KVM: X86 emulator: fix source operand decoding for 8bit mov[zs]x instructions

Source operand for one byte mov[zs]x is decoded incorrectly if it is in
high byte register. Fix that.

Cc: stable@vger.kernel.org
Signed-off-by: Gleb Natapov <gleb@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 46f63b8d09f4..8e517bba6a7c 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4172,6 +4172,10 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
                 break;
         case OpMem8:
                 ctxt->memop.bytes = 1;
+                if (ctxt->memop.type == OP_REG) {
+                        ctxt->memop.addr.reg = decode_register(ctxt, ctxt->modrm_rm, 1);
+                        fetch_register_operand(&ctxt->memop);
+                }
                 goto mem_common;
         case OpMem16:
                 ctxt->memop.bytes = 2;