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FreeBSD-EN-19:13.mds                                            Errata Notice
                                                          The FreeBSD Project

Topic:          Kernel panic from Intel CPU vulnerability mitigation

Category:       core
Module:         kernel
Announced:      2019-07-24
Credits:        Schuendehuette, Matthias
                All supported versions of FreeBSD.
Corrected:      2019-07-14 05:40:03 UTC (stable/12, 12.0-STABLE)
                2019-07-24 12:50:46 UTC (releng/12.0, 12.0-RELEASE-p8)
                2019-07-14 05:41:43 UTC (stable/11, 11.2-STABLE)
                2019-07-24 12:50:46 UTC (releng/11.2, 11.2-RELEASE-p12)
                2019-07-24 12:50:46 UTC (releng/11.3, 11.3-RELEASE-p1)

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

In a previous update FreeBSD added mitigations for an Intel CPU
vulnerability known as "microarchitectural data sampling."

II.  Problem Description

Under certain configurations a pointer to the mitigation routine may be
dereferenced before it is initialized.

III. Impact

Depending on system configuration, version, and architecture, the system
may panic early in boot process, and thus be unusable.

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, and reboot.

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
# shutdown -r +10min "Errata update"

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 11.2, FreeBSD 11.3]
# fetch https://security.FreeBSD.org/patches/EN-19:13/mds.11.patch
# fetch https://security.FreeBSD.org/patches/EN-19:13/mds.11.patch.asc
# gpg --verify mds.11.patch.asc

[FreeBSD 12.0]
# fetch https://security.FreeBSD.org/patches/EN-19:13/mds.12.patch
# fetch https://security.FreeBSD.org/patches/EN-19:13/mds.12.patch.asc
# gpg --verify mds.12.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/                                                        r349983
releng/12.0/                                                      r350280
stable/11/                                                        r349985
releng/11.2/                                                      r350280
releng/11.3/                                                      r350280
- -------------------------------------------------------------------------

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 latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-19:13.mds.asc>
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