Date: Mon, 03 Aug 2015 12:39:38 +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 139 (CVE-2015-5166) - Use after free in QEMU/Xen block unplug protocol -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory CVE-2015-5166 / XSA-139 version 2 Use after free in QEMU/Xen block unplug protocol UPDATES IN VERSION 2 ==================== CVE assigned. Public release. Updated status of the patches. ISSUE DESCRIPTION ================= When unplugging an emulated block device the device was not fully unplugged, meaning a second unplug attempt would attempt to unplug the device a second time using a previously freed pointer. IMPACT ====== An HVM guest which has access to an emulated IDE disk device may be able to exploit this vulnerability in order to take over the qemu process elevating its privilege to that of the qemu process. VULNERABLE SYSTEMS ================== All Xen systems running x86 HVM guests using the upstream based "qemu-xen" are vulnerable. Systems using the "qemu-xen-traditional" version of the qemu device model, either in a stubdomain or as a domain 0 process, are not vulnerable. Systems running only PV guests are NOT vulnerable. ARM systems are not vulnerable. MITIGATION ========== There is no known mitigation for this issue. CREDITS ======= This issue was discovered by Donghai Zhu of Alibaba. RESOLUTION ========== The attached patches have been proposed as fixes for the issue. However they have not been finalised by upstream. A revised advisory will be issued in the event that the final patches differ from those included here. xsa139-qemuu-unstable.patch qemu-upstream, xen-unstable xsa139-qemuu-4.5.patch qemu-upstream, Xen 4.5.x, Xen 4.4.x, Xen 4.3.x, Xen 4.2.x $ sha256sum xsa139*.patch dead84667dd4868d0688dc4e62a54a14883e6f0352cf3318b277aa37e27c9261 xsa139-qemuu-unstable.patch 3aa775255053d1d14a3e383998240eb3520aea7de137cdb7624b169db8b06d85 xsa139-qemuu-4.5.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 v1.4.12 (GNU/Linux) iQEcBAEBAgAGBQJVv2B2AAoJEIP+FMlX6CvZyOIIAJyuhk8W+BkgL8eejTfV0dlH 38QKpakRSIRXOB3Px3pyyssmk/3Qa/5HiYK3jn4/5JmKnCbXUcevBSnxBPJqbugc iNhQC7e6um8Ah6V9YkoixdjNrRs7TAyHhR43xK4WBZ89XlbFEI8eGnG8pf/zRLp5 S5eRfqcJRo5T4uZLABN2K2Vko/sLvzeCzikDQoBIgYoIqpyC6X4svzcJre6GsEfp gZtR+TXvcMXpbndmlEGqhLznlC8iQYA6bpI0PQ22n2ANDzmnzR3u6+nrHCmzCmoY PNykUGi3+8OIkwoyosoZv6//L9Bx2U2iKFWqhDdqAi6p8krqhVQCxMZ18IbsyVI= =iCoi -----END PGP SIGNATURE----- Download attachment "xsa139-qemuu-unstable.patch" of type "application/octet-stream" (1176 bytes) Download attachment "xsa139-qemuu-4.5.patch" of type "application/octet-stream" (1120 bytes)
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