-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory CVE-2017-10919 / XSA-223 version 3 ARM guest disabling interrupt may crash Xen UPDATES IN VERSION 3 ==================== CVE assigned. ISSUE DESCRIPTION ================= Virtual interrupt injection could be triggered by a guest when sending an SGI (e.g IPI) to any vCPU or by configuring timers. When the virtual interrupt is masked, a missing check in the injection path may result in reading invalid hardware register or crashing the host. IMPACT ====== A guest may cause a hypervisor crash, resulting in a Denial of Service (DoS). VULNERABLE SYSTEMS ================== All Xen versions which support ARM are affected. x86 systems are not affected. MITIGATION ========== On systems where the guest kernel is controlled by the host rather than guest administrator, running only kernels which do not disable SGI and PPI (i.e IRQ < 32) will prevent untrusted guest users from exploiting this issue. However untrusted guest administrators can still trigger it unless further steps are taken to prevent them from loading code into the kernel (e.g by disabling loadable modules etc) or from using other mechanisms which allow them to run code at kernel privilege. CREDITS ======= This issue was discovered by Julien Grall of ARM. RESOLUTION ========== Applying the attached patch resolves this issue. xsa223.patch xen-unstable, Xen 4.8.x, Xen 4.7.x, Xen 4.6.x, Xen 4.5.x $ sha256sum xsa223* b5c8d8e8dac027069bec7dd812cff3f6f99e5949dd4a8ee729255c38274958b1 xsa223.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deployment notice is retained in post-embargo publicly released Xen Project advisories, even though it is then no longer applicable.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 iQEcBAEBCAAGBQJZX5I2AAoJEIP+FMlX6CvZuooH/0bkL0vO55m0gAFI/5Ipsopj tsvHObMSeeXRbn9IlhHgqG1HMtiMxMrT5ucQk66jW9oaEX4wxSbeZfDj7F0YlS7q krtRpQsxd0cwL5vN5aGSTs7e8O3G2pXUcVszp/lifZs/17QzjWZTPafQcthcAcRk ohX46fW8GROCXltHXI5epV7vxfD6JiKcejGNa/DUk65qPawjL/kcO2hrcGT8SS6f wlMNnR3ECwcMf0KYxvXrMyyLkfjKhQJDX3Ue6gRretBZ/llSRa75SWNWdGo3lQN1 7y2OuNbr4b2LISZE4f+F0xwMpuBTSnBnrVbyYSyGbBLULsGQF9Di7ok4bqPsuGA= =TPUB -----END PGP SIGNATURE-----