patches/kernel/0113-selftests-x86-ldt_gdt-Robustify-against-set_thread_a.patch

   1 From bd7ec1093f8a0a743215207ebc14cc6947ea23a0 Mon Sep 17 00:00:00 2001
   2 From: Andy Lutomirski <luto@kernel.org>
   3 Date: Sat, 4 Nov 2017 04:19:49 -0700
   4 Subject: [PATCH 113/241] selftests/x86/ldt_gdt: Robustify against
   5  set_thread_area() and LAR oddities
   6 MIME-Version: 1.0
   7 Content-Type: text/plain; charset=UTF-8
   8 Content-Transfer-Encoding: 8bit
   9
  10 CVE-2017-5754
  11
  12 Bits 19:16 of LAR's result are undefined, and some upcoming
  13 improvements to the test case seem to trigger this.  Mask off those
  14 bits to avoid spurious failures.
  15
  16 commit 5b781c7e317f ("x86/tls: Forcibly set the accessed bit in TLS
  17 segments") adds a valid case in which LAR's output doesn't quite
  18 agree with set_thread_area()'s input.  This isn't triggered in the
  19 test as is, but it will be if we start calling set_thread_area()
  20 with the accessed bit clear.  Work around this discrepency.
  21
  22 I've added a Fixes tag so that -stable can pick this up if neccesary.
  23
  24 Signed-off-by: Andy Lutomirski <luto@kernel.org>
  25 Cc: Borislav Petkov <bpetkov@suse.de>
  26 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  27 Cc: Peter Zijlstra <peterz@infradead.org>
  28 Cc: Thomas Gleixner <tglx@linutronix.de>
  29 Fixes: 5b781c7e317f ("x86/tls: Forcibly set the accessed bit in TLS segments")
  30 Link: http://lkml.kernel.org/r/b82f3f89c034b53580970ac865139fd8863f44e2.1509794321.git.luto@kernel.org
  31 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  32 (cherry picked from commit d60ad744c9741586010d4bea286f09a063a90fbd)
  33 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  34 Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
  35 (cherry picked from commit d4c2ffcf3efe0d9610919fd48f5a1a5e38c28c07)
  36 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  37 ---
  38  tools/testing/selftests/x86/ldt_gdt.c | 10 +++++++++-
  39  1 file changed, 9 insertions(+), 1 deletion(-)
  40
  41 diff --git a/tools/testing/selftests/x86/ldt_gdt.c b/tools/testing/selftests/x86/ldt_gdt.c
  42 index b9a22f18566a..b2c54f4673f2 100644
  43 --- a/tools/testing/selftests/x86/ldt_gdt.c
  44 +++ b/tools/testing/selftests/x86/ldt_gdt.c
  45 @@ -114,7 +114,15 @@ static void check_valid_segment(uint16_t index, int ldt,
  46                 return;
  47         }
  48
  49 -       if (ar != expected_ar) {
  50 +       /* The SDM says "bits 19:16 are undefined".  Thanks. */
  51 +       ar &= ~0xF0000;
  52 +
  53 +       /*
  54 +        * NB: Different Linux versions do different things with the
  55 +        * accessed bit in set_thread_area().
  56 +        */
  57 +       if (ar != expected_ar &&
  58 +           (ldt || ar != (expected_ar | AR_ACCESSED))) {
  59                 printf("[FAIL]\t%s entry %hu has AR 0x%08X but expected 0x%08X\n",
  60                        (ldt ? "LDT" : "GDT"), index, ar, expected_ar);
  61                 nerrs++;
  62 --
  63 2.14.2
  64