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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2021.3295 PCI devices with RMRRs not deassigned correctly 6 October 2021 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Xen Publisher: Xen Operating System: Virtualisation Impact/Access: Increased Privileges -- Existing Account Denial of Service -- Existing Account Reduced Security -- Existing Account Resolution: Patch/Upgrade CVE Names: CVE-2021-28702 Original Bulletin: http://xenbits.xen.org/xsa/advisory-386.html - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory CVE-2021-28702 / XSA-386 PCI devices with RMRRs not deassigned correctly ISSUE DESCRIPTION ================= Certain PCI devices in a system might be assigned Reserved Memory Regions (specified via Reserved Memory Region Reporting, "RMRR"). These are typically used for platform tasks such as legacy USB emulation. If such a device is passed through to a guest, then on guest shutdown the device is not properly deassigned. The IOMMU configuration for these devices which are not properly deassigned ends up pointing to a freed data structure, including the IO Pagetables. Subsequent DMA or interrupts from the device will have unpredictable behaviour, ranging from IOMMU faults to memory corruption. IMPACT ====== Administrators of guests which have been assigned RMRR-using PCI devices can cause denial of service and other problems, possibly including escalation of privilege. VULNERABLE SYSTEMS ================== All versions of Xen from at least 4.4 onwards are vulnerable. Only Intel x86 systems are affected. AMD x86 systems, and Arm systems, are all unaffected. Only systems using PCI passthrough are affected. (And then, only if the assigned devices have RMRRs, but whether a device advertises RMRRs is not easy to discern.) MITIGATION ========== There is no mitigation (other than not passing through PCI devices with RMRRs to guests). RESOLUTION ========== Applying the appropriate attached patch resolves this issue. Note that patches for released versions are generally prepared to apply to the stable branches, and may not apply cleanly to the most recent release tarball. Downstreams are encouraged to update to the tip of the stable branch before applying these patches. xsa386.patch xen-unstable - Xen 4.12.x $ sha256sum xsa386* f2f83c825e249bba9454437b48bbd8307fe7a224f56484388a67af124dfd279b xsa386.patch $ NOTE CONCERNING LACK OF EMBARGO =============================== This issue was reported and debugged in public before the security nature became apparent. - -----BEGIN PGP SIGNATURE----- iQFABAEBCAAqFiEEI+MiLBRfRHX6gGCng/4UyVfoK9kFAmFcnH8MHHBncEB4ZW4u b3JnAAoJEIP+FMlX6CvZje0H+QE5A0ZvoaJ5VupZYjAt5ynbQjVqxwxqAxZDTvP7 t3gtpsHSYgrHW+3giULxjGU0ZUGF9daO1JEIZCPCbUdIlmGqGEXdDoqtz0GrXCJJ swQFeXQVmn9lV4KMTHO0BvGw5aZOft1VgGNrixd3vckFl7c5G8sWFdl7IU7FPDTQ LiLMg6f1oOntBYjNZUZ2210jqct9GZ4ugURRufwZrwYIpc9H5pFnZAFHKismX/2m x/PCdmOCeivytmUPA4k62oJVpJdysAL+31XkZz8bbAhjFsUmYBJscW2T5mSfaYIp TaSrg9WBV+TVW7aNE2iittE2O0/YyOWfpUVh6lliECeFdd0= =aNEo - -----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: https://www.auscert.org.au/bulletins/ =========================================================================== 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 iQIVAwUBYVzipeNLKJtyKPYoAQguFw/+LD7pA0OAaARCJPvh7PfRqwtJq4wQC1Dl 6AdJVtMjKev5DMS5fcdecEa4EAVoFPPPZZ08hzBFbvgkG/2yAMByac93Q8vtjOyl bROPjOlQvEAQa2C9qkNmV8SqPy4uF7e21pvML1r6X7/smG3EEkov4s0Y7H7gfYnp AvTYItFlp8zupC+YiqKa5CG5g4Fd4mEUuBVi+ZrjBPVJCd76oO6lIlksQVZwlzN/ /Q2ViRMZ9pG4UA/qVZLtTDLizOU8qkdE2ZOT3lzrUL5apBIflhGlaKb1NtfsHGtv OLR8IiOxbaeQUGSvJ+PfgLrurJRiybBoAVdbRcNUmLp/C3NsOJK9f6s9A+pojtPT vNChz7BTCHjGTAj5MqyRkt/Z/oyiSGPYuGbMuPrcbfHAmPTosx5W0wAXvgpTye+9 tq/JoBoxOdMmUgdC0x1qA8IA8LSsozBN857ljGCMzoXYaadzeogrvAhOUr26ttI/ qLTtNPMRAOYCR4HsZZ3qhXwr2x+5DrDZyk6Bj5/ZEtrnt1vj3s8DtYbggEDAhpQD u1yOb0bbiWx89j19YF+wSpVNCmLcswNTiWCH8JujTn37Pn+D2BvXkD5Q0dbOS8IS o9ankgeALV3Dp9CyXvTtM6MNNkUvHHSs7uDghbtpyfg5vUFANUt61SBFBTER/Hkf TTnpYYdtWlI= =Fyml -----END PGP SIGNATURE-----