Date: Tue, 20 Jun 2017 12:00:08 +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 221 - NULL pointer deref in event channel poll -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Xen Security Advisory XSA-221 version 2 NULL pointer deref in event channel poll UPDATES IN VERSION 2 ==================== Public release. ISSUE DESCRIPTION ================= When polling event channels, in general arbitrary port numbers can be specified. Specifically, there is no requirement that a polled event channel ports has ever been created. When the code was generalised from an earlier implementation, introducing some intermediate pointers, a check should have been made that these intermediate pointers are non-NULL. However, that check was omitted. IMPACT ====== A malicious or buggy guest may cause the hypervisor to access addresses it doesn't control, usually leading to a host crash (Denial of Service). Information leaks cannot be excluded. VULNERABLE SYSTEMS ================== Xen versions 4.4 and newer are vulnerable. Xen versions 4.3 and earlier are not affected. Both x86 and ARM systems are vulnerable. While all guest kinds can cause a Denial of Service, only x86 PV guests may be able to leverage the possible information leaks. MITIGATION ========== There is no known mitigation. CREDITS ======= This issue was discovered by Ankur Arora of Oracle. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa221.patch Xen 4.4.x and later, including xen-unstable $ sha256sum xsa221* 2425396a713466808b0f75f91337be4dd20a4dee7733972b04489773c6e97655 xsa221.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deployment notice is retained in post-embargo publicly released Xen Project advisories, even though it is then no longer applicable.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 iQEcBAEBCAAGBQJZSQ3TAAoJEIP+FMlX6CvZw20H/jCUm+eX4rPUCQ6CL+Ya/dXH th34nPKQnq60gm3469sDQQMNbuvfgBItAAAjO87NC6P2BSyYPMny5SvqSsmkWow1 8OkAWq5ZZ3L7ksPhkP6aco+ks1a99SxJX4YfjwOFq9ct6/zfrcW1ThEqs9j87JeP 6RGPYgXc0mP9IOk27JnUVgiej7/v4a8v5FcWrG3bHpw2vp9tY3hdvkfc6wJiuplx kkqIVkqTpCNu7QYGv3de1RpDeI5mN8TGY+6ahs9eZFEFmRGWiAahhZRnwGVNE7Tl QcHzaphlzp/etub8sHgZPH90xLaeILJ+9oz29b/SLUVqahRxzTD1bLUElEu2su0= =xR3U -----END PGP SIGNATURE----- Download attachment "xsa221.patch" of type "application/octet-stream" (7411 bytes)
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