Some futex functions in futex.c for Linux kernel 2.6.x perform get_user calls while holding the mmap_sem semaphore, which could allow local users to cause a deadlock condition in do_page_fault by triggering get_user faults while another thread is executing mmap or other functions.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10037
http://www.securityfocus.com/archive/1/427980/100/0/threaded
http://www.redhat.com/support/errata/RHSA-2005-420.html
http://lkml.org/lkml/2005/2/22/123
http://linux.bkbits.net:8080/linux-2.6/cset%40421cfc11zFsK9gxvSJ2t__FCmuUd3Q