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AUSCERT External Security Bulletin Redistribution
ESB-2005.0368 -- FreeBSD-SA-05:07.ldt
Local kernel memory disclosure in i386_get_ldt
6 May 2005
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: kernel
Publisher: FreeBSD
Operating System: FreeBSD prior to 5.4-RELEASE
Platform: IA-32
AMD64
Impact: Access Privileged Data
Access: Existing Account
CVE Names: CAN-2005-1400
Original Bulletin:
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:07.ldt.asc
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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
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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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