CVE-2026-72181: mips: sched: Fix CPUMASK_OFFSTACK memory corruption

CVE-2026-72181: mips: sched: Fix CPUMASK_OFFSTACK memory corruption

[Greg Kroah-Hartman]

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

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

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

mips: sched: Fix CPUMASK_OFFSTACK memory corruption

This patch addresses a critical memory management flaw. When
CONFIG_CPUMASK_OFFSTACK is enabled, cpumask_var_t is a pointer.
Consequently, sizeof(new_mask) evaluates to the pointer size, causing
copy_from_user() to clobber the mask pointer. Furthermore, the old
logic performed copy_from_user() before allocating the mask.

Fix this by allocating new_mask first. To handle variable-sized user
masks correctly, use cpumask_size() to truncate overly large user masks
or pad undersized masks with zeros before copying the data directly into
the allocated buffer.

The Linux kernel CVE team has assigned CVE-2026-72181 to this issue.


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

	Issue introduced in 2.6.23 with commit 295cbf6d63165fe4253cf1d9ceadcda47a318b48 and fixed in 5.15.212 with commit d20ee42f8226607b5693b2bc2f115ca2d270221a
	Issue introduced in 2.6.23 with commit 295cbf6d63165fe4253cf1d9ceadcda47a318b48 and fixed in 6.1.178 with commit 15ba8053fe4162c933855f1676fb321cdb6251c7
	Issue introduced in 2.6.23 with commit 295cbf6d63165fe4253cf1d9ceadcda47a318b48 and fixed in 6.6.145 with commit 3446ffb5d03c36f9ce88ede7ca5be319a2968d96
	Issue introduced in 2.6.23 with commit 295cbf6d63165fe4253cf1d9ceadcda47a318b48 and fixed in 6.12.97 with commit 87a56c1e8e36d06ebe8640432f911538ded7827d
	Issue introduced in 2.6.23 with commit 295cbf6d63165fe4253cf1d9ceadcda47a318b48 and fixed in 6.18.40 with commit 1caee6e084a96ada94658f261ced377d85af3f03
	Issue introduced in 2.6.23 with commit 295cbf6d63165fe4253cf1d9ceadcda47a318b48 and fixed in 7.1.5 with commit a1dd41d00c57efb1fbc6f361c5f48c9d00cca51c
	Issue introduced in 2.6.23 with commit 295cbf6d63165fe4253cf1d9ceadcda47a318b48 and fixed in 7.2-rc1 with commit 98e37db4a34d3af3fb2f4648295c25b5e40b20e3

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-2026-72181
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:
	arch/mips/kernel/mips-mt-fpaff.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/d20ee42f8226607b5693b2bc2f115ca2d270221a
	https://git.kernel.org/stable/c/15ba8053fe4162c933855f1676fb321cdb6251c7
	https://git.kernel.org/stable/c/3446ffb5d03c36f9ce88ede7ca5be319a2968d96
	https://git.kernel.org/stable/c/87a56c1e8e36d06ebe8640432f911538ded7827d
	https://git.kernel.org/stable/c/1caee6e084a96ada94658f261ced377d85af3f03
	https://git.kernel.org/stable/c/a1dd41d00c57efb1fbc6f361c5f48c9d00cca51c
	https://git.kernel.org/stable/c/98e37db4a34d3af3fb2f4648295c25b5e40b20e3