The do_task_stat function in fs/proc/array.c in the Linux kernel before 2.6.39-rc1 does not perform an expected uid check, which makes it easier for local users to defeat the ASLR protection mechanism by reading the start_code and end_code fields in the /proc/#####/stat file for a process executing a PIE binary.
http://downloads.avaya.com/css/P8/documents/100145416
http://rhn.redhat.com/errata/RHSA-2011-0833.html
http://www.kernel.org/pub/linux/kernel/v2.6/testing/v2.6.39/ChangeLog-2.6.39-rc1
http://www.securityfocus.com/bid/47791
http://www.spinics.net/lists/mm-commits/msg82726.html