linux-kernel - [PATCH 3.16 020/192] kvm: vmx: Check value written to IA32

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Message-ID: <lsq.1507553064.823548669@decadent.org.uk>
Date:   Mon, 09 Oct 2017 13:44:24 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Radim Krčmář" <rkrcmar@...hat.com>,
        "Jim Mattson" <jmattson@...gle.com>
Subject: [PATCH 3.16 020/192] kvm: vmx: Check value written to IA32_BNDCFGS

3.16.49-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Jim Mattson <jmattson@...gle.com>

commit 4531662d1abf6c1f0e5c2b86ddb60e61509786c8 upstream.

Bits 11:2 must be zero and the linear addess in bits 63:12 must be
canonical. Otherwise, WRMSR(BNDCFGS) should raise #GP.

Fixes: 0dd376e709975779 ("KVM: x86: add MSR_IA32_BNDCFGS to msrs_to_save")
Signed-off-by: Jim Mattson <jmattson@...gle.com>
Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
[bwh: Backported to 3.16: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/include/uapi/asm/msr-index.h | 2 ++
 arch/x86/kvm/vmx.c                    | 3 +++
 2 files changed, 5 insertions(+)

--- a/arch/x86/include/uapi/asm/msr-index.h
+++ b/arch/x86/include/uapi/asm/msr-index.h
@@ -298,6 +298,8 @@
 #define MSR_IA32_TSC_ADJUST             0x0000003b
 #define MSR_IA32_BNDCFGS		0x00000d90
 
+#define MSR_IA32_BNDCFGS_RSVD		0x00000ffc
+
 #define FEATURE_CONTROL_LOCKED				(1<<0)
 #define FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX	(1<<1)
 #define FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX	(1<<2)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2589,6 +2589,9 @@ static int vmx_set_msr(struct kvm_vcpu *
 	case MSR_IA32_BNDCFGS:
 		if (!vmx_mpx_supported() || !guest_cpuid_has_mpx(vcpu))
 			return 1;
+		if (is_noncanonical_address(data & PAGE_MASK) ||
+		    (data & MSR_IA32_BNDCFGS_RSVD))
+			return 1;
 		vmcs_write64(GUEST_BNDCFGS, data);
 		break;
 	case MSR_IA32_TSC: