linux-kernel - Re: [PATCHv5 03/19] mm/ksm: Do not merge pages with different KeyIDs

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]

Message-ID: <20180719073240.autom4g4cdm3jgd6@kshutemo-mobl1>
Date:   Thu, 19 Jul 2018 10:32:40 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv5 03/19] mm/ksm: Do not merge pages with different KeyIDs

On Wed, Jul 18, 2018 at 10:38:27AM -0700, Dave Hansen wrote:
> On 07/17/2018 04:20 AM, Kirill A. Shutemov wrote:
> > Pages encrypted with different encryption keys are not allowed to be
> > merged by KSM. Otherwise it would cross security boundary.
> 
> Let's say I'm using plain AES (not AES-XTS).  I use the same key in two
> keyid slots.  I map a page with the first keyid and another with the
> other keyid.
> 
> Won't they have the same cipertext?  Why shouldn't we KSM them?

We compare plain text, not ciphertext. And for good reason.

Comparing ciphertext would only make KSM successful for AES-ECB that
doesn't dependent on physical address of the page.

MKTME only supports AES-XTS (no plans to support AES-ECB). It effectively
disables KSM if we go with comparing ciphertext.

-- 
 Kirill A. Shutemov