patches/kernel/0224-kvm-x86-fix-RSM-when-PCID-is-non-zero.patch

   1 From 59b914593681a98524e4f3ba239544f77f03d14a Mon Sep 17 00:00:00 2001
   2 From: Paolo Bonzini <pbonzini@redhat.com>
   3 Date: Thu, 21 Dec 2017 00:49:14 +0100
   4 Subject: [PATCH 224/233] kvm: x86: fix RSM when PCID is non-zero
   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 rsm_load_state_64() and rsm_enter_protected_mode() load CR3, then
  12 CR4 & ~PCIDE, then CR0, then CR4.
  13
  14 However, setting CR4.PCIDE fails if CR3[11:0] != 0.  It's probably easier
  15 in the long run to replace rsm_enter_protected_mode() with an emulator
  16 callback that sets all the special registers (like KVM_SET_SREGS would
  17 do).  For now, set the PCID field of CR3 only after CR4.PCIDE is 1.
  18
  19 Reported-by: Laszlo Ersek <lersek@redhat.com>
  20 Tested-by: Laszlo Ersek <lersek@redhat.com>
  21 Fixes: 660a5d517aaab9187f93854425c4c63f4a09195c
  22 Cc: stable@vger.kernel.org
  23 Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
  24 (cherry picked from commit fae1a3e775cca8c3a9e0eb34443b310871a15a92)
  25 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  26 Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
  27 (cherry picked from commit dba4ceb9a91ed2d11a47722436b3c0be15e791d4)
  28 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  29 ---
  30  arch/x86/kvm/emulate.c | 32 +++++++++++++++++++++++++-------
  31  1 file changed, 25 insertions(+), 7 deletions(-)
  32
  33 diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
  34 index fb0055953fbc..155f2af2cb39 100644
  35 --- a/arch/x86/kvm/emulate.c
  36 +++ b/arch/x86/kvm/emulate.c
  37 @@ -2399,9 +2399,21 @@ static int rsm_load_seg_64(struct x86_emulate_ctxt *ctxt, u64 smbase, int n)
  38  }
  39
  40  static int rsm_enter_protected_mode(struct x86_emulate_ctxt *ctxt,
  41 -                                    u64 cr0, u64 cr4)
  42 +                                   u64 cr0, u64 cr3, u64 cr4)
  43  {
  44         int bad;
  45 +       u64 pcid;
  46 +
  47 +       /* In order to later set CR4.PCIDE, CR3[11:0] must be zero.  */
  48 +       pcid = 0;
  49 +       if (cr4 & X86_CR4_PCIDE) {
  50 +               pcid = cr3 & 0xfff;
  51 +               cr3 &= ~0xfff;
  52 +       }
  53 +
  54 +       bad = ctxt->ops->set_cr(ctxt, 3, cr3);
  55 +       if (bad)
  56 +               return X86EMUL_UNHANDLEABLE;
  57
  58         /*
  59          * First enable PAE, long mode needs it before CR0.PG = 1 is set.
  60 @@ -2420,6 +2432,12 @@ static int rsm_enter_protected_mode(struct x86_emulate_ctxt *ctxt,
  61                 bad = ctxt->ops->set_cr(ctxt, 4, cr4);
  62                 if (bad)
  63                         return X86EMUL_UNHANDLEABLE;
  64 +               if (pcid) {
  65 +                       bad = ctxt->ops->set_cr(ctxt, 3, cr3 | pcid);
  66 +                       if (bad)
  67 +                               return X86EMUL_UNHANDLEABLE;
  68 +               }
  69 +
  70         }
  71
  72         return X86EMUL_CONTINUE;
  73 @@ -2430,11 +2448,11 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt, u64 smbase)
  74         struct desc_struct desc;
  75         struct desc_ptr dt;
  76         u16 selector;
  77 -       u32 val, cr0, cr4;
  78 +       u32 val, cr0, cr3, cr4;
  79         int i;
  80
  81         cr0 =                      GET_SMSTATE(u32, smbase, 0x7ffc);
  82 -       ctxt->ops->set_cr(ctxt, 3, GET_SMSTATE(u32, smbase, 0x7ff8));
  83 +       cr3 =                      GET_SMSTATE(u32, smbase, 0x7ff8);
  84         ctxt->eflags =             GET_SMSTATE(u32, smbase, 0x7ff4) | X86_EFLAGS_FIXED;
  85         ctxt->_eip =               GET_SMSTATE(u32, smbase, 0x7ff0);
  86
  87 @@ -2476,14 +2494,14 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt, u64 smbase)
  88
  89         ctxt->ops->set_smbase(ctxt, GET_SMSTATE(u32, smbase, 0x7ef8));
  90
  91 -       return rsm_enter_protected_mode(ctxt, cr0, cr4);
  92 +       return rsm_enter_protected_mode(ctxt, cr0, cr3, cr4);
  93  }
  94
  95  static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt, u64 smbase)
  96  {
  97         struct desc_struct desc;
  98         struct desc_ptr dt;
  99 -       u64 val, cr0, cr4;
 100 +       u64 val, cr0, cr3, cr4;
 101         u32 base3;
 102         u16 selector;
 103         int i, r;
 104 @@ -2500,7 +2518,7 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt, u64 smbase)
 105         ctxt->ops->set_dr(ctxt, 7, (val & DR7_VOLATILE) | DR7_FIXED_1);
 106
 107         cr0 =                       GET_SMSTATE(u64, smbase, 0x7f58);
 108 -       ctxt->ops->set_cr(ctxt, 3,  GET_SMSTATE(u64, smbase, 0x7f50));
 109 +       cr3 =                       GET_SMSTATE(u64, smbase, 0x7f50);
 110         cr4 =                       GET_SMSTATE(u64, smbase, 0x7f48);
 111         ctxt->ops->set_smbase(ctxt, GET_SMSTATE(u32, smbase, 0x7f00));
 112         val =                       GET_SMSTATE(u64, smbase, 0x7ed0);
 113 @@ -2528,7 +2546,7 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt, u64 smbase)
 114         dt.address =                GET_SMSTATE(u64, smbase, 0x7e68);
 115         ctxt->ops->set_gdt(ctxt, &dt);
 116
 117 -       r = rsm_enter_protected_mode(ctxt, cr0, cr4);
 118 +       r = rsm_enter_protected_mode(ctxt, cr0, cr3, cr4);
 119         if (r != X86EMUL_CONTINUE)
 120                 return r;
 121
 122 --
 123 2.14.2
 124