linux-kernel - Re: [PATCH] KVM: VMX: Forbid userspace MSR filters for x2APIC

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:   Tue, 20 Oct 2020 12:34:46 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Alexander Graf <graf@...zon.de>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        Aaron Lewis <aaronlewis@...gle.com>,
        Peter Xu <peterx@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH] KVM: VMX: Forbid userspace MSR filters for x2APIC

On 20/10/20 11:48, Alexander Graf wrote:
> 
>     count: 1,
>     default_allow: false,
>     ranges: [
>         {
>             flags: KVM_MSR_FILTER_READ,
>             nmsrs: 1,
>             base: MSR_EFER,
>             bitmap: { 1 },
>         },
>     ],
> }
> 
> That filter would set all x2apic registers to "deny", but would not be
> caught by the code above. Conversely, a range that explicitly allows
> x2apic ranges with default_allow=0 would be rejected by this patch.

Yes, but the idea is that x2apic registers are always allowed, even
overriding default_allow, and therefore it makes no sense to have them
in a range.  The patch is only making things fail early for userspace,
the policy is defined by Sean's patch.

Paolo