>>> On 18.07.18 at 14:30, <andrew.coop...@citrix.com> wrote:
> If valid_xcr0() accepts a new_bv which exceeds xfeature_mask, then something
> is broken with the CPUID policiy derivation or auditing logic. If hardware
> rejects new_bv, then something is broken with Xen's xstate logic.
With what I've said about valid_xcr0() in reply to patch 1, this is
incorrect, and hence both text and first half of the code change
need re-doing. Provided that's what we want in the first place,
but I'd have to see the new version in order to be able to sensibly
judge.
Jan
> In both cases, crash the domain with an obvious error message, to help
> highlight the issues.
>
> Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
> ---
> CC: Jan Beulich <jbeul...@suse.com>
> ---
> xen/arch/x86/xstate.c | 18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c
> index 44b993f..06c94f8 100644
> --- a/xen/arch/x86/xstate.c
> +++ b/xen/arch/x86/xstate.c
> @@ -708,11 +708,27 @@ int handle_xsetbv(u32 index, u64 new_bv)
> if ( index != XCR_XFEATURE_ENABLED_MASK )
> return -EOPNOTSUPP;
>
> - if ( (new_bv & ~xfeature_mask) || !valid_xcr0(curr->domain, new_bv) )
> + if ( !valid_xcr0(curr->domain, new_bv) )
> return -EINVAL;
>
> + if ( new_bv & ~xfeature_mask )
> + {
> + gprintk(XENLOG_ERR,
> + "new_bv %016" PRIx64 " exceeds hardware max %016" PRIx64
> "\n",
> + new_bv, xfeature_mask);
> + domain_crash(curr->domain);
> +
> + return -EINVAL;
> + }
> +
> if ( !set_xcr0(new_bv) )
> + {
> + gprintk(XENLOG_ERR, "new_bv %016" PRIx64 " rejected by hardware\n",
> + new_bv);
> + domain_crash(curr->domain);
> +
> return -EFAULT;
> + }
>
> mask = new_bv & ~curr->arch.xcr0_accum;
> curr->arch.xcr0 = new_bv;
> --
> 2.1.4
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