CVE-2022-49933: KVM: VMX: Reset eVMCS controls in VP assist page during hardware disabling

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

KVM: VMX: Reset eVMCS controls in VP assist page during hardware disabling

Reset the eVMCS controls in the per-CPU VP assist page during hardware
disabling instead of waiting until kvm-intel's module exit.  The controls
are activated if and only if KVM creates a VM, i.e. don't need to be
reset if hardware is never enabled.

Doing the reset during hardware disabling will naturally fix a potential
NULL pointer deref bug once KVM disables CPU hotplug while enabling and
disabling hardware (which is necessary to fix a variety of bugs).  If the
kernel is running as the root partition, the VP assist page is unmapped
during CPU hot unplug, and so KVM's clearing of the eVMCS controls needs
to occur with CPU hot(un)plug disabled, otherwise KVM could attempt to
write to a CPU's VP assist page after it's unmapped.

The Linux kernel CVE team has assigned CVE-2022-49933 to this issue.


Affected and fixed versions
===========================

	Fixed in 6.1.20 with commit afb26bfc01db6ef4728e96314f08431934ffe833
	Fixed in 6.2.7 with commit 01aa8e5704bac9fcd7401eb1a74a375fba594203
	Fixed in 6.3 with commit 2916b70fc342719f570640de07251b7f91feebdb

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-49933
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	arch/x86/kvm/vmx/vmx.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/afb26bfc01db6ef4728e96314f08431934ffe833
	https://git.kernel.org/stable/c/01aa8e5704bac9fcd7401eb1a74a375fba594203
	https://git.kernel.org/stable/c/2916b70fc342719f570640de07251b7f91feebdb