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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2015.2305 Xen Security Advisory CVE-2015-6654 / XSA-141 3 September 2015 =========================================================================== 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-2015-6654 Original Bulletin: http://xenbits.xen.org/xsa/advisory-141.html - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory CVE-2015-6654 / XSA-141 version 3 printk is not rate-limited in xenmem_add_to_physmap_one UPDATES IN VERSION 3 ==================== Public release. ISSUE DESCRIPTION ================= XENMAPSPACE_gmfn_foreign dumps the p2m, on ARM, when it fails to get a reference on the foreign page. However, dump_p2m_lookup does not use rate-limited printk. A malicious infrastructure domain, which is allowed to map memory of a foreign guest, would be able to flood the Xen console. IMPACT ====== Domains deliberately given partial management control may be able to deny service to other parts of the system. As a result, in a system designed to enhance security by radically disaggregating the management, the security may be reduced. But, the security will be no worse than a non-disaggregated design. VULNERABLE SYSTEMS ================== This issue is only relevant to systems which intend to increase security through the use of advanced disaggregated management techniques. This does not include systems using libxl, libvirt, xm/xend, XCP/XenServer, OpenStack or CloudStack (unless substantially modified or supplemented, as compared to versions supplied by the respective upstreams). This issue is not relevant to stub device models, driver domains, or stub xenstored. Those disaggregation techniques do not rely on granting the semi-privileged support domains access to the affected hypercall, and are believed to provide the intended security benefits. Only ARM systems are potentially affected. All Xen versions which support ARM are potentially affected. MITIGATION ========== Reducing the hypervisor log level can be used to suppress messages. Switching from disaggregated to a non-disaggregated operation does NOT mitigate these vulnerabilities. Rather, it simply recategorises the vulnerability to hostile management code, regarding it "as designed"; thus it merely reclassifies these issues as "not a bug". Users and vendors of disaggregated systems should not change their configuration. CREDITS ======= This issue was discovered by Julien Grall of Citrix. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa141.patch Xen 4.4.x, 4.5.x, xen-unstable $ sha256sum xsa141*.patch 12358565dc443e1855a1b5776fa9008c5ea5e5854bd4e93b88ab4178c698fc2a xsa141.patch $ DEPLOYMENT DURING EMBARGO ========================= Deployment of the patches and/or mitigations described above (or others which are substantially similar) is permitted during the embargo, even on public-facing systems with untrusted guest users and administrators. But: 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 v1.4.12 (GNU/Linux) iQEcBAEBAgAGBQJV5aV+AAoJEIP+FMlX6CvZz74H/jn2L3URqeatI7eBXRtpC9SL DshKXMZRC746x5W06nsFp9dxr/ggSrMG1avM3q/V2dF5Sb/RDyH3A4D8DVhZOFQh jxYScztKJI2OjRmPJvPatVR9oYBQhLpwg8yE3ye6//ObHCO3PSqX28VqWkS8gZha E3Cr3PpbWN1nO1PkHZBqq9BRT7B6Nq/1HE3TnbgjYVWUryWMUUp6GZOZ9QYOTbQB F5I7oimZ/mW2B4PL9p2lCKnCBDJIELpeE6sZAmv8yeQg7Lq7UhwWnB57U8gOOe1I uzV5z852a9Hqdn8flUOGn0eQxputFRdOTamaMqQ2UtG2f0E+l2R6ahD1CGyTmBM= =pKQu - -----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). 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