FreeBSD-SA-11:05.unix: Buffer overflow in handling of UNIX socket addresses

A local user can cause the FreeBSD kernel to panic.

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FreeBSD-SA-11:05.unix                                       Security Advisory
                                                          The FreeBSD Project

Topic:          Buffer overflow in handling of UNIX socket addresses

Category:       core
Module:         kern
Announced:      2011-09-28
Credits:        Mateusz Guzik
Affects:        All supported versions of FreeBSD.
Corrected:      2011-09-28 08:47:17 UTC (RELENG_7, 7.4-STABLE)
                2011-09-28 08:47:17 UTC (RELENG_7_4, 7.4-RELEASE-p3)
                2011-09-28 08:47:17 UTC (RELENG_7_3, 7.3-RELEASE-p7)
                2011-09-28 08:47:17 UTC (RELENG_8, 8.2-STABLE)
                2011-09-28 08:47:17 UTC (RELENG_8_2, 8.2-RELEASE-p3)
                2011-09-28 08:47:17 UTC (RELENG_8_1, 8.1-RELEASE-p5)
                2011-09-28 08:47:17 UTC (RELENG_9, 9.0-RC1)

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:>.

I.   Background

UNIX-domain sockets, also known as "local" sockets, are a mechanism for
interprocess communication.  They are similar to Internet sockets (and
utilize the same system calls) but instead of relying on IP addresses
and port numbers, UNIX-domain sockets have addresses in the local file
system address space.

II.  Problem Description

When a UNIX-domain socket is attached to a location using the bind(2)
system call, the length of the provided path is not validated.  Later,
when this address was returned via other system calls, it is copied into
a fixed-length buffer.

III. Impact

A local user can cause the FreeBSD kernel to panic.  It may also be
possible to execute code with elevated privileges ("gain root"), escape
from a jail, or to bypass security mechanisms in other ways.

IV.  Workaround

No workaround is available, but systems without untrusted local users
are not vulnerable.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 7-STABLE or 8-STABLE, or to
the RELENG_8_2, RELENG_8_1, RELENG_7_4, or RELENG_7_3 security
branch dated after the correction date.

2) To update your vulnerable system via a source code patch:

The following patch has been verified to apply to FreeBSD 7.4, 7.3,
8.2 and 8.1 systems.

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

# fetch
# fetch

b) Apply the patch.

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:> and reboot the

3) To update your vulnerable system via a binary patch:

Systems running 7.4-RELEASE, 7.3-RELEASE, 8.2-RELEASE, or 8.1-RELEASE on
the i386 or amd64 platforms can be updated via the freebsd-update(8)

# freebsd-update fetch
# freebsd-update install

VI.  Correction details

The following list contains the revision numbers of each file that was
corrected in FreeBSD.


Branch                                                           Revision
- -------------------------------------------------------------------------
  src/UPDATING                                             1.507.
  src/UPDATING                                             1.507.
  src/UPDATING                                             1.632.
  src/UPDATING                                             1.632.
- -------------------------------------------------------------------------


Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/7/                                                         r225827
releng/7.4/                                                       r225827
releng/7.3/                                                       r225827
stable/8/                                                         r225827
releng/8.2/                                                       r225827
releng/8.1/                                                       r225827
stable/9/                                                         r225827
- -------------------------------------------------------------------------

The latest revision of this advisory is available at
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