Ubuntu 3835-1: Linux kernel vulnerabilities

    Date03 Dec 2018
    CategoryUbuntu
    2367
    Posted ByAnthony Pell
    Several security issues were fixed in the Linux kernel.
    ==========================================================================
    Ubuntu Security Notice USN-3835-1
    December 03, 2018
    
    linux, linux-gcp, linux-kvm, linux-raspi2 vulnerabilities
    ==========================================================================
    
    A security issue affects these releases of Ubuntu and its derivatives:
    
    - Ubuntu 18.10
    
    Summary:
    
    Several security issues were fixed in the Linux kernel.
    
    Software Description:
    - linux: Linux kernel
    - linux-gcp: Linux kernel for Google Cloud Platform (GCP) systems
    - linux-kvm: Linux kernel for cloud environments
    - linux-raspi2: Linux kernel for Raspberry Pi 2
    
    Details:
    
    Jann Horn discovered that the procfs file system implementation in the
    Linux kernel did not properly restrict the ability to inspect the kernel
    stack of an arbitrary task. A local attacker could use this to expose
    sensitive information. (CVE-2018-17972)
    
    Jann Horn discovered that the mremap() system call in the Linux kernel did
    not properly flush the TLB when completing, potentially leaving access to a
    physical page after it has been released to the page allocator. A local
    attacker could use this to cause a denial of service (system crash), expose
    sensitive information, or possibly execute arbitrary code. (CVE-2018-18281)
    
    It was discovered that the BPF verifier in the Linux kernel did not
    correctly compute numeric bounds in some situations. A local attacker could
    use this to cause a denial of service (system crash) or possibly execute
    arbitrary code. (CVE-2018-18445)
    
    Daniel Dadap discovered that the module loading implementation in the Linux
    kernel did not properly enforce signed module loading when booted with UEFI
    Secure Boot in some situations. A local privileged attacker could use this
    to execute untrusted code in the kernel. (CVE-2018-18653)
    
    Jann Horn discovered that the Linux kernel mishandles mapping UID or GID
    ranges inside nested user namespaces in some situations. A local attacker
    could use this to bypass access controls on resources outside the
    namespace. (CVE-2018-18955)
    
    Philipp Wendler discovered that the overlayfs implementation in the Linux
    kernel did not properly verify the directory contents permissions from
    within a unprivileged user namespace. A local attacker could use this to
    expose sensitive information (protected file names). (CVE-2018-6559)
    
    Update instructions:
    
    The problem can be corrected by updating your system to the following
    package versions:
    
    Ubuntu 18.10:
      linux-image-4.18.0-1004-gcp     4.18.0-1004.5
      linux-image-4.18.0-1005-kvm     4.18.0-1005.5
      linux-image-4.18.0-1007-raspi2  4.18.0-1007.9
      linux-image-4.18.0-12-generic   4.18.0-12.13
      linux-image-4.18.0-12-generic-lpae  4.18.0-12.13
      linux-image-4.18.0-12-lowlatency  4.18.0-12.13
      linux-image-4.18.0-12-snapdragon  4.18.0-12.13
      linux-image-gcp                 4.18.0.1004.4
      linux-image-generic             4.18.0.12.13
      linux-image-generic-lpae        4.18.0.12.13
      linux-image-gke                 4.18.0.1004.4
      linux-image-kvm                 4.18.0.1005.5
      linux-image-lowlatency          4.18.0.12.13
      linux-image-raspi2              4.18.0.1007.4
      linux-image-snapdragon          4.18.0.12.13
    
    After a standard system update you need to reboot your computer to make
    all the necessary changes.
    
    ATTENTION: Due to an unavoidable ABI change the kernel updates have
    been given a new version number, which requires you to recompile and
    reinstall all third party kernel modules you might have installed.
    Unless you manually uninstalled the standard kernel metapackages
    (e.g. linux-generic, linux-generic-lts-RELEASE, linux-virtual,
    linux-powerpc), a standard system upgrade will automatically perform
    this as well.
    
    References:
      https://usn.ubuntu.com/usn/usn-3835-1
      CVE-2018-17972, CVE-2018-18281, CVE-2018-18445, CVE-2018-18653,
      CVE-2018-18955, CVE-2018-6559
    
    Package Information:
      https://launchpad.net/ubuntu/+source/linux/4.18.0-12.13
      https://launchpad.net/ubuntu/+source/linux-gcp/4.18.0-1004.5
      https://launchpad.net/ubuntu/+source/linux-kvm/4.18.0-1005.5
      https://launchpad.net/ubuntu/+source/linux-raspi2/4.18.0-1007.9
    
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