patches/kernel/0250-x86-pti-Unbreak-EFI-old_memmap.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Jiri Kosina <jkosina@suse.cz>
   3 Date: Fri, 5 Jan 2018 22:35:41 +0100
   4 Subject: [PATCH] x86/pti: Unbreak EFI old_memmap
   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 EFI_OLD_MEMMAP's efi_call_phys_prolog() calls set_pgd() with swapper PGD that
  12 has PAGE_USER set, which makes PTI set NX on it, and therefore EFI can't
  13 execute it's code.
  14
  15 Fix that by forcefully clearing _PAGE_NX from the PGD (this can't be done
  16 by the pgprot API).
  17
  18 _PAGE_NX will be automatically reintroduced in efi_call_phys_epilog(), as
  19 _set_pgd() will again notice that this is _PAGE_USER, and set _PAGE_NX on
  20 it.
  21
  22 Tested-by: Dimitri Sivanich <sivanich@hpe.com>
  23 Signed-off-by: Jiri Kosina <jkosina@suse.cz>
  24 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  25 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  26 Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
  27 Cc: Andrea Arcangeli <aarcange@redhat.com>
  28 Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
  29 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  30 Cc: Matt Fleming <matt@codeblueprint.co.uk>
  31 Cc: Peter Zijlstra <peterz@infradead.org>
  32 Cc: Thomas Gleixner <tglx@linutronix.de>
  33 Cc: linux-efi@vger.kernel.org
  34 Cc: stable@vger.kernel.org
  35 Link: http://lkml.kernel.org/r/nycvar.YFH.7.76.1801052215460.11852@cbobk.fhfr.pm
  36 (cherry picked from commit de53c3786a3ce162a1c815d0c04c766c23ec9c0a)
  37 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  38 Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
  39 (cherry picked from commit 31afacd8089f54061e718e5d491f11747755c503)
  40 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  41 ---
  42  arch/x86/platform/efi/efi_64.c | 2 ++
  43  1 file changed, 2 insertions(+)
  44
  45 diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
  46 index b104224d3d6c..987a38e82f73 100644
  47 --- a/arch/x86/platform/efi/efi_64.c
  48 +++ b/arch/x86/platform/efi/efi_64.c
  49 @@ -133,7 +133,9 @@ pgd_t * __init efi_call_phys_prolog(void)
  50                                 pud[j] = *pud_offset(p4d_k, vaddr);
  51                         }
  52                 }
  53 +               pgd_offset_k(pgd * PGDIR_SIZE)->pgd &= ~_PAGE_NX;
  54         }
  55 +
  56  out:
  57         __flush_tlb_all();
  58
  59 --
  60 2.14.2
  61