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FreeBSD-SA-05:03.amd64                                      Security Advisory
                                                          The FreeBSD Project

Topic:          unprivileged hardware access on amd64

Category:       core
Module:         sys_amd64
Announced:      2004-04-06
Credits:        Jari Kirma
Affects:        All FreeBSD/amd64 5.x releases prior to 5.4-RELEASE
Corrected:      2005-04-06 01:05:51 UTC (RELENG_5, 5.4-STABLE)
                2005-04-06 01:06:15 UTC (RELENG_5_4, 5.4-RELEASE)
                2005-04-06 01:06:44 UTC (RELENG_5_3, 5.3-RELEASE-p8)

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

I.   Background

The AMD64 architecture has two mechanisms for permitting processes to
access hardware: Kernel code can access hardware directly by reason of
its elevated privilege level, while user code can access a subset of
hardware determined by a bitmap.

II.  Problem Description

The bitmap which determines which hardware can be accessed by unprivileged
processes was not initialized properly.

III. Impact

Unprivileged users on amd64 systems can gain direct access to some
hardware, allowing for denial of service, disclosure of sensitive
information, or possible privilege escalation.

IV.  Workaround

No workaround is known for amd64 systems; other platforms are not
affected by this issue.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 5-STABLE or to the RELENG_5_3
security branch dated after the correction date.

2) To patch your present system:

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

# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:03/amd64.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:03/amd64.patch.asc

b) Apply the patch.

# 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 revision numbers of each file that was
corrected in FreeBSD.

Branch                                                           Revision
  Path
- -------------------------------------------------------------------------
RELENG_5
  src/sys/amd64/amd64/machdep.c                                1.618.2.10
  src/sys/amd64/amd64/mp_machdep.c                              1.242.2.8
  src/sys/amd64/include/tss.h                                    1.16.2.1
RELENG_5_4
  src/UPDATING                                             1.342.2.24.2.2
  src/sys/amd64/amd64/machdep.c                             1.618.2.9.2.1
  src/sys/amd64/amd64/mp_machdep.c                          1.242.2.7.2.1
  src/sys/amd64/include/tss.h                                    1.16.6.1
RELENG_5_3
  src/UPDATING                                            1.342.2.13.2.11
  src/sys/conf/newvers.sh                                  1.62.2.15.2.13
  src/sys/amd64/amd64/machdep.c                             1.618.2.1.2.1
  src/sys/amd64/amd64/mp_machdep.c                          1.242.2.2.2.1
  src/sys/amd64/include/tss.h                                    1.16.4.1
- -------------------------------------------------------------------------

The latest revision of this advisory is available at
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:03.amd64.asc
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