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Unity Linux 20.1070e Security Update: kernel (UTSA-2025-987617)

medium Nessus Plugin ID 271053

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-2025-987617 advisory.

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

 powerpc/smp: do not decrement idle task preempt count in CPU offline

 With PREEMPT_COUNT=y, when a CPU is offlined and then onlined again, we get:

 BUG: scheduling while atomic: swapper/1/0/0x00000000 no locks held by swapper/1/0.
 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.15.0-rc2+ #100 Call Trace:
 dump_stack_lvl+0xac/0x108
 __schedule_bug+0xac/0xe0
 __schedule+0xcf8/0x10d0 schedule_idle+0x3c/0x70 do_idle+0x2d8/0x4a0 cpu_startup_entry+0x38/0x40 start_secondary+0x2ec/0x3a0 start_secondary_prolog+0x10/0x14

 This is because powerpc's arch_cpu_idle_dead() decrements the idle task's preempt count, for reasons explained in commit a7c2bb8279d2 (powerpc:
 Re-enable preemption before cpu_die()), specifically start_secondary() expects a preempt_count() of 0.

 However, since commit 2c669ef6979c (powerpc/preempt: Don't touch the idle task's preempt_count during hotplug) and commit f1a0a376ca0c (sched/core:
 Initialize the idle task with preemption disabled), that justification no longer holds.

 The idle task isn't supposed to re-enable preemption, so remove the vestigial preempt_enable() from the CPU offline path.

 Tested with pseries and powernv in qemu, and pseries on PowerVM.

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.

See Also

http://www.nessus.org/u?16b9b514

http://www.nessus.org/u?8aaf7932

https://nvd.nist.gov/vuln/detail/CVE-2021-47454

Plugin Details

Severity: Medium

ID: 271053

File Name: unity_linux_UTSA-2025-987617.nasl

Version: 1.1

Type: local

Published: 10/21/2025

Updated: 10/21/2025

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

CVSS v2

Risk Factor: Medium

Base Score: 4.6

Temporal Score: 3.4

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

CVSS Score Source: CVE-2021-47454

CVSS v3

Risk Factor: Medium

Base Score: 5.5

Temporal Score: 4.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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: 10/15/2025

Vulnerability Publication Date: 7/21/2021

Reference Information

CVE: CVE-2021-47454