Date: Tue, 20 Jun 2017 12:00:09 +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 225 - arm: vgic: Out-of-bound access when sending SGIs -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory XSA-225 version 2 arm: vgic: Out-of-bound access when sending SGIs UPDATES IN VERSION 2 ==================== Public release. ISSUE DESCRIPTION ================= ARM guests can send SGI (i.e. IPI) targeting a list of vCPUs using the MMIO register GICD_SGIR (GICv2) or System Register ICC_SGI1R (GICv3). However, the emulation code does not sanitize the list and will directly access an array without checking whether the array index is within bounds. IMPACT ====== A guest may cause a hypervisor crash, resulting in a Denial of Service (DoS). VULNERABLE SYSTEMS ================== Xen versions 4.6 and onwards are affected. Xen versions 4.5 and earlier are not affected. Only ARM systems 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 only send sane IPIs (i.e. targeting valid CPUs) 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. xsa225.patch xen-unstable, Xen 4.8.x, Xen 4.7.x, Xen 4.6.x $ sha256sum xsa225* a52d90a2586b74d6dd0d17390c940bf414c1332a6b4ccb87f10b7d97af3b3877 xsa225.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 iQEcBAEBCAAGBQJZSQ3mAAoJEIP+FMlX6CvZ/TAH/Role6HA+csMGO/DshXbfuhN /S+DOPKU7NwynExZhf43Afj37EI4cw3xUcpRrZJbRExhGtlnBInsjUq8V9kmWcZL pJOgVcTOMyeR6Mc3B/tLqamH49uJdEGoi3zHVtckXY/A8a8+iyT5faSibmsWgl1t mYylB33xg9JmQ6gEa4NtbXOFi/f7BHjXUqVr8+P/KAyqvEramxoH+lp21Wrc1JZd wvpeEVnIlXjNBJB3ERqIENc/E0jlHY73mTLPK1br8OkkrJPnwkbC246Nd1cIosVt v8fe/Lin8yq2K+dPU6VFk/ZawDmOUtOtwJCL8klteIs6iiT+m2F3nGHMoQAGaBk= =lwE9 -----END PGP SIGNATURE----- Download attachment "xsa225.patch" of type "application/octet-stream" (1491 bytes)
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