Patch "KVM: x86: Add memory barrier on vmcs field lookup" has been added to the 4.9-stable tree

Patch "KVM: x86: Add memory barrier on vmcs field lookup" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    KVM: x86: Add memory barrier on vmcs field lookup

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kvm-x86-add-memory-barrier-on-vmcs-field-lookup.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 75f139aaf896d6fdeec2e468ddfa4b2fe469bf40 Mon Sep 17 00:00:00 2001
From: Andrew Honig <ahonig@google.com>
Date: Wed, 10 Jan 2018 10:12:03 -0800
Subject: KVM: x86: Add memory barrier on vmcs field lookup

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
@@ -857,8 +857,16 @@ 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];


Patches currently in stable-queue which might be from ahonig@google.com are

queue-4.9/kvm-vmx-scrub-hardware-gprs-at-vm-exit.patch
queue-4.9/kvm-x86-add-memory-barrier-on-vmcs-field-lookup.patch