CVE-2026-74272: cxl/region: Resolve region deletion races

CVE-2026-74272: cxl/region: Resolve region deletion races

[Greg Kroah-Hartman]

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

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

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

cxl/region: Resolve region deletion races

Sungwoo noticed that the sysfs trigger to delete a region may try to delete
a region multiple times. It also has no exclusion relative to the kernel
releasing the region via CXL root device teardown.

Instead of installing new cxl root devres actions per region, use the
existing root decoder unregistration event to remove all remaining regions.
An xarray of regions replaces a devres list of regions.

This handles 3 separate issues with the old approach:

1/ sysfs users racing to delete the same region: no longer possible now
   that the regions_lock is held over the lookup and deletion.

2/ multiple actions triggering deletion of the same region: solved by
   erasing regions while holding @regions_lock, and only proceeding on
   successful erasure.

3/ userspace racing devres_release_all() to trigger the devres not found
   warning: solved by sysfs unregistration not requiring a release action

The Linux kernel CVE team has assigned CVE-2026-74272 to this issue.


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

	Issue introduced in 6.0 with commit 779dd20cfb56c510f89877cca45529fa9f8bc450 and fixed in 7.1.5 with commit be44c1c04f85d7b7ac1c597a30b443bbd346acbd
	Issue introduced in 6.0 with commit 779dd20cfb56c510f89877cca45529fa9f8bc450 and fixed in 7.2-rc1 with commit 4dd86ca99ffcc413cbf79063fd9956ef54e0ca91

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-2026-74272
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/core.h
	drivers/cxl/core/port.c
	drivers/cxl/core/region.c
	drivers/cxl/cxl.h


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/be44c1c04f85d7b7ac1c597a30b443bbd346acbd
	https://git.kernel.org/stable/c/4dd86ca99ffcc413cbf79063fd9956ef54e0ca91