On Tue, May 10, 2022 at 3:44 PM Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
> On Thu, May 5, 2022 at 6:08 PM Xie Yongji <xieyongji@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
> > Signed-off-by: Fam Zheng <fam.zheng@xxxxxxxxxxxxx>
> > ---
> > 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?
>
It will be reset to -1 in return_from_indirect().
Thanks,
Yongji
