Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2015.0839 A number of vulnerabilities have been identified in Xen 2 April 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-2015-2756 CVE-2015-2752 CVE-2015-2751 Original Bulletin: http://xenbits.xenproject.org/xsa/advisory-125.html http://xenbits.xenproject.org/xsa/advisory-126.html http://xenbits.xenproject.org/xsa/advisory-127.html Comment: This bulletin contains three (3) Xen security advisories. - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory CVE-2015-2752 / XSA-125 version 3 Long latency MMIO mapping operations are not preemptible UPDATES IN VERSION 3 ==================== CVE assigned. Public release. ISSUE DESCRIPTION ================= The XEN_DOMCTL_memory_mapping hypercall allows long running operations without implementing preemption. This hypercall is used by the device model as part of the emulation associated with configuration of PCI devices passed through to HVM guests and is therefore indirectly exposed to those guests. This can cause a physical CPU to become busy for a significant period, leading to a host denial of service in some cases. If a host denial of service is not triggered then it may instead be possible to deny service to the domain running the device model, e.g. domain 0. This hypercall is also exposed more generally to all toolstacks. However the uses of it in libxl based toolstacks are not believed to open up any avenue of attack from an untrusted guest. Other toolstacks may be vulnerable however. IMPACT ====== The vulnerability is exposed via HVM guests which have a PCI device assigned to them. A malicious HVM guest in such a configuration can mount a denial of service attack affecting the whole system via its associated device model (qemu-dm). A guest is able to trigger this hypercall via operations which it is legitimately expected to perform, therefore running the device model as a stub domain does not offer protection against the host denial of service issue. However it does offer some protection against secondary issues such as denial of service against dom0. VULNERABLE SYSTEMS ================== The issue is exposed via x86 HVM VMs which have been assigned a PCI device. x86 PV domains, x86 HVM domains without passthrough devices and ARM domains do not expose this vulnerability. Xen 3.2.x and later are vulnerable. Xen 3.1.x and earlier have not been inspected. MITIGATION ========== Running only PV guests will avoid this issue. This issue can be avoided by not assigning devices with large MMIO regions to untrusted HVM guests. CREDITS ======= This issue was discovered by Konrad Rzeszutek Wilk of Oracle. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa125.patch Xen 4.5.x, xen-unstable xsa125-4.4.patch Xen 4.4.x xsa125-4.3.patch Xen 4.3.x xsa125-4.2.patch Xen 4.2.x $ sha256sum xsa125*.patch be0c7cceb1af4b7b1341f37c1e20cf804ea3ac7d3c2ca2e5599f936479d5e0de xsa125.patch 5f081407c2955787c6e40daa847f3c4131694dff3bb0bc0ee55495f555c7bb52 xsa125-4.2.patch 3b0641ef2a23f12872267940c408097cb353e57a6e0396a64cdf13592a14f65b xsa125-4.3.patch 2180e657b34d8628d4e0157adf2a36904bb6feaf55d53338e4457ef77d867a31 xsa125-4.4.