Re: [PATCH v4 1/2] x86/hvm: fix segment validation

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 22/11/13 14:20, Jan Beulich wrote:
> Also Coverity CID 1055180.
>     
> Reported-by: David Binderman <dcb314@hotmail.com>
> Signed-off-by: Tim Deegan <tim@xen.org>
>
> Use _SEGMENT_* instead of plain numbers and adjust a comment.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

>
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -2280,7 +2280,7 @@ static int hvm_load_segment_selector(
>              if ( !(desc.b & (1u<<11)) )
>                  goto unmap_and_fail;
>              /* Non-conforming segment: check DPL against RPL. */
> -            if ( ((desc.b & (6u<<9)) != 6) && (dpl != rpl) )
> +            if ( !(desc.b & _SEGMENT_EC) && (dpl != rpl) )
>                  goto unmap_and_fail;
>              break;
>          case x86_seg_ss:
> @@ -2299,8 +2299,13 @@ static int hvm_load_segment_selector(
>              /* Readable code or data segment? */
>              if ( (desc.b & (5u<<9)) == (4u<<9) )
>                  goto unmap_and_fail;
> -            /* Non-conforming segment: check DPL against RPL and CPL. */
> -            if ( ((desc.b & (6u<<9)) != 6) && ((dpl < cpl) || (dpl < rpl)) )
> +            /*
> +             * Data or non-conforming code segment:
> +             * check DPL against RPL and CPL.
> +             */
> +            if ( ((desc.b & (_SEGMENT_EC|_SEGMENT_CODE)) !=
> +                  (_SEGMENT_EC|_SEGMENT_CODE))
> +                 && ((dpl < cpl) || (dpl < rpl)) )
>                  goto unmap_and_fail;
>              break;
>          }
>
>
>