patches/kernel/0240-x86-cpu-x86-pti-Do-not-enable-PTI-on-AMD-processors.patch

   1 From 309461b2f634fc18271468b4396551ddf6a1dba8 Mon Sep 17 00:00:00 2001
   2 From: Tom Lendacky <thomas.lendacky@amd.com>
   3 Date: Tue, 26 Dec 2017 23:43:54 -0600
   4 Subject: [PATCH 240/242] x86/cpu, x86/pti: Do not enable PTI on AMD processors
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 CVE-2017-5754
  10
  11 AMD processors are not subject to the types of attacks that the kernel
  12 page table isolation feature protects against.  The AMD microarchitecture
  13 does not allow memory references, including speculative references, that
  14 access higher privileged data when running in a lesser privileged mode
  15 when that access would result in a page fault.
  16
  17 Disable page table isolation by default on AMD processors by not setting
  18 the X86_BUG_CPU_INSECURE feature, which controls whether X86_FEATURE_PTI
  19 is set.
  20
  21 Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
  22 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  23 Reviewed-by: Borislav Petkov <bp@suse.de>
  24 Cc: Dave Hansen <dave.hansen@linux.intel.com>
  25 Cc: Andy Lutomirski <luto@kernel.org>
  26 Cc: stable@vger.kernel.org
  27 Link: https://lkml.kernel.org/r/20171227054354.20369.94587.stgit@tlendack-t1.amdoffice.net
  28
  29 (cherry picked from commit 694d99d40972f12e59a3696effee8a376b79d7c8)
  30 Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
  31 (cherry picked from commit 9d334f48f017b9c6457c6ba321e5a53a1cc6a5c7)
  32 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  33 ---
  34  arch/x86/kernel/cpu/common.c | 4 ++--
  35  1 file changed, 2 insertions(+), 2 deletions(-)
  36
  37 diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
  38 index 99f37d1636ff..1854dd8071a6 100644
  39 --- a/arch/x86/kernel/cpu/common.c
  40 +++ b/arch/x86/kernel/cpu/common.c
  41 @@ -899,8 +899,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
  42
  43         setup_force_cpu_cap(X86_FEATURE_ALWAYS);
  44
  45 -       /* Assume for now that ALL x86 CPUs are insecure */
  46 -       setup_force_cpu_bug(X86_BUG_CPU_INSECURE);
  47 +       if (c->x86_vendor != X86_VENDOR_AMD)
  48 +               setup_force_cpu_bug(X86_BUG_CPU_INSECURE);
  49
  50         fpu__init_system(c);
  51  }
  52 --
  53 2.14.2
  54