FreeBSD Security Advisory FreeBSD-SA-09:14.devfs

2009-10-03T00:00:00
ID SECURITYVULNS:DOC:22546
Type securityvulns
Reporter Securityvulns
Modified 2009-10-03T00:00:00

Description

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1

============================================================================= FreeBSD-SA-09:14.devfs Security Advisory The FreeBSD Project

Topic: Devfs / VFS NULL pointer race condition

Category: core Module: kern Announced: 2009-10-02 Credits: Przemyslaw Frasunek Affects: FreeBSD 6.x and 7.x Corrected: 2009-05-18 10:41:59 UTC (RELENG_7, 7.2-STABLE) 2009-10-02 18:09:56 UTC (RELENG_7_2, 7.2-RELEASE-p4) 2009-10-02 18:09:56 UTC (RELENG_7_1, 7.1-RELEASE-p8) 2009-10-02 18:09:56 UTC (RELENG_6, 6.4-STABLE) 2009-10-02 18:09:56 UTC (RELENG_6_4, 6.4-RELEASE-p7) 2009-10-02 18:09:56 UTC (RELENG_6_3, 6.3-RELEASE-p13)

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

I. Background

The device file system (devfs) provides access to system devices, such as storage devices and serial ports, via the file system namespace.

VFS is the Virtual File System, which abstracts file system operations in the kernel from the actual underlying file system.

II. Problem Description

Due to the interaction between devfs and VFS, a race condition exists where the kernel might dereference a NULL pointer.

III. Impact

Successful exploitation of the race condition 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

An errata note, FreeBSD-EN-09:05.null has been released simultaneously to this advisory, and contains a kernel patch implementing a workaround for a more broad class of vulnerabilities. However, prior to those changes, no workaround is available.

V. Solution

Perform one of the following:

1) Upgrade your vulnerable system to 6-STABLE, or 7-STABLE, or to the RELENG_7_2, RELENG_7_1, RELENG_6_4, or RELENG_6_3 security branch dated after the correction date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 6.3, 6.4, 7.1, and 7.2 systems.

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

[FreeBSD 6.x]

fetch http://security.FreeBSD.org/patches/SA-09:14/devfs6.patch

fetch http://security.FreeBSD.org/patches/SA-09:14/devfs6.patch.asc

[FreeBSD 7.x]

fetch http://security.FreeBSD.org/patches/SA-09:14/devfs7.patch

fetch http://security.FreeBSD.org/patches/SA-09:14/devfs7.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.

CVS:

Branch Revision Path


RELENG_6 src/sys/fs/devfs/devfs_vnops.c 1.114.2.17 RELENG_6_4 src/UPDATING 1.416.2.40.2.11 src/sys/conf/newvers.sh 1.69.2.18.2.13 src/sys/fs/devfs/devfs_vnops.c 1.114.2.16.2.2 RELENG_6_3 src/UPDATING 1.416.2.37.2.18 src/sys/conf/newvers.sh 1.69.2.15.2.17 src/sys/fs/devfs/devfs_vnops.c 1.114.2.15.2.1 RELENG_7 src/sys/fs/devfs/devfs_vnops.c 1.149.2.9 RELENG_7_2 src/UPDATING 1.507.2.23.2.7 src/sys/conf/newvers.sh 1.72.2.11.2.8 src/sys/fs/devfs/devfs_vnops.c 1.149.2.8.2.2 RELENG_7_1 src/UPDATING 1.507.2.13.2.11 src/sys/conf/newvers.sh 1.72.2.9.2.12 src/sys/fs/devfs/devfs_vnops.c 1.149.2.4.2.2


Subversion:

Branch/path Revision


stable/6/ r197715 releng/6.4/ r197715 releng/6.3/ r197715 stable/7/ r192301 releng/7.2/ r197715 releng/7.1/ r197715


VII. References

The latest revision of this advisory is available at http://security.FreeBSD.org/advisories/FreeBSD-SA-09:14.devfs.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD)

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