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AUSCERT External Security Bulletin Redistribution
ESB-2003.0557 -- FreeBSD-SA-03:10.ibcs2
Kernel memory disclosure via ibcs2
11 August 2003
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AusCERT Security Bulletin Summary
---------------------------------
Product: Intel Binary Compatibility Specification 2
(iBCS2)
Publisher: FreeBSD
Operating System: FreeBSD 5.1-RELEASE-p1
FreeBSD 4.8-RELEASE-p2 and prior
Impact: Execute Arbitrary Code/Commands
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FreeBSD-SA-03:10.ibcs2 Security Advisory
The FreeBSD Project
Topic: Kernel memory disclosure via ibcs2
Category: core
Module: sys
Announced: 2003-08-10
Credits: David Rhodus <drhodus@catpa.com>
Affects: All FreeBSD releases up to and including 4.8-RELEASE-p2,
5.1-RELEASE-p1
Corrected: 2003-08-10 23:30:18 UTC (RELENG_4)
2003-08-10 23:28:16 UTC (RELENG_5_1)
2003-08-10 23:29:10 UTC (RELENG_5_0)
2003-08-10 23:31:11 UTC (RELENG_4_8)
2003-08-10 23:31:51 UTC (RELENG_4_7)
2003-08-10 23:32:22 UTC (RELENG_4_6)
2003-08-10 23:32:44 UTC (RELENG_4_5)
2003-08-10 23:33:18 UTC (RELENG_4_4)
2003-08-10 23:33:50 UTC (RELENG_4_3)
2003-08-10 23:35:21 UTC (RELENG_3)
FreeBSD only: YES
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
FreeBSD contains a kernel option (IBCS2) and kernel loadable module
(ibcs2.ko) that provide system call translation for running Intel
Binary Compatibility Specification 2 (iBCS2) compliant programs.
It is not enabled in FreeBSD by default.
II. Problem Description
The iBCS2 system call translator for statfs(2) erroneously used the
user-supplied length parameter when copying a kernel data structure
into userland. If the length parameter were larger than required,
then instead of copying only the statfs-related data structure,
additional kernel memory would also be made available to the user.
III. Impact
If iBCS2 support were enabled, a malicious user could call the iBCS2
version of statfs(2) with an arbitrarily large length parameter,
causing the kernel to return a large portion of kernel memory. 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.
iBCS2 support is only present if the system administrator has enabled
it by including `option IBCS2' in the kernel configuration file, or
loaded it dynamically using kldload(8) or by setting `ibcs2_enable' in
rc.conf(5).
IV. Workaround
Disable iBCS2 support if it is enabled.
V. Solution
1) Upgrade your vulnerable system to 4.8-STABLE, or to any of the
RELENG_4_8 (4.8-RELEASE-p3), RELENG_4_7 (4.7-RELEASE-p13), or
RELENG_5_1 (5.1-RELEASE-p2) security branches dated after the
respective correction dates.
2) To patch your present system:
a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility. The following patch
has been tested to apply to all FreeBSD 3.x, 4.x, and 5.x releases.
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:10/ibcs2.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:10/ibcs2.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.
Path Revision
Branch
- - -------------------------------------------------------------------------
src/UPDATING
RELENG_5_1 1.251.2.3
RELENG_5_0 1.229.2.16
RELENG_4_8 1.73.2.80.2.5
RELENG_4_7 1.73.2.74.2.16
RELENG_4_6 1.73.2.68.2.44
RELENG_4_5 1.73.2.50.2.46
RELENG_4_4 1.73.2.43.2.47
RELENG_4_3 1.73.2.28.2.34
src/sys/conf/newvers.sh
RELENG_5_1 1.50.2.4
RELENG_5_0 1.48.2.11
RELENG_4_8 1.44.2.29.2.4
RELENG_4_7 1.44.2.26.2.15
RELENG_4_6 1.44.2.23.2.33
RELENG_4_5 1.44.2.20.2.30
RELENG_4_4 1.44.2.17.2.38
RELENG_4_3 1.44.2.14.2.24
src/sys/i386/ibcs2/ibcs2_stat.c
RELENG_4 1.10.2.1
RELENG_5_1 1.21.2.1
RELENG_5_0 1.16.2.2
RELENG_4_8 1.10.14.1
RELENG_4_7 1.10.12.1
RELENG_4_6 1.10.10.1
RELENG_4_5 1.10.8.1
RELENG_4_4 1.10.6.1
RELENG_4_3 1.10.4.1
RELENG_3 1.8.2.1
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