-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ============================================================================= FreeBSD-SA-10:06.nfsclient Security Advisory The FreeBSD Project
Topic: Unvalidated input in nfsclient Category: core Module: nfsclient Announced: 2010-05-27 Credits: Patroklos Argyroudis Affects: FreeBSD 7.2 and later. Corrected: 2010-05-27 03:15:04 UTC (RELENG_8, 8.1-PRERELEASE) 2010-05-27 03:15:04 UTC (RELENG_8_0, 8.0-RELEASE-p3) 2010-05-27 03:15:04 UTC (RELENG_7, 7.3-STABLE) 2010-05-27 03:15:04 UTC (RELENG_7_3, 7.3-RELEASE-p1) 2010-05-27 03:15:04 UTC (RELENG_7_2, 7.2-RELEASE-p8) CVE Name: CVE-2010-2020 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 The Network File System (NFS) allows a host to export some or all of its file systems so that other hosts can access them over the network and mount them as if they were on local disks. FreeBSD includes server and client implementations of NFS. II. Problem Description The NFS client subsystem fails to correctly validate the length of a parameter provided by the user when a filesystem is mounted. III. Impact A user who can mount filesystems can execute arbitrary code in the kernel. On systems where the non-default vfs.usermount feature has been enabled, unprivileged users may be able to gain superuser ("root") privileges. IV. Workaround Do not allow untrusted users to mount filesystems. To prevent unprivileged users from mounting filesystems, set the vfs.usermount sysctl variable to zero: # sysctl vfs.usermount=0 Note that the default value of this variable is zero, i.e., FreeBSD is not affected by this vulnerability in its default configuration, and FreeBSD system administrators are strongly encouraged not to change this setting. V. Solution NOTE WELL: Even with this fix allowing users to mount arbitrary media should not be considered safe. Most of the file systems in FreeBSD were not built to protect safeguard against malicious devices. While such bugs in file systems are fixed when found, a complete audit has not been perfomed on the file system code. Perform one of the following: 1) Upgrade your vulnerable system to 7-STABLE or 8-STABLE, or to the RELENG_8_0, RELENG_7_3, or RELENG_7_2 security branch dated after the correction date. 2) To update your vulnerable system via a source code patch: The following patches have been verified to apply to FreeBSD 7.2, 7.3 and 8.0 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-10:06/nfsclient.patch # fetch http://security.FreeBSD.org/patches/SA-10:06/nfsclient.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 7.2-RELEASE, 7.3-RELEASE, or 8.0-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/nfsclient/nfs_vfsops.c 1.193.2.7 src/lib/libc/sys/mount.2 1.45.2.1 RELENG_7_3 src/UPDATING 1.507.2.34.2.3 src/sys/conf/newvers.sh 1.72.2.16.2.5 src/sys/nfsclient/nfs_vfsops.c 1.193.2.5.4.2 src/lib/libc/sys/mount.2 1.45.12.2 RELENG_7_2 src/UPDATING 1.507.2.23.2.11 src/sys/conf/newvers.sh 1.72.2.11.2.12 src/sys/nfsclient/nfs_vfsops.c 1.193.2.5.2.2 src/lib/libc/sys/mount.2 1.45.8.2 RELENG_8 src/sys/nfsclient/nfs_vfsops.c 1.226.2.7 src/lib/libc/sys/mount.2 1.45.10.2 RELENG_8_0 src/UPDATING 1.632.2.7.2.6 src/sys/conf/newvers.sh 1.83.2.6.2.6 src/sys/nfsclient/nfs_vfsops.c 1.226.2.2.2.2 src/lib/libc/sys/mount.2 1.45.10.1.2.2 - ------------------------------------------------------------------------- Subversion: Branch/path Revision - ------------------------------------------------------------------------- stable/6/ r208586 releng/6.4/ r208586 stable/7/ r208586 releng/7.3/ r208586 releng/7.2/ r208586 releng/7.1/ r208586 stable/8/ r208586 releng/8.0/ r208586 - ------------------------------------------------------------------------- VII. References http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-2020 http://census-labs.com/news/2010/05/26/freebsd-kernel-nfsclient/ The latest revision of this advisory is available at http://security.FreeBSD.org/advisories/FreeBSD-SA-10:06.nfsclient.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iEYEARECAAYFAkv95SUACgkQFdaIBMps37Km5gCdG4RNPkwuDsx05w3CfwLd/aM1 NusAn0dzFUcuGlMgNb9V43yUFVFa+NbX =zMAI -----END PGP SIGNATURE-----