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) iQEcBAEBAgAGBQJVGo5JAAoJEIP+FMlX6CvZlEAIAMdSMKpxum+J9IbUFCqcHFa4 F8zQDkz2hMCY3OjTAq9+n6KR2LLyKDn2hGDP0Mspbo67lRBEjSkp7KEXCoDrA294 YsVuJn8y0T3yPH9du3m0f2vi49MrhnxnUZLNyKCpkxTiClrC/7JX3OZxQTQIGpzf EIsjYP+/w9ava5XYbGKorwlLvGpjRmnZpCDTrZlqKV2bK2O6pWzyvp5zD99FORcJ YVRIGebKu8szbSHZs9ectt4xkZwYrzSjj0+PtryvwLSpSYi0zTWIu9rrgd/ZCXfL tgD+i9zoc2E1ydPlvdKRXEdRHY9gGcaimfbTqYn1ttJ6qQcnbMoRQor4X+v92NU= =m83F - -----END PGP SIGNATURE----- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory CVE-2015-2756 / XSA-126 version 3 Unmediated PCI command register access in qemu UPDATES IN VERSION 3 ==================== Public release. ISSUE DESCRIPTION ================= HVM guests are currently permitted to modify the memory and I/O decode bits in the PCI command register of devices passed through to them. Unless the device is an SR-IOV virtual function, after disabling one or both of these bits subsequent accesses to the MMIO or I/O port ranges would - on PCI Express devices - lead to Unsupported Request responses. The treatment of such errors is platform specific. Furthermore (at least) devices under control of the Linux pciback driver in the host are handed to guests with the aforementioned bits turned off. This means that such accesses can similarly lead to Unsupported Request responses until these flags are set as needed by the guest. IMPACT ====== In the event that the platform surfaces aforementioned UR responses as Non-Maskable Interrupts, and either the OS is configured to treat NMIs as fatal or (e.g. via ACPI's APEI) the platform tells the OS to treat these errors as fatal, the host would crash, leading to a Denial of Service. VULNERABLE SYSTEMS ================== Xen versions 3.3 and onwards are vulnerable due to supporting PCI pass-through. Only x86 systems are vulnerable. ARM systems are not vulnerable. Only HVM guests with their device model run in Dom0 can take advantage of this vulnerability. Any domain which is given access to a non-SR-IOV virtual function PCI Express device can take advantage of this vulnerability. MITIGATION ========== This issue can be avoided by not assigning PCI Express devices other than SR-IOV virtual functions to untrusted HVM guests. This issue can also be avoided by only using PV guests or HVM guests with their device model run in a separate (stub) domain. CREDITS ======= This issue was discovered by Jan Beulich of SUSE. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa126-qemuu.patch qemu-upstream-unstable, Xen 4.5.x, Xen 4.4.x xsa126-qemuu-4.3.patch qemu-upstream-unstable, Xen 4.3.x xsa126-qemut.patch qemu-xen-unstable, Xen 4.5.x, Xen 4.4.x, Xen 4.3.x, Xen 4.2.x For those already having the original patch in place, applying the appropriate attached incremental patch addresses the regression. xsa126-qemuu-incr.patch qemu-upstream-unstable, Xen 4.5.x, Xen 4.4.x xsa126-qemuu-4.3-incr.patch qemu-upstream-unstable, Xen 4.3.x xsa126-qemut-incr.patch qemu-xen-unstable, Xen 4.5.x, Xen 4.4.x, Xen 4.3.x, Xen 4.2.x $ sha256sum xsa126*.patch bd69a0d18127793a9aa2097062ecaef76df6e6b8f729406d7d52cf66519e3b0d xsa126-qemut-incr.patch 2a9b8f73b2a4f0cfb6b724c9a0a72dbf08cae87cd382f61f563218c32d1036a7 xsa126-qemut.patch 658bc483d1110e4e04de2d70fba1cdb20c5cecdc2f419db2d82bddc3ae1690b6 xsa126-qemuu-4.3-incr.patch 090d9262a9e9d24f0f4eca35cb0d56831d5cec6a6ba38b4c7e276d767de660c1 xsa126-qemuu-4.3.patch 3f7b6737c08ff7e119bec16c8c3b3cb832429f1410e687edf622fab57a22842e xsa126-qemuu-incr.patch eb5b93600267639b2cda1c5e2f937ddbecbf6c8cbd19dbb355224c39c2e40d3e xsa126-qemuu.