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From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Dave Hansen <dave.hansen@intel.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Ingo Molnar <mingo@redhat.com>,
	x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Kai Huang <kai.huang@linux.intel.com>,
	Jacob Pan <jacob.jun.pan@linux.intel.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCHv5 02/19] mm: Do not use zero page in encrypted pages
Date: Fri, 20 Jul 2018 15:16:16 +0300	[thread overview]
Message-ID: <20180720121616.oqzoj6dgm6iws5xz@kshutemo-mobl1> (raw)
In-Reply-To: <d50d89d2-f93b-4b4b-bf8d-2f53cedebcd1@intel.com>

On Thu, Jul 19, 2018 at 06:58:14AM -0700, Dave Hansen wrote:
> On 07/19/2018 12:16 AM, Kirill A. Shutemov wrote:
> > On Wed, Jul 18, 2018 at 10:36:24AM -0700, Dave Hansen wrote:
> >> On 07/17/2018 04:20 AM, Kirill A. Shutemov wrote:
> >>> Zero page is not encrypted and putting it into encrypted VMA produces
> >>> garbage.
> >>>
> >>> We can map zero page with KeyID-0 into an encrypted VMA, but this would
> >>> be violation security boundary between encryption domains.
> >> Why?  How is it a violation?
> >>
> >> It only matters if they write secrets.  They can't write secrets to the
> >> zero page.
> > I believe usage of zero page is wrong here. It would indirectly reveal
> > content of supposedly encrypted memory region.
> > 
> > I can see argument why it should be okay and I don't have very strong
> > opinion on this.
> 
> I think we should make the zero page work.  If folks are
> security-sensitive, they need to write to guarantee it isn't being
> shared.  That's a pretty low bar.
> 
> I'm struggling to think of a case where an attacker has access to the
> encrypted data, the virt->phys mapping, *and* can glean something
> valuable from the presence of the zero page.

Okay.

> Please spend some time and focus on your patch descriptions.  Use facts
> that are backed up and are *precise* or tell the story of how your patch
> was developed.  In this case, citing the "security boundary" is not
> precise enough without explaining what the boundary is and how it is
> violated.

Fair enough. I'll go though all commit messages once again. Sorry.

