FreeBSD Security Advisory FreeBSD-SA-12:04.sysret [REVISED]

Type securityvulns
Reporter Securityvulns
Modified 2012-06-25T00:00:00



============================================================================= FreeBSD-SA-12:04.sysret Security Advisory The FreeBSD Project

Topic: Privilege escalation when returning from kernel

Category: core Module: sys_amd64 Announced: 2012-06-12 Credits: Rafal Wojtczuk, John Baldwin Affects: All supported versions of FreeBSD Corrected: 2012-06-12 12:10:10 UTC (RELENG_7, 7.4-STABLE) 2012-06-12 12:10:10 UTC (RELENG_7_4, 7.4-RELEASE-p9) 2012-06-12 12:10:10 UTC (RELENG_8, 8.3-STABLE) 2012-06-12 12:10:10 UTC (RELENG_8_3, 8.3-RELEASE-p3) 2012-06-12 12:10:10 UTC (RELENG_8_2, 8.2-RELEASE-p9) 2012-06-18 21:00:54 UTC (RELENG_8_1, 8.1-RELEASE-p12) 2012-06-12 12:10:10 UTC (RELENG_9, 9.0-STABLE) 2012-06-12 12:10:10 UTC (RELENG_9_0, 9.0-RELEASE-p3) CVE Name: CVE-2012-0217

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

  1. Revision History

v1.0 2012-06-12 Initial release. v1.1 2012-06-19 Corrected patch FreeBSD 8.1.

I. Background

The FreeBSD operating system implements a rings model of security, where privileged operations are done in the kernel, and most applications request access to these operations by making a system call, which puts the CPU into the required privilege level and passes control to the kernel.

II. Problem Description

FreeBSD/amd64 runs on CPUs from different vendors. Due to varying behaviour of CPUs in 64 bit mode a sanity check of the kernel may be insufficient when returning from a system call.

III. Impact

Successful exploitation of the problem can lead to local kernel privilege escalation, kernel data corruption and/or crash.

To exploit this vulnerability, an attacker must be able to run code with user privileges on the target system.

IV. Workaround

No workaround is available.

However FreeBSD/amd64 running on AMD CPUs is not vulnerable to this particular problem.

Systems with 64 bit capable CPUs, but running the 32 bit FreeBSD/i386 kernel are not vulnerable, nor are systems running on different processor architectures.

V. Solution

Perform one of the following:

1) Upgrade your vulnerable system to 7-STABLE, 8-STABLE, or 9-STABLE, or to the RELENG_7_4, RELENG_8_3, RELENG_8_2, RELENG_8_1, or RELENG_9_0 security branch dated after the correction date.

2) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to FreeBSD 7.4, 8.3, 8.2, 8.1 and 9.0 systems.

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

[7.4, 8.3, 8.2, 9.0]






[8.1 if original sysret.patch has been applied]



b) Apply the patch.

cd /usr/src

patch < /path/to/patch

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

3) To update your vulnerable system via a binary patch:

Systems running 7.4-RELEASE, 8.3-RELEASE, 8.2-RELEASE, 8.1-RELEASE, or 9.0-RELEASE on the i386 or amd64 platforms can be updated via the freebsd-update(8) utility:

freebsd-update fetch

freebsd-update install

VI. Correction details

The following list contains the revision numbers of each file that was corrected in FreeBSD.


Branch Revision Path

RELENG_7 src/sys/amd64/amd64/trap.c 1.319.2.14 RELENG_7_4 src/UPDATING 1.507. src/sys/conf/ src/sys/amd64/amd64/trap.c 1.319. RELENG_8 src/sys/amd64/amd64/trap.c 1.332.2.24 RELENG_8_3 src/UPDATING 1.632. src/sys/conf/ src/sys/amd64/amd64/trap.c 1.332. RELENG_8_2 src/UPDATING 1.632. src/sys/conf/ src/sys/amd64/amd64/trap.c 1.332. RELENG_8_1 src/UPDATING 1.632. src/sys/conf/ src/sys/amd64/amd64/trap.c 1.332. RELENG_9 src/sys/amd64/amd64/trap.c 1.357.2.9 RELENG_9_0 src/UPDATING 1.702. src/sys/conf/ src/sys/amd64/amd64/trap.c 1.357.


Branch/path Revision

stable/7/ r236953 releng/7.4/ r236953 stable/8/ r236953 releng/8.3/ r236953 releng/8.2/ r236953 releng/8.1/ r237242 stable/9/ r236953 releng/9.0/ r236953

VII. References

The latest revision of this advisory is available at -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9

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