131 lines
4.7 KiB
Text
131 lines
4.7 KiB
Text
-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA512
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=============================================================================
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FreeBSD-EN-18:18.zfs Errata Notice
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The FreeBSD Project
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Topic: ZFS vnode reclaim deadlock
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Category: core
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Module: kernel
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Announced: 2018-12-19
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Credits: Allan Jude
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Affects: FreeBSD 11.2
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Corrected: 2018-12-11 19:34:25 UTC (stable/11, 11.2-STABLE)
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2018-12-19 18:05:50 UTC (releng/11.2, 11.2-RELEASE-p7)
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For general information regarding FreeBSD Errata Notices and Security
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Advisories, including descriptions of the fields above, security
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branches, and the following sections, please visit
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<URL:https://security.FreeBSD.org/>.
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I. Background
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ZFS is one of several filesystems available on FreeBSD. ZFS supports
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many advanced features, including checksumming, transparent compression,
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and snapshots.
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ZFS saves synchronous writes to the ZFS Intent Log (ZIL), which may be a
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separate log device (SLOG), so they can be replayed in the event of a
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power failure or system crash. This ensures that the contents of write()
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calls that succeeded will still be available after the system
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unexpectedly reboots.
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II. Problem Description
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There is a possible deadlock between zil_commit() and zfs_zget() during
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the vnode reclaim process. If zfs_zget() is not able to take the vnode
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exclusive lock, it will retry indefinately, blocking forward progress.
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III. Impact
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Processes may hang on the waitchan "zilog->zl_writer_lock".
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IV. Workaround
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Increasing the maximum number of vnodes (kern.maxvnodes) may decrease
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the frequency of this deadlock. Systems not using ZFS are not affected.
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V. Solution
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Perform one of the following:
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1) Upgrade your system to a supported FreeBSD stable or release / security
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branch (releng) dated after the correction date.
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2) To update your system via a binary patch:
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Systems running a RELEASE version of FreeBSD on the i386 or amd64
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platforms can be updated via the freebsd-update(8) utility:
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# freebsd-update fetch
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# freebsd-update install
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3) To update your system via a source code patch:
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The following patches have been verified to apply to the applicable
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FreeBSD release branches.
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a) Download the relevant patch from the location below, and verify the
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detached PGP signature using your PGP utility.
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[FreeBSD 11.2]
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# fetch https://security.FreeBSD.org/patches/EN-18:18/zfs.patch
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# fetch https://security.FreeBSD.org/patches/EN-18:18/zfs.patch.asc
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# gpg --verify zfs.patch.asc
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b) Apply the patch. Execute the following commands as root:
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# cd /usr/src
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# patch < /path/to/patch
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c) Recompile your kernel as described in
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<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
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system.
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VI. Correction details
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The following list contains the correction revision numbers for each
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affected branch.
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Branch/path Revision
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- -------------------------------------------------------------------------
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stable/11/ r341828
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releng/11.2/ r342226
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- -------------------------------------------------------------------------
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To see which files were modified by a particular revision, run the
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following command, replacing NNNNNN with the revision number, on a
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machine with Subversion installed:
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# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base
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Or visit the following URL, replacing NNNNNN with the revision number:
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<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>
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VII. References
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<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=229614>
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The latest revision of this advisory is available at
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<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-18:18.zfs.asc>
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