From: Jan Beulich <jbeulich@suse.com>
Date: Thu, 2 Mar 2017 15:08:27 +0000 (+0100)
Subject: x86emul: correct decoding of vzero{all,upper}
X-Git-Tag: archive/raspbian/4.11.1-1+rpi1~1^2~66^2~2592
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=26735f30dffe1091686bbe921aacbea8ba371cc8;p=xen.git

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@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
---

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c
index a65026a3b6..667049df2f 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -2375,12 +2375,21 @@ 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;