linux-kernel - Re: [RFC PATCH 0/3] KVM: Introduce "VM bugged" concept

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Message-ID: <100a603f-193c-5a46-d428-cfc0ce0a8fe4@redhat.com>
Date:   Fri, 25 Sep 2020 23:05:48 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Marc Zyngier <maz@...nel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Huacai Chen <chenhc@...ote.com>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        linux-mips@...r.kernel.org, Paul Mackerras <paulus@...abs.org>,
        kvm-ppc@...r.kernel.org,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>
Subject: Re: [RFC PATCH 0/3] KVM: Introduce "VM bugged" concept

On 25/09/20 18:32, Marc Zyngier wrote:
> I'm quite like the idea. However, I wonder whether preventing the
> vcpus from re-entering the guest is enough. When something goes really
> wrong, is it safe to allow the userspace process to terminate normally
> and free the associated memory? And is it still safe to allow new VMs
> to be started?

For something that bad, where e.g. you can't rule out future memory
corruptions via use-after-free bugs or similar, you're probably entering
BUG_ON territory.

Paolo