From security-advisories@freebsd.org Tue Aug 6 21:19:54 2002 From: FreeBSD Security Advisories To: Bugtraq Date: Mon, 5 Aug 2002 16:52:02 -0700 (PDT) Subject: FreeBSD Security Advisory FreeBSD-SA-02:37.kqueue -----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-02:37.kqueue Security Advisory The FreeBSD Project Topic: local users can panic the system using the kqueue mechanism Category: core Module: kqueue Announced: 2002-08-05 Credits: Mark Delany Affects: FreeBSD 4.3-RELEASE FreeBSD 4.4-RELEASE FreeBSD 4.5-RELEASE FreeBSD 4.6-RELEASE FreeBSD 4.6-STABLE prior to the correction date Corrected: 2002-08-05 15:05:15 (RELENG_4) 2002-08-05 15:13:48 (RELENG_4_6) 2002-08-05 15:13:44 (RELENG_4_5) 2002-08-05 15:13:40 (RELENG_4_4) FreeBSD only: YES I. Background The kqueue mechanism allows a process to register interest in particular events on particular file descriptors, and receive asynchronous notification when these events occur on the selected descriptors. II. Problem Description If a pipe was created with the pipe(2) system call, and one end of the pipe was closed, registering an EVFILT_WRITE filter on the other end would cause a kernel panic. A common scenario in which this could occur is when a process uses a pipe to communicate with a child and uses kqueue to monitor the pipe, and the child dies shortly after the fork(2) call, before the parent has had time to register the filter. III. Impact A local attacker may cause the system to panic by executing their own malicious application. IV. Workaround There is no known workaround. V. Solution The following patch has been verified to apply to FreeBSD 4.4, 4.5, and 4.6 systems. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:37/kqueue.patch # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:37/kqueue.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 - ------------------------------------------------------------------------- sys/kern/sys_pipe.c RELENG_4 1.60.2.13 RELENG_4_6 1.60.2.12.2.1 RELENG_4_5 1.60.2.11.2.1 RELENG_4_4 1.60.2.10.2.1 - ------------------------------------------------------------------------- -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.7 (FreeBSD) iQCVAwUBPU8OFlUuHi5z0oilAQFTugP/S+2u/BK8Oz53oFTcTY84ReNRJZMEJ8dX PVHMWZ7xl4stYoeo8iX+moq+R2riZqEfzT+lx1lYZBkYkkmIwGxI+6qJgBqkPriL acswOhfdzLSgwIoXNJsGdO9vlYwsNqiRsf5Yay+gKDqRUxCPA27X528uc1jhtAdd UzagA6Lhrk8= =uTZC -----END PGP SIGNATURE-----