Re: [PATCH 1/2] xen/xenbus: avoid large structs and arrays on the stack

[Jürgen Groß <jgross@xxxxxxxx>]

On 11.05.20 20:01, Boris Ostrovsky wrote:
> On 5/11/20 3:31 AM, Juergen Gross wrote:
> >   
> >   static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
>
> I wonder whether we can drop valloc/vfree from xenbus_ring_ops' names.
I can do that.

> > +                                     struct map_ring_valloc *info,
> >                                       grant_ref_t *gnt_ref,
> >                                       unsigned int nr_grefs,
> >                                       void **vaddr)
> >   {
> > -       struct xenbus_map_node *node;
> > +       struct xenbus_map_node *node = info->node;
> >         int err;
> >         void *addr;
> >         bool leaked = false;
> > -       struct map_ring_valloc_hvm info = {
> > -               .idx = 0,
> > -       };
> >         unsigned int nr_pages = XENBUS_PAGES(nr_grefs);
> >   
> > -	if (nr_grefs > XENBUS_MAX_RING_GRANTS)
> > -               return -EINVAL;
> > -
> > -       *vaddr = NULL;
> > -
> > -       node = kzalloc(sizeof(*node), GFP_KERNEL);
> > -       if (!node)
> > -               return -ENOMEM;
> > -
> >         err = alloc_xenballooned_pages(nr_pages, node->hvm.pages);
> >         if (err)
> >                 goto out_err;
> >   
> >   	gnttab_foreach_grant(node->hvm.pages, nr_grefs,
> >                              xenbus_map_ring_setup_grant_hvm,
> > -                            &info);
> > +                            info);
> >   
> >   	err = __xenbus_map_ring(dev, gnt_ref, nr_grefs, node->handles,
> > -                               info.phys_addrs, GNTMAP_host_map, &leaked);
> > +                               info, GNTMAP_host_map, &leaked);
> >         node->nr_handles = nr_grefs;
> >   
> >   	if (err)
> > @@ -641,11 +654,13 @@ static int xenbus_map_ring_valloc_hvm(struct 
> > xenbus_device *dev,
> >         spin_unlock(&xenbus_valloc_lock);
> >   
> >   	*vaddr = addr;
> > +       info->node = NULL;
>
> Is this so that xenbus_map_ring_valloc() doesn't free it accidentally?
Yes.


Juergen