Re: [Xen-devel] [PATCH 17/20] arch/x86: use XSM hooks for get_pg_owner access checks

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.09.12 at 21:49, Daniel De Graaf <dgdegra@xxxxxxxxxxxxx> wrote:
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -2882,11 +2882,6 @@ static struct domain *get_pg_owner(domid_t domid)
>          pg_owner = rcu_lock_domain(dom_io);
>          break;
>      case DOMID_XEN:
> -        if ( !IS_PRIV(curr) )
> -        {
> -            MEM_LOG("Cannot set foreign dom");
> -            break;
> -        }
>          pg_owner = rcu_lock_domain(dom_xen);
>          break;
>      default:
> @@ -2895,12 +2890,6 @@ static struct domain *get_pg_owner(domid_t domid)
>              MEM_LOG("Unknown domain '%u'", domid);
>              break;
>          }
> -        if ( !IS_PRIV_FOR(curr, pg_owner) )
> -        {
> -            MEM_LOG("Cannot set foreign dom");
> -            rcu_unlock_domain(pg_owner);
> -            pg_owner = NULL;
> -        }
>          break;
>      }
>  
> @@ -3008,6 +2997,13 @@ long do_mmuext_op(
>          goto out;
>      }
>  
> +    rc = xsm_mmuext_op(d, pg_owner);
> +    if ( rc )
> +    {
> +        rcu_unlock_domain(pg_owner);
> +        goto out;
> +    }
> +

While this part is fine, ...

>      for ( i = 0; i < count; i++ )
>      {
>          if ( hypercall_preempt_check() )
> @@ -3483,11 +3479,6 @@ long do_mmu_update(
>              rc = -EINVAL;
>              goto out;
>          }
> -        if ( !IS_PRIV_FOR(d, pt_owner) )
> -        {
> -            rc = -ESRCH;
> -            goto out;
> -        }

... this one isn't (at least in conjunction with them all becoming
indirect calls unconditionally) - you replace a single validation per
set of requests with one validation per request.

Jan


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