Unity Linux 20.1050a Security Update: kernel (UTSA-2026-100542)

high Nessus Plugin ID 336121

Synopsis

The Unity Linux host is missing one or more security updates.

Description

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2026-100542 advisory.

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

dm cache policy smq: fix missing locks in invalidating cache blocks

In passthrough mode, the policy invalidate_mapping operation is called simultaneously from multiple workers, thus it should be protected by a lock. Otherwise, we might end up with data races on the allocated blocks counter, or even use-after-free issues with internal data structures when doing concurrent writes.

Note that the existing FIXME in smq_invalidate_mapping() doesn't affect passthrough mode since migration tasks don't exist there, but would need attention if supporting fast device shrinking via suspend/resume without target reloading.

Reproduce steps:

1. Create a cache device consisting of 1024 cache entries

dmsetup create cmeta --table 0 8192 linear /dev/sdc 0 dmsetup create cdata --table 0 131072 linear /dev/sdc 8192 dmsetup create corig --table 0 262144 linear /dev/sdc 262144 dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct dmsetup create cache --table 0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0

2. Populate the cache, and record the number of cached blocks

fio --name=populate --filename=/dev/mapper/cache --rw=randwrite --bs=4k \
--size=64m --direct=1 nr_cached=$(dmsetup status cache | awk '{split($7, a, /); print a[1]}')

3. Reload the cache into passthrough mode

dmsetup suspend cache dmsetup reload cache --table 0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 passthrough smq 0 dmsetup resume cache

4. Write to the passthrough cache. By setting multiple jobs with I/O size equal to the cache block size, cache blocks are invalidated concurrently from different workers.

fio --filename=/dev/mapper/cache --name=test --rw=randwrite --bs=64k \
--direct=1 --numjobs=2 --randrepeat=0 --size=64m

5. Check if demoted matches cached block count. These numbers should match but may differ due to the data race.

nr_demoted=$(dmsetup status cache | awk '{print $12}') echo $nr_cached, $nr_demoted

Tenable has extracted the preceding description block directly from the Unity Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Update the affected kernel package.

Plugin Details

Severity: High

ID: 336121

File Name: unity_linux_UTSA-2026-100542.nasl

Version: 1.1

Type: Local

Family: Unity Linux Local Security Checks

Published: 8/17/2026

Updated: 8/17/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.9

Percentile: 58.16

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5

Vector: CVSS2#AV:L/AC:L/Au:S/C:C/I:C/A:C

CVSS Score Source: CVE-2026-53062

CVSS v3

Risk Factor: High

Base Score: 7.8

Temporal Score: 6.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Required KB Items: Host/local_checks_enabled, Host/cpu, Host/UOS-Server/release, Host/UOS-Server/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 8/13/2026

Vulnerability Publication Date: 6/22/2026

Reference Information

CVE: CVE-2026-53062

Detections

Analytics