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  • [FreeBSD-Announce] FreeBSD Errata Notice FreeBSD-EN-18:08.lazyfpu

    From FreeBSD Errata Notices@21:1/5 to All on Wed Sep 12 06:00:00 2018
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    ============================================================================= FreeBSD-EN-18:08.lazyfpu Errata Notice
    The FreeBSD Project

    Topic: LazyFPU remediation causes potential data corruption

    Category: core
    Module: kernel
    Announced: 2018-09-12
    Credits: Gleb Kurtsou
    Affects: FreeBSD 10.4-STABLE, 11.1 and later.
    Corrected: 2018-07-31 10:18:30 UTC (stable/11, 11.1-STABLE)
    2018-09-12 05:08:49 UTC (releng/11.2, 11.2-RELEASE-p3)
    2018-09-12 05:08:49 UTC (releng/11.1, 11.1-RELEASE-p14)
    2018-08-03 14:12:37 UTC (stable/10, 10.4-STABLE)

    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/>.

    Special Note: While SA-18:07.lazyfpu has been fixed in 10.4-STABLE, it has
    yet to be released for 10.4-RELEASE. As such, this EN does not apply for
    that release. Once SA-18:07.lazyfpu has been updated for 10.4-RELEASE,
    this EN will be incorporated at that time.

    I. Background

    The recent security advisory titled SA-18:07.lazyfpu resolved an issue in the floating point unit (FPU) state handling.

    II. Problem Description

    As a result of fixing the issue described in SA-18:07.lazyfpu, a regression
    was introduced. FPU state manipulation did not sufficiently prevent context switches potentially allowing partially modified FPU context to be switched out. Upon returning the thread to a running state, stale FPU context could
    be reloaded.

    III. Impact

    The regression could potentially cause an inconsistent FPU state, leading to data corruption.

    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.

    [FreeBSD 11.x]
    # fetch https://security.FreeBSD.org/patches/EN-18:08/lazyfpu-11.patch
    # fetch https://security.FreeBSD.org/patches/EN-18:08/lazyfpu-11.patch.asc
    # gpg --verify lazyfpu-11.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/ r337254 stable/11/ r336963 releng/11.1/ r338607 releng/11.2/ r338607
    - -------------------------------------------------------------------------

    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

    The security advisory that introduced the regression is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-18:07.lazyfpu.asc>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-18:08.lazyfpu.asc> -----BEGIN PGP SIGNATURE-----

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