Date: Thu, 04 Jan 2018 13:02:49 +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-team-members@....org> Subject: Xen Security Advisory 253 - x86: memory leak with MSR emulation -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory XSA-253 version 2 x86: memory leak with MSR emulation UPDATES IN VERSION 2 ==================== Public release. ISSUE DESCRIPTION ================= In Xen 4.10, new infrastructure was introduced as part of an overhaul to how MSR emulation happens for guests. Unfortunately, one tracking structure isn't freed when a vcpu is destroyed. IMPACT ====== A memory allocation of 8 bytes is leaked each time a vcpu is destroyed. 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). VULNERABLE SYSTEMS ================== Xen versions 4.10 and later are affected. Xen 4.9 and earlier are not affected. Only x86 systems are affected. ARM systems are not. 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 Andrew Cooper of Citrix. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa253.patch Xen 4.10, xen-unstable $ sha256sum xsa253* bba1abb5e4368421de29385e37f8477bf3534d3ba3ff7e2aae9c9d3da53f1393 xsa253.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deployment notice is retained in post-embargo publicly released Xen Project advisories, even though it is then no longer applicable.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 iQEcBAEBCAAGBQJaTiXyAAoJEIP+FMlX6CvZ/CIH/3LEbyAmWUSs4C2Rt0EENDLO JnnAGXWIy3DsffGiG9zOhfYiItn2iD+J+EcO+WC5lGPBSkX1KiXdsWVla/dJuy0F frx5pdqJNSHFihK/6fGU0WnSBFz6o2gkn2hOnzWfpxNLiJMrHCI6GEOcdMx6xtOQ 9QZAa7rCN1aRx0Lx1LjuvaqPwy4rJ294zLnwarMoN10KZ3oRVbQ8mf4kN+/X+hlK 9MxUj99WYZWcJhcRLGiQALPdRQeabh72/ZTFsfIAwPxaEgT6YhwFrFDG526iNcM0 MkruO8HeD+byrQrni/qgB5EAIyPsFuBfvzddHzPA+9sSrf4QDjQWPFihQ3ti+xg= =sQVC -----END PGP SIGNATURE----- Download attachment "xsa253.patch" of type "application/octet-stream" (739 bytes)
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