Unity Linux 20.1070a Security Update: kernel (UTSA-2025-988988)

high Nessus Plugin ID 273883

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-2025-988988 advisory.

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

spi: bcm2835: Fix out-of-bounds access with more than 4 slaves

Commit 571e31fa60b3 (spi: bcm2835: Cache CS register value for
->prepare_message()) limited the number of slaves to 3 at compile-time.
The limitation was necessitated by a statically-sized array prepare_cs[] in the driver private data which contains a per-slave register value.

The commit sought to enforce the limitation at run-time by setting the controller's num_chipselect to 3: Slaves with a higher chipselect are rejected by spi_add_device().

However the commit neglected that num_chipselect only limits the number of *native* chipselects. If GPIO chipselects are specified in the device tree for more than 3 slaves, num_chipselect is silently raised by of_spi_get_gpio_numbers() and the result are out-of-bounds accesses to the statically-sized array prepare_cs[].

As a bandaid fix which is backportable to stable, raise the number of allowed slaves to 24 (which ought to be enough for anybody), enforce the limitation on slave ->setup and revert num_chipselect to 3 (which is the number of native chipselects supported by the controller).
An upcoming for-next commit will allow an arbitrary number of slaves.

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: 273883

File Name: unity_linux_UTSA-2025-988988.nasl

Version: 1.1

Type: local

Family: Unity Linux Local Security Checks

Published: 11/5/2025

Updated: 11/5/2025

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.7

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-2021-47282

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: 11/5/2025

Vulnerability Publication Date: 5/21/2024

Reference Information

CVE: CVE-2021-47282

Detections

Analytics