CVE-2022-4994: KVM: x86: wean fast IN from emulator_pio_in

From: Greg Kroah-Hartman <[email protected]>

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

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

KVM: x86: wean fast IN from emulator_pio_in

Use __emulator_pio_in() directly for fast PIO instead of bouncing through
emulator_pio_in() now that __emulator_pio_in() fills "val" when handling
in-kernel PIO.  vcpu->arch.pio.count is guaranteed to be '0', so this a
pure nop.

emulator_pio_in_emulated is now the last caller of emulator_pio_in.

No functional change intended.

The Linux kernel CVE team has assigned CVE-2022-4994 to this issue.


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

	Issue introduced in 4.10 with commit 8370c3d08bd98576d97514eca29970e03767a5d1 and fixed in 6.0 with commit dc7a4bfde507ffe1d8bef49aba1322f1d20c2cb3

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-2022-4994
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/x86.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/dc7a4bfde507ffe1d8bef49aba1322f1d20c2cb3