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

[JÃrgen GroÃ]

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