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  • FreeBSD Errata Notice FreeBSD-EN-22:16.kqueue

    From FreeBSD Errata Notices@21:1/5 to All on Tue Aug 9 23:00:10 2022
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    ============================================================================= FreeBSD-EN-22:16.kqueue Errata Notice
    The FreeBSD Project

    Topic: kevent(2) timers fire too often

    Category: core
    Module: kqueue
    Announced: 2022-08-09
    Affects: FreeBSD 13.1
    Corrected: 2022-06-08 00:42:21 UTC (stable/13, 13.1-STABLE)
    2022-08-09 20:01:21 UTC (releng/13.1, 13.1-RELEASE-p1)

    For general information regarding FreeBSD Errata Notices and Security Advisories, including descriptions of the fields above, security
    branches, and the following sections, please visit <URL:https://security.FreeBSD.org/>.

    I. Background

    kevent(2) is a system call which provides a generic method of notifying
    the caller when a caller-specified event happens or a condition holds.
    One use for kevent(2) is to wait for a specified timeout to elapse.
    This is implemented by the EVFILT_TIMER filter type.

    II. Problem Description

    In FreeBSD 13.1, periodic events of type EVFILT_TIMER will return at
    only half of the requested frequency, following the first event.

    III. Impact

    The bug may cause misbehaviour in software that makes use of periodic kevent(2)-based timers.

    IV. Workaround

    No workaround is available.

    V. Solution

    Upgrade your system to a supported FreeBSD stable or release / security
    branch (releng) dated after the correction date and reboot.

    Perform one of the following:

    1) To update your system via a binary patch:

    Systems running a RELEASE version of FreeBSD on the amd64, i386, or
    (on FreeBSD 13 and later) arm64 platforms can be updated via the freebsd-update(8) utility:

    # freebsd-update fetch
    # freebsd-update install
    # shutdown -r +10min "Rebooting for an errata update"

    2) To update your system via a source code patch:

    The following patches have been verified to apply to the applicable
    FreeBSD release branches.

    a) Download the relevant patch from the location below, and verify the
    detached PGP signature using your PGP utility.

    # fetch https://security.FreeBSD.org/patches/EN-22:16/kqueue.patch
    # fetch https://security.FreeBSD.org/patches/EN-22:16/kqueue.patch.asc
    # gpg --verify kqueue.patch.asc

    b) Apply the patch. Execute the following commands as root:

    # cd /usr/src
    # patch < /path/to/patch

    c) Recompile your kernel as described in <URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
    system.

    VI. Correction details

    This issue is corrected by the corresponding Git commit hash or Subversion revision number in the following stable and release branches:

    Branch/path Hash Revision
    - ------------------------------------------------------------------------- stable/13/ 129112f80d2b stable/13-n251040 releng/13.1/ c48048ebdbed releng/13.1-n250150
    - -------------------------------------------------------------------------

    Run the following command to see which files were modified by a
    particular commit:

    # git show --stat <commit hash>

    Or visit the following URL, replacing NNNNNN with the hash:

    <URL:https://cgit.freebsd.org/src/commit/?id=NNNNNN>

    To determine the commit count in a working tree (for comparison against
    nNNNNNN in the table above), run:

    # git rev-list --count --first-parent HEAD

    VII. References

    <URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=264131>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-22:16.kqueue.asc> -----BEGIN PGP SIGNATURE-----

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