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FreeBSD-SA-14:22.namei Security Advisory
The FreeBSD Project

Topic: memory leak in sandboxed namei lookup

Category: core
Module: kernel
Announced: 2014-10-21
Credits: Mateusz Guzik
Affects: FreeBSD 9.1 and later.
Corrected: 2014-10-21 20:20:07 UTC (stable/10, 10.1-PRERELEASE)
2014-10-21 20:20:36 UTC (releng/10.1, 10.1-RC2-p1)
2014-10-21 20:20:36 UTC (releng/10.1, 10.1-RC1-p1)
2014-10-21 20:20:36 UTC (releng/10.1, 10.1-BETA3-p1)
2014-10-21 20:21:10 UTC (releng/10.0, 10.0-RELEASE-p10)
2014-10-21 20:20:17 UTC (stable/9, 9.3-STABLE)
2014-10-21 20:21:10 UTC (releng/9.3, 9.3-RELEASE-p3)
2014-10-21 20:21:10 UTC (releng/9.2, 9.2-RELEASE-p13)
2014-10-21 20:21:10 UTC (releng/9.1, 9.1-RELEASE-p20)
CVE Name: CVE-2014-3711

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/>.

I. Background

The namei kernel facility is responsible for performing and caching
translations from path names to file system objects (vnodes).

Capsicum is a lightweight capability and sandbox framework using a
hybrid capability system model. It is often used to create sandboxes
for applications that process data from untrusted sources.

II. Problem Description

The namei facility will leak a small amount of kernel memory every
time a sandboxed process looks up a nonexistent path name.

III. Impact

A remote attacker that can cause a sandboxed process (for instance, a
web server) to look up a large number of nonexistent path names can
cause memory exhaustion.

IV. Workaround

Systems that do not have Capsicum enabled or do not run services that
use Capsicum are not vulnerable.

On systems that have Capsicum compiled into the kernel, it can be
disabled by executing the following command as root:

# sysctl kern.features.security_capabilities=0

Services that use Capsicum are usually able to run without it, albeit
with reduced security.

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.

2) 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

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.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

[FreeBSD 9.x]
# fetch http://security.FreeBSD.org/patches/SA-14:22/namei-9.patch
# fetch http://security.FreeBSD.org/patches/SA-14:22/namei-9.patch.asc
# gpg –verify namei-9.patch.asc

[FreeBSD 10.x]
# fetch http://security.FreeBSD.org/patches/SA-14:22/namei-10.patch
# fetch http://security.FreeBSD.org/patches/SA-14:22/namei-10.patch.asc
# gpg –verify namei-10.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
system.

VI. Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path Revision
– ————————————————————————-
stable/9/ r273412
releng/9.1/ r273415
releng/9.2/ r273415
releng/9.3/ r273415
stable/10/ r273411
releng/10.0/ r273415
releng/10.1/ r273414
– ————————————————————————-

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:http://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-3711>

The latest revision of this advisory is available at
<URL:http://security.FreeBSD.org/advisories/FreeBSD-SA-14:22.namei.asc>
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