information disclosure when using HTT

Type securityvulns
Reporter Securityvulns
Modified 2005-05-13T00:00:00



============================================================================= FreeBSD-SA-05:09.htt Security Advisory The FreeBSD Project

Topic: information disclosure when using HTT

Category: core Module: sys Announced: 2005-05-13 Revised: 2005-05-13 Credits: Colin Percival Affects: All FreeBSD/i386 and FreeBSD/amd64 releases. Corrected: 2005-05-13 00:13:00 UTC (RELENG_5, 5.4-STABLE) 2005-05-13 00:13:00 UTC (RELENG_5_4, 5.4-RELEASE-p1) 2005-05-13 00:13:00 UTC (RELENG_5_3, 5.3-RELEASE-p15) 2005-05-13 00:13:00 UTC (RELENG_4, 4.11-STABLE) 2005-05-13 00:13:00 UTC (RELENG_4_11, 4.11-RELEASE-p9) 2005-05-13 00:13:00 UTC (RELENG_4_10, 4.10-RELEASE-p14) CVE Name: CAN-2005-0109

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

I. Background

"Hyper-Threading Technology" is the name used for the implementation of simultaneous multithreading on Intel Pentium 4, Mobile Pentium 4, and Xeon processors.

II. Problem Description

A security flaw involving operating systems running on Hyper-Threading Technology processors was has been reported. Complete details are not available at the time of this writing. However, a workaround has been issued. It is expected that more details will be available tomorrow, at which time a revised version of this advisory will be published.

III. Impact

Information may be disclosed to local users, allowing in many cases for privilege escalation.

IV. Workaround

Systems not using processors with Hyper-Threading support are not affected by this issue. On systems which are affected, the security flaw can be eliminated by setting the "machdep.hlt_logical_cpus" tunable:

echo "machdep.hlt_logical_cpus=1" >> /boot/loader.conf

The system must be rebooted in order for tunables to take effect.

Use of this workaround is not recommended on "dual-core" systems, as this workaround will also disable one of the processor cores.

V. Solution

Perform one of the following:

1) Upgrade your vulnerable system to 4-STABLE or 5-STABLE, or to the RELENG_5_4, 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, 5.3, and 5.4 systems.

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

[FreeBSD 4.10]



[FreeBSD 4.11]



[FreeBSD 5.x]



b) Apply the patch.

cd /usr/src

patch < /path/to/patch

c) Recompile your kernel as described in <URL:> and reboot the system.

NOTE: For users that are certain that their environment is not affected by this vulnerability, such as single-user systems, Hyper-Threading Technology may be re-enabled by setting the tunable "machdep.hyperthreading_allowed".

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/mp_machdep.c src/sys/i386/include/cpufunc.h RELENG_4_11 src/UPDATING src/sys/conf/ src/sys/i386/i386/mp_machdep.c src/sys/i386/include/cpufunc.h RELENG_4_10 src/UPDATING src/sys/conf/ src/sys/i386/i386/mp_machdep.c src/sys/i386/include/cpufunc.h RELENG_5 src/sys/amd64/amd64/mp_machdep.c src/sys/amd64/include/cpufunc.h src/sys/i386/i386/mp_machdep.c src/sys/i386/include/cpufunc.h RELENG_5_4 src/UPDATING 1.342. src/sys/amd64/amd64/mp_machdep.c src/sys/amd64/include/cpufunc.h src/sys/conf/ src/sys/i386/i386/mp_machdep.c src/sys/i386/include/cpufunc.h RELENG_5_3 src/UPDATING 1.342. src/sys/amd64/amd64/mp_machdep.c src/sys/amd64/include/cpufunc.h src/sys/conf/ src/sys/i386/i386/mp_machdep.c src/sys/i386/include/cpufunc.h

VII. References

The latest revision of this advisory is available at -----BEGIN PGP SIGNATURE-----

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