137 lines
5.2 KiB
Text
137 lines
5.2 KiB
Text
-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA512
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=============================================================================
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FreeBSD-EN-16:04.hyperv Errata Notice
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The FreeBSD Project
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Topic: Hyper-V KVP (Key-Value Pair) daemon indefinite sleep
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Category: core
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Module: hyperv
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Announced: 2016-03-16
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Credits: Microsoft Open Source Technology Center(OSTC)
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Affects: FreeBSD 10.x
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Corrected: 2015-12-18 14:52:12 UTC (stable/10, 10.2-STABLE)
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2016-03-16 22:31:04 UTC (releng/10.2, 10.2-RELEASE-p14)
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2016-03-16 22:30:56 UTC (releng/10.1, 10.1-RELEASE-p31)
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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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Hyper-V is a native hypervisor running on Windows operating system. It can
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run FreeBSD 10.x as guest in virtual machine.
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Data Exchange is an integration service, also known as a key-value pair or
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KVP, that can be used to share information between virtual machines and the
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Hyper-V host. For more information, see
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<URL:https://technet.microsoft.com/en-us/library/dn798287.aspx>.
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II. Problem Description
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The KVP driver code doesn't implement the KVP device's .d_poll callback
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correctly: when there is no data available to the user-mode KVP daemon, the
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driver forgets to remember the daemon and wake up the daemon later. As a
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result, the daemon can't be woken up in a predictable period of time, and
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the host side's KVP query can hang for an unexpected period of time and get
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timeout, and finally the host can think the VM is irresponsive or unhealthy.
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III. Impact
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When a FreeBSD 10.x virtual machine runs on Hyper-V, the host may not get the
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expected response of a KVP query. When a virtual machine runs on Azure, the
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host may try to recover the "irresponsive" virtual machine by killing it and
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starting it later, causing unnecessary virtual machine downtime.
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IV. Workaround
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Don't run the KVP daemon on a virtual machine. With this, the host will know
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that KVP functionality is not working at all, so the host won't try to send KVP
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query to virtual machine.
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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. Reboot is required.
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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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Reboot is required.
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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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# fetch https://security.FreeBSD.org/patches/EN-16:04/hyperv.patch
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# fetch https://security.FreeBSD.org/patches/EN-16:04/hyperv.patch.asc
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# gpg --verify hyperv.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/10/ r292438
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releng/10.1/ r296954
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releng/10.2/ r296955
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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://technet.microsoft.com/en-us/library/dn798287.aspx>.
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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-16:04.hyperv.asc>
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