Date: Wed, 21 Dec 2016 12:01:32 +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 203 (CVE-2016-10025) - x86: missing NULL pointer check in VMFUNC emulation -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory CVE-2016-10025 / XSA-203 version 3 x86: missing NULL pointer check in VMFUNC emulation UPDATES IN VERSION 3 ==================== Public release. ISSUE DESCRIPTION ================= When support for the Intel VMX VMFUNC leaf 0 was added, a new optional function pointer hvmemul_vmfunc was added to the hvm_emulate_ops table. As is intended, that new function pointer is NULL on non-VMX hardware, including AMD SVM hardware. However at a call site, the necessary NULL check was omitted before the indirect function call. IMPACT ====== Malicious guests may cause a hypervisor crash, resulting in a Denial of Service (DoS). VULNERABLE SYSTEMS ================== Xen versions 4.6 and newer are vulnerable. Xen versions 4.5 and earlier are not vulnerable. Only HVM guests can exploit the vulnerability. PV guests cannot exploit the vulnerability. Only x86 systems using SVM (AMD virtualisation extensions) rather than VMX (Intel virtualisation extensions) are vulnerable. This applies to HVM guests on AMD x86 CPUs. Therefore AMD x86 hardware is vulnerable; Intel hardware is not vulnerable. ARM systems are not vulnerable. MITIGATION ========== Running only PV guests will avoid this vulnerability. Running HVM guests on only VMX capable hardware will also avoid this vulnerability. CREDITS ======= This issue was discovered by Jan Beulich of SUSE. RESOLUTION ========== Applying the appropriate attached patch resolves this issue. xsa203.patch xen-unstable xsa203-4.8.patch Xen 4.8.x xsa203-4.7.patch Xen 4.7.x, Xen 4.6.x $ sha256sum xsa203* 9af7e862705987a60de1def81ed179931c3f683d05b05c2708cf16bb85d203c9 xsa203.patch 7cc04278778fe885e4c3ae3f846d099075a38bccfafe6dff018ba525499b4e46 xsa203-4.7.patch 4218fcfff11ec4788462a3ea9dddecb25b9d9fb1beaad17ca0f723b07b6675e4 xsa203-4.8.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 iQEcBAEBAgAGBQJYWm8VAAoJEIP+FMlX6CvZid4H/RlcaSaA1qky6vTKjaW4xUiX /48Fvz3H8Ioau3Mlqy9WGqoq7HnuhJl2MUuq47vpwChOlYvvNXeRe47sVHsLwz1O /yImaOc0cZEYsyECpddsVSOdwFEMnR38WFWirH4xboGx8NjWeQg3Fsmwh1r8iHsm HyR2kRktw/Tu2hpc8BaipsYObglvLGQGy06KwwIB0MPycm20MpR4W41a5vc6iE+1 oKMIag/UD+W1eR7zWkftHnEcG+QNfbpWfU7rKPOrQSX5nuXHCXTcu6JQbzlPD8JS h+A5r+/tfyQPLTWxoBkH4wbMwdqDPNo1AuiDaGD8KWD97m/j2pFaZKl7lGk8X9w= =TUeg -----END PGP SIGNATURE----- Download attachment "xsa203.patch" of type "application/octet-stream" (610 bytes) Download attachment "xsa203-4.7.patch" of type "application/octet-stream" (602 bytes) Download attachment "xsa203-4.8.patch" of type "application/octet-stream" (619 bytes)
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