linux-kernel - Re: [PATCH 0/2] KVM: fixes for the kernel-hardening tree

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Message-Id: <2a38de15-4378-d766-0f12-0d29ac17b264@de.ibm.com>
Date:   Mon, 23 Oct 2017 13:10:00 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     David Hildenbrand <david@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     kernel-hardening@...ts.openwall.com,
        Kees Cook <keescook@...omium.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Cornelia Huck <cohuck@...hat.com>,
        James Hogan <james.hogan@...tec.com>,
        Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH 0/2] KVM: fixes for the kernel-hardening tree



On 10/23/2017 11:52 AM, 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.
> 
> Christian, are you already looking into this?

Not yet. I am in preparation for travel.

> 
>>
>> Many thanks to Thomas Gleixner for reporting this to me.
>>
>> Paolo
>>
>> Paolo Bonzini (2):
>>   KVM: allow setting a usercopy region in struct kvm_vcpu
>>   KVM: fix KVM_XEN_HVM_CONFIG ioctl
>>
>>  arch/x86/include/asm/kvm_host.h |  3 +++
>>  arch/x86/kvm/svm.c              |  4 ++--
>>  arch/x86/kvm/vmx.c              |  4 ++--
>>  arch/x86/kvm/x86.c              | 17 ++++++++++++++---
>>  include/linux/kvm_host.h        | 13 +++++++++++--
>>  virt/kvm/kvm_main.c             | 13 ++++++++-----
>>  6 files changed, 40 insertions(+), 14 deletions(-)
>>
> 
>