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Date: Wed, 25 Oct 2017 11:45:21 +0200
From: David Hildenbrand <>
To: Paolo Bonzini <>, Cornelia Huck <>
Cc:,,, Kees Cook <>,
 Radim Krčmář <>,
 Christoffer Dall <>,
 Marc Zyngier <>,
 Christian Borntraeger <>,
 James Hogan <>, Paul Mackerras <>
Subject: Re: [PATCH 0/2] KVM: fixes for the kernel-hardening tree

On 23.10.2017 16:15, Paolo Bonzini wrote:
> On 23/10/2017 14:39, Cornelia Huck wrote:
>> On Mon, 23 Oct 2017 11:52:51 +0200
>> David Hildenbrand <> wrote:
>>> On 21.10.2017 01:25, Paolo Bonzini wrote:
>>>> Two KVM ioctls (KVM_GET/SET_CPUID2) directly access the cpuid_entries
>>>> field of struct kvm_vcpu_arch.  Therefore, the new usercopy hardening
>>>> work in linux-next, which forbids copies from and to slab objects
>>>> unless they are from kmalloc or explicitly whitelisted, breaks KVM
>>>> completely.
>>>> This series fixes it by adding the two new usercopy arguments
>>>> to kvm_init (more precisely to a new function kvm_init_usercopy,
>>>> while kvm_init passes zeroes as a default).
>>>> There's also another broken ioctl, KVM_XEN_HVM_CONFIG, but it is
>>>> obsolete and not a big deal at all.
>>>> I'm Ccing all submaintainers in case they have something similar
>>>> going on in their kvm_arch and kvm_vcpu_arch structs.  KVM has a
>>>> pretty complex userspace API, so thorough with linux-next is highly
>>>> recommended.  
>>> I assume on s390x, at least
>>> kvm_arch_vcpu_ioctl_get_one_reg() and
>>> kvm_arch_vcpu_ioctl_set_one_reg()
>>> have to be fixed.
>> At a glance, seems like it.
>>> Christian, are you already looking into this?
>> I'm afraid I'm also busy with travel preparation/travel, so I'd be glad
>> for any takers.
> Let's do a generic fix now, so that we don't need to rush the switch to
> explicit whitelisting.

You mean a arch specific fix (allow writes/reads to arch) or even more

Otherwise I can you send a patch to fix these two functions.

> Paolo




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