-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-16:15.sysarch [REVISED] Security Advisory The FreeBSD Project Topic: Incorrect argument validation in sysarch(2) Category: core Module: kernel Announced: 2016-10-25 Credits: Core Security, ahaha from Chaitin Tech Affects: All supported versions of FreeBSD. Corrected: 2016-10-25 17:14:50 UTC (stable/11, 11.0-STABLE) 2016-10-25 17:11:20 UTC (releng/11.0, 11.0-RELEASE-p2) 2016-10-25 17:16:08 UTC (stable/10, 10.3-STABLE) 2016-10-25 17:11:15 UTC (releng/10.3, 10.3-RELEASE-p11) 2016-10-25 17:11:11 UTC (releng/10.2, 10.2-RELEASE-p24) 2016-10-25 17:11:07 UTC (releng/10.1, 10.1-RELEASE-p41) 2016-10-25 17:16:58 UTC (stable/9, 9.3-STABLE) 2016-10-25 17:11:02 UTC (releng/9.3, 9.3-RELEASE-p49) CVE Name: CVE-2016-1885 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/>. 0. Revision history v1.0 2016-03-16 Initial release. v1.1 2016-10-25 Revised patch to address a problem pointed out by ahaha from Chaitin Tech. I. Background The IA-32 architecture allows programs to define segments, which provides based and size-limited view into the program address space. The memory-resident processor structure, called Local Descriptor Table, usually abbreviated LDT, contains definitions of the segments. Since incorrect or malicious segments would breach system integrity, operating systems do not provide processes direct access to the LDT, instead they provide system calls which allow controlled installation and removal of segments. II. Problem Description A special combination of sysarch(2) arguments, specify a request to uninstall a set of descriptors from the LDT. The start descriptor is cleared and the number of descriptors are provided. Due to lack of sufficient bounds checking during argument validity verification, unbound zero'ing of the process LDT and adjacent memory can be initiated from usermode. III. Impact This vulnerability could cause the kernel to panic. In addition it is possible to perform a local Denial of Service against the system by unprivileged processes. IV. Workaround No workaround is available, but only the amd64 architecture is affected. V. Solution Perform one of the following: 1) Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date. Reboot is required. 2) To update your vulnerable system via a binary patch: Systems running a RELEASE version of FreeBSD platforms can be updated via the freebsd-update(8) utility: # freebsd-update fetch # freebsd-update install Reboot is required. 3) To update your vulnerable system via a source code patch: The following patches have been verified to apply to the applicable FreeBSD release branches. [*** v1.1 NOTE ***] If your sources are not yet patched using the initially published advisory patches, then you need to apply both sysarch.patch and sysarch-01.patch. If your sources are already updated, or patched with patches from the initial advisory, then you need to apply sysarch-01.patch only. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. [ FreeBSD system not patched with original SA-16:15 patch] # fetch https://security.FreeBSD.org/patches/SA-16:15/sysarch.patch # fetch https://security.FreeBSD.org/patches/SA-16:15/sysarch.patch.asc # gpg --verify sysarch.patch.asc [ FreeBSD system that has been patched with original SA-16:15 patch] # fetch https://security.FreeBSD.org/patches/SA-16:15/sysarch-01.patch # fetch https://security.FreeBSD.org/patches/SA-16:15/sysarch-01.patch.asc # gpg --verify sysarch-01.patch.asc b) Apply the patch(es). Execute the following commands as root for every patch file downloaded: # 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/9/ r307941 releng/9.3/ r307931 stable/10/ r307940 releng/10.1/ r307932 releng/10.2/ r307933 releng/10.3/ r307934 stable/11/ r307938 releng/11.0/ r307935 - ------------------------------------------------------------------------- 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://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-1885> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-16:15.sysarch.asc> -----BEGIN PGP SIGNATURE----- iQIcBAEBCgAGBQJYD5VZAAoJEO1n7NZdz2rnYT4QAMmnfUBnxiNHfzaEDMe2oU+H WIVFzFtU5FTAm3wJ3JORU1euqhusDoB7D8nova30alM2bHHd86epBGgym1Q+hxR2 qTI+d8QimvQUWelz7DWPh0h3ZNlVfDxY8vKlr5SS0W/HOMjbG/O6U1AIw5p7cPaa LkDpqo2IN8xBL6tJFUKNEQS/GzuU2HtfKhQK0/ojT4DW61AkOZn4SZzzYBz3iO4p a8Otv4+aHzyNjTZRm/33SrFzdG0RZWyT/WXsEHlv5NiXVMPML+oY918jppqClkoO pwjcneWTqgYrE4vvVOADKOlWyNa4jFmPQSW7MmNEaF4RMd8TMcE/cBTKOi41YuOp la1JzvtWUnou7oQqy/xKr0S/Wa2x6ZhR4vBg28fkfrQhn55N+qqDicQ3F907dOm5 A0ERHKgImlWSGM+Sf2CJyrUJUNUye0bVQMhrM4e3psZ7Jr20IXjnhppr1mufCjTH H+aEHv43o/1HuoltnjstiBZ/CZpFdIXkBpsHtzteZR2y+pmZFA9bB4uZeeML0mj3 /cxj8rgPRmcjk6nSsnLWhq2YEFAZBC/lv43wqSrXE9+BBpSh6zM5NCTPb50/dBqf V553uuGEvJlHmOAoveXxYyxKcGpgZAcgJjWpAkCpoVxgdrbtLcPY5Z+8cy8fMO3G YHOkZydbLPaXOXimZfut =NWuL -----END PGP SIGNATURE-----