Ubuntu 18.04 LTS / 20.04 LTS : Linux kernel (Azure) regression (USN-5091-3)

##
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-5091-3. The text
# itself is copyright (C) Canonical, Inc. See
# <https://ubuntu.com/security/notices>. Ubuntu(R) is a registered
# trademark of Canonical, Inc.
##

include('compat.inc');

if (description)
{
  script_id(154162);
  script_version("1.8");
  script_set_attribute(attribute:"plugin_modification_date", value:"2024/08/27");
  script_xref(name:"USN", value:"5091-3");

  script_name(english:"Ubuntu 18.04 LTS / 20.04 LTS : Linux kernel (Azure) regression (USN-5091-3)");

  script_set_attribute(attribute:"synopsis", value:
"The remote Ubuntu host is missing a security update.");
  script_set_attribute(attribute:"description", value:
"The remote Ubuntu 18.04 LTS / 20.04 LTS host has a package installed that is affected by a vulnerability as referenced
in the USN-5091-3 advisory.

    USN-5091-1 fixed vulnerabilities in Linux 5.4-based kernels. Unfortunately, for Linux kernels intended for
    use within Microsoft Azure environments, that update introduced a regression that could cause the kernel
    to fail to boot in large Azure instance types. This update fixes the problem.

    We apologize for the inconvenience.

    Original advisory details:

    Ofek Kirzner, Adam Morrison, Benedict Schlueter, and Piotr Krysiuk

    discovered that the BPF verifier in the Linux kernel missed possible

    mispredicted branches due to type confusion, allowing a side-channel

    attack. An attacker could use this to expose sensitive information.

    (CVE-2021-33624)

    It was discovered that the tracing subsystem in the Linux kernel did not

    properly keep track of per-cpu ring buffer state. A privileged attacker

    could use this to cause a denial of service. (CVE-2021-3679)

    Alexey Kardashevskiy discovered that the KVM implementation for PowerPC

    systems in the Linux kernel did not properly validate RTAS arguments in

    some situations. An attacker in a guest vm could use this to cause a denial

    of service (host OS crash) or possibly execute arbitrary code.

    (CVE-2021-37576)

    It was discovered that the Virtio console implementation in the Linux

    kernel did not properly validate input lengths in some situations. A local

    attacker could possibly use this to cause a denial of service (system

    crash). (CVE-2021-38160)

    Michael Wakabayashi discovered that the NFSv4 client implementation in the

    Linux kernel did not properly order connection setup operations. An

    attacker controlling a remote NFS server could use this to cause a denial

    of service on the client. (CVE-2021-38199)

    It was discovered that the MAX-3421 host USB device driver in the Linux

    kernel did not properly handle device removal events. A physically

    proximate attacker could use this to cause a denial of service (system

    crash). (CVE-2021-38204)

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

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version
number.");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/notices/USN-5091-3");
  script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
  script_set_attribute(attribute:"risk_factor", value:"None");

  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:"2021/10/15");
  script_set_attribute(attribute:"patch_publication_date", value:"2021/10/15");
  script_set_attribute(attribute:"plugin_publication_date", value:"2021/10/15");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:20.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1061-azure");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

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

  script_copyright(english:"Ubuntu Security Notice (C) 2021-2024 Canonical, Inc. / NASL script (C) 2021-2024 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("linux_alt_patch_detect.nasl", "ssh_get_info.nasl");
  script_require_keys("Host/cpu", "Host/Ubuntu", "Host/Ubuntu/release", "Host/Debian/dpkg-l");

  exit(0);
}

include('debian_package.inc');
include('ksplice.inc');

if ( ! get_kb_item('Host/local_checks_enabled') ) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
var os_release = get_kb_item('Host/Ubuntu/release');
if ( isnull(os_release) ) audit(AUDIT_OS_NOT, 'Ubuntu');
os_release = chomp(os_release);
if (! ('18.04' >< os_release || '20.04' >< os_release)) audit(AUDIT_OS_NOT, 'Ubuntu 18.04 / 20.04', 'Ubuntu ' + os_release);
if ( ! get_kb_item('Host/Debian/dpkg-l') ) audit(AUDIT_PACKAGE_LIST_MISSING);

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('x86_64' >!< cpu && cpu !~ "^i[3-6]86$" && 's390' >!< cpu && 'aarch64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'Ubuntu', cpu);

var kernel_mappings = {
  '18.04': {
    '5.4.0': {
      'azure': '5.4.0-1061'
    }
  },
  '20.04': {
    '5.4.0': {
      'azure': '5.4.0-1061'
    }
  }
};

var host_kernel_release = get_kb_item('Host/uptrack-uname-r');
if (empty_or_null(host_kernel_release)) host_kernel_release = get_kb_item_or_exit('Host/uname-r');
var host_kernel_base_version = get_kb_item_or_exit('Host/Debian/kernel-base-version');
var host_kernel_type = get_kb_item_or_exit('Host/Debian/kernel-type');
if(empty_or_null(kernel_mappings[os_release][host_kernel_base_version][host_kernel_type])) audit(AUDIT_INST_VER_NOT_VULN, 'kernel ' + host_kernel_release);

var extra = '';
var kernel_fixed_version = kernel_mappings[os_release][host_kernel_base_version][host_kernel_type] + "-" + host_kernel_type;
if (deb_ver_cmp(ver1:host_kernel_release, ver2:kernel_fixed_version) < 0)
{
  extra += 'Running Kernel level of ' + host_kernel_release + ' does not meet the minimum fixed level of ' + kernel_fixed_version + ' for this advisory.\n\n';
}
  else
{
  audit(AUDIT_PATCH_INSTALLED, 'Kernel package for USN-5091-3');
}

if (get_one_kb_item('Host/ksplice/kernel-cves'))
{
  var cve_list = make_list();
  if (ksplice_cves_check(cve_list))
  {
    audit(AUDIT_PATCH_INSTALLED, 'KSplice hotfix for USN-5091-3');
  }
  else
  {
    extra = extra + ksplice_reporting_text();
  }
}
if (extra) {
  security_report_v4(
    port       : 0,
    severity   : SECURITY_NOTE,
    extra      : extra
  );
  exit(0);
}