FreeBSD Security Advisory FreeBSD-SA-16:15.sysarch [REVISED]
Mark Picone
mark.picone at deakin.edu.au
Wed Oct 26 23:18:50 UTC 2016
Since the security team have had the procedure of publishing security advisories for vulnerabilities once a fix available: https://www.freebsd.org/doc/handbook/security-advisories.html
-----Original Message-----
From: owner-freebsd-security at freebsd.org [mailto:owner-freebsd-security at freebsd.org] On Behalf Of Pawel Jakub Dawidek
Sent: Wednesday, 26 October 2016 3:28 PM
To: freebsd-security at freebsd.org
Subject: Re: FreeBSD Security Advisory FreeBSD-SA-16:15.sysarch [REVISED]
Hi guys,
since when do we publish security advisories for local DoSes?
On Tue, Oct 25, 2016 at 05:36:41PM +0000, FreeBSD Security Advisories wrote:
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> FreeBSD-SA-16:15.sysarch [REVISED] Security Advisory
> The FreeBSD
> Project
>
> Topic: Incorrect argument validation in sysarch(2)
>
> Category: core
> Module: kernel
> Announced: 2016-10-25
> Credits: Core Security, ahaha from Chaitin Tech
> Affects: All supported versions of FreeBSD.
> Corrected: 2016-10-25 17:14:50 UTC (stable/11, 11.0-STABLE)
> 2016-10-25 17:11:20 UTC (releng/11.0, 11.0-RELEASE-p2)
> 2016-10-25 17:16:08 UTC (stable/10, 10.3-STABLE)
> 2016-10-25 17:11:15 UTC (releng/10.3, 10.3-RELEASE-p11)
> 2016-10-25 17:11:11 UTC (releng/10.2, 10.2-RELEASE-p24)
> 2016-10-25 17:11:07 UTC (releng/10.1, 10.1-RELEASE-p41)
> 2016-10-25 17:16:58 UTC (stable/9, 9.3-STABLE)
> 2016-10-25 17:11:02 UTC (releng/9.3, 9.3-RELEASE-p49)
> CVE Name: CVE-2016-1885
>
> For general information regarding FreeBSD Security Advisories,
> including descriptions of the fields above, security branches, and the
> following sections, please visit <URL:https://security.FreeBSD.org/>.
>
> 0. Revision history
>
> v1.0 2016-03-16 Initial release.
> v1.1 2016-10-25 Revised patch to address a problem pointed out by
> ahaha from Chaitin Tech.
>
> I. Background
>
> The IA-32 architecture allows programs to define segments, which
> provides based and size-limited view into the program address space.
> The memory-resident processor structure, called Local Descriptor
> Table, usually abbreviated LDT, contains definitions of the segments.
> Since incorrect or malicious segments would breach system integrity,
> operating systems do not provide processes direct access to the LDT,
> instead they provide system calls which allow controlled installation
> and removal of segments.
>
> II. Problem Description
>
> A special combination of sysarch(2) arguments, specify a request to
> uninstall a set of descriptors from the LDT. The start descriptor is
> cleared and the number of descriptors are provided. Due to lack of
> sufficient bounds checking during argument validity verification,
> unbound zero'ing of the process LDT and adjacent memory can be
> initiated from usermode.
>
> III. Impact
>
> This vulnerability could cause the kernel to panic. In addition it is
> possible to perform a local Denial of Service against the system by
> unprivileged processes.
>
> IV. Workaround
>
> No workaround is available, but only the amd64 architecture is affected.
>
> V. Solution
>
> Perform one of the following:
>
> 1) Upgrade your vulnerable system to a supported FreeBSD stable or
> release / security branch (releng) dated after the correction date.
>
> Reboot is required.
>
> 2) To update your vulnerable system via a binary patch:
>
> Systems running a RELEASE version of FreeBSD platforms can be updated
> via the freebsd-update(8) utility:
>
> # freebsd-update fetch
> # freebsd-update install
>
> Reboot is required.
>
> 3) To update your vulnerable system via a source code patch:
>
> The following patches have been verified to apply to the applicable
> FreeBSD release branches.
>
> [*** v1.1 NOTE ***] If your sources are not yet patched using the
> initially published advisory patches, then you need to apply both
> sysarch.patch and sysarch-01.patch. If your sources are already
> updated, or patched with patches from the initial advisory, then you
> need to apply sysarch-01.patch only.
>
> a) Download the relevant patch from the location below, and verify the
> detached PGP signature using your PGP utility.
>
> [ FreeBSD system not patched with original SA-16:15 patch] # fetch
> https://security.FreeBSD.org/patches/SA-16:15/sysarch.patch
> # fetch
> https://security.FreeBSD.org/patches/SA-16:15/sysarch.patch.asc
> # gpg --verify sysarch.patch.asc
>
> [ FreeBSD system that has been patched with original SA-16:15 patch] #
> fetch https://security.FreeBSD.org/patches/SA-16:15/sysarch-01.patch
> # fetch
> https://security.FreeBSD.org/patches/SA-16:15/sysarch-01.patch.asc
> # gpg --verify sysarch-01.patch.asc
>
> b) Apply the patch(es). Execute the following commands as root for
> every patch file downloaded:
>
> # 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/9/ r307941
> releng/9.3/ r307931
> stable/10/ r307940
> releng/10.1/ r307932
> releng/10.2/ r307933
> releng/10.3/ r307934
> stable/11/ r307938
> releng/11.0/ r307935
> -
> ----------------------------------------------------------------------
> ---
>
> 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://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-1885>
>
> The latest revision of this advisory is available at
> <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-16:15.sysarch.
> asc>
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--
Pawel Jakub Dawidek http://www.wheelsystems.com
FreeBSD committer http://www.FreeBSD.org
Am I Evil? Yes, I Am! http://mobter.com
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