Re: [Xen-devel] [PATCH] x86: fix hypercall continuation cancellation in XENMAPSPACE_gmfn_range compat wrapper

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 28/11/2012 07:43, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:

> When no continuation was established, there must also not be an attempt
> to cancel it - hypercall_cancel_continuation(), in the non-HVM, non-
> multicall case, adjusts the guest mode return address in a way assuming
> that an earlier call hypercall_create_continuation() took place.
> 
> Once touching this code, also restructure it slightly to improve
> readability and switch to using the more relaxed copy function (copying
> from the same guest memory already validated the virtual address
> range).
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: Keir Fraser <keir@xxxxxxx>

> --- a/xen/arch/x86/x86_64/compat/mm.c
> +++ b/xen/arch/x86/x86_64/compat/mm.c
> @@ -66,21 +66,20 @@ int compat_arch_memory_op(int op, XEN_GU
>          XLAT_add_to_physmap(nat, &cmp);
>          rc = arch_memory_op(op, guest_handle_from_ptr(nat, void));
>  
> -        if ( cmp.space == XENMAPSPACE_gmfn_range )
> +        if ( !rc || cmp.space != XENMAPSPACE_gmfn_range )
> +            break;
> +
> +        XLAT_add_to_physmap(&cmp, nat);
> +        if ( __copy_to_guest(arg, &cmp, 1) )
>          {
> -            if ( rc )
> -            {
> -                XLAT_add_to_physmap(&cmp, nat);
> -                if ( copy_to_guest(arg, &cmp, 1) )
> -                {
> -                    hypercall_cancel_continuation();
> -                    return -EFAULT;
> -                }
> -            }
>              if ( rc == __HYPERVISOR_memory_op )
> -                hypercall_xlat_continuation(NULL, 0x2, nat, arg);
> +                hypercall_cancel_continuation();
> +            return -EFAULT;
>          }
>  
> +        if ( rc == __HYPERVISOR_memory_op )
> +            hypercall_xlat_continuation(NULL, 0x2, nat, arg);
> +
>          break;
>      }
>  
> 
> 
> 
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