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  • [FreeBSD-Announce] FreeBSD Security Advisory FreeBSD-SA-17:08.ptrace

    From FreeBSD Security Advisories@21:1/5 to All on Thu Nov 16 00:00:00 2017
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    ============================================================================= FreeBSD-SA-17:08.ptrace Security Advisory
    The FreeBSD Project

    Topic: Kernel data leak via ptrace(PT_LWPINFO)

    Category: core
    Module: ptrace
    Announced: 2017-11-15
    Credits: John Baldwin
    Affects: All supported versions of FreeBSD.
    Corrected: 2017-11-10 12:28:43 UTC (stable/11, 11.1-STABLE)
    2017-11-15 22:39:41 UTC (releng/11.1, 11.1-RELEASE-p4)
    2017-11-15 22:40:15 UTC (releng/11.0, 11.0-RELEASE-p15)
    2017-11-10 12:31:58 UTC (stable/10, 10.4-STABLE)
    2017-11-15 22:40:32 UTC (releng/10.4, 10.4-RELEASE-p3)
    2017-11-15 22:40:46 UTC (releng/10.3, 10.3-RELEASE-p24)
    CVE Name: CVE-2017-1086

    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

    The ptrace(2) syscall provides the facility for a debugger to control the execution of the target process and to obtain necessary status information about it. The struct ptrace_lwpinfo structure is reported by one of the ptrace(2) subcommand and contains a lot of the information about the stopped thread (light-weight process or LWP, thus the name).

    II. Problem Description

    Not all information in the struct ptrace_lwpinfo is relevant for the state
    of any thread, and the kernel does not fill the irrelevant bytes or short strings. Since the structure filled by the kernel is allocated on the
    kernel stack and copied to userspace, a leak of information of the kernel
    stack of the thread is possible from the debugger.

    III. Impact

    Some bytes from the kernel stack of the thread using ptrace(PT_LWPINFO)
    call can be observed in userspace.

    IV. Workaround

    No workaround is available.

    V. Solution

    Perform one of the following:

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

    Afterward, reboot the system.

    2) 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

    Afterward, reboot the system.

    3) 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-17:08/ptrace.patch
    # fetch https://security.FreeBSD.org/patches/SA-17:08/ptrace.patch.asc
    # gpg --verify ptrace.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/ r325643 releng/10.3/ r325871 releng/10.4/ r325870 stable/11/ r325642 releng/11.0/ r325869 releng/11.1/ r325868
    - -------------------------------------------------------------------------

    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-2017-1086>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-17:08.ptrace.asc> -----BEGIN PGP SIGNATURE-----

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