patches/kernel/0198-x86-mm-pti-Share-cpu_entry_area-with-user-space-page.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Andy Lutomirski <luto@kernel.org>
   3 Date: Mon, 4 Dec 2017 15:07:45 +0100
   4 Subject: [PATCH] x86/mm/pti: Share cpu_entry_area with user space page tables
   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 Share the cpu entry area so the user space and kernel space page tables
  12 have the same P4D page.
  13
  14 Signed-off-by: Andy Lutomirski <luto@kernel.org>
  15 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  16 Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
  17 Cc: Borislav Petkov <bp@alien8.de>
  18 Cc: Brian Gerst <brgerst@gmail.com>
  19 Cc: Dave Hansen <dave.hansen@linux.intel.com>
  20 Cc: David Laight <David.Laight@aculab.com>
  21 Cc: Denys Vlasenko <dvlasenk@redhat.com>
  22 Cc: Eduardo Valentin <eduval@amazon.com>
  23 Cc: Greg KH <gregkh@linuxfoundation.org>
  24 Cc: H. Peter Anvin <hpa@zytor.com>
  25 Cc: Josh Poimboeuf <jpoimboe@redhat.com>
  26 Cc: Juergen Gross <jgross@suse.com>
  27 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  28 Cc: Peter Zijlstra <peterz@infradead.org>
  29 Cc: Will Deacon <will.deacon@arm.com>
  30 Cc: aliguori@amazon.com
  31 Cc: daniel.gruss@iaik.tugraz.at
  32 Cc: hughd@google.com
  33 Cc: keescook@google.com
  34 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  35 (cherry picked from commit f7cfbee91559ca7e3e961a00ffac921208a115ad)
  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 6e8142de3a6e84a82a421b66a74ba37976912282)
  39 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  40 ---
  41  arch/x86/mm/pti.c | 25 +++++++++++++++++++++++++
  42  1 file changed, 25 insertions(+)
  43
  44 diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
  45 index d58bcee470fc..59290356f19f 100644
  46 --- a/arch/x86/mm/pti.c
  47 +++ b/arch/x86/mm/pti.c
  48 @@ -264,6 +264,29 @@ pti_clone_pmds(unsigned long start, unsigned long end, pmdval_t clear)
  49         }
  50  }
  51
  52 +/*
  53 + * Clone a single p4d (i.e. a top-level entry on 4-level systems and a
  54 + * next-level entry on 5-level systems.
  55 + */
  56 +static void __init pti_clone_p4d(unsigned long addr)
  57 +{
  58 +       p4d_t *kernel_p4d, *user_p4d;
  59 +       pgd_t *kernel_pgd;
  60 +
  61 +       user_p4d = pti_user_pagetable_walk_p4d(addr);
  62 +       kernel_pgd = pgd_offset_k(addr);
  63 +       kernel_p4d = p4d_offset(kernel_pgd, addr);
  64 +       *user_p4d = *kernel_p4d;
  65 +}
  66 +
  67 +/*
  68 + * Clone the CPU_ENTRY_AREA into the user space visible page table.
  69 + */
  70 +static void __init pti_clone_user_shared(void)
  71 +{
  72 +       pti_clone_p4d(CPU_ENTRY_AREA_BASE);
  73 +}
  74 +
  75  /*
  76   * Initialize kernel page table isolation
  77   */
  78 @@ -273,4 +296,6 @@ void __init pti_init(void)
  79                 return;
  80
  81         pr_info("enabled\n");
  82 +
  83 +       pti_clone_user_shared();
  84  }
  85 --
  86 2.14.2
  87