FreeBSD Security Advisories
2009-Jun-10 10:42 UTC
FreeBSD Security Advisory FreeBSD-SA-09:09.pipe
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ============================================================================FreeBSD-SA-09:09.pipe Security Advisory The FreeBSD Project Topic: Local information disclosure via direct pipe writes Category: core Module: kern Announced: 2009-06-10 Credits: Pieter de Boer Affects: All supported versions of FreeBSD. Corrected: 2009-06-10 10:31:11 UTC (RELENG_7, 7.2-STABLE) 2009-06-10 10:31:11 UTC (RELENG_7_2, 7.2-RELEASE-p1) 2009-06-10 10:31:11 UTC (RELENG_7_1, 7.1-RELEASE-p6) 2009-06-10 10:31:11 UTC (RELENG_6, 6.4-STABLE) 2009-06-10 10:31:11 UTC (RELENG_6_4, 6.4-RELEASE-p5) 2009-06-10 10:31:11 UTC (RELENG_6_3, 6.3-RELEASE-p11) 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 One of the most commonly used forms of interprocess communication on FreeBSD and other UNIX-like systems is the (anonymous) pipe. In this mechanism, a pair of file descriptors is created, and data written to one descriptor can be read from the other. FreeBSD's pipe implementation contains an optimization known as "direct writes". In this optimization, rather than copying data into kernel memory when the write(2) system call is invoked and then copying the data again when the read(2) system call is invoked, the FreeBSD kernel takes advantage of virtual memory mapping to allow the data to be copied directly between processes. II. Problem Description An integer overflow in computing the set of pages containing data to be copied can result in virtual-to-physical address lookups not being performed. III. Impact An unprivileged process can read pages of memory which belong to other processes or to the kernel. These may contain information which is sensitive in itself; or may contain passwords or cryptographic keys which can be indirectly exploited to gain sensitive information or access. IV. Workaround No workaround is available, but systems without untrusted local users are not vulnerable. System administrators are reminded that even if a system is not intended to have untrusted local users, it may be possible for an attacker to exploit some other vulnerability to obtain local user access to a system. 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. # fetch http://security.FreeBSD.org/patches/SA-09:09/pipe.patch # fetch http://security.FreeBSD.org/patches/SA-09:09/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/sys_pipe.c 1.184.2.5 RELENG_6_4 src/UPDATING 1.416.2.40.2.9 src/sys/conf/newvers.sh 1.69.2.18.2.11 src/sys/kern/sys_pipe.c 1.184.2.4.2.2 RELENG_6_3 src/UPDATING 1.416.2.37.2.16 src/sys/conf/newvers.sh 1.69.2.15.2.15 src/sys/kern/sys_pipe.c 1.184.2.2.6.2 RELENG_7 src/sys/kern/sys_pipe.c 1.191.2.5 RELENG_7_2 src/UPDATING 1.507.2.23.2.4 src/sys/conf/newvers.sh 1.72.2.11.2.5 src/sys/kern/sys_pipe.c 1.191.2.3.4.2 RELENG_7_1 src/UPDATING 1.507.2.13.2.9 src/sys/conf/newvers.sh 1.72.2.9.2.10 src/sys/kern/sys_pipe.c 1.191.2.3.2.2 - ------------------------------------------------------------------------- Subversion: Branch/path Revision - ------------------------------------------------------------------------- stable/6/ r193893 releng/6.4/ r193893 releng/6.3/ r193893 stable/7/ r193893 releng/7.2/ r193893 releng/7.1/ r193893 - ------------------------------------------------------------------------- VII. References The latest revision of this advisory is available at http://security.FreeBSD.org/advisories/FreeBSD-SA-09:09.pipe.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkovjN0ACgkQFdaIBMps37JkXwCgmLcEMOMAEIXRoJ220zwZhMKn f+gAn1bZyLMhfZU7TI0xxhizwetDwMVI =J37B -----END PGP SIGNATURE-----