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  • [FreeBSD-Announce] FreeBSD Errata Notice FreeBSD-EN-18:12.mem

    From FreeBSD Errata Notices@21:1/5 to All on Thu Sep 27 21:00:00 2018
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    ============================================================================= FreeBSD-EN-18:12.mem Errata Notice
    The FreeBSD Project

    Topic: Small kernel memory disclosures in two system calls

    Category: core
    Module: kernel
    Announced: 2018-09-27
    Credits: Thomas Barabosch, Fraunhofer FKIE
    Affects: All supported versions of FreeBSD.
    Corrected: 2018-09-27 18:42:40 UTC (stable/11, 11.2-STABLE)
    2018-09-27 18:36:30 UTC (releng/11.2, 11.2-RELEASE-p4)
    2018-09-27 18:36:30 UTC (releng/11.1, 11.1-RELEASE-p15)
    2018-09-27 18:44:40 UTC (stable/10, 10.4-STABLE)
    2018-09-27 18:36:30 UTC (releng/10.4, 10.4-RELEASE-p13)
    CVE Name: CVE-2018-17155

    For general information regarding FreeBSD Errata Notices and Security Advisories, including descriptions of the fields above, security
    branches, and the following sections, please visit <URL:https://security.FreeBSD.org/>.

    I. Background

    The kernel provides an interface for userland programs via system calls. Two
    of these system calls are named getcontext and swapcontext.

    II. Problem Description

    Due to insufficient initialization of memory copied to userland in the getcontext and swapcontext system calls, small amounts of kernel memory may
    be disclosed to userland processes.

    III. Impact

    An unprivileged local user may be able to create a specific program to read
    the contents of small portions 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 include a user-entered password.

    IV. Workaround

    No workaround is available.

    V. Solution

    Perform one of the following:

    1) Upgrade your system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date.

    Afterward, reboot the system.

    2) To update your system via a binary patch:

    Systems running a RELEASE version of FreeBSD on the i386 or amd64
    platforms can be updated via the freebsd-update(8) utility:

    # freebsd-update fetch
    # freebsd-update install

    Afterward, reboot the system.

    3) To update your system via a source code patch:

    The following patches have been verified to apply to the applicable
    FreeBSD release branches.

    a) Download the relevant patch from the location below, and verify the
    detached PGP signature using your PGP utility.

    # fetch https://security.FreeBSD.org/patches/EN-18:12/mem.patch
    # fetch https://security.FreeBSD.org/patches/EN-18:12/mem.patch.asc
    # gpg --verify mem.patch.asc

    b) Apply the patch. Execute the following commands as root:

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

    c) Recompile your kernel as described in <URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
    system.

    VI. Correction details

    The following list contains the correction revision numbers for each
    affected branch.

    Branch/path Revision
    - ------------------------------------------------------------------------- stable/10/ r339984 releng/10.4/ r338981 stable/11/ r339983 releng/11.1/ r338981 releng/11.2/ r338981
    - -------------------------------------------------------------------------

    To see which files were modified by a particular revision, run the
    following command, replacing NNNNNN with the revision number, on a
    machine with Subversion installed:

    # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

    Or visit the following URL, replacing NNNNNN with the revision number:

    <URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

    VII. References

    <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-17155>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-18:12.mem.asc> -----BEGIN PGP SIGNATURE-----

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