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Message-Id: <20200210122317.508860753@linuxfoundation.org>
Date: Mon, 10 Feb 2020 04:33:02 -0800
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 4.19 124/195] KVM: x86: Refactor prefix decoding to prevent Spectre-v1/L1TF attacks
From: Marios Pomonis <pomonis@...gle.com>
commit 125ffc5e0a56a3eded608dc51e09d5ebf72cf652 upstream.
This fixes Spectre-v1/L1TF vulnerabilities in
vmx_read_guest_seg_selector(), vmx_read_guest_seg_base(),
vmx_read_guest_seg_limit() and vmx_read_guest_seg_ar(). When
invoked from emulation, these functions contain index computations
based on the (attacker-influenced) segment value. Using constants
prevents the attack.
Cc: stable@...r.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
arch/x86/kvm/emulate.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5164,16 +5164,28 @@ int x86_decode_insn(struct x86_emulate_c
ctxt->ad_bytes = def_ad_bytes ^ 6;
break;
case 0x26: /* ES override */
+ has_seg_override = true;
+ ctxt->seg_override = VCPU_SREG_ES;
+ break;
case 0x2e: /* CS override */
+ has_seg_override = true;
+ ctxt->seg_override = VCPU_SREG_CS;
+ break;
case 0x36: /* SS override */
+ has_seg_override = true;
+ ctxt->seg_override = VCPU_SREG_SS;
+ break;
case 0x3e: /* DS override */
has_seg_override = true;
- ctxt->seg_override = (ctxt->b >> 3) & 3;
+ ctxt->seg_override = VCPU_SREG_DS;
break;
case 0x64: /* FS override */
+ has_seg_override = true;
+ ctxt->seg_override = VCPU_SREG_FS;
+ break;
case 0x65: /* GS override */
has_seg_override = true;
- ctxt->seg_override = ctxt->b & 7;
+ ctxt->seg_override = VCPU_SREG_GS;
break;
case 0x40 ... 0x4f: /* REX */
if (mode != X86EMUL_MODE_PROT64)
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