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

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

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.


> +                                   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?


-boris


> +
>       return 0;
>  
>

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