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

From: FreeBSD Security Advisories (
Date: 12/02/04

  • Next message: Masachika ISHIZUKA: "Re: FreeBSD Security Advisory FreeBSD-SA-04:17.procfs"
    Date: Thu, 2 Dec 2004 00:12:27 GMT
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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

    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

    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
    # fetch

    [FreeBSD 5.x]
    # fetch
    # fetch

    b) Apply the patch.

    # cd /usr/src
    # patch < /path/to/patch

    c) Recompile your kernel as described in
    <URL:> and reboot the

    VI. Correction details

    The following list contains the revision numbers of each file that was
    corrected in FreeBSD.

    Branch Revision
    - -------------------------------------------------------------------------
      src/UPDATING 1.342.
    - -------------------------------------------------------------------------

    -----END PGP SIGNATURE-----
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