FreeBSD Errata Notice FreeBSD-EN-18:17.vm
19 December, 2018 by email@example.com | freebsd
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-EN-18:17.vm Errata Notice The FreeBSD Project Topic: Kernel panic under load on Intel "Skylake" CPUs Category: core Module: kernel Announced: 2018-12-19 Credits: Mark Johnston Affects: FreeBSD 11.2 Corrected: 2018-12-02 18:08:27 UTC (stable/11, 11.2-STABLE) 2018-19-19 18:00:58 UTC (releng/11.2, 11.2-RELEASE-p7) 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 The physical page allocator is a component of the kernel responsible for tracking usage of the system's RAM by the kernel and by userland applications. It maintains lists of unused memory pages which may be returned by the allocator upon demand. It also maintains an integer count of the number of pages stored in these lists. II. Problem Description The kernel contains handling for an Intel erratum affecting Skylake-X CPUs. The erratum description states that a processor may hang when performing a certain synchronization operation within a particular 4MB region of physical memory. FreeBSD works around the erratum by using a blacklisting mechanism to ensure that the physical page allocator never returns pages in that region. However, this blacklisting mechanism contained a bug such that the removal of pages in the region was not reflected in the free page count. III. Impact The discrepancy between the free page count and the physical page allocator's state can trigger a NULL pointer dereference when the system is under heavy load, resulting in a panic. IV. Workaround Only systems using a Skylake-X or Skylake Server CPU are affected. Affected systems can work around the problem by setting the "hw.skz63_enable" to 0 in /boot/loader.conf, causing the handling for the Intel erratum to be disabled upon a reboot of the system. However, this raises the possibility of being affected by the erratum if software running on the system makes use of Intel TSX. 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 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 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 11.2] # fetch https://security.FreeBSD.org/patches/EN-18:17/vm.patch # fetch https://security.FreeBSD.org/patches/EN-18:17/vm.patch.asc # gpg --verify vm.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/11/ r341401 releng/11.2/ r342225 - ------------------------------------------------------------------------- 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://bugs.freebsd.org/bugzilla/show_bug.cgi?id=231296> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-18:17.vm.asc> -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE/A6HiuWv54gCjWNV05eS9J6n5cIFAlwannZfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEZD MEU4NzhBRTVBRkU3ODgwMjhENjM1NUQzOTc5MkY0OUVBN0U1QzIACgkQ05eS9J6n 5cKsAxAAkr/ufB1aKSSib0n/e6PXE1FOnjUGgpK+LiiSG+QdW/6oMv/yto+4Qbj2 3Ht3TPyuoTqwQmHHiSzpnnnRHGDrdffiRYQsziFR89c8iyw7Qni8BYlK2YLYYw9i TVyT6sxkorpTPZpGQZNaRBwZoWCLaxBvfKC0wVcli9gByOfb5T5J4puUNT4EXIpb eaimCWG24vsIkWlHeC/8ulHsjEEDBatyfWWl95i8JVMqBDdHZypryJkO0jBo5Uig PIighKIqDiEwwvjtHfGh4iAn3mFINDbMDdjXyMWYqDbgvX3J6cCv6qaY7p2eizQN taN1rbC+7MJIFEkTFASvbJq7KOc/PcXOLU4O3964HZbbowdQNwAxQAuMGN6GNLmJ ydHE7Atei1Py8q3gg9uMpX0TVikzfOL6iBmdzEkg2mgXIeyISLn5BTuE/k9hkVwi 6Boeec1qshtx04gF0xzsp/KPropad4nV09/E4cuo5jHuaq3WgpnDVzVhGEmFZpY7 Z5B8vHqSc7Ng0xZoQYIcYbGCVBaWNF4WCf/1DZhU44mXkob+CRkv+kROFkfn8lY3 2Jzjp7LWqPv9CFxIJ7q4BnDTyhxkQksm646tII1JNMcjY0hzFjQDUrVmDRb8ak/E LsJNDKicqGdCdrHeA8jZm7RxwAmdkhyF/uumPYxJg64Y9DU23SM= =QgI2 -----END PGP SIGNATURE----- _______________________________________________ firstname.lastname@example.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-announce To unsubscribe, send any mail to "email@example.com"