linux-kernel - [patch 117/123] KVM: x86 emulator: Forbid modifying CS segment register by mov instruction

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Message-Id: <20100313001515.372453718@kvm.kroah.org>
Date:	Fri, 12 Mar 2010 16:13:35 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Gleb Natapov <gleb@...hat.com>, Avi Kivity <avi@...hat.com>
Subject: [patch 117/123] KVM: x86 emulator: Forbid modifying CS segment register by mov instruction

2.6.33-stable review patch.  If anyone has any objections, please let me know.

-----------------

From: Gleb Natapov <gleb@...hat.com>

commit 8b9f44140bc4afd2698413cd9960c3912168ee91 upstream.

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

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

---
 arch/x86/kvm/emulate.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1987,6 +1987,12 @@ 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);
 


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