Date: Thu, 20 Nov 2014 16:26:46 +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 113 - Guest effectable page reference leak in MMU_MACHPHYS_UPDATE handling -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory XSA-113 Guest effectable page reference leak in MMU_MACHPHYS_UPDATE handling ISSUE DESCRIPTION ================= An error handling path in the processing of MMU_MACHPHYS_UPDATE failed to drop a page reference which was acquired in an earlier processing step. 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 at least 3.2.x onwards are vulnerable on x86 systems. Older versions have not been inspected. ARM systems are not vulnerable. This vulnerability is only applicable to Xen systems using stub domains or other forms of disaggregation of control domains for HVM guests. MITIGATION ========== Running only PV guests will avoid 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.) NOTE REGARDING LACK OF EMBARGO ============================== A draft of this advisory was mistakenly sent to xen-devel. The Xen Project Security Team apologises for this error. We are working to share best working practices amongst the team to reduce the risks of recurrance. CREDITS ======= This issue was discovered by Andrew Cooper of Citrix. RESOLUTION ========== Applying the attached patch resolves this issue. xsa113.patch xen-unstable, Xen 4.4.x, Xen 4.3.x, Xen 4.2.x $ sha256sum xsa113*.patch a0f2b792a6b4648151f85fe13961b0bf309a568ed03e1b1d4ea01e4eabf1b18e xsa113.patch $ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQEcBAEBAgAGBQJUbhNoAAoJEIP+FMlX6CvZ5v8H/0cwnDOmSUZQ5Wm6ULUQH0w+ Jbsf6JPBRyDch1nCv/d8X27vSfmB8JH0m+LclEH0F1XSUiu5p4y46ZKk7Zfm4+gD xq6/eKyXKwCXinAwEcLtvfONrajQQvzk2y4XZpE+g9U00AwvsBXM3AdqPup8cyQl OLQO9Oq+xiqusCXIQeCb/KnoVUGS9PqlG/RT3rKKorYzuQjG7VURU3uKA1Vju7oD ITzbNCjTjnA7cFVSk6g9ZG6k40nGkVKIv+pPFfZAE6/UqiCF91oNzVAYVnA0X0oL YoAFxvVFOHp78192jW/7S8uacG+bskJNAr+NYIuaBlykka6Vbef6esWOW3UZEhA= =LDjw -----END PGP SIGNATURE----- Download attachment "xsa113.patch" of type "application/octet-stream" (1281 bytes)
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