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FreeBSD-SA-05:07.ldt                                        Security Advisory
                                                          The FreeBSD Project

Topic:          Local kernel memory disclosure in i386_get_ldt

Category:       core
Module:         sys_i386
Announced:      2005-05-06
Credits:        Christer Oberg
Affects:        All FreeBSD/i386 4.x releases since 4.7-RELEASE
                All FreeBSD/i386 5.x and FreeBSD/amd64 5.x releases
                prior to 5.4-RELEASE
Corrected:      2005-05-06 02:40:19 UTC (RELENG_5, 5.4-STABLE)
                2005-05-06 02:40:49 UTC (RELENG_5_4, 5.4-RELEASE)
                2005-05-06 02:40:32 UTC (RELENG_5_3, 5.3-RELEASE-p12)
                2005-05-06 02:39:35 UTC (RELENG_4, 4.11-STABLE)
                2005-05-06 02:40:05 UTC (RELENG_4_11, 4.11-RELEASE-p6)
                2005-05-06 02:39:52 UTC (RELENG_4_10, 4.10-RELEASE-p11)
CVE Name:       CAN-2005-1400

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 i386_get_ldt(2) system call allows a process to request that a portion of its Local Descriptor Table be copied from the kernel into userland.

II.  Problem Description

The i386_get_ldt(2) syscall performs insufficient validation of its input arguments.  In particular, negative or very large values may allow inappropriate data to be copied from the kernel.

III. Impact

Kernel memory may be disclosed to the user process.  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 known for i386 and amd64 systems; other platforms are not affected by this issue.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 4-STABLE or 5-STABLE, or to the RELENG_5_3, RELENG_4_11, or RELENG_4_10 security branch dated after the correction date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 4.10, 4.11, and 5.3 systems.

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

[FreeBSD 4.x]
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:07/ldt4.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:07/ldt4.patch.asc

[FreeBSD 5.x]
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:07/ldt5.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:07/ldt5.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_4
  src/sys/i386/i386/sys_machdep.c                                1.47.2.4
RELENG_4_11
  src/UPDATING                                              1.73.2.91.2.7
  src/sys/conf/newvers.sh                                  1.44.2.39.2.10
  src/sys/i386/i386/sys_machdep.c                            1.47.2.3.8.1
RELENG_4_10
  src/UPDATING                                             1.73.2.90.2.12
  src/sys/conf/newvers.sh                                  1.44.2.34.2.13
  src/sys/i386/i386/sys_machdep.c                            1.47.2.3.6.1
RELENG_5
  src/sys/i386/i386/sys_machdep.c                                1.92.2.3
RELENG_5_4
  src/UPDATING                                             1.342.2.24.2.6
  src/sys/i386/i386/sys_machdep.c                            1.92.2.1.2.1
RELENG_5_3
  src/UPDATING                                            1.342.2.13.2.15
  src/sys/conf/newvers.sh                                  1.62.2.15.2.17
  src/sys/i386/i386/sys_machdep.c                                1.92.4.1
- -------------------------------------------------------------------------

The latest revision of this advisory is available at ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:07.ldt.asc
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