patches/kernel/0124-x86-Make-X86_BUG_FXSAVE_LEAK-detectable-in-CPUID-on-.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Rudolf Marek <r.marek@assembler.cz>
   3 Date: Tue, 28 Nov 2017 22:01:06 +0100
   4 Subject: [PATCH] x86: Make X86_BUG_FXSAVE_LEAK detectable in CPUID on AMD
   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 [ Note, this is a Git cherry-pick of the following commit:
  12
  13     2b67799bdf25 ("x86: Make X86_BUG_FXSAVE_LEAK detectable in CPUID on AMD")
  14
  15   ... for easier x86 PTI code testing and back-porting. ]
  16
  17 The latest AMD AMD64 Architecture Programmer's Manual
  18 adds a CPUID feature XSaveErPtr (CPUID_Fn80000008_EBX[2]).
  19
  20 If this feature is set, the FXSAVE, XSAVE, FXSAVEOPT, XSAVEC, XSAVES
  21 / FXRSTOR, XRSTOR, XRSTORS always save/restore error pointers,
  22 thus making the X86_BUG_FXSAVE_LEAK workaround obsolete on such CPUs.
  23
  24 Signed-Off-By: Rudolf Marek <r.marek@assembler.cz>
  25 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  26 Reviewed-by: Borislav Petkov <bp@suse.de>
  27 Tested-by: Borislav Petkov <bp@suse.de>
  28 Cc: Andy Lutomirski <luto@amacapital.net>
  29 Link: https://lkml.kernel.org/r/bdcebe90-62c5-1f05-083c-eba7f08b2540@assembler.cz
  30 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  31 (cherry picked from commit f2dbad36c55e5d3a91dccbde6e8cae345fe5632f)
  32 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  33 Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
  34 (cherry picked from commit 281b622113c66ba2de9b7725e1d232ea3c282114)
  35 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  36 ---
  37  arch/x86/include/asm/cpufeatures.h | 1 +
  38  arch/x86/kernel/cpu/amd.c          | 7 +++++--
  39  2 files changed, 6 insertions(+), 2 deletions(-)
  40
  41 diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
  42 index 0ea630bb3e74..d57a174ec97c 100644
  43 --- a/arch/x86/include/asm/cpufeatures.h
  44 +++ b/arch/x86/include/asm/cpufeatures.h
  45 @@ -265,6 +265,7 @@
  46  /* AMD-defined CPU features, CPUID level 0x80000008 (EBX), word 13 */
  47  #define X86_FEATURE_CLZERO             (13*32+ 0) /* CLZERO instruction */
  48  #define X86_FEATURE_IRPERF             (13*32+ 1) /* Instructions Retired Count */
  49 +#define X86_FEATURE_XSAVEERPTR         (13*32+ 2) /* Always save/restore FP error pointers */
  50
  51  /* Thermal and Power Management Leaf, CPUID level 0x00000006 (EAX), word 14 */
  52  #define X86_FEATURE_DTHERM             (14*32+ 0) /* Digital Thermal Sensor */
  53 diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
  54 index 3b9e220621f8..2a5328cc03a6 100644
  55 --- a/arch/x86/kernel/cpu/amd.c
  56 +++ b/arch/x86/kernel/cpu/amd.c
  57 @@ -760,8 +760,11 @@ static void init_amd(struct cpuinfo_x86 *c)
  58         case 0x15: init_amd_bd(c); break;
  59         }
  60
  61 -       /* Enable workaround for FXSAVE leak */
  62 -       if (c->x86 >= 6)
  63 +       /*
  64 +        * Enable workaround for FXSAVE leak on CPUs
  65 +        * without a XSaveErPtr feature
  66 +        */
  67 +       if ((c->x86 >= 6) && (!cpu_has(c, X86_FEATURE_XSAVEERPTR)))
  68                 set_cpu_bug(c, X86_BUG_FXSAVE_LEAK);
  69
  70         cpu_detect_cache_sizes(c);
  71 --
  72 2.14.2
  73