From: Gleb Natapov <gleb@redhat.com>
Date: Thu, 18 Feb 2010 10:14:59 +0000 (+0200)
Subject: KVM: x86 emulator: Forbid modifying CS segment register by mov instruction
X-Git-Tag: firefly_0821_release~10186^2~2039
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=3e338f53281fc492a931928e6e53ec15eaf9cf3d;p=firefly-linux-kernel-4.4.55.git

KVM: x86 emulator: Forbid modifying CS segment register by mov instruction

commit 8b9f44140bc4afd2698413cd9960c3912168ee91 upstream.

Inject #UD if guest attempts to do so. This is in accordance to Intel
SDM.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 5ca9556f221e..e9604420b778 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1875,6 +1875,12 @@ special_insn:
 		int err;
 
 		sel = c->src.val;
+
+		if (c->modrm_reg == VCPU_SREG_CS) {
+			kvm_queue_exception(ctxt->vcpu, UD_VECTOR);
+			goto done;
+		}
+
 		if (c->modrm_reg == VCPU_SREG_SS)
 			toggle_interruptibility(ctxt, X86_SHADOW_INT_MOV_SS);