Re: [PATCH v2 1/2] KVM: s390: Disallow invalid bits in kvm_valid_regs and kvm_dirty_regs

David Hildenbrand
2019-09-04T09:05:25Z

On 04.09.19 10:51, Thomas Huth wrote:
> If unknown bits are set in kvm_valid_regs or kvm_dirty_regs, this
> clearly indicates that something went wrong in the KVM userspace
> application. The x86 variant of KVM already contains a check for
> bad bits, so let's do the same on s390x now, too.
>
> Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
> arch/s390/include/uapi/asm/kvm.h | 6 ++++++
> arch/s390/kvm/kvm-s390.c | 4 ++++
> 2 files changed, 10 insertions(+)
>
> diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
> index 47104e5b47fd..436ec7636927 100644
> --- a/arch/s390/include/uapi/asm/kvm.h
> +++ b/arch/s390/include/uapi/asm/kvm.h
> @@ -231,6 +231,12 @@ struct kvm_guest_debug_arch {
> #define KVM_SYNC_GSCB (1UL << 9)
> #define KVM_SYNC_BPBC (1UL << 10)
> #define KVM_SYNC_ETOKEN (1UL << 11)
> +
> +#define KVM_SYNC_S390_VALID_FIELDS \
> + (KVM_SYNC_PREFIX | KVM_SYNC_GPRS | KVM_SYNC_ACRS | KVM_SYNC_CRS | \
> + KVM_SYNC_ARCH0 | KVM_SYNC_PFAULT | KVM_SYNC_VRS | KVM_SYNC_RICCB | \
> + KVM_SYNC_FPRS | KVM_SYNC_GSCB | KVM_SYNC_BPBC | KVM_SYNC_ETOKEN)
> +

We didn't care about the S390 for the actual flags, why care now?

> /* length and alignment of the sdnx as a power of two */
> #define SDNXC 8
> #define SDNXL (1UL << SDNXC)
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 49d7722229ae..a7d7dedfe527 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -3998,6 +3998,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> if (kvm_run->immediate_exit)
> return -EINTR;
>
> + if (kvm_run->kvm_valid_regs & ~KVM_SYNC_S390_VALID_FIELDS ||
> + kvm_run->kvm_dirty_regs & ~KVM_SYNC_S390_VALID_FIELDS)
> + return -EINVAL;
> +
> vcpu_load(vcpu);
>
> if (guestdbg_exit_pending(vcpu)) {
>

Reviewed-by: David Hildenbrand <david@redhat.com>

--

Thanks,

David / dhildenb