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Date: Thu, 29 Feb 2024 15:53:11 +0000
From: Lee Jones <lee@...nel.org>
To: linux-cve-announce@...r.kernel.org
Cc: Lee Jones <lee@...nel.org>
Subject: CVE-2024-26620: s390/vfio-ap: always filter entire AP matrix

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

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

s390/vfio-ap: always filter entire AP matrix

The vfio_ap_mdev_filter_matrix function is called whenever a new adapter or
domain is assigned to the mdev. The purpose of the function is to update
the guest's AP configuration by filtering the matrix of adapters and
domains assigned to the mdev. When an adapter or domain is assigned, only
the APQNs associated with the APID of the new adapter or APQI of the new
domain are inspected. If an APQN does not reference a queue device bound to
the vfio_ap device driver, then it's APID will be filtered from the mdev's
matrix when updating the guest's AP configuration.

Inspecting only the APID of the new adapter or APQI of the new domain will
result in passing AP queues through to a guest that are not bound to the
vfio_ap device driver under certain circumstances. Consider the following:

guest's AP configuration (all also assigned to the mdev's matrix):
14.0004
14.0005
14.0006
16.0004
16.0005
16.0006

unassign domain 4
unbind queue 16.0005
assign domain 4

When domain 4 is re-assigned, since only domain 4 will be inspected, the
APQNs that will be examined will be:
14.0004
16.0004

Since both of those APQNs reference queue devices that are bound to the
vfio_ap device driver, nothing will get filtered from the mdev's matrix
when updating the guest's AP configuration. Consequently, queue 16.0005
will get passed through despite not being bound to the driver. This
violates the linux device model requirement that a guest shall only be
given access to devices bound to the device driver facilitating their
pass-through.

To resolve this problem, every adapter and domain assigned to the mdev will
be inspected when filtering the mdev's matrix.

The Linux kernel CVE team has assigned CVE-2024-26620 to this issue.


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

	Issue introduced in 6.0 with commit 48cae940c31d and fixed in 6.1.76 with commit d6b8d034b576
	Issue introduced in 6.0 with commit 48cae940c31d and fixed in 6.6.15 with commit c69d82119761
	Issue introduced in 6.0 with commit 48cae940c31d and fixed in 6.7.3 with commit cdd134d56138
	Issue introduced in 6.0 with commit 48cae940c31d and fixed in 6.8-rc1 with commit 850fb7fa8c68

Please see https://www.kernel.org or 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-2024-26620
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:
	drivers/s390/crypto/vfio_ap_ops.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/d6b8d034b576f406af920a7bee81606c027b24c6
	https://git.kernel.org/stable/c/c69d821197611678533fb3eb784fc823b921349a
	https://git.kernel.org/stable/c/cdd134d56138302976685e6c7bc4755450b3880e
	https://git.kernel.org/stable/c/850fb7fa8c684a4c6bf0e4b6978f4ddcc5d43d11

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