linux-kernel - [PATCH v11 4/9] KVM: VMX: Check CET dependencies on CR settings

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20200326081847.5870-5-weijiang.yang@intel.com>
Date:   Thu, 26 Mar 2020 16:18:41 +0800
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, sean.j.christopherson@...el.com,
        jmattson@...gle.com
Cc:     yu.c.zhang@...ux.intel.com, Yang Weijiang <weijiang.yang@...el.com>
Subject: [PATCH v11 4/9] KVM: VMX: Check CET dependencies on CR settings

CR4.CET is master control bit for CET function.
There're mutual constrains between CR0.WP and CR4.CET, so need
to check the dependent bit while changing the control registers.

Note:
1)The processor does not allow CR4.CET to be set if CR0.WP = 0,
  similarly, it does not allow CR0.WP to be cleared while
  CR4.CET = 1. In either case, KVM would inject #GP to guest.

2)SHSTK and IBT features share one control MSR:
  MSR_IA32_{U,S}_CET, which means it's difficult to hide
  one feature from another in the case of SHSTK != IBT,
  after discussed in community, it's agreed to allow guest
  control two features independently as it won't introduce
  security hole.

Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 4 ++++
 arch/x86/kvm/x86.c     | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index bd7cd175fd81..87f101750746 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3089,6 +3089,10 @@ int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 			return 1;
 	}

+	if ((cr4 & X86_CR4_CET) && (!is_cet_supported(vcpu) ||
+	    !(kvm_read_cr0(vcpu) & X86_CR0_WP)))
+		return 1;
+
 	if (vmx->nested.vmxon && !nested_cr4_valid(vcpu, cr4))
 		return 1;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 830afe5038d1..90acdbbb8a5a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -804,6 +804,9 @@ int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 	if (!(cr0 & X86_CR0_PG) && kvm_read_cr4_bits(vcpu, X86_CR4_PCIDE))
 		return 1;

+	if (!(cr0 & X86_CR0_WP) && kvm_read_cr4_bits(vcpu, X86_CR4_CET))
+		return 1;
+
 	kvm_x86_ops->set_cr0(vcpu, cr0);

 	if ((cr0 ^ old_cr0) & X86_CR0_PG) {
-- 
2.17.2