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) iQEcBAEBAgAGBQJVGo5NAAoJEIP+FMlX6CvZvt4IAIeNbTd6EQJE4CnuU6fH9lA3 0fO7FrUEMn7cfiptLy86y01C0d7YqF1MCbO3TKfJ0NJSjvl5CQ/WDuPwjdbD28eW Zi2NZFRRy0JnLM3bgHxYB5Ik7voO6QPm4+BSZxM9rdiOhKwOY1LLyDbRlC5GvsVr 5J87gm1tfcQVHNDkVZp6ZlzQh5Kl3iSFp6KvzwsIagoJucsPVEHsoBWF84I+3peu miT3gQqPeZg3PxplKNBkFZOr4hfE1vkYEmopnPY+ClSqsIB0XWM8XSbr8IByXI/E VBAAsssFYV3mwNSoVrip+CWumi32ocikfxly+GlZxNWiMO4T57La6CJcmjQqaEE= =wvTM - -----END PGP SIGNATURE----- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory CVE-2015-2751 / XSA-127 version 2 Certain domctl operations may be abused to lock up the host UPDATES IN VERSION 2 ==================== CVE assigned. Public release. ISSUE DESCRIPTION ================= XSA-77 put the majority of the domctl operations on a list excepting them from having security advisories issued for them if any effects their use might have could hamper security. Subsequently some of them got declared disaggregation safe, but for a small subset this was not really correct: Their (mis-)use may result in host lockups. As a result, the potential security benefits of toolstack disaggregation are not always fully realised. IMPACT ====== Domains deliberately given partial management control may be able to deny service to the entire host. 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 ================== Xen versions 4.3 onwards are vulnerable. Xen versions 4.2 and earlier do not have the described disaggregation functionality and hence are not vulnerable. MITIGATION ========== The issues discussed in this advisory are themselves bugs in features used for a security risk mitigation. There is no further mitigation available, beyond general measures to try to avoid parts of the system management becoming controlled by attackers. Those are the kind of measures which we expect any users of radical disaggregation to have already deployed. 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. The robustness benefits of disaggregation are unaffected, and (depending on system design) security benefits are likely to remain despite the vulnerabilities. CREDITS ======= This issue was discovered by Andrew Cooper of Citrix. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa127-unstable.patch xen-unstable xsa127-4.x.patch Xen 4.5.x, Xen 4.4.x, Xen 4.3.x $ sha256sum xsa127*.patch 5b98280738a205c40f56d0a7feb6ea6cd867da7ac1e0d9f4fc4620bae2c09171 xsa127.patch e5fd3c126ae10fe45283e6eb1a4216b75057f1772d869d2b3a26398b0984c7bd xsa127-4.x.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) iQEcBAEBAgAGBQJVGo5PAAoJEIP+FMlX6CvZMhoH/0zH/JpvOk+dTQHVBN5uYjDB hkW5+/K4NfqRpnxQmTNJ6F5j0gcjbPCusf1yjdwjsAkToX2Y3TmqQAulpzkpT1z2 vvnIl8nYvD92fL1C8U9EBAXj62QmxN/IoX8rSl+g8byhoSO4WmUkbqseOb6LlcV3 wq/H15ZFfE6FjDQQGaFasbYyDOgBQiWFEmrBo2Zx7Qkendv5lt0YV/6/j3m1R8Hm D9fEchB07zKO49YkKnRrucDSf/9JTJI8W8M4Hmm9ykXncdUVI7xTSa66/XDOegcL ArBl9aXvuN9jMETS/JJBkEwqvULTQMy+Ac4NxBJE2W0allkKZxCcHMq50oSq3t0= =qqy0 - -----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). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBVRynSRLndAQH1ShLAQL78g//e3UQQfE908vUbh5XU6+43yTWXPIjDVZI 8pIZYTiakKZbKHkzNu52ANV62AeWQht69ZOHM7Q5Ft1lptoel3Sf67rCCucS5dca O1wE3KfJjf1nWIsgyZtUzg/0v0tth7KDADkXwmws2O4KV36Lx+xDWNxzIS/j6RbQ fMzR0TyNxnTxyiK/ZiPKn0yjENvpshyHbSn7TcnekzA87iDbP6ZmTBtJ1GMN6I3t slIR6G5Fbzo38SAdpeWqrCjbK+td0STLskj8xrX3DDiAL5giT6Y1E+UXspFEhvpV B7YBVdoVLE5fJ/pPZb082pPIVj0YK/oH+QlbHxv0crYNFuLeci2E0hsOOSl+TR6P XmR+CXjGQ3dh2FUV6EY1Z+i2rq/+AyGUX6KQ2izYbl2qeLpNc0zrf7edRaNu2ne6 TsD9a5xnJ2hHl8n41HJ5DrJZM24pLX72ZxS+coyvY6Oc08baFzeEk1W5yLAci3BO fkPDsEUBo7ffPJ+XN0kMvFd3cFXXWA7dIgRzE7q7uEe6FXeV+Ak0mxpvx9vCsynX X2hkyL6GstHacZz2rtk+rV6H6yKp5w8wJGFB8pevnxI/syfKrjJSTYtFeNUh7VRI QaecUbS4cgQvx/em1SQT5/oZUH9hYDZQV9+lUWSxyLl6tXOeUrPXiLqp74XXZhwc vG2RxS0r9d8= =5OxD -----END PGP SIGNATURE-----