CVE-2026-72015: fs/resctrl: Fix double-add of pseudo-locked region's RMID to free list

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

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

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

fs/resctrl: Fix double-add of pseudo-locked region's RMID to free list

A pseudo-locked group's RMID is freed when it is created. On unmount
rmdir_all_sub() unconditionally frees all RMID of all groups, resulting
in a double-free of the pseudo-locked group's RMID. The consequence of this
is that the original free results in the pseudo-locked group's RMID being
added to the rmid_free_lru linked list and the second free then attempts
to add the same RMID entry to the rmid_free_lru again.

Do not double-free a pseudo-locked group's RMID.

The Linux kernel CVE team has assigned CVE-2026-72015 to this issue.


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

	Issue introduced in 4.19 with commit e0bdfe8e36f3fbbdc91e70bf927f743ca23917b0 and fixed in 6.6.148 with commit 9168176894332312c12ef052e784735dbf4ffe3f
	Issue introduced in 4.19 with commit e0bdfe8e36f3fbbdc91e70bf927f743ca23917b0 and fixed in 6.12.101 with commit b2fe9e140aa94b2816aab7ebc692b543e418f5e3
	Issue introduced in 4.19 with commit e0bdfe8e36f3fbbdc91e70bf927f743ca23917b0 and fixed in 6.18.40 with commit 52007bfdce5310e8c8a29849bfbfb188a1e50ca0
	Issue introduced in 4.19 with commit e0bdfe8e36f3fbbdc91e70bf927f743ca23917b0 and fixed in 7.1.5 with commit f7628eea9212e185a09df3aea603ca8580b8678d
	Issue introduced in 4.19 with commit e0bdfe8e36f3fbbdc91e70bf927f743ca23917b0 and fixed in 7.2-rc3 with commit b9f089723aee892efc77c349ae47a6b452b293c4

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-2026-72015
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:
	fs/resctrl/rdtgroup.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/9168176894332312c12ef052e784735dbf4ffe3f
	https://git.kernel.org/stable/c/b2fe9e140aa94b2816aab7ebc692b543e418f5e3
	https://git.kernel.org/stable/c/52007bfdce5310e8c8a29849bfbfb188a1e50ca0
	https://git.kernel.org/stable/c/f7628eea9212e185a09df3aea603ca8580b8678d
	https://git.kernel.org/stable/c/b9f089723aee892efc77c349ae47a6b452b293c4