Date: Tue, 05 Oct 2021 18:43:10 +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 386 v1 (CVE-2021-28702) - PCI devices with RMRRs not deassigned correctly -----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----- Download attachment "xsa386.patch" of type "application/octet-stream" (1183 bytes)
Powered by blists - more mailing lists
Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.