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Date: Thu, 18 Jan 2018 16:02:31 -0800
From: Dan Williams <dan.j.williams@...el.com>
To: linux-kernel@...r.kernel.org
Cc: linux-arch@...r.kernel.org, kernel-hardening@...ts.openwall.com,
Andrew Honig <ahonig@...gle.com>, stable@...r.kernel.org,
gregkh@...uxfoundation.org, Paolo Bonzini <pbonzini@...hat.com>,
tglx@...utronix.de, alan@...ux.intel.com, torvalds@...ux-foundation.org,
akpm@...ux-foundation.org, Jim Mattson <jmattson@...gle.com>
Subject: [PATCH v4 09/10] kvm, x86: fix spectre-v1 mitigation
Commit 75f139aaf896 "KVM: x86: Add memory barrier on vmcs field lookup"
added a raw 'asm("lfence");' to prevent a bounds check bypass of
'vmcs_field_to_offset_table'. This does not work for some AMD cpus, see
the 'ifence' helper, and it otherwise does not use the common
'array_ptr' helper designed for these types of fixes. Convert this to
use 'array_ptr'.
Cc: Andrew Honig <ahonig@...gle.com>
Cc: Jim Mattson <jmattson@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
arch/x86/kvm/vmx.c | 19 +++++++------------
1 file changed, 7 insertions(+), 12 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c829d89e2e63..20b9b0b5e336 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -34,6 +34,7 @@
#include <linux/tboot.h>
#include <linux/hrtimer.h>
#include <linux/frame.h>
+#include <linux/nospec.h>
#include "kvm_cache_regs.h"
#include "x86.h"
@@ -898,21 +899,15 @@ static const unsigned short vmcs_field_to_offset_table[] = {
static inline short vmcs_field_to_offset(unsigned long field)
{
- BUILD_BUG_ON(ARRAY_SIZE(vmcs_field_to_offset_table) > SHRT_MAX);
-
- if (field >= ARRAY_SIZE(vmcs_field_to_offset_table))
- return -ENOENT;
+ const unsigned short *offset;
- /*
- * FIXME: Mitigation for CVE-2017-5753. To be replaced with a
- * generic mechanism.
- */
- asm("lfence");
+ BUILD_BUG_ON(ARRAY_SIZE(vmcs_field_to_offset_table) > SHRT_MAX);
- if (vmcs_field_to_offset_table[field] == 0)
+ offset = array_ptr(vmcs_field_to_offset_table, field,
+ ARRAY_SIZE(vmcs_field_to_offset_table));
+ if (!offset || *offset == 0)
return -ENOENT;
-
- return vmcs_field_to_offset_table[field];
+ return *offset;
}
static inline struct vmcs12 *get_vmcs12(struct kvm_vcpu *vcpu)
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