Re: [Xen-devel] [PATCH] x86/mmuext: don't allow copying/clearing non-RAM pages

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 21/06/17 11:10, Jan Beulich wrote:
> The two operations really aren't meant for anything else.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, however...

>
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -3229,6 +3229,7 @@ long do_mmuext_op(
>          switch ( op.cmd )
>          {
>              struct page_info *page;
> +            p2m_type_t p2mt;
>  
>          case MMUEXT_PIN_L1_TABLE:
>              type = PGT_l1_page_table;
> @@ -3528,7 +3529,12 @@ long do_mmuext_op(
>          }
>  
>          case MMUEXT_CLEAR_PAGE:
> -            page = get_page_from_gfn(pg_owner, op.arg1.mfn, NULL, P2M_ALLOC);
> +            page = get_page_from_gfn(pg_owner, op.arg1.mfn, &p2mt, 
> P2M_ALLOC);
> +            if ( unlikely(p2mt != p2m_ram_rw) && page )

... it would seem more natural to have the null pointer check before the
p2mt check.

~Andrew

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