linux-kernel - Re: [PATCH v3 22/28] KVM: x86/mmu: Zap defunct roots via asynchronous worker

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CALzav=dzqOp-css8kgqHhCLJnbUrUZt+e_YStCj2HFy0oD+vGg@mail.gmail.com>
Date:   Wed, 2 Mar 2022 10:33:22 -0800
From:   David Matlack <dmatlack@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        David Hildenbrand <david@...hat.com>,
        kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ben Gardon <bgardon@...gle.com>,
        Mingwei Zhang <mizhang@...gle.com>
Subject: Re: [PATCH v3 22/28] KVM: x86/mmu: Zap defunct roots via asynchronous worker

On Wed, Mar 2, 2022 at 9:35 AM Sean Christopherson <seanjc@...gle.com> wrote:
>
> On Wed, Mar 02, 2022, Paolo Bonzini wrote:
> > However, I think we now need a module_get/module_put when creating/destroying
> > a VM; the workers can outlive kvm_vm_release and therefore any reference
> > automatically taken by VFS's fops_get/fops_put.
>
> Haven't read the rest of the patch, but this caught my eye.  We _already_ need
> to handle this scenario.  As you noted, any worker, i.e. anything that takes a
> reference via kvm_get_kvm() without any additional guarantee that the module can't
> be unloaded is suspect. x86 is mostly fine, though kvm_setup_async_pf() is likely
> affected, and other architectures seem to have bugs.
>
> Google has an internal patch that addresses this.  I believe David is going to post
> the fix... David?

This was towards the back of my queue but I can bump it to the front.
I'll have the patches out this week.