From ${URL} : 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 @maintainer(s): after the bump, in case we need to stabilize the package, please let us know if it is ready for the stabilization or not.
fixed in version: xen-4.2.4-r5, xen-4.3.2-r5, xen-4.4.0-r6 Arches, please test and mark stable: =app-emulation/xen-4.2.4-r5 Target keywords : "amd64 x86" =app-emulation/xen-4.3.2-r5 Target keywords : "amd64"
amd64 stable
x86 stable. Maintainer(s), please cleanup. Security, please vote.
this patch cause regressions, upstream have reverted it, current no new patches posted [xen-4.4-testing test] 29686: regressions - FAIL[1] [1] http://www.gossamer-threads.com/lists/xen/devel/344143
CVE-2014-5149 (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2014-5149): Certain MMU virtualization operations in Xen 4.2.x through 4.4.x, when using shadow pagetables, are not preemptible, which allows local HVM guest to cause a denial of service (vcpu consumption) by invoking these operations, which process every page assigned to a guest, a different vulnerability than CVE-2014-5146. CVE-2014-5146 (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2014-5146): Certain MMU virtualization operations in Xen 4.2.x through 4.4.x before the xsa97-hap patch, when using Hardware Assisted Paging (HAP), are not preemptible, which allows local HVM guest to cause a denial of service (vcpu consumption) by invoking these operations, which process every page assigned to a guest, a different vulnerability than CVE-2014-5149.
Maintainer(s), Thank you for you for cleanup. Added to an existing GLSA Request.
This issue was resolved and addressed in GLSA 201504-04 at https://security.gentoo.org/glsa/201504-04 by GLSA coordinator Yury German (BlueKnight).