From ${URL}: ISSUE DESCRIPTION ================= The FLASK_{GET,SET}BOOL, FLASK_USER and FLASK_CONTEXT_TO_SID suboperations of the flask hypercall are vulnerable to an integer overflow on the input size. The hypercalls attempt to allocate a buffer which is 1 larger than this size and is therefore vulnerable to integer overflow and an attempt to allocate then access a zero byte buffer. Xen 3.3 through 4.1, while not affected by the above overflow, have a different overflow issue on FLASK_{GET,SET}BOOL and expose unreasonably large memory allocation to aribitrary guests. Xen 3.2 (and presumably earlier) exhibit both problems, with the overflow issue being present for more than just the suboperations listed above. The FLASK_GETBOOL op is available to all domains. The FLASK_SETBOOL op is only available to domains which are granted access via the Flask policy. However the permissions check is performed only after running the vulnerable code and the vulnerability via this subop is exposed to all domains. The FLASK_USER and FLASK_CONTEXT_TO_SID ops are only available to domains which are granted access via the Flask policy. IMPACT ====== Attempting to access the result of a zero byte allocation results in a processor fault leading to a denial of service. Patches available at http://xenbits.xen.org/xsa/advisory-84.html
CVE-2014-1894 (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2014-1894): Multiple integer overflows in unspecified suboperations in the flask hypercall in Xen 3.2.x and earlier, when XSM is enabled, allow local users to cause a denial of service (processor fault) via unspecified vectors, a different vulnerability than CVE-2014-1891, CVE-2014-1892, and CVE-2014-1893. CVE-2014-1893 (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2014-1893): Multiple integer overflows in the (1) FLASK_GETBOOL and (2) FLASK_SETBOOL suboperations in the flask hypercall in Xen 4.1.x, 3.3.x, 3.2.x, and earlier, when XSM is enabled, allow local users to cause a denial of service (processor fault) via unspecified vectors, a different vulnerability than CVE-2014-1891, CVE-2014-1892, and CVE-2014-1894. CVE-2014-1892 (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2014-1892): Xen 3.3 through 4.1, when XSM is enabled, allows local users to cause a denial of service via vectors related to a "large memory allocation," a different vulnerability than CVE-2014-1891, CVE-2014-1893, and CVE-2014-1894. CVE-2014-1891 (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2014-1891): Multiple integer overflows in the (1) FLASK_GETBOOL, (2) FLASK_SETBOOL, (3) FLASK_USER, and (4) FLASK_CONTEXT_TO_SID suboperations in the flask hypercall in Xen 4.3.x, 4.2.x, 4.1.x, 3.2.x, and earlier, when XSM is enabled, allow local users to cause a denial of service (processor fault) via unspecified vectors, a different vulnerability than CVE-2014-1892, CVE-2014-1893, and CVE-2014-1894.
Fixed as part of Bug 500530. Adding to existing GLSA.
This issue was resolved and addressed in GLSA 201407-03 at http://security.gentoo.org/glsa/glsa-201407-03.xml by GLSA coordinator Mikle Kolyada (Zlogene).
