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Category:   OS (UNIX)  >   FreeBSD Kernel Vendors:   FreeBSD
(FreeBSD Issues Fix for FreeBSD Kernel) Intel CPUs Let Local Users Obtain or Infer Portions of L1 Cache Memory on the Target System
SecurityTracker Alert ID:  1041489
SecurityTracker URL:  http://securitytracker.com/id/1041489
CVE Reference:   CVE-2018-3620, CVE-2018-3646   (Links to External Site)
Date:  Aug 15 2018
Impact:   Disclosure of system information, Disclosure of user information
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 11.1, 11.2
Description:   A vulnerability was reported in Intel CPUs. A local user can obtain potentially sensitive information from system memory. FreeBSD Kernel is affected.

A local user can conduct a speculative execution side-channel attack against the L1 cache to infer potentially sensitive information from L1 cache memory on the target system.

This method is referred to as the "L1 Terminal Fault (L1TF)" or "Foreshadow" attack.

Microprocessors that support Intel Software Guard Extensions (SGX) are affected [CVE-2018-3615].

Other Intel microprocessors that use speculative execution and address translations may be affected [CVE-2018-3620].

Other Intel microprocessors that use speculative execution and address translations and that host virtual systems may be affected [CVE-2018-3646].

The following models are affected:

Core i3 processor (45nm and 32nm)
Core i5 processor (45nm and 32nm)
Core i7 processor (45nm and 32nm)
Core M processor family (45nm and 32nm)
2nd generation Core processors
3rd generation Core processors
4th generation Core processors
5th generation Core processors
6th generation Core processors
7th generation Core processors
8th generation Core processors
Core X-series Processor Family for X99 platforms
Core X-series Processor Family for X299 platforms
Xeon processor 3400 series
Xeon processor 3600 series
Xeon processor 5500 series
Xeon processor 5600 series
Xeon processor 6500 series
Xeon processor 7500 series
Xeon Processor E3 Family
Xeon Processor E3 v2 Family
Xeon Processor E3 v3 Family
Xeon Processor E3 v4 Family
Xeon Processor E3 v5 Family
Xeon Processor E3 v6 Family
Xeon Processor E5 Family
Xeon Processor E5 v2 Family
Xeon Processor E5 v3 Family
Xeon Processor E5 v4 Family
Xeon Processor E7 Family
Xeon Processor E7 v2 Family
Xeon Processor E7 v3 Family
Xeon Processor E7 v4 Family
Xeon Processor Scalable Family
Xeon Processor D (1500, 2100)

The original advisory is available at:

https://foreshadowattack.eu/

Raoul Strackx, Jo Van Bulck, and Frank Piessens of imec-DistriNet, KU Leuven, Marina Minkin and Mark Silberstein of Technion, Ofir Weisse, Daniel Genkin, Baris Kasikci, and Thomas F. Wenisch of University of Michigan, and Yuval Yarom of University of Adelaide and Data61 reported this vulnerability.

Impact:   A local user can obtain potentially sensitive information from L1 cache memory on the target system.
Solution:   FreeBSD has issued a fix for CVE-2018-3620 and CVE-2018-3646 for FreeBSD Kernel.

The FreeBSD advisory is available at:

https://security.FreeBSD.org/advisories/FreeBSD-SA-18:09.l1tf.asc

Vendor URL:  security.FreeBSD.org/advisories/FreeBSD-SA-18:09.l1tf.asc (Links to External Site)
Cause:   Access control error

Message History:   This archive entry is a follow-up to the message listed below.
Aug 14 2018 Intel CPUs Let Local Users Obtain or Infer Portions of L1 Cache Memory on the Target System



 Source Message Contents

Subject:  FreeBSD Security Advisory FreeBSD-SA-18:09.l1tf

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

=============================================================================
FreeBSD-SA-18:09.l1tf                                       Security Advisory
                                                          The FreeBSD Project

Topic:          L1 Terminal Fault (L1TF) Kernel Information Disclosure

Category:       core
Module:         Kernel
Announced:      2018-08-14
Affects:        All supported versions of FreeBSD.
Corrected:      2018-08-14 17:51:12 UTC (stable/11, 11.1-STABLE)
                2018-08-15 02:30:11 UTC (releng/11.2, 11.2-RELEASE-p2)
                2018-08-15 02:30:11 UTC (releng/11.1, 11.1-RELEASE-p13)
CVE Name:       CVE-2018-3620, CVE-2018-3646

Special Note:   Speculative execution vulnerability mitigation remains a work
                in progress.  This advisory addresses the issue in FreeBSD
                11.1 and later.  We expect to update this advisory to include
                10.4 at a later time.

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

When a program accesses data in memory via a logical address it is translated
to a physical address in RAM by the CPU.  Accessing an unmapped logical
address results in what is known as a terminal fault.

II.  Problem Description

On certain Intel 64-bit x86 systems there is a period of time during terminal
fault handling where the CPU may use speculative execution to try to load
data.  The CPU may speculatively access the level 1 data cache (L1D).  Data
which would otherwise be protected may then be determined by using side
channel methods.

This issue affects bhyve on FreeBSD/amd64 systems.

III. Impact

An attacker executing user code, or kernel code inside of a virtual machine,
may be able to read secret data from the kernel or from another virtual
machine.

IV.  Workaround

No workaround is available.

V.   Solution

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

Perform one of the following:

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 +30 "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.

[FreeBSD 11.2]
# fetch https://security.FreeBSD.org/patches/SA-18:09/l1tf-11.2.patch
# fetch https://security.FreeBSD.org/patches/SA-18:09/l1tf-11.2.patch.asc
# gpg --verify l1tf-11.2.patch.asc

[FreeBSD 11.1]
# fetch https://security.FreeBSD.org/patches/SA-18:09/l1tf-11.1.patch
# fetch https://security.FreeBSD.org/patches/SA-18:09/l1tf-11.1.patch.asc
# gpg --verify l1tf-11.1.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

CVE-2018-3620 (L1 Terminal Fault-OS)
- ------------------------------------
FreeBSD reserves the the memory page at physical address 0, so it will not
contain secret data.  FreeBSD zeros the paging data structures for unmapped
addresses, so that speculatively executed L1 Terminal Faults will access only
the reserved, unused page.

CVE-2018-3646 (L1 Terminal Fault-VMM)
- -------------------------------------
Patched systems flush the L1 data cache prior to guest entry, so that there
is no secret data in cache for a terminal fault (from the the guest) to
access.

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

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/11/                                                        r337794
releng/11.1/                                                      r337828
releng/11.2/                                                      r337828
- -------------------------------------------------------------------------

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

More information on L1 Terminal Fault is available at:

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-3620>

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-3646>

<URL:https://software.intel.com/security-software-guidance/software-guidance/l1-terminal-fault>

<URL:https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00161.html>

The FreeBSD Security Team thanks Intel for disclosing the issue.

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-18:09.l1tf.asc>
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