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Subject[PATCH 4.14 061/118] KVM: x86: Add memory barrier on vmcs field lookup
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Andrew Honig <ahonig@google.com>

commit 75f139aaf896d6fdeec2e468ddfa4b2fe469bf40 upstream.

This adds a memory barrier when performing a lookup into
the vmcs_field_to_offset_table. This is related to
CVE-2017-5753.

Signed-off-by: Andrew Honig <ahonig@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kvm/vmx.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -888,8 +888,16 @@ static inline short vmcs_field_to_offset
{
BUILD_BUG_ON(ARRAY_SIZE(vmcs_field_to_offset_table) > SHRT_MAX);

- if (field >= ARRAY_SIZE(vmcs_field_to_offset_table) ||
- vmcs_field_to_offset_table[field] == 0)
+ if (field >= ARRAY_SIZE(vmcs_field_to_offset_table))
+ return -ENOENT;
+
+ /*
+ * FIXME: Mitigation for CVE-2017-5753. To be replaced with a
+ * generic mechanism.
+ */
+ asm("lfence");
+
+ if (vmcs_field_to_offset_table[field] == 0)
return -ENOENT;

return vmcs_field_to_offset_table[field];

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