linux-cve-announce - CVE-2024-26761: cxl/pci: Fix disabling memory if DVSEC CXL Range does not match a CFMWS window

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Date: Wed,  3 Apr 2024 19:31:28 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-26761: cxl/pci: Fix disabling memory if DVSEC CXL Range does not match a CFMWS window

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

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

cxl/pci: Fix disabling memory if DVSEC CXL Range does not match a CFMWS window

The Linux CXL subsystem is built on the assumption that HPA == SPA.
That is, the host physical address (HPA) the HDM decoder registers are
programmed with are system physical addresses (SPA).

During HDM decoder setup, the DVSEC CXL range registers (cxl-3.1,
8.1.3.8) are checked if the memory is enabled and the CXL range is in
a HPA window that is described in a CFMWS structure of the CXL host
bridge (cxl-3.1, 9.18.1.3).

Now, if the HPA is not an SPA, the CXL range does not match a CFMWS
window and the CXL memory range will be disabled then. The HDM decoder
stops working which causes system memory being disabled and further a
system hang during HDM decoder initialization, typically when a CXL
enabled kernel boots.

Prevent a system hang and do not disable the HDM decoder if the
decoder's CXL range is not found in a CFMWS window.

Note the change only fixes a hardware hang, but does not implement
HPA/SPA translation. Support for this can be added in a follow on
patch series.

The Linux kernel CVE team has assigned CVE-2024-26761 to this issue.

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

	Issue introduced in 5.19 with commit 34e37b4c432c and fixed in 6.1.80 with commit 031217128990
	Issue introduced in 5.19 with commit 34e37b4c432c and fixed in 6.6.19 with commit 2cc1a530ab31
	Issue introduced in 5.19 with commit 34e37b4c432c and fixed in 6.7.7 with commit 3a3181a71935
	Issue introduced in 5.19 with commit 34e37b4c432c and fixed in 6.8 with commit 0cab68720598

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-2024-26761
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/cxl/core/pci.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/031217128990d7f0ab8c46db1afb3cf1e075fd29
	https://git.kernel.org/stable/c/2cc1a530ab31c65b52daf3cb5d0883c8b614ea69
	https://git.kernel.org/stable/c/3a3181a71935774bda2398451256d7441426420b
	https://git.kernel.org/stable/c/0cab687205986491302cd2e440ef1d253031c221