-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ============================================================================= FreeBSD-SA-03:16.filedesc Security Advisory The FreeBSD Project Topic: file descriptor leak in readv Category: core Module: kernel Announced: 2003-10-02 Credits: Joost Pol Affects: FreeBSD 4.3-RELEASE through 4.8-RELEASE 4-STABLE prior to the correction date Corrected: 2003-10-02 15:08:01 UTC (RELENG_4, 4.9-RC) 2003-10-02 15:54:48 UTC (RELENG_4_8, 4.8-RELEASE-p11) 2003-10-02 15:55:54 UTC (RELENG_4_7, 4.7-RELEASE-p21) 2003-10-02 15:56:56 UTC (RELENG_4_6, 4.6-RELEASE-p24) 2003-10-02 15:57:48 UTC (RELENG_4_5, 4.5-RELEASE-p35) 2003-10-02 15:58:53 UTC (RELENG_4_4, 4.4-RELEASE-p45) 2003-10-02 16:05:44 UTC (RELENG_4_3, 4.3-RELEASE-p41) FreeBSD only: YES For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit . I. Background The readv(2) system call performs a scatter read: it reads from the input file descriptor and stores the data into multiple buffers as instructed by the caller. II. Problem Description A programming error in the readv system call can result in the given file descriptor's reference count being erroneously incremented. III. Impact A local attacker may cause the operating system to crash by repeatedly calling readv on a file descriptor until the reference count wraps to a negative value, and then calling close on that file descriptor. Similarly, it may be possible to cause a file descriptor to reference unallocated kernel memory, but remain valid. If a new file is later opened and the kernel allocates the new file structure at the same memory location, then an attacker may be able to gain read or write access to that file. This may in turn lead to privilege escalation. IV. Workaround There is no workaround. V. Solution The following patch has been verified to apply to FreeBSD 4.3, 4.4, 4.5, 4.6, 4.7, and 4.8 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-03:16/filedesc.patch # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:16/filedesc.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. Branch Revision Path - ------------------------------------------------------------------------- RELENG_4 src/sys/kern/sys_generic.c 1.55.2.11 RELENG_4_8 src/UPDATING 1.73.2.80.2.13 src/sys/conf/newvers.sh 1.44.2.29.2.12 src/sys/kern/sys_generic.c 1.55.2.10.12.1 RELENG_4_7 src/UPDATING 1.73.2.74.2.24 src/sys/conf/newvers.sh 1.44.2.26.2.23 src/sys/kern/sys_generic.c 1.55.2.10.10.1 RELENG_4_6 src/UPDATING 1.73.2.68.2.53 src/sys/conf/newvers.sh 1.44.2.23.2.41 src/sys/kern/sys_generic.c 1.55.2.10.8.1 RELENG_4_5 src/UPDATING 1.73.2.50.2.52 src/sys/conf/newvers.sh 1.44.2.20.2.36 src/sys/kern/sys_generic.c 1.55.2.10.6.1 RELENG_4_4 src/UPDATING 1.73.2.43.2.53 src/sys/conf/newvers.sh 1.44.2.17.2.44 src/sys/kern/sys_generic.c 1.55.2.10.4.1 RELENG_4_3 src/UPDATING 1.73.2.28.2.40 src/sys/conf/newvers.sh 1.44.2.14.2.30 src/sys/kern/sys_generic.c 1.55.2.10.2.1 - ------------------------------------------------------------------------- VII. References -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.3 (FreeBSD) iD8DBQE/fGDRFdaIBMps37IRAnkpAKCFM8MrujjJN1tc4lZwii573usNvgCfdBeP APcFpW5FsH+sLkWczgjj6eE= =6zO7 -----END PGP SIGNATURE-----