Date: Tue, 12 Aug 2014 13:03:26 +0000 From: Xen.org security team <security@....org> To: xen-announce@...ts.xen.org, xen-devel@...ts.xen.org, xen-users@...ts.xen.org, oss-security@...ts.openwall.com CC: Xen.org security team <security@....org> Subject: Xen Security Advisory 97 (CVE-2014-5146,CVE-2014-5149) - Long latency virtual-mmu operations are not preemptible -----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----- [ CONTENT OF TYPE application/octet-stream SKIPPED ] [ CONTENT OF TYPE application/octet-stream SKIPPED ] [ CONTENT OF TYPE application/octet-stream SKIPPED ] [ CONTENT OF TYPE application/octet-stream SKIPPED ] [ CONTENT OF TYPE application/octet-stream SKIPPED ]
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