FreeBSD Security Advisories
2009-Oct-02 20:12 UTC
FreeBSD Security Advisory FreeBSD-SA-09:13.pipe
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ============================================================================FreeBSD-SA-09:13.pipe Security Advisory The FreeBSD Project Topic: kqueue pipe race conditions Category: core Module: kern Announced: 2009-10-02 Credits: Przemyslaw Frasunek Affects: FreeBSD 6.x Corrected: 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 Pipes are a form of inter-process communication (IPC) provided by the FreeBSD kernel. kqueue is an event management API that applications can use to monitor pipes and other kernel services. II. Problem Description A race condition exists in the pipe close() code relating to kqueues, causing use-after-free for kernel memory, which may lead to an exploitable NULL pointer vulnerability in the kernel, kernel memory corruption, and other unpredictable results. 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 on the target system. IV. Workaround An errata notice, 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 to the 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 and 6.4. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. # fetch http://security.FreeBSD.org/patches/SA-09:13/pipe.patch # fetch http://security.FreeBSD.org/patches/SA-09:13/pipe.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/kern/kern_event.c 1.93.2.7 src/sys/kern/kern_fork.c 1.252.2.8 src/sys/kern/sys_pipe.c 1.184.2.6 src/sys/sys/event.h 1.32.2.1 src/sys/sys/pipe.h 1.29.2.1 RELENG_6_4 src/UPDATING 1.416.2.40.2.11 src/sys/conf/newvers.sh 1.69.2.18.2.13 src/sys/kern/kern_event.c 1.93.2.6.6.2 src/sys/kern/kern_fork.c 1.252.2.7.4.2 src/sys/kern/sys_pipe.c 1.184.2.4.2.3 src/sys/sys/event.h 1.32.12.2 src/sys/sys/pipe.h 1.29.16.2 RELENG_6_3 src/UPDATING 1.416.2.37.2.18 src/sys/conf/newvers.sh 1.69.2.15.2.17 src/sys/kern/kern_event.c 1.93.2.6.4.1 src/sys/kern/kern_fork.c 1.252.2.7.2.1 src/sys/kern/sys_pipe.c 1.184.2.2.6.3 src/sys/sys/event.h 1.32.10.1 src/sys/sys/pipe.h 1.29.12.1 - ------------------------------------------------------------------------- Subversion: Branch/path Revision - ------------------------------------------------------------------------- stable/6/ r197715 releng/6.4/ r197715 releng/6.3/ r197715 - ------------------------------------------------------------------------- VII. References http://svn.freebsd.org/viewvc/base?view=revision&revision=179243 The latest revision of this advisory is available at http://security.FreeBSD.org/advisories/FreeBSD-SA-09:13.pipe.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iD8DBQFKxlthFdaIBMps37IRAlk2AJ9mUrNPd1RMztbzO4w7g+AxosqJzgCgmr5l FKxrbF0G4v9P6SyyfAdVOFY=TWhC -----END PGP SIGNATURE-----