Date: Fri, 08 Nov 2013 16:21:13 +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 75 - Host crash due to guest VMX instruction execution -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory XSA-75 Host crash due to guest VMX instruction execution ISSUE DESCRIPTION ================= Permission checks on the emulation paths (intended for guests using nested virtualization) for VMLAUNCH and VMRESUME were deferred too much. The hypervisor would try to use internal state which is not set up unless nested virtualization is actually enabled for a guest. IMPACT ====== A malicious or misbehaved HVM guest, including malicious or misbehaved user mode code run in the guest, might be able to crash the host. VULNERABLE SYSTEMS ================== Xen 4.2.x and later are vulnerable. Xen 4.1.x and earlier are not vulnerable. Only HVM guests run on VMX capable (e.g. Intel) hardware can take advantage of this vulnerability. MITIGATION ========== Running only PV guests, or running HVM guests on SVM capable (e.g. AMD) hardware will avoid this issue. Enabling nested virtualization for a HVM guest running on VMX capable hardware would also allow avoiding the issue. However this functionality is still considered experimental, and is not covered by security support from the Xen Project security team. This approach is therefore not recommended for use in production. CREDITS ======= This issue was discovered by Jeff Zimmerman. NOTE REGARDING LACK OF EMBARGO ============================== This issue was disclosed publicly on the xen-devel mailing list. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa75-4.3-unstable.patch Xen 4.3.x, xen-unstable xsa75-4.2.patch Xen 4.2.x $ sha256sum xsa75*.patch 0b2da4ede6507713c75e313ba468b1fd7110e5696974ab72e2135f41ee393a8b xsa75-4.2.patch 91936421279fd2fa5321d9ed5a2b71fe76bc0e1348e67126e8b9cde0cb1d32b2 xsa75-4.3-unstable.patch $ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQEcBAEBAgAGBQJSfQ8xAAoJEIP+FMlX6CvZ8JQIAMc9IH79JeoZPAe/Fvz8TrdF FM7FkB/+sob4ybEFXnaSsK/7v7+A1e2qti/UVZfgcKEa8LG7aAIXFqsMXqErvME2 7D+r0Kt7QfvK5BvOygACCMsNV5muUTndVO8NUtHm8wDJk6yuSMWVnA/c3p+OSkH0 h63cfkrf9iYSYrPdCt4iO+/JKDVZl3bQAmHOFHvGTqsN7FMgOGexn+9RlNwWNmlU jvMxPLmwaerwd85fqLwEjajWT1TJlqro5xx4darKp8pokY+DVEtV4MGHXgllHVym t7g56Ph7YXPqTIJV4+PmrNQNwFPvsgBeFVyno3oa95IT4F55Fja0LiJUxREDHhU= =AbJ0 -----END PGP SIGNATURE----- Download attachment "xsa75-4.2.patch" of type "application/octet-stream" (1586 bytes) Download attachment "xsa75-4.3-unstable.patch" of type "application/octet-stream" (1747 bytes)
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