[Xen-changelog] [xen stable-4.8] x86emul: correct decoding of vzero{all, upper}

[patchbot@xxxxxxx]

commit e26a2a00169bad403c9dcc597218080626cee861
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Mar 14 12:42:58 2017 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Mar 14 12:42:58 2017 +0100

    x86emul: correct decoding of vzero{all,upper}
    
    These VEX encoded insns aren't followed by a ModR/M byte.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 26735f30dffe1091686bbe921aacbea8ba371cc8
    master date: 2017-03-02 16:08:27 +0100
---
 xen/arch/x86/x86_emulate/x86_emulate.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c 
b/xen/arch/x86/x86_emulate/x86_emulate.c
index 6fca427..a0330a4 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -2133,12 +2133,21 @@ x86_decode(
 
                 opcode |= b | MASK_INSR(vex.pfx, X86EMUL_OPC_PFX_MASK);
 
+                if ( !(d & ModRM) )
+                {
+                    modrm_reg = modrm_rm = modrm_mod = modrm = 0;
+                    break;
+                }
+
                 modrm = insn_fetch_type(uint8_t);
                 modrm_mod = (modrm & 0xc0) >> 6;
 
                 break;
             }
+    }
 
+    if ( d & ModRM )
+    {
         modrm_reg = ((rex_prefix & 4) << 1) | ((modrm & 0x38) >> 3);
         modrm_rm  = modrm & 0x07;
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.8

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