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  • [FreeBSD-Announce] FreeBSD Security Advisory FreeBSD-SA-19:23.midi

    From FreeBSD Security Advisories@21:1/5 to All on Tue Aug 20 21:00:01 2019
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    ============================================================================= FreeBSD-SA-19:23.midi Security Advisory
    The FreeBSD Project

    Topic: kernel memory disclosure from /dev/midistat

    Category: core
    Module: sound
    Announced: 2019-08-20
    Credits: Peter Holm, Mark Johnston
    Affects: All supported versions of FreeBSD.
    Corrected: 2019-08-20 17:53:16 UTC (stable/12, 12.0-STABLE)
    2019-08-20 17:50:33 UTC (releng/12.0, 12.0-RELEASE-p10)
    2019-08-20 17:54:18 UTC (stable/11, 11.3-STABLE)
    2019-08-20 17:50:33 UTC (releng/11.3, 11.3-RELEASE-p3)
    2019-08-20 17:50:33 UTC (releng/11.2, 11.2-RELEASE-p14)
    CVE Name: CVE-2019-5612

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

    I. Background

    /dev/midistat is a device file which can be read to obtain a
    human-readable list of the available MIDI-capable devices in the system.

    II. Problem Description

    The kernel driver for /dev/midistat implements a handler for read(2).
    This handler is not thread-safe, and a multi-threaded program can
    exploit races in the handler to cause it to copy out kernel memory
    outside the boundaries of midistat's data buffer.

    III. Impact

    The races allow a program to read kernel memory within a 4GB window
    centered at midistat's data buffer. The buffer is allocated each
    time the device is opened, so an attacker is not limited to a static
    4GB region of memory.

    On 32-bit platforms, an attempt to trigger the race may cause a page
    fault in kernel mode, leading to a panic.

    IV. Workaround

    No workaround is available. Custom kernels without "device sound"
    are not vulnerable.

    V. Solution

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

    1) To update your vulnerable 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
    # shutdown -r +10min "Rebooting for security update"

    2) To update your vulnerable 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/SA-19:23/midi.patch
    # fetch https://security.FreeBSD.org/patches/SA-19:23/midi.patch.asc
    # gpg --verify midi.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/12/ r351264 releng/12.0/ r351260 stable/11/ r351265 releng/11.3/ r351260 releng/11.2/ r351260
    - -------------------------------------------------------------------------

    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

    <other info on vulnerability>

    <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-5612>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:23.midi.asc> -----BEGIN PGP SIGNATURE-----

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