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  • [FreeBSD-Announce] FreeBSD Errata Notice FreeBSD-EN-18:18.zfs

    From FreeBSD Errata Notices@21:1/5 to All on Wed Dec 19 22:00:00 2018
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    ============================================================================= FreeBSD-EN-18:18.zfs Errata Notice
    The FreeBSD Project

    Topic: ZFS vnode reclaim deadlock

    Category: core
    Module: kernel
    Announced: 2018-12-19
    Credits: Allan Jude
    Affects: FreeBSD 11.2
    Corrected: 2018-12-11 19:34:25 UTC (stable/11, 11.2-STABLE)
    2018-12-19 18:05:50 UTC (releng/11.2, 11.2-RELEASE-p7)

    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

    ZFS is one of several filesystems available on FreeBSD. ZFS supports
    many advanced features, including checksumming, transparent compression,
    and snapshots.

    ZFS saves synchronous writes to the ZFS Intent Log (ZIL), which may be a separate log device (SLOG), so they can be replayed in the event of a
    power failure or system crash. This ensures that the contents of write()
    calls that succeeded will still be available after the system
    unexpectedly reboots.

    II. Problem Description

    There is a possible deadlock between zil_commit() and zfs_zget() during
    the vnode reclaim process. If zfs_zget() is not able to take the vnode exclusive lock, it will retry indefinately, blocking forward progress.

    III. Impact

    Processes may hang on the waitchan "zilog->zl_writer_lock".

    IV. Workaround

    Increasing the maximum number of vnodes (kern.maxvnodes) may decrease
    the frequency of this deadlock. Systems not using ZFS are not affected.

    V. Solution

    Perform one of the following:

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

    2) To update your system via a binary patch:

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

    # freebsd-update fetch
    # freebsd-update install

    3) 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.

    [FreeBSD 11.2]
    # fetch https://security.FreeBSD.org/patches/EN-18:18/zfs.patch
    # fetch https://security.FreeBSD.org/patches/EN-18:18/zfs.patch.asc
    # gpg --verify zfs.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

    The following list contains the correction revision numbers for each
    affected branch.

    Branch/path Revision
    - ------------------------------------------------------------------------- stable/11/ r341828 releng/11.2/ r342226
    - -------------------------------------------------------------------------

    To see which files were modified by a particular revision, run the
    following command, replacing NNNNNN with the revision number, on a
    machine with Subversion installed:

    # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

    Or visit the following URL, replacing NNNNNN with the revision number:

    <URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

    VII. References

    <URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=229614>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-18:18.zfs.asc> -----BEGIN PGP SIGNATURE-----

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