Re: [Xen-devel] [PATCH] Extra check in grant table code for mapping of shared frame

["Jan Beulich" <JBeulich@xxxxxxxx>]

 >>> On 13.09.12 at 17:27, Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx> wrote:
> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -649,9 +649,12 @@ __gnttab_map_grant_ref(
>      }
>      else if ( owner == rd || owner == dom_cow )
>      {
> -        if ( gnttab_host_mapping_get_page_type(op, ld, rd) &&
> -             !get_page_type(pg, PGT_writable_page) )
> -            goto could_not_pin;
> +        if ( gnttab_host_mapping_get_page_type(op, ld, rd) )
> +        {
> +            if ( (owner == dom_cow) ||
> +                 !get_page_type(pg, PGT_writable_page) )
> +                goto could_not_pin;
> +        }
>  
>          nr_gets++;
>          if ( op->flags & GNTMAP_host_map )

Isn't that only half of it, in that the error/unmap paths need to
also consider that get_page_type() wasn't called? There's
quite a few calls to gnttab_host_mapping_get_page_type()/
put_page_type() sequences there.

Jan


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