Patch "KVM: VMX: remove I/O port 0x80 bypass on Intel hosts" has been added to the 4.9-stable tree

Patch "KVM: VMX: remove I/O port 0x80 bypass on Intel hosts" 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: VMX: remove I/O port 0x80 bypass on Intel hosts

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-vmx-remove-i-o-port-0x80-bypass-on-intel-hosts.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 d59d51f088014f25c2562de59b9abff4f42a7468 Mon Sep 17 00:00:00 2001
From: Andrew Honig <ahonig@google.com>
Date: Fri, 1 Dec 2017 10:21:09 -0800
Subject: KVM: VMX: remove I/O port 0x80 bypass on Intel hosts
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Andrew Honig <ahonig@google.com>

commit d59d51f088014f25c2562de59b9abff4f42a7468 upstream.

This fixes CVE-2017-1000407.

KVM allows guests to directly access I/O port 0x80 on Intel hosts.  If
the guest floods this port with writes it generates exceptions and
instability in the host kernel, leading to a crash.  With this change
guest writes to port 0x80 on Intel will behave the same as they
currently behave on AMD systems.

Prevent the flooding by removing the code that sets port 0x80 as a
passthrough port.  This is essentially the same as upstream patch
99f85a28a78e96d28907fe036e1671a218fee597, except that patch was
for AMD chipsets and this patch is for Intel.

Signed-off-by: Andrew Honig <ahonig@google.com>
Signed-off-by: Jim Mattson <jmattson@google.com>
Fixes: fdef3ad1b386 ("KVM: VMX: Enable io bitmaps to avoid IO port 0x80 VMEXITs")
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kvm/vmx.c |    5 -----
 1 file changed, 5 deletions(-)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6413,12 +6413,7 @@ static __init int hardware_setup(void)
 	memset(vmx_vmread_bitmap, 0xff, PAGE_SIZE);
 	memset(vmx_vmwrite_bitmap, 0xff, PAGE_SIZE);
 
-	/*
-	 * Allow direct access to the PC debug port (it is often used for I/O
-	 * delays, but the vmexits simply slow things down).
-	 */
 	memset(vmx_io_bitmap_a, 0xff, PAGE_SIZE);
-	clear_bit(0x80, vmx_io_bitmap_a);
 
 	memset(vmx_io_bitmap_b, 0xff, PAGE_SIZE);
 


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

queue-4.9/kvm-vmx-remove-i-o-port-0x80-bypass-on-intel-hosts.patch