linux-kernel - [PATCH v4 0/5] x86/sev-es: Mitigate some HV attack vectors

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Date:   Wed, 28 Oct 2020 17:46:54 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     x86@...nel.org
Cc:     Joerg Roedel <joro@...tes.org>, Joerg Roedel <jroedel@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Martin Radev <martin.b.radev@...il.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 0/5] x86/sev-es: Mitigate some HV attack vectors

From: Joerg Roedel <jroedel@...e.de>

Hi,

here are some enhancements to the SEV(-ES) code in the Linux kernel to
self-protect it against some newly detected hypervisor attacks. There are 3
attacks addressed here:

	1) Hypervisor does not present the SEV-enabled bit via CPUID

	2) The Hypervisor presents the wrong C-bit position via CPUID

	3) An encrypted RAM page is mapped as MMIO in the nested
	   page-table, causing #VC exceptions and possible leak of the
	   data to the hypervisor or data/code injection from the
	   Hypervisor.

The attacks are described in more detail in this paper:

	https://arxiv.org/abs/2010.07094

Please review.

Thanks,

        Joerg

Changes to v3:

	- Addressed Boris' review comments

Changes to v2:

	- Use %r8/%r9 to modify %cr4 in sev_verify_cbit()
	  and return the new page-table pointer in that function.

Changes to v1:

	- Disable CR4.PGE during C-bit test

	- Do not safe/restore caller-safed registers in
	  set_sev_encryption_mask()

Joerg Roedel (5):
  x86/boot/compressed/64: Introduce sev_status
  x86/boot/compressed/64: Add CPUID sanity check to early #VC handler
  x86/boot/compressed/64: Check SEV encryption in 64-bit boot-path
  x86/head/64: Check SEV encryption before switching to kernel
    page-table
  x86/sev-es: Do not support MMIO to/from encrypted memory

 arch/x86/boot/compressed/ident_map_64.c |  1 +
 arch/x86/boot/compressed/mem_encrypt.S  | 20 +++++-
 arch/x86/boot/compressed/misc.h         |  2 +
 arch/x86/kernel/head_64.S               | 16 +++++
 arch/x86/kernel/sev-es-shared.c         | 26 +++++++
 arch/x86/kernel/sev-es.c                | 20 ++++--
 arch/x86/kernel/sev_verify_cbit.S       | 90 +++++++++++++++++++++++++
 arch/x86/mm/mem_encrypt.c               |  1 +
 8 files changed, 168 insertions(+), 8 deletions(-)
 create mode 100644 arch/x86/kernel/sev_verify_cbit.S

-- 
2.28.0