Unity Linux 20.1070e Security Update: kernel (UTSA-2026-131729)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
##

include('compat.inc');

if (description)
{
  script_id(366592);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/10/16");

  script_cve_id("CVE-2025-21693");

  script_name(english:"Unity Linux 20.1070e Security Update: kernel (UTSA-2026-131729)");

  script_set_attribute(attribute:"synopsis", value:
"The Unity Linux host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the
UTSA-2026-131729 advisory.

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

    mm: zswap: properly synchronize freeing resources during CPU hotunplug

    In zswap_compress() and zswap_decompress(), the per-CPU acomp_ctx of the
    current CPU at the beginning of the operation is retrieved and used
    throughout.  However, since neither preemption nor migration are disabled,
    it is possible that the operation continues on a different CPU.

    If the original CPU is hotunplugged while the acomp_ctx is still in use,
    we run into a UAF bug as some of the resources attached to the acomp_ctx
    are freed during hotunplug in zswap_cpu_comp_dead() (i.e.
    acomp_ctx.buffer, acomp_ctx.req, or acomp_ctx.acomp).

    The problem was introduced in commit 1ec3b5fe6eec (mm/zswap: move to use
    crypto_acomp API for hardware acceleration) when the switch to the
    crypto_acomp API was made.  Prior to that, the per-CPU crypto_comp was
    retrieved using get_cpu_ptr() which disables preemption and makes sure the
    CPU cannot go away from under us.  Preemption cannot be disabled with the
    crypto_acomp API as a sleepable context is needed.

    Use the acomp_ctx.mutex to synchronize CPU hotplug callbacks allocating
    and freeing resources with compression/decompression paths.  Make sure
    that acomp_ctx.req is NULL when the resources are freed.  In the
    compression/decompression paths, check if acomp_ctx.req is NULL after
    acquiring the mutex (meaning the CPU was offlined) and retry on the new
    CPU.

    The initialization of acomp_ctx.mutex is moved from the CPU hotplug
    callback to the pool initialization where it belongs (where the mutex is
    allocated).  In addition to adding clarity, this makes sure that CPU
    hotplug cannot reinitialize a mutex that is already locked by
    compression/decompression.

    Previously a fix was attempted by holding cpus_read_lock() [1].  This
    would have caused a potential deadlock as it is possible for code already
    holding the lock to fall into reclaim and enter zswap (causing a
    deadlock).  A fix was also attempted using SRCU for synchronization, but
    Johannes pointed out that synchronize_srcu() cannot be used in CPU hotplug
    notifiers [2].

    Alternative fixes that were considered/attempted and could have worked:
    - Refcounting the per-CPU acomp_ctx. This involves complexity in
      handling the race between the refcount dropping to zero in
      zswap_[de]compress() and the refcount being re-initialized when the
      CPU is onlined.
    - Disabling migration before getting the per-CPU acomp_ctx [3], but
      that's discouraged and is a much bigger hammer than needed, and could
      result in subtle performance issues.

    [1]https://lkml.kernel.org/[email protected]/
    [2]https://lkml.kernel.org/[email protected]/
    [3]https://lkml.kernel.org/[email protected]/

    [[email protected]: remove comment]
      Link: https://lkml.kernel.org/r/CAJD7tkaxS1wjn+swugt8QCvQ-rVF5RZnjxwPGX17k8x9zSManA@mail.gmail.com

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.");
  # https://src.uniontech.com/#/security_advisory_detail?utsa_id=UTSA-2026-131729
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?1e676363");
  # https://lore.kernel.org/linux-cve-announce/2025021056-CVE-2025-21693-b6d1@gregkh
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?2c358084");
  script_set_attribute(attribute:"see_also", value:"https://nvd.nist.gov/vuln/detail/CVE-2025-21693");
  script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:S/C:C/I:C/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2025-21693");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");

  script_set_attribute(attribute:"vuln_publication_date", value:"2025/02/10");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/10/16");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/10/16");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Unity Linux Local Security Checks");

