On Thu, May 5, 2022 at 6:08 PM Xie Yongji <xieyon...@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 <xieyon...@bytedance.com>
> Signed-off-by: Fam Zheng <fam.zh...@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
>
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