The CRC32C feature in the Btrfs implementation in the Linux kernel before 3.8-rc1 allows local users to cause a denial of service (extended runtime of kernel code) by creating many different files whose names are associated with the same CRC32C hash value.
http://crypto.junod.info/2012/12/13/hash-dos-and-btrfs/
http://lists.opensuse.org/opensuse-security-announce/2013-03/msg00004.html
http://openwall.com/lists/oss-security/2012/12/13/20
http://www.kernel.org/pub/linux/kernel/v3.x/testing/patch-3.8-rc1.bz2
http://www.ubuntu.com/usn/USN-1944-1
http://www.ubuntu.com/usn/USN-1945-1
http://www.ubuntu.com/usn/USN-1946-1
http://www.ubuntu.com/usn/USN-1947-1
http://www.ubuntu.com/usn/USN-2017-1
https://github.com/torvalds/linux/commit/9c52057c698fb96f8f07e7a4bcf4801a092bda89