  script_copyright(english:"This script is Copyright (C) 2026 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info2.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/UOS-Server/release", "Host/UOS-Server/rpm-list", "Host/cpu");

  exit(0);
}
include('rpm2.inc');

if (!get_kb_item('Host/local_checks_enabled')) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
var os_product = get_kb_item('installed_os/local/SSH/0/product');
if (isnull(os_product) || 'UOS Server' >!< os_product) audit(AUDIT_OS_NOT, 'UOS Server');
var os_version = get_kb_item('installed_os/local/SSH/0/version');
if (isnull(os_version)) audit(AUDIT_UNKNOWN_APP_VER, 'UOS Server');
if (! preg(pattern:"^(20.1070e)([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'UOS Server 20.1070e', 'UOS Server ' + os_version);

if (!get_kb_item('Host/UOS-Server/rpm-list')) audit(AUDIT_PACKAGE_LIST_MISSING);

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('aarch64' >!< cpu && 'amd64' >!< cpu && 'sw_64' >!< cpu && 'x86_64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'UOS Server', cpu);


var constraints = [
  {
    'release': '20',
    'sp': '1070e',
    'pkgs': [
      {'reference':'kernel-5.10.0-79.26.uel20', 'sp':'1070e', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-5.10.0-79.26.uel20', 'sp':'1070e', 'cpu':'amd64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-5.10.0-79.26.uel20', 'sp':'1070e', 'cpu':'sw_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-5.10.0-79.26.uel20', 'sp':'1070e', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE}
    ]
  }
];

var os_release = get_one_kb_item('installed_os/local/SSH/0/release');
var os_sp = get_one_kb_item('Host/*/minor_release');

var flag = 0;
var reference;
var sp;
var _cpu;
var el_string;
var rpm_spec_vers_cmp;
var epoch;
var allowmaj;
var exists_check;
var cves;
foreach var constraint ( constraints ) {
  # Check that the target release is equal to the affected release
  if (!empty_or_null(constraint['release'])){
    if (constraint['release'] != os_release) continue;
  }
  if (!empty_or_null(constraint['sp'])){
    if (constraint['sp'] != os_sp) continue;
  }
  foreach var pkg ( constraint['pkgs'] ) {
    reference = NULL;
    sp = NULL;
    _cpu = NULL;
    el_string = NULL;
    rpm_spec_vers_cmp = NULL;
    epoch = NULL;
    allowmaj = NULL;
    exists_check = NULL;
    cves = NULL;
    if (!empty_or_null(pkg['reference'])) reference = pkg['reference'];
    if (!empty_or_null(pkg['sp'])) sp = pkg['sp'];
    if (!empty_or_null(pkg['cpu'])) _cpu = pkg['cpu'];
    if (!empty_or_null(pkg['el_string'])) el_string = pkg['el_string'];
    if (!empty_or_null(pkg['rpm_spec_vers_cmp'])) rpm_spec_vers_cmp = pkg['rpm_spec_vers_cmp'];
    if (!empty_or_null(pkg['epoch'])) epoch = pkg['epoch'];
    if (!empty_or_null(pkg['allowmaj'])) allowmaj = pkg['allowmaj'];
    if (!empty_or_null(pkg['exists_check'])) exists_check = pkg['exists_check'];
    if (!empty_or_null(pkg['cves'])) cves = pkg['cves'];
    if (reference &&
        ## (no known rpm to check OR known rpm_exists)
        (!exists_check || rpm_exists(rpm:exists_check)) &&
        rpm_check(sp:sp, cpu:_cpu, reference:reference, epoch:epoch, el_string:el_string, rpm_spec_vers_cmp:rpm_spec_vers_cmp, allowmaj:allowmaj, cves:cves)) flag++;
  }
}


if (flag)
{
  security_report_v4(
      port       : 0,
      severity   : SECURITY_WARNING,
      extra      : rpm_report_get()
  );
  exit(0);
}
else
{
  var tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, 'kernel');
}