Date: Wed, 15 Feb 2017 12:05:58 +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 207 - memory leak when destroying guest without PT devices -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory XSA-207 version 2 memory leak when destroying guest without PT devices UPDATES IN VERSION 2 ==================== Public release. ISSUE DESCRIPTION ================= Certain internal state is set up, during domain construction, in preparation for possible pass-through device assignment. On ARM and AMD V-i hardware this setup includes memory allocation. On guest teardown, cleanup was erroneously only performed when the guest actually had a pass-through device assigned. IMPACT ====== A malicious guest may, by frequently rebooting over extended periods of time, run the system out of memory, resulting in a Denial of Service (DoS). The leak is no more than 4kbytes per guest boot. VULNERABLE SYSTEMS ================== Xen versions 3.3 and later are affected. ARM systems, and x86 AMD systems, are affected. Intel systems, and systems without IOMMU/SMMU hardware, are unaffected. All guest kinds can exploit this vulnerability. MITIGATION ========== Limiting the frequency with which a guest is able to reboot, will limit the memory leak. Rebooting each host (after migrating its guests) periodically will reclaim the leaked space. CREDITS ======= This issue was discovered by Oleksandr Tyshchenko of EPAM Systems. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa207.patch xen-unstable, Xen 4.8.x, Xen 4.7.x, Xen 4.6.x, Xen 4.5.x xsa207-4.4.patch Xen 4.4.x $ sha256sum xsa207* e9bcf807b3785ac4d78b621fba4a9395cd713d6e57cdaa66559bccf95ded1cd9 xsa207.patch 5f391cc621d619ee33c90398bda24588ebf8320750db4545677bb5222150ae6d xsa207-4.4.patch $ DEPLOYMENT DURING EMBARGO ========================= Deployment of the patches described above is permitted during the embargo, as is the mitigation of migrating a VM which has no devices assigned from IOMMU-capable hardware to IOMMU-incapable hardware, even on public-facing systems with untrusted guest users and administrators. HOWEVER, moving a VM from AMD to Intel hardware, in response to this vulnerability, is *not* permitted. This is because such a change is visible to guests, and would not normally be expected. Furthermore: Distribution of updated software is prohibited (except to other members of the predisclosure list). Predisclosure list members who wish to deploy significantly different patches and/or mitigations, please contact the Xen Project Security Team. (Note: this during-embargo deployment notice is retained in post-embargo publicly released Xen Project advisories, even though it is then no longer applicable. This is to enable the community to have oversight of the Xen Project Security Team's decisionmaking.) For more information about permissible uses of embargoed information, consult the Xen Project community's agreed Security Policy: http://www.xenproject.org/security-policy.html -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJYpEP+AAoJEIP+FMlX6CvZPrMIAL7ULaO/oOicZzGHzMO0f1r6 MZDBPeLAg5EQ3oGl1oZenlEEQgSflzj2YHdwjdps2kZpJBaRJjNPmqOC3ZxetlyF +cEJWpw6u0IDRzukEWkQlFGQS68ShLjRcKWDi5+ftjo4rFh34uybrgRv7/nKtiuG ZLX7dqKZuqYBSYvSXjA8UejB//psGOu4jqNh15t0bxtQqc5BlgdJebOkKlgrxL2M BqI/kiZoRuKkDVBu2786oo3w8BCjyBktDR0B9dzRY6MEdTXqb+mE8IO7G492KQTk /ZW9rKeijauKLNgsSkZlqtA0TPTp7tujh9XxE/JfB8UcYFez86NWoBBY4g+Q3SQ= =kwFG -----END PGP SIGNATURE----- [ CONTENT OF TYPE application/octet-stream SKIPPED ] [ CONTENT OF TYPE application/octet-stream SKIPPED ]
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