FreeBSD Security Advisories
2011-Oct-04 19:16 UTC
FreeBSD Security Advisory FreeBSD-SA-11:05.unix [REVISED]
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ============================================================================FreeBSD-SA-11:05.unix Security Advisory The FreeBSD Project Topic: Buffer overflow in handling of UNIX socket addresses Category: core Module: kern Announced: 2011-09-28 Credits: Mateusz Guzik Affects: All supported versions of FreeBSD. Corrected: 2011-10-04 19:07:38 UTC (RELENG_7, 7.4-STABLE) 2011-10-04 19:07:38 UTC (RELENG_7_4, 7.4-RELEASE-p4) 2011-10-04 19:07:38 UTC (RELENG_7_3, 7.3-RELEASE-p8) 2011-10-04 19:07:38 UTC (RELENG_8, 8.2-STABLE) 2011-10-04 19:07:38 UTC (RELENG_8_2, 8.2-RELEASE-p4) 2011-10-04 19:07:38 UTC (RELENG_8_1, 8.1-RELEASE-p6) 2011-10-04 19:07:38 UTC (RELENG_9, 9.0-RC1) 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/>. 0. Revision History v1.0 2011-09-28 Initial release. v1.1 2011-10-04 Updated patch to add linux emulation bug fix. I. Background UNIX-domain sockets, also known as "local" sockets, are a mechanism for interprocess communication. They are similar to Internet sockets (and utilize the same system calls) but instead of relying on IP addresses and port numbers, UNIX-domain sockets have addresses in the local file system address space. FreeBSD contains "linux emulation" support via system call translation in order to make it possible to use certain linux applications without recompilation. II. Problem Description When a UNIX-domain socket is attached to a location using the bind(2) system call, the length of the provided path is not validated. Later, when this address was returned via other system calls, it is copied into a fixed-length buffer. Linux uses a larger socket address structure for UNIX-domain sockets than FreeBSD, and the FreeBSD's linux emulation code did not translate UNIX-domain socket addresses into the correct size of structure. III. Impact A local user can cause the FreeBSD kernel to panic. It may also be possible to execute code with elevated privileges ("gain root"), escape from a jail, or to bypass security mechanisms in other ways. The patch provided with the initial version of this advisory exposed the pre-existing bug in FreeBSD's linux emulation code, resulting in attempts to use UNIX sockets from linux applications failing. The most common instance where UNIX sockets were used by linux applications is in the context of the X windowing system, including the widely used linux "flash" web browser plugin. IV. Workaround No workaround is available, but systems without untrusted local users are not vulnerable. V. Solution Perform one of the following: 1) Upgrade your vulnerable system to 7-STABLE or 8-STABLE, or to the RELENG_8_2, RELENG_8_1, RELENG_7_4, or RELENG_7_3 security branch dated after the correction date. 2) To update your vulnerable system via a source code patch: The following patch has been verified to apply to FreeBSD 7.4, 7.3, 8.2 and 8.1 systems. 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-11:05/unix2.patch # fetch http://security.FreeBSD.org/patches/SA-11:05/unix2.patch.asc NOTE: The patch distributed at the time of the original advisory fixed the security vulnerability but exposed the pre-existing bug in the linux emulation subsystem. Systems to which the original patch was applied should be patched with the following corrective patch, which contains only the additional changes required to fix the newly-exposed linux emulation bug: # fetch http://security.FreeBSD.org/patches/SA-11:05/unix-linux.patch # fetch http://security.FreeBSD.org/patches/SA-11:05/unix-linux.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. 3) To update your vulnerable system via a binary patch: Systems running 7.4-RELEASE, 7.3-RELEASE, 8.2-RELEASE, or 8.1-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. CVS: Branch Revision Path - ------------------------------------------------------------------------- RELENG_7 src/sys/kern/uipc_usrreq.c 1.206.2.13 src/sys/compat/linux/linux_socket.c 1.74.2.15 RELENG_7_4 src/UPDATING 1.507.2.36.2.5 src/sys/conf/newvers.sh 1.72.2.18.2.8 src/sys/kern/uipc_usrreq.c 1.206.2.11.4.2 src/sys/compat/linux/linux_socket.c 1.74.2.13.2.2 RELENG_7_3 src/UPDATING 1.507.2.34.2.9 src/sys/conf/newvers.sh 1.72.2.16.2.11 src/sys/kern/uipc_usrreq.c 1.206.2.11.2.2 src/sys/compat/linux/linux_socket.c 1.74.2.12.2.2 RELENG_8 src/sys/kern/uipc_usrreq.c 1.233.2.6 src/sys/compat/linux/linux_socket.c 1.101.2.5 RELENG_8_2 src/UPDATING 1.632.2.19.2.5 src/sys/conf/newvers.sh 1.83.2.12.2.8 src/sys/kern/uipc_usrreq.c 1.233.2.2.2.2 src/sys/compat/linux/linux_socket.c 1.101.2.3.4.2 RELENG_8_1 src/UPDATING 1.632.2.14.2.8 src/sys/conf/newvers.sh 1.83.2.10.2.9 src/sys/kern/uipc_usrreq.c 1.233.2.1.4.2 src/sys/compat/linux/linux_socket.c 1.101.2.3.2.2 RELENG_9 src/sys/kern/uipc_usrreq.c 1.244.2.2 src/sys/compat/linux/linux_socket.c 1.108.2.2 - ------------------------------------------------------------------------- Subversion: Branch/path Revision - ------------------------------------------------------------------------- stable/7/ r226023 releng/7.4/ r226023 releng/7.3/ r226023 stable/8/ r226023 releng/8.2/ r226023 releng/8.1/ r226023 stable/9/ r226023 - ------------------------------------------------------------------------- The latest revision of this advisory is available at http://security.FreeBSD.org/advisories/FreeBSD-SA-11:05.unix.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (FreeBSD) iEYEARECAAYFAk6LWp4ACgkQFdaIBMps37LlGQCgl5uCTA/QydDSsIuBR/TOxTRD Bg0AnjL43sOhR5yIp8xNAkMZxwfl3YiE =Df+l -----END PGP SIGNATURE-----