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FreeBSD Security Advisory FreeBSD-SA-04:17.procfs


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Date: Thu, 2 Dec 2004 00:12:26 GMT
From: FreeBSD Security Advisories <security-advisories@freebsd.org.>
To: Bugtraq <bugtraq@securityfocus.com.>
Subject: FreeBSD Security Advisory FreeBSD-SA-04:17.procfs

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FreeBSD-SA-04:17.procfs Security Advisory The FreeBSD Project Topic: Kernel memory disclosure in procfs and linprocfs Category: core Module: sys Announced: 2004-12-01 Credits: Bryan Fulton, Ted Unangst, and the SWAT analysis tool Coverity, Inc. Affects: All FreeBSD releases Corrected: 2004-12-01 21:33:35 UTC (RELENG_5, 5.3-STABLE) 2004-12-01 21:34:23 UTC (RELENG_5_3, 5.3-RELEASE-p2) 2004-12-01 21:34:43 UTC (RELENG_5_2, 5.2.1-RELEASE-p13) 2004-12-01 21:33:57 UTC (RELENG_4, 4.10-STABLE) 2004-12-01 21:35:10 UTC (RELENG_4_10, 4.10-RELEASE-p5) 2004-12-01 21:35:57 UTC (RELENG_4_8, 4.8-RELEASE-p27) CVE Name: CAN-2004-1066 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:http://www.freebsd.org/security/>;. I. Background The process file system, procfs(5), implements a view of the system process table inside the file system. It is normally mounted on /proc, and is required for the complete operation of programs such as ps(1) and w(1). The Linux process file system, linprocfs(5), emulates a subset of Linux's process file system and is required for the complete operation of some Linux binaries. II. Problem Description The implementation of the /proc/curproc/cmdline pseudofile in the procfs(5) file system on FreeBSD 4.x and 5.x, and of the /proc/self/cmdline pseudofile in the linprocfs(5) file system on FreeBSD 5.x reads a process' argument vector from the process address space. During this operation, a pointer was dereferenced directly without the necessary validation steps being performed. III. Impact A malicious local user could perform a local denial of service attack by causing a system panic; or he could read parts of kernel memory. Such memory might contain sensitive information, such as portions of the file cache or terminal buffers. This information might be directly useful, or it might be leveraged to obtain elevated privileges in some way. For example, a terminal buffer might contain a user-entered password. FreeBSD 4.x does not implement the /proc/self/cmdline pseudofile in its linprocfs(5) file system, and is therefore only affected if the procfs(5) file system is mounted. In its default configuration, FreeBSD 5.x does not utilize procfs(5) or linprocfs(5) and will therefore be unaffected by this vulnerability unless the configuration is changed. IV. Workaround Unmount the procfs and linprocfs file systems if they are mounted. Execute the following command as root: umount -A -t procfs,linprocfs Also, remove or comment out any lines in fstab(5) that reference `procfs' or `linprocfs', so that they will not be re-mounted at next reboot. V. Solution Perform one of the following: 1) Upgrade your vulnerable system to 4-STABLE or 5-STABLE, or to the RELENG_5_3, RELENG_5_2, RELENG_4_10, or RELENG_4_8 security branch dated after the correction date. 2) To patch your present system: The following patches have been verified to apply to FreeBSD 4.8, 4.10, 5.2, and 5.3 systems. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. [FreeBSD 4.x] # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:17/procfs4.patch # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:17/procfs4.patch.asc [FreeBSD 5.x] # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:17/procfs5.patch # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:17/procfs5.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. Branch Revision Path - ------------------------------------------------------------------------- RELENG_4 src/sys/miscfs/procfs/procfs_status.c 1.20.2.6 RELENG_4_10 src/UPDATING 1.73.2.90.2.6 src/sys/conf/newvers.sh 1.44.2.34.2.7 src/sys/miscfs/procfs/procfs_status.c 1.20.2.5.4.1 RELENG_4_8 src/UPDATING 1.73.2.80.2.30 src/sys/conf/newvers.sh 1.44.2.29.2.28 src/sys/miscfs/procfs/procfs_status.c 1.20.2.4.8.2 RELENG_5 src/sys/compat/linprocfs/linprocfs.c 1.84.2.1 src/sys/fs/procfs/procfs_status.c 1.52.2.1 RELENG_5_3 src/UPDATING 1.342.2.13.2.5 src/sys/compat/linprocfs/linprocfs.c 1.84.4.1 src/sys/conf/newvers.sh 1.62.2.15.2.7 src/sys/fs/procfs/procfs_status.c 1.52.4.1 RELENG_5_2 src/UPDATING 1.282.2.21 src/sys/compat/linprocfs/linprocfs.c 1.78.2.1 src/sys/conf/newvers.sh 1.56.2.20 src/sys/fs/procfs/procfs_status.c 1.49.2.1 - ------------------------------------------------------------------------- -----BEGIN PGP SIGNATURE----- iD8DBQFBrlpUFdaIBMps37IRAkqSAJ9bJt5VXd0g+OpZq76O84LGEtw3HgCfayws iuc0B5+J0K67LvDIUA6+wck= =2l7f -----END PGP SIGNATURE-----

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