FreeBSD Errata Notices
2018-Sep-27 20:08 UTC
[FreeBSD-Announce] FreeBSD Errata Notice FreeBSD-EN-18:12.mem
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============================================================================FreeBSD-EN-18:12.mem
Errata Notice
The FreeBSD Project
Topic: Small kernel memory disclosures in two system calls
Category: core
Module: kernel
Announced: 2018-09-27
Credits: Thomas Barabosch, Fraunhofer FKIE
Affects: All supported versions of FreeBSD.
Corrected: 2018-09-27 18:42:40 UTC (stable/11, 11.2-STABLE)
2018-09-27 18:36:30 UTC (releng/11.2, 11.2-RELEASE-p4)
2018-09-27 18:36:30 UTC (releng/11.1, 11.1-RELEASE-p15)
2018-09-27 18:44:40 UTC (stable/10, 10.4-STABLE)
2018-09-27 18:36:30 UTC (releng/10.4, 10.4-RELEASE-p13)
CVE Name: CVE-2018-17155
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
The kernel provides an interface for userland programs via system calls. Two
of these system calls are named getcontext and swapcontext.
II. Problem Description
Due to insufficient initialization of memory copied to userland in the
getcontext and swapcontext system calls, small amounts of kernel memory may
be disclosed to userland processes.
III. Impact
An unprivileged local user may be able to create a specific program to read
the contents of small portions of kernel memory.
Such memory might contain sensitive information, such as portions of the file
cache or terminal buffers. This information might be directly useful, or it
might be leveraged to obtain elevated privileges in some way; for example,
a terminal buffer might include a user-entered password.
IV. Workaround
No workaround is available.
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.
Afterward, reboot the system.
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
Afterward, reboot the system.
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.
# fetch https://security.FreeBSD.org/patches/EN-18:12/mem.patch
# fetch https://security.FreeBSD.org/patches/EN-18:12/mem.patch.asc
# gpg --verify mem.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/10/ r339984
releng/10.4/ r338981
stable/11/ r339983
releng/11.1/ r338981
releng/11.2/ r338981
- -------------------------------------------------------------------------
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-2018-17155>
The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-18:12.mem.asc>
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Jonathan Chen
2018-Sep-27 20:31 UTC
[FreeBSD-Announce] FreeBSD Errata Notice FreeBSD-EN-18:12.mem
On Fri, 28 Sep 2018 at 08:19, FreeBSD Errata Notices <errata-notices at freebsd.org> wrote:> > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA512 > > ============================================================================> FreeBSD-EN-18:12.mem Errata Notice > The FreeBSD Project > > Topic: Small kernel memory disclosures in two system calls[...]> VI. Correction details > > The following list contains the correction revision numbers for each > affected branch. > > Branch/path Revision > - ------------------------------------------------------------------------- > stable/10/ r339984 > releng/10.4/ r338981 > stable/11/ r339983 > releng/11.1/ r338981 > releng/11.2/ r338981 > - -------------------------------------------------------------------------Actually, the commit on the stable/11 appears to be 338983 and not 339983. Cheers. -- Jonathan Chen <jonc at chen.org.nz>