kernel/trace/trace_syscalls.c in the Linux kernel through 3.17.2 does not properly handle private syscall numbers during use of the perf subsystem, which allows local users to cause a denial of service (out-of-bounds read and OOPS) or bypass the ASLR protection mechanism via a crafted application.
https://exchange.xforce.ibmcloud.com/vulnerabilities/98557
https://bugzilla.redhat.com/show_bug.cgi?id=1161565
http://www.securityfocus.com/bid/70972
http://www.openwall.com/lists/oss-security/2014/11/06/11
http://rhn.redhat.com/errata/RHSA-2015-0864.html
http://rhn.redhat.com/errata/RHSA-2015-0290.html