FreeBSD Security Advisories
2018-Aug-15 05:47 UTC
[FreeBSD-Announce] 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> -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.2.9 (FreeBSD) iQIzBAEBCgAdFiEE/A6HiuWv54gCjWNV05eS9J6n5cIFAltztc8ACgkQ05eS9J6n 5cLwEhAAos2Bnilthrbd+uQr1IGASD96aZZ5iXvn1Ibls03Vtd0kG9EcU30gFVG0 HSg47qT7r5qJQUdhuSYxspgS9ZxXpRez1vnAz7cSGHL9FdecyfHWmHvGor5tz84/ CgX4jCCAZfqDBquYD+ioqiLX7p1ZTRKfHBQOHcGgMfMq8UQUsg1YriXabEqnavU6 W0h/eCGBo/Dbvl7004Gx0hKmDO2YQxt9aPWfInXWx1VOMf+wNWpcrvU6rJ4kOnL9 7BXi+c5+vwlVXDvjrTwP9X+9DDa0MJcMoy2JCyCa/0W7lQ9nADLfUiXLsTvLDo6V 6/sooFbqlO+Qz37XHlXOXaoVGZGw+NtJRcnD+w8ueP9ts02SsECoxofN8tPOzGsT T285qAwv8D8uuBLU3dc9y+assEe3j/4Aqb1Eil6Eh1MsHypEvyN5z9+PIpbN2tWK qqCtzgqx037Jvjo6DwjwMUd+DikObGjZyK4pwP8KIeccOIBrUAA1Xel7Xr74xuwq LwqtcHb2MWeFD0Mw+oW9viuJKrxyu6aiQfU6FsuGVmHjtXGxi+aWyGQqed+q8FcU w/J6fq4kmBVVqNNrAMc/bWKU3IXAj4c48H0CSiCoX4dE4waRQ+cEetKkSWVGYnXj 3QdoyPsiqo8Goo34Cn0Ipf9GWDeNVv32iz0fXtr4LtoVZKCx9oc=G5SD -----END PGP SIGNATURE-----