Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2014.1445 Xen Security Advisory CVE-2014-5146,CVE-2014-5149 / XSA-97 version 3 25 August 2014 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Xen Publisher: Xen Operating System: Xen UNIX variants (UNIX, Linux, OSX) Impact/Access: Denial of Service -- Existing Account Resolution: Patch/Upgrade CVE Names: CVE-2014-5149 CVE-2014-5146 Original Bulletin: http://xenbits.xen.org/xsa/advisory-97.html - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory CVE-2014-5146,CVE-2014-5149 / XSA-97 version 3 Long latency virtual-mmu operations are not preemptible UPDATES IN VERSION 3 ==================== Public release. ISSUE DESCRIPTION ================= Some MMU virtualization operations on HVM guests must process every page assigned to a guest. For larger guests, this can tie up a vcpu for a significant amount of time, as the operations are not preemptible. For guests using Hardware Assisted Paging (HAP, see below) this is CVE-2014-5146. For guests not using HAP this is CVE-2014-5149. IMPACT ====== A malicious HVM guest with a large allocation of shadow/p2m RAM can mount a denial of service attack affecting the whole system. VULNERABLE SYSTEMS ================== ARM systems are not vulnerable. All x86 Xen versions are vulnerable. The vulnerability is only exposed to HVM guests. In the default configuration, the vulnerability is only exposed to large guests (guests assigned more than 128Gbytes of memory). MITIGATION ========== Running only PV guests, or only smaller guests will avoid this problem. Since the vulnerability actually depends on the guest's shadow memory, if you are overriding the default allocation (which is about 0.5% of guest RAM) by using the "shadow_memory=" VM configuration file option, you should adjust your idea of a 'smaller' guest accordingly. CREDITS ======= This issue was discovered by Jan Beulich. RESOLUTION ========== For HAP-enabled guests, the attached patch resolves ths issue. HAP (Hardware Assisted Paging, aka nested paging) is enabled by default if the system is suitably capable. The VM configuration file can disable or enable HAP explicitly by setting "hap=0" or "hap=1". HAP can also be globally disabled by specifying "hap=off" on the hypervisor command line. There is no resolution for guests using shadow pagetables (i.e., not using HAP) at this time. xsa97-hap-unstable.patch xen-unstable xsa97-hap-4.4.patch Xen 4.4.x xsa97-hap-4.3.patch Xen 4.3.x xsa97-hap-4.2-prereq.patch, xsa97-hap-4.2.patch Xen 4.2.x $ sha256sum xsa97*.patch c9e0e9f136db1b976ea371be10430598a7f21b4a33b4849f2081566657ff5da1 xsa97-hap-4.2.patch c525a99263eed6f93fad685ae9dad1ae10c8930345ec52659211541640797bb5 xsa97-hap-4.2-prereq.patch cfab6521221a5058a0dfbb6d59c3c4cd0e7f4239bb6cbee2723de22c33caafda xsa97-hap-4.3.patch 138511f2fd8362366e09dda18443387886ec4397eecc1a2f6a7e85643bd415e8 xsa97-hap-4.4.patch 58c56daa01f20be0317700d383dfbba8de35695bd38a9860c0c0463181d76351 xsa97-hap-unstable.patch $ - -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQEcBAEBAgAGBQJT6hBmAAoJEIP+FMlX6CvZ8sgIAIqtUEu6CS5+H3enavmmLhuh PGLCqQOBVWn99+m6bMqk+WvZOkW9CLxiX6+78XsheJlmUFBtHc3rG53wR0voo6Vr BXyU3XY2n4aEh1klstS3gq/J37L86fEi2a+MaAePbPZ4qdWvFh3zDhRrLTQ/TDvK 0tfze9fF6K24Ab7jAcstF2gn+NhrrS3L3pvvgD/P5T1LR8HrEsyyhTlf7c34T5cp RnSM19CUqAVAJeyN6WI2meZ3C+nvxLiNRUEQQikf4yCKqGxevzjBLAbXlcw4ELnF 9rG7Yd1aRJh4pQkViFDIdB3x8Xb9HuT7kFsQ7kBZc3an9JkbxxTGQd82XjODM1Q= =A/Ph - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBU/q1KRLndAQH1ShLAQKtng/+OCmrQt9c+uVQxzJtAJ5GOc3ZgV+ud0HN WnHYcpge1xcKnlJT8HaDalajM9VY6z6ebXs4HjEQzqMuygkXwz5GOLqNM7ir/s1E fbp28Iyu5P1G/KayKw+tWJoZalXmQJcjJgDwc7JLngxiCdKtJDuKkEbsNPlREvJ3 9briEiL2Cvc67zax0L1PjF7IfK4NqN5uSx+rqcvKvlLSpcPL413jqplg6VZZlsx6 k4iJoEkgpXbqzMR6xxfFWWRruD9ugbc45SRurRAaftyCfooH+AkYFTYgjoEcTs1f jwGFq8s8F2Yefx7vSQe77+BU3UGe3W5Q/VkMqs6VaQUaqMuTXVNCwzxHq1DBfnbW H4D97AFqN0vVNvegaAm8UbaUOcUtiyjfURWWhdUsLiVf5ej/v+x2Y6QG0wnHxAjA CQIxUBTu2aNYdgzJC21oRVw/+Ck6VhJsxAiVs3/deieGSh3ilUmprxpTluiYvxNu Thg6rF0ltVQySfQ0ALhun/3061FPOmKXb3/gw0RmFceJxyuuakSFF3cOdk+xX4Wv uR3IRGzrg7/z8w7o9xpi/h5JVUnk6RdIg6uvjgVp5E7rEpkWndXgGNL/QsT0lMmP RcAnsXSxV/DN3fKM4tv6E1e98kb7S15QBV5YuPCUjMbYVOdE9sm+O7/TjE8WXG1r T7u1lBvZvfw= =Nf40 -----END PGP SIGNATURE-----