Published: 22 March 2013
Race condition in the install_user_keyrings function in security/keys/process_keys.c in the Linux kernel before 3.8.3 allows local users to cause a denial of service (NULL pointer dereference and system crash) via crafted keyctl system calls that trigger keyring operations in simultaneous threads.
From the Ubuntu security team
Mateusz Guzik discovered a race in the Linux kernel's keyring. A local user could exploit this flaw to cause a denial of service (system crash).