Date: Tue, 12 Jun 2012 13:03:19 +0100 From: Xen.org security team <security@....org> To: xen-announce@...ts.xensource.com, xen-devel@...ts.xensource.com, xen-users@...ts.xensource.com, oss-security@...ts.openwall.com Subject: Xen Security Advisory 8 (CVE-2012-0218) - syscall/enter guest DoS -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory CVE-2012-0218 / XSA-8 version 7 guest denial of service on syscall/sysenter exception generation UPDATES IN VERSION 7 ==================== Public release. Previous versions were embargoed. ISSUE DESCRIPTION ================= When guest user code running inside a Xen guest operating system attempts to execute a syscall or sysenter instruction, but when the guest operating system has not registered a handler for that instruction, a General Protection Fault may need to be injected into the guest. It has been discovered that the code in Xen which does this fails to clear a flag requesting exception injection, with the result that a future exception taken by the guest and handled entirely inside Xen will also be injected into the guest despite Xen having handled it already, probably crashing the guest. IMPACT ====== User space processes on some guest operating systems may be able to crash the guest. VULNERABLE SYSTEMS ================== HVM guests are not vulnerable. 32- and 64-bit PV guests may be vulnerable, depending on the CPU hardware, the guest operating system, and its exact kernel version and configuration. MITIGATION ========== This issue can be mitigated by running HVM (fully-virtualised). In some cases this issue can be mitigated by upgrading the guest kernel to one which installs hooks for sysenter and/or syscall, as applicable. RESOLUTION ========== Applying the appropriate attached patch will resolve the issue. These patches also resolve the (more serious) issue described in XSA-7 (CVE-2012-0217). These changes have been made to the staging Xen repositories: XSA-7: XSA-8: xen-unstable.hg 25480:76eaf5966c05 25200:80f4113be500+25204:569d6f05e1ef xen-4.1-testing.hg 23299:f08e61b9b33f 23300:0fec1afa4638 xen-4.0-testing.hg 21590:dd367837e089 21591:adb943a387c8 xen-3.4-testing.hg 19996:894aa06e4f79 19997:ddb7578abb89 PATCH INFORMATION ================= The attached patches resolve both this issue and that reported in XSA-7 (CVE-2012-0217). xen-unstable 25204:569d6f05e1ef or later xsa7-xsa8-unstable-recent.patch xen-unstable 25199:6092641e3644 or earlier xsa7-xsa8-unstable-apr16.patch Xen 4.1, 4.1.x xsa7-xsa8-xen-4.1.patch Xen 4.0, 4.0.x xsa7-xsa8-xen-4.0.patch Xen 3.4, 3.4.x xsa7-xsa8-xen-3.4.patch $ sha256sum xsa7-xsa8-*patch 00853d799d24af16b17c8bbbdb5bb5144a8a7fad31467c4be3d879244774f8d2 xsa7-xsa8-unstable-apr16.patch 71f9907a58c1a1cd601d8088faf8791923d78f77065b94dba8df2a61f512530d xsa7-xsa8-unstable-recent.patch 55fb925a7f4519ea31a0bc42d3ee83093bb7abd98b3a0e4f58591f1ae738840a xsa7-xsa8-xen-3.4.patch 6a7e39121ec1f134351fdf34f494d108500aaa4190a9f7965e81c4e96270924e xsa7-xsa8-xen-4.0.patch 52d8288718b4a833eb437fd18d92b7d412fbe01900dbd0b437744a1df4d459da xsa7-xsa8-xen-4.1.patch NOTE REGARDING EMBARGO ====================== The fix for this issue has already been published as xen-unstable.hg changesets 25200:80f4113be500 and 25204:569d6f05e1ef. However, this has not been flagged as a security problem, and since the affected area of code is the same as that for XSA-7 (CVE-2012-0217), we have concluded that this advisory should be under the same embargo as XSA-7. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iQEcBAEBAgAGBQJP1yqMAAoJEIP+FMlX6CvZQRoH/1Do71YkaMvKoPo/VCHqUuB1 5mJve/SiTK5Y5kggnLfnpZeuLjlntHCT5F//Do7N21WDVdwZXFBItlvjhKyNGA0Y ohqzqzAQ0c2l/mE3ToaLhhtuFb8U06q8Ud+pQ9QbMHHpJvGXPzDbNG12L/fZDwyf ZbMqB2j8+TVuRXPlbdZabNUAcZ+HOJHb1NloKCbX0qwMG4p5FJ3OdkDX7r5OjPKj sIJAaltBINGjRrqYMLB4UUQdrftu1ftfU/GFVYy8+t3uNj0fBgkCPUlGbbQs2SF2 +VtLUUG6rzVlRdHyhVMswz3sZtR7Tow6xwPk3Sr4yfrI15rH2pUJI7if8vZ1ZQ8= =elZi -----END PGP SIGNATURE----- Download attachment "xsa7-xsa8-unstable-recent.patch" of type "application/octet-stream" (1589 bytes) Download attachment "xsa7-xsa8-unstable-apr16.patch" of type "application/octet-stream" (5044 bytes) Download attachment "xsa7-xsa8-xen-4.1.patch" of type "application/octet-stream" (4939 bytes) Download attachment "xsa7-xsa8-xen-4.0.patch" of type "application/octet-stream" (3960 bytes) Download attachment "xsa7-xsa8-xen-3.4.patch" of type "application/octet-stream" (3960 bytes)
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