CVE-2026-72173: fs/proc/task_mmu: do not warn on seeing non-migration pmd entry

CVE-2026-72173: fs/proc/task_mmu: do not warn on seeing non-migration pmd entry

[Greg Kroah-Hartman]

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

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

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

fs/proc/task_mmu: do not warn on seeing non-migration pmd entry

Patch series "mm/hmm: A fix and a selftest", v3.

Patch 1 fixes a stale warning present from the time when only migration
softleaf entries were supported at the PMD level.

Patch 2 adds some code into hmm-tests.c which exercises the pagemap path
for PMD device-private entries.


This patch (of 2):

pagemap_pmd_range_thp() warns if a non-present PMD is not a migration
entry.  This became false once device-private entries at the PMD level
were added.

Therefore, remove the stale migration-only assertion.

The Linux kernel CVE team has assigned CVE-2026-72173 to this issue.


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

	Issue introduced in 6.19 with commit a30b48bf1b244f11bf9b6d20cdccfe0c2264130c and fixed in 7.1.5 with commit 319caaca072adc564ac9c5357ed013909f23d5ab
	Issue introduced in 6.19 with commit a30b48bf1b244f11bf9b6d20cdccfe0c2264130c and fixed in 7.2-rc1 with commit cd1fc0e3c1f67c0c31dfc215e5d9b771133dedc0

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-2026-72173
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/proc/task_mmu.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/319caaca072adc564ac9c5357ed013909f23d5ab
	https://git.kernel.org/stable/c/cd1fc0e3c1f67c0c31dfc215e5d9b771133dedc0