Date: Wed, 14 May 2014 12:04:18 +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 95 - input handling vulnerabilities loading guest kernel on ARM -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Xen Security Advisory XSA-95 version 2 input handling vulnerabilities loading guest kernel on ARM UPDATES IN VERSION 2 ==================== Public release. ISSUE DESCRIPTION ================= When loading a 32-bit ARM guest kernel the Xen tools did not correctly validate the length of the kernel against the actual image size. This would then lead to an overrun on the input buffer when loading the kernel into guest RAM. Furthermore when checking a 32-bit guest kernel for an appended DTB, the Xen tools were prone to additional overruns also leading to an overrun on the input buffer when loading the kernel into guest RAM. Also, the tools would access a field in the putative DTB header without checking for its alignment. When loading a 64-bit ARM guest kernel the tools similarly did not fully validate the requested load addresses, possibly leading to an overrun on the input buffer when loading the kernel into guest RAM. IMPACT ====== An attacker who can control the kernel used to boot a guest can exploit these issues. Exploiting the overflow issues allows information which follows the guest kernel in the toolstack address space to be copied into the guest's memory, constituting an information leak. Alternatively either the overflow or alignment issues could be used to crash the toolstack process, leading to a denial of service. VULNERABLE SYSTEMS ================== ARM systems are vulnerable from Xen 4.4 onwards. MITIGATION ========== Ensuring that guests use only trustworthy kernels will avoid this problem. CREDITS ======= This issue was discovered by Thomas Leonard. RESOLUTION ========== Applying the attached patch resolves this issue. xsa95.patch xen-unstable, Xen 4.4.x $ sha256sum xsa95*.patch 1ab63ff126b92e752e88b240838dd66b66415604eaa3e49e373cb50ad3cdd0af xsa95.patch $ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQEcBAEBAgAGBQJTc0j+AAoJEIP+FMlX6CvZAYIH/29FLbtbM/jnSuMksWvf1G6g OgM3BhKGWAiNpebvPhhzqsKODchxpbrtGbLEIS9YDD8Qz5pQlnrLMsSBaSnrZvAs 5tQR5EKWpvDZry6THnxVP9OGxzR23+JEPtd1FQuNKiG68MeKmmFiAIGR1HfowSTs VOoAWZ1h8ep85iI4qz1U4+wbTBAhNwFpM1JH/IUmSTlWbSxXpQomX/lQqrPpiHEs 8zVBMni8HNYlWBEeWTktpc45JXBhbbNSGaqduEO3s8WJBpJd1D+YJ8u+nz2AJVVu JF6AkC1EL+cR6P7FSQZ+FrA9Spj+kND/SXlPNO/KLMn8QSlItMTUO2qH6UwcPKI= =2MET -----END PGP SIGNATURE----- Download attachment "xsa95.patch" of type "application/octet-stream" (3213 bytes)
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