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Home » Security Advisories» FreeBSD » Kernel memory disclosure via ibcs2

Kernel memory disclosure via ibcs2

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.

  • Vendor: FreeBSD
  • Vendor ID: SA-03:10
  • Date: August 10, 2003


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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
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
.

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

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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