Date: Tue, 23 Sep 2014 12:14:24 +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 104 - Race condition in HVMOP_track_dirty_vram -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory XSA-104 version 2 Race condition in HVMOP_track_dirty_vram UPDATES IN VERSION 2 ==================== Public Release. ISSUE DESCRIPTION ================= The routine controlling the setup of dirty video RAM tracking latches the value of a pointer before taking the respective guarding lock, thus making it possible for a stale pointer to be used by the time the lock got acquired and the pointer gets dereferenced. The hypercall providing access to the affected function is available to the domain controlling HVM guests. IMPACT ====== Malicious or buggy stub domain kernels or tool stacks otherwise living outside of Domain0 can mount a denial of service attack which, if successful, can affect the whole system. Only domains controlling HVM guests can exploit this vulnerability. (This includes domains providing hardware emulation services to HVM guests.) VULNERABLE SYSTEMS ================== Xen versions from 4.0.0 onwards are vulnerable. This vulnerability is only applicable to Xen systems using stub domains or other forms of disaggregation of control domains for HVM guests. MITIGATION ========== There is no mitigation available for this issue. (The security of a Xen system using stub domains is still better than with a qemu-dm running as an unrestricted dom0 process. Therefore users with these configurations should not switch to an unrestricted dom0 qemu-dm.) CREDITS ======= This issue was discovered by Andrew Cooper at Citrix. RESOLUTION ========== Applying the attached patch resolves this issue. xsa104.patch xen-unstable, Xen 4.4.x, Xen 4.3.x, Xen 4.2.x $ sha256sum xsa104*.patch fc02f6365ca79a6ef386c882b57fab8b56aa12b54fc9b05054552f0f25e32047 xsa104.patch $ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQEcBAEBAgAGBQJUIWPgAAoJEIP+FMlX6CvZoIYH/3HEaknB8j0LpU/OQzO/zhLV EJzzXY4kzsabm3HP0bisTMpa8oMdFCnedcGzegqt/Ig+9CRwtbAijD/IokoODhAC GPYDxZag52l/7PT/qG9WtbGX8CYEHFYLsHZc0Xi3Jo/3cRfdZ8F38UlvjPJVDyXO s3CAHEoPGcgUgCf0kKVADDta80k8USz6ptugqnkagHByF6TK+Fl/EfGpUpx36RWF 6Sl0rtZeKdlqM9uZdf71EKJD1T8/F8CW2h7aKgRYD3IJb/yFpcbYVy+ePtl/XBT+ TDo7ZeqCcuNcge8fiWngD5MvjfDygkkgL7FzNAzGVQcK8NND3NSlctu9Qe8CqJA= =+BMV -----END PGP SIGNATURE----- Download attachment "xsa104.patch" of type "application/octet-stream" (1651 bytes)
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