linux-kernel - Re: [PATCH v9 42/43] virt: sevguest: Add support to derive key

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Message-ID: <YgJLJJiosIOHLWYz@zn.tnic>
Date:   Tue, 8 Feb 2022 11:51:16 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Dov Murik <dovmurik@...ux.ibm.com>
Cc:     Brijesh Singh <brijesh.singh@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        brijesh.ksingh@...il.com, tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        Liam Merwick <liam.merwick@...cle.com>
Subject: Re: [PATCH v9 42/43] virt: sevguest: Add support to derive key

On Tue, Feb 08, 2022 at 09:56:52AM +0200, Dov Murik wrote:
> Just to be clear, I didn't mean necessarily "leak the key to the
> untrusted host" (even if a page is converted back from private to
> shared, it is encrypted, so host can't read its contents).  But even
> *inside* the guest, when dealing with sensitive data like keys, we
> should minimize the amount of copies that float around (I assume this is
> the reason for most of the uses of memzero_explicit() in the kernel).

I don't know about Brijesh but I understood you exactly as you mean it.
And yap, I agree we should always clear such sensitive buffers.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette