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    Ubuntu 4367-2: Linux kernel regression

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    USN-4367-1 introduced a regression in the Linux kernel.
    Ubuntu Security Notice USN-4367-2
    May 28, 2020
    linux regression
    A security issue affects these releases of Ubuntu and its derivatives:
    - Ubuntu 20.04 LTS
    USN-4367-1 introduced a regression in the Linux kernel.
    Software Description:
    - linux: Linux kernel
    USN-4367-1 fixed vulnerabilities in the 5.4 Linux kernel. Unfortunately,
    that update introduced a regression in overlayfs. This update corrects
    the problem.
    We apologize for the inconvenience.
    Original advisory details:
     It was discovered that the btrfs implementation in the Linux kernel did not
     properly detect that a block was marked dirty in some situations. An
     attacker could use this to specially craft a file system image that, when
     unmounted, could cause a denial of service (system crash). (CVE-2019-19377)
     It was discovered that the linux kernel did not properly validate certain
     mount options to the tmpfs virtual memory file system. A local attacker
     with the ability to specify mount options could use this to cause a denial
     of service (system crash). (CVE-2020-11565)
     It was discovered that the block layer in the Linux kernel contained a race
     condition leading to a use-after-free vulnerability. A local attacker could
     possibly use this to cause a denial of service (system crash) or execute
     arbitrary code. (CVE-2020-12657)
    Update instructions:
    The problem can be corrected by updating your system to the following
    package versions:
    Ubuntu 20.04 LTS:
      linux-image-5.4.0-33-generic    5.4.0-33.37
      linux-image-5.4.0-33-generic-lpae  5.4.0-33.37
      linux-image-5.4.0-33-lowlatency  5.4.0-33.37
    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.
    Package Information:

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