-- 
 Kirill A. Shutemov

  reply	other threads:[~2018-07-20 12:16 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-17 11:20 [PATCHv5 00/19] MKTME enabling Kirill A. Shutemov
2018-07-17 11:20 ` [PATCHv5 01/19] mm: Do no merge VMAs with different encryption KeyIDs Kirill A. Shutemov
2018-07-17 11:20 ` [PATCHv5 02/19] mm: Do not use zero page in encrypted pages Kirill A. Shutemov
2018-07-18 17:36   ` Dave Hansen
2018-07-19  7:16     ` Kirill A. Shutemov
2018-07-19 13:58       ` Dave Hansen
2018-07-20 12:16         ` Kirill A. Shutemov [this message]
2018-07-17 11:20 ` [PATCHv5 03/19] mm/ksm: Do not merge pages with different KeyIDs Kirill A. Shutemov
2018-07-18 17:38   ` Dave Hansen
2018-07-19  7:32     ` Kirill A. Shutemov
2018-07-19 14:02       ` Dave Hansen
2018-07-20 12:23         ` Kirill A. Shutemov
2018-07-17 11:20 ` [PATCHv5 04/19] mm/page_alloc: Unify alloc_hugepage_vma() Kirill A. Shutemov
2018-07-18 17:43   ` Dave Hansen
2018-07-17 11:20 ` [PATCHv5 05/19] mm/page_alloc: Handle allocation for encrypted memory Kirill A. Shutemov
2018-07-18 23:03   ` Dave Hansen
2018-07-19  8:27     ` Kirill A. Shutemov
2018-07-19 14:05       ` Dave Hansen
2018-07-20 12:25         ` Kirill A. Shutemov
2018-07-26 14:25       ` Michal Hocko
2018-07-17 11:20 ` [PATCHv5 06/19] mm/khugepaged: Handle encrypted pages Kirill A. Shutemov
2018-07-18 23:11   ` Dave Hansen
2018-07-19  8:59     ` Kirill A. Shutemov
2018-07-19 14:13       ` Dave Hansen
2018-07-20 12:29         ` Kirill A. Shutemov
2018-07-17 11:20 ` [PATCHv5 07/19] x86/mm: Mask out KeyID bits from page table entry pfn Kirill A. Shutemov
2018-07-18 23:13   ` Dave Hansen
2018-07-19  9:54     ` Kirill A. Shutemov
2018-07-19 14:19       ` Dave Hansen
2018-07-20 12:31         ` Kirill A. Shutemov
2018-07-17 11:20 ` [PATCHv5 08/19] x86/mm: Introduce variables to store number, shift and mask of KeyIDs Kirill A. Shutemov
2018-07-18 23:19   ` Dave Hansen
2018-07-19 10:21     ` Kirill A. Shutemov
2018-07-19 12:37       ` Thomas Gleixner
2018-07-19 13:12         ` Kirill A. Shutemov
2018-07-19 13:18           ` Thomas Gleixner
2018-07-19 13:23             ` Kirill A. Shutemov
2018-07-19 13:40               ` Thomas Gleixner
2018-07-20 12:34                 ` Kirill A. Shutemov
2018-07-20 13:17                   ` Thomas Gleixner
2018-07-20 13:40                     ` Kirill A. Shutemov
2018-07-19 14:23       ` Dave Hansen
2018-07-20 12:34         ` Kirill A. Shutemov
2018-07-31  0:08   ` Kai Huang
2018-07-17 11:20 ` [PATCHv5 09/19] x86/mm: Preserve KeyID on pte_modify() and pgprot_modify() Kirill A. Shutemov
2018-07-18 23:30   ` Dave Hansen
2018-07-20 12:42     ` Kirill A. Shutemov
2018-07-17 11:20 ` [PATCHv5 10/19] x86/mm: Implement page_keyid() using page_ext Kirill A. Shutemov
2018-07-18 23:38   ` Dave Hansen
2018-07-23  9:45     ` Kirill A. Shutemov
2018-07-23 17:22       ` Alison Schofield
2018-07-17 11:20 ` [PATCHv5 11/19] x86/mm: Implement vma_keyid() Kirill A. Shutemov
2018-07-18 23:40   ` Dave Hansen
2018-07-23  9:47     ` Kirill A. Shutemov
2018-07-17 11:20 ` [PATCHv5 12/19] x86/mm: Implement prep_encrypted_page() and arch_free_page() Kirill A. Shutemov
2018-07-18 23:53   ` Dave Hansen
2018-07-23  9:50     ` Kirill A. Shutemov
2018-07-17 11:20 ` [PATCHv5 13/19] x86/mm: Rename CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING Kirill A. Shutemov
2018-07-17 11:20 ` [PATCHv5 14/19] x86/mm: Allow to disable MKTME after enumeration Kirill A. Shutemov
2018-07-17 11:20 ` [PATCHv5 15/19] x86/mm: Detect MKTME early Kirill A. Shutemov
2018-07-17 11:20 ` [PATCHv5 16/19] x86/mm: Calculate direct mapping size Kirill A. Shutemov
2018-07-17 11:20 ` [PATCHv5 17/19] x86/mm: Implement sync_direct_mapping() Kirill A. Shutemov
2018-07-19  0:01   ` Dave Hansen
2018-07-23 10:04     ` Kirill A. Shutemov
2018-07-23 12:25       ` Dave Hansen
2018-07-17 11:20 ` [PATCHv5 18/19] x86/mm: Handle encrypted memory in page_to_virt() and __pa() Kirill A. Shutemov
2018-07-18 22:21   ` Thomas Gleixner
2018-07-23 10:12     ` Kirill A. Shutemov
2018-07-26 17:26       ` Dave Hansen
2018-07-27 13:49         ` Kirill A. Shutemov
2018-07-17 11:20 ` [PATCHv5 19/19] x86: Introduce CONFIG_X86_INTEL_MKTME Kirill A. Shutemov
2018-08-15  7:48   ` Pavel Machek
2018-08-17  9:24     ` Kirill A. Shutemov

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