CVE-2026-68345: arm_mpam: guard MBWU state before adding it to garbage

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

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

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

arm_mpam: guard MBWU state before adding it to garbage

__destroy_component_cfg() adds each RIS mbwu_state object to the MPAM
garbage list when destroying component configuration.

However, mbwu_state is allocated per RIS and only for RISes with MBWU
monitors. A component can therefore have comp->cfg allocated while some
RISes still have ris->mbwu_state set to NULL.

Passing a NULL mbwu_state to add_to_garbage() dereferences the NULL
pointer inside the macro.

Skip RISes that do not have an mbwu_state object before adding them to
the garbage list.

The Linux kernel CVE team has assigned CVE-2026-68345 to this issue.


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

	Issue introduced in 6.19 with commit 41e8a14950e1732af51cfec8fa09f8ded02a5ca9 and fixed in 7.1.6 with commit ca1f96334267ab8d47b2c9d535cdc9920fdde269
	Issue introduced in 6.19 with commit 41e8a14950e1732af51cfec8fa09f8ded02a5ca9 and fixed in 7.2-rc5 with commit 977f52909c624210178a1247fab0b02b110c1106

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-2026-68345
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/resctrl/mpam_devices.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/ca1f96334267ab8d47b2c9d535cdc9920fdde269
	https://git.kernel.org/stable/c/977f52909c624210178a1247fab0b02b110c1106