126 lines
4.6 KiB
Text
126 lines
4.6 KiB
Text
-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA512
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=============================================================================
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FreeBSD-EN-19:05.kqueue Errata Notice
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The FreeBSD Project
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Topic: kqueue race condition and kernel panic
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Category: core
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Module: kqueue
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Announced: 2019-01-09
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Credits: Mark Johnston
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Affects: FreeBSD 11.2
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Corrected: 2018-11-24 17:11:47 UTC (stable/11, 11.2-STABLE)
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2019-01-09 18:57:38 UTC (releng/11.2, 11.2-RELEASE-p8)
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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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kevent(2) is a system call which provides a generic method of notifying the
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caller when a caller-specified event happens or a condition holds. One use
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for kevent(2) is to wait for a specified timeout to elapse.
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II. Problem Description
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The kevent(2) implementation in the kernel contains a race condition which
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can be triggered when an event is added and fires shortly after. Most event
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types are not affected, but timer events can trigger the race if the timeout
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duration is very short.
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III. Impact
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The race condition can cause corruption of a queue structure, leading to
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a kernel panic when it is later accessed. Applications using kevent(2) may
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trigger the panic if their usage causes the race condition to occur.
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IV. Workaround
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No workaround is available.
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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, and reboot.
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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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# shutdown -r +30 "Rebooting for errata update"
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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-19:05/kqueue.patch
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# fetch https://security.FreeBSD.org/patches/EN-19:05/kqueue.patch.asc
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# gpg --verify kqueue.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/ r340904
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releng/11.2/ r342899
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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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The latest revision of this advisory is available at
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<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-19:05.kqueue.asc>
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