The NFS implementation in Linux kernel before 2.6.31-rc6 calls certain functions without properly initializing certain data, which allows local users to cause a denial of service (NULL pointer dereference and O_DIRECT oops), as demonstrated using diotest4 from LTP.
https://exchange.xforce.ibmcloud.com/vulnerabilities/72297
https://bugzilla.redhat.com/show_bug.cgi?id=755455
http://www.securityfocus.com/bid/51366
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commitdiff%3Bh=1ae88b2e4