Date: Fri, 03 Jun 2016 09:47:18 +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@....org> Subject: Xen Security Advisory 181 - arm: Host crash caused by VMID exhaustion -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory XSA-181 arm: Host crash caused by VMID exhaustion ISSUE DESCRIPTION ================= VMIDs are a finite hardware resource, and allocated as part of domain creation. If no free VMIDs are available when trying to create a new domain, a bug in the error path causes a NULL pointer to be used, resulting in a Data Abort and host crash. IMPACT ====== Attempting to create too many concurrent domains causes a host crash rather than a graceful error. A malicious device driver domain can hold references to domains, preventing its VMID being released. VULNERABLE SYSTEMS ================== Xen versions 4.4 and later are affected. Older Xen versions are unaffected. x86 systems are not affected. Only arm systems with less-privileged device driver domains can expose this vulnerability. MITIGATION ========== There is no mitigation. Not using driver domains reclassifies the problem, but does not fix it. NOTE REGARDING LACK OF EMBARGO ============================== The crash was discussed publicly on xen-devel, before it was appreciated that there was a security problem. CREDITS ======= This issue was discovered by Aaron Cornelius of DornerWorks. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa181.patch xen-unstable, Xen 4.6.x, 4.5.x xsa181-4.4.patch Xen 4.4.x $ sha256sum xsa181* 6756fcf44446675e5277f6d6c0e8a0aaa51a7909ad9a55af89a09367fded8733 xsa181.patch 97a90c7cb42466647622cb2ed98de531b7ba2e174a1bc639a32a6f1b626d503f xsa181-4.4.patch $ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQEcBAEBAgAGBQJXUVIbAAoJEIP+FMlX6CvZAe8IAIwe1A/05KM9PfJTCwb23WEs pfSiEZy7KzmavYwzV4TLwzWuCNzkRAuEejvQ9dTFnk8ZBkCZIbAaMoCPJljK/8gg oBcn0cXE9Kz9kWBk+JCWHynboVh010p+7DGlcvrxmAwxJCUjGy4YcajDZ4uGJoHA pgJxIk/w4CIzF+AQYm7bRW8dHF3yym4V6dmR4pGqXeYS41XbMqpEenGBggoBeH+C TJLUzaNZfATcPK5NUCqBD7IiQtHyYJT8xEtIKDH4hfjEzffydHbErDb/lKk3fxK0 ECzrhdWMExnkUX4VkC393QaqGf78P6sa+psfZt4I7DDFDI2uEvXYmgVXjOuvSpg= =hUSO -----END PGP SIGNATURE----- Download attachment "xsa181.patch" of type "application/octet-stream" (1243 bytes) Download attachment "xsa181-4.4.patch" of type "application/octet-stream" (1285 bytes)
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