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FreeBSD Errata Notice FreeBSD-EN-18:05.mem

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FreeBSD-EN-18:05.mem                                            Errata Notice
                                                          The FreeBSD Project

Topic:          Multiple small kernel memory disclosures

Category:       core
Module:         kernel
Announced:      2018-05-08
Credits:        Ilja van Sprundel, IOActive
                Vlad Tsyrklevich
Affects:        All supported versions of FreeBSD.
Corrected:      2018-04-08 20:50:16 UTC (stable/11, 11.1-STABLE)
                2018-05-08 17:14:54 UTC (releng/11.1, 11.1-RELEASE-p10)
                2018-04-09 12:55:09 UTC (stable/10, 10.4-STABLE)
                2018-05-08 17:14:54 UTC (releng/10.4, 10.4-RELEASE-p9)
CVE Name:       CVE-2018-6920, CVE-2018-6921

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

FreeBSD includes drivers for Atheros wireless interfaces, a TCP network
stack, and the ability to execute Linux binaries.

II.  Problem Description

Due to insufficient initialization of memory copied to userland in the
components described above small amounts of kernel memory may be disclosed
to userland processes.

The disclosure in the Atheros wireless driver and Linux subsystem applies to
both FreeBSD 10.x and 11.x (CVE-2018-6920).

The disclosure in the TCP network stack was introduced in 11.0.  As such,
only FreeBSD 11.x is affected by this issue (CVE-2018-6921).

III. Impact

A user who can access these drivers, use TCP sockets, or execute Linux
binaries may be able 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.

[FreeBSD 11.1]
# fetch https://security.FreeBSD.org/patches/EN-18:05/mem.11.1.patch
# fetch https://security.FreeBSD.org/patches/EN-18:05/mem.11.1.patch.asc
# gpg --verify mem.11.1.patch.asc

[FreeBSD 10.4]
# fetch https://security.FreeBSD.org/patches/EN-18:05/mem.10.4.patch
# fetch https://security.FreeBSD.org/patches/EN-18:05/mem.10.4.patch.asc
# gpg --verify mem.10.4.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/                                                        r332321
releng/10.4/                                                      r333372
stable/11/                                                        r332303
releng/11.1/                                                      r333372
- -------------------------------------------------------------------------

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-2018-6920>

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-6921>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-18:05.mem.asc>
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