Re: [PATCH v4 1/4] KVM: s390: vsie: Fix STFLE interpretive execution identification

Janosch Frank
2023-12-20T10:40:35Z

On 12/19/23 15:08, Nina Schoetterl-Glausch wrote:
> STFLE can be interpretively executed.
> This occurs when the facility list designation is unequal to zero.
> Perform the check before applying the address mask instead of after.
>
> Fixes: 66b630d5b7f2 ("KVM: s390: vsie: support STFLE interpretation")
> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Acked-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>

Reviewed-by: Janosch Frank <frankja@linux.ibm.com>

> ---
> arch/s390/kvm/vsie.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
> index 8207a892bbe2..35937911724e 100644
> --- a/arch/s390/kvm/vsie.c
> +++ b/arch/s390/kvm/vsie.c
> @@ -984,10 +984,15 @@ static void retry_vsie_icpt(struct vsie_page *vsie_page)
> static int handle_stfle(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> {
> struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
> - __u32 fac = READ_ONCE(vsie_page->scb_o->fac) & 0x7ffffff8U;
> + __u32 fac = READ_ONCE(vsie_page->scb_o->fac);
>
> if (fac && test_kvm_facility(vcpu->kvm, 7)) {
> retry_vsie_icpt(vsie_page);
> + /*
> + * The facility list origin (FLO) is in bits 1 - 28 of the FLD
> + * so we need to mask here before reading.
> + */
> + fac = fac & 0x7ffffff8U;
> if (read_guest_real(vcpu, fac, &vsie_page->fac,
> sizeof(vsie_page->fac)))
> return set_validity_icpt(scb_s, 0x1090U);