Unity Linux 20.1070a Security Update: kernel (UTSA-2025-989415)

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

include('compat.inc');

if (description)
{
  script_id(273963);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2025/11/05");

  script_cve_id("CVE-2021-47553");

  script_name(english:"Unity Linux 20.1070a Security Update: kernel (UTSA-2025-989415)");

  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-2025-989415 advisory.

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

    sched/scs: Reset task stack state in bringup_cpu()

    To hot unplug a CPU, the idle task on that CPU calls a few layers of C
    code before finally leaving the kernel. When KASAN is in use, poisoned
    shadow is left around for each of the active stack frames, and when
    shadow call stacks are in use. When shadow call stacks (SCS) are in use
    the task's saved SCS SP is left pointing at an arbitrary point within
    the task's shadow call stack.

    When a CPU is offlined than onlined back into the kernel, this stale
    state can adversely affect execution. Stale KASAN shadow can alias new
    stackframes and result in bogus KASAN warnings. A stale SCS SP is
    effectively a memory leak, and prevents a portion of the shadow call
    stack being used. Across a number of hotplug cycles the idle task's
    entire shadow call stack can become unusable.

    We previously fixed the KASAN issue in commit:

      e1b77c92981a5222 (sched/kasan: remove stale KASAN poison after hotplug)

    ... by removing any stale KASAN stack poison immediately prior to
    onlining a CPU.

    Subsequently in commit:

      f1a0a376ca0c4ef1 (sched/core: Initialize the idle task with preemption disabled)

    ... the refactoring left the KASAN and SCS cleanup in one-time idle
    thread initialization code rather than something invoked prior to each
    CPU being onlined, breaking both as above.

    We fixed SCS (but not KASAN) in commit:

      63acd42c0d4942f7 (sched/scs: Reset the shadow stack when idle_task_exit)

    ... but as this runs in the context of the idle task being offlined it's
    potentially fragile.

    To fix these consistently and more robustly, reset the SCS SP and KASAN
    shadow of a CPU's idle task immediately before we online that CPU in
    bringup_cpu(). This ensures the idle task always has a consistent state
    when it is running, and removes the need to so so when exiting an idle
    task.

    Whenever any thread is created, dup_task_struct() will give the task a
    stack which is free of KASAN shadow, and initialize the task's SCS SP,
    so there's no need to specially initialize either for idle thread within
    init_idle(), as this was only necessary to handle hotplug cycles.

    I've tested this on arm64 with:

    * gcc 11.1.0, defconfig +KASAN_INLINE, KASAN_STACK
    * clang 12.0.0, defconfig +KASAN_INLINE, KASAN_STACK, SHADOW_CALL_STACK

    ... offlining and onlining CPUS with:

    | while true; do
    |   for C in /sys/devices/system/cpu/cpu*/online; do
    |     echo 0 > $C;
    |     echo 1 > $C;
    |   done
    | done

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-2025-989415
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?44e9858a");
  # https://lore.kernel.org/linux-cve-announce/2024052442-CVE-2021-47553-1026@gregkh
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?cc24797a");
  script_set_attribute(attribute:"see_also", value:"https://nvd.nist.gov/vuln/detail/CVE-2021-47553");
  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-2021-47553");

  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:"2021/07/21");
  script_set_attribute(attribute:"patch_publication_date", value:"2025/11/05");
  script_set_attribute(attribute:"plugin_publication_date", value:"2025/11/05");

  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) 2025 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:"^20.1070a([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'UOS Server 20.1070a', '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 && 'loongarch64' >!< cpu && 'x86_64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'UOS Server', cpu);


var constraints = [
  {
    'release': '20',
    'sp': '1070a',
    'pkgs': [
      {'reference':'kernel-5.10.0-79.4.2', 'sp':'1070a', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-5.10.0-79.4.2', 'sp':'1070a', 'cpu':'amd64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-5.10.0-79.4.2', 'sp':'1070a', 'cpu':'loongarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-5.10.0-79.4.2', 'sp':'1070a', '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');
}