The copy_from_user_mmap_sem function in fs/splice.c in the Linux kernel 2.6.22 through 2.6.24 does not validate a certain userspace pointer before dereference, which allow local users to read from arbitrary kernel memory locations.
https://www.redhat.com/archives/fedora-package-announce/2008-February/msg00255.html
https://www.redhat.com/archives/fedora-package-announce/2008-February/msg00254.html
https://www.exploit-db.com/exploits/5093
http://www.vupen.com/english/advisories/2008/0487/references
http://www.securityfocus.com/bid/27796
http://www.securityfocus.com/bid/27704
http://www.securityfocus.com/archive/1/487982/100/0/threaded
http://www.debian.org/security/2008/dsa-1494
http://secunia.com/advisories/28896