linux-kernel - Re: [tip: x86/seves] x86/kvm: Add KVM-specific VMMCALL handling under SEV-ES

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] [day] [month] [year] [list]

Message-ID: <20201030102314.GP22179@suse.de>
Date:   Fri, 30 Oct 2020 11:23:14 +0100
From:   Joerg Roedel <jroedel@...e.de>
To:     Erdem Aktas <erdemaktas@...gle.com>
Cc:     linux-kernel@...r.kernel.org,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        linux-tip-commits@...r.kernel.org, Borislav Petkov <bp@...e.de>,
        x86 <x86@...nel.org>
Subject: Re: [tip: x86/seves] x86/kvm: Add KVM-specific VMMCALL handling
 under SEV-ES

On Wed, Oct 28, 2020 at 11:03:05AM -0700, Erdem Aktas wrote:
> I might be missing something here but I think what you say is only
> correct for the kvm_hypercall4 cases. All other functions use a
> smaller number of registers. #VC blindly assumes that all those
> registers are used in the vmcall and exposes them.

Right, I think we should fix that in the guest and zero out the unused
registers. VMMCALL can come from userspace after all, and the #VC
handler does not look at the hypercall numbers.

Further, on the host side KVM will unconditionally read out all 4
registers too, which requires us to set them valid in the GHCB.

Regards,

	Joerg