patches/kernel/0253-x86-tboot-Unbreak-tboot-with-PTI-enabled.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Dave Hansen <dave.hansen@linux.intel.com>
   3 Date: Sat, 6 Jan 2018 18:41:14 +0100
   4 Subject: [PATCH] x86/tboot: Unbreak tboot with PTI enabled
   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 This is another case similar to what EFI does: create a new set of
  12 page tables, map some code at a low address, and jump to it.  PTI
  13 mistakes this low address for userspace and mistakenly marks it
  14 non-executable in an effort to make it unusable for userspace.
  15
  16 Undo the poison to allow execution.
  17
  18 Fixes: 385ce0ea4c07 ("x86/mm/pti: Add Kconfig")
  19 Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
  20 Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
  21 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  22 Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
  23 Cc: Tim Chen <tim.c.chen@linux.intel.com>
  24 Cc: Jon Masters <jcm@redhat.com>
  25 Cc: Dave Hansen <dave.hansen@intel.com>
  26 Cc: Andi Kleen <andi@firstfloor.org>
  27 Cc: Jeff Law <law@redhat.com>
  28 Cc: Paolo Bonzini <pbonzini@redhat.com>
  29 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  30 Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
  31 Cc: David" <dwmw@amazon.co.uk>
  32 Cc: Nick Clifton <nickc@redhat.com>
  33 Cc: stable@vger.kernel.org
  34 Link: https://lkml.kernel.org/r/20180108102805.GK25546@redhat.com
  35 (cherry picked from commit 262b6b30087246abf09d6275eb0c0dc421bcbe38)
  36 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  37 Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
  38 (cherry picked from commit f03e9108405491791f0b883a2d95e2620ddfce64)
  39 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  40 ---
  41  arch/x86/kernel/tboot.c | 1 +
  42  1 file changed, 1 insertion(+)
  43
  44 diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
  45 index a4eb27918ceb..75869a4b6c41 100644
  46 --- a/arch/x86/kernel/tboot.c
  47 +++ b/arch/x86/kernel/tboot.c
  48 @@ -127,6 +127,7 @@ static int map_tboot_page(unsigned long vaddr, unsigned long pfn,
  49         p4d = p4d_alloc(&tboot_mm, pgd, vaddr);
  50         if (!p4d)
  51                 return -1;
  52 +       pgd->pgd &= ~_PAGE_NX;
  53         pud = pud_alloc(&tboot_mm, p4d, vaddr);
  54         if (!pud)
  55                 return -1;
  56 --
  57 2.14.2
  58