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Subject: Re: [PATCH v2 1/2] KVM: s390: Disallow invalid bits in kvm_valid_regs
 and kvm_dirty_regs
To:     Thomas Huth <thuth@redhat.com>, kvm@vger.kernel.org,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>
Cc:     Cornelia Huck <cohuck@redhat.com>, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20190904085200.29021-1-thuth@redhat.com>
 <20190904085200.29021-2-thuth@redhat.com>
From:   David Hildenbrand <david@redhat.com>
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Organization: Red Hat GmbH
Message-ID: <b34a237f-77a5-2939-624d-0240451f2976@redhat.com>
Date:   Wed, 4 Sep 2019 11:05:17 +0200
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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