                                 break;
>                 }
> --
> 2.20.1
>