Back to list
FreeBSD Security Advisory FreeBSD-SA-14:12.ktrace
Jun 03 2014 07:34PM
FreeBSD Security Advisories (security-advisories freebsd org)
-----BEGIN PGP SIGNED MESSAGE-----
FreeBSD-SA-14:12.ktrace Security Advisory
The FreeBSD Project
Topic: ktrace kernel memory disclosure
Credits: Jilles Tjoelker
Affects: FreeBSD 8.4, FreeBSD 9.1 and FreeBSD 9.2
Corrected: 2014-06-03 19:02:33 UTC (stable/9, 9.3-BETA1)
2014-06-03 19:02:33 UTC (stable/9, 9.3-BETA1-p1)
2014-06-03 19:03:11 UTC (releng/9.2, 9.2-RELEASE-p7)
2014-06-03 19:03:11 UTC (releng/9.1, 9.1-RELEASE-p14)
2014-06-03 19:02:42 UTC (stable/8, 8.4-STABLE)
2014-06-03 19:03:23 UTC (releng/8.4, 8.4-RELEASE-p11)
CVE Name: CVE-2014-3873
For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:http://security.FreeBSD.org/>.
The ktrace utility enables kernel trace logging for the specified processes,
commonly used for diagnostic or debugging purposes. The kernel operations
that are traced include system calls, namei translations, signal processing,
and I/O as well as data associated with these operations.
The utility may be used only with a kernel that has been built with the
``KTRACE'' option in the kernel configuration file, which is enabled by
II. Problem Description
Due to an overlooked merge to -STABLE branches, the size for page fault
kernel trace entries was set incorrectly.
A user who can enable kernel process tracing could end up reading the
contents 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
The system administrator may set sysctl security.bsd.unprivileged_proc_debug
to 0 to prevent non-privileged users from using all process debugging
facilities provided by the kernel, that includes ktrace functionality.
Please note that this flag have broad effect and may break applications,
as some of them may rely on certain debugging facilities to function.
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.
2) To update your vulnerable 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 http://security.FreeBSD.org/patches/SA-14:12/ktrace.patch
# fetch http://security.FreeBSD.org/patches/SA-14:12/ktrace.patch.asc
# gpg --verify ktrace.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:http://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
3) To update your vulnerable 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
VI. Correction details
The following list contains the correction revision numbers for each
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:
The latest revision of this advisory is available at
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.22 (FreeBSD)
-----END PGP SIGNATURE-----
[ reply ]
Copyright 2010, SecurityFocus