fs/exec.c in Linux 2.6, when one thread is tracing another thread that shares the same memory map, might allow local users to cause a denial of service (deadlock) by forcing a core dump when the traced thread is in the TASK_TRACED state.
Ubuntu Security Notice USN-199-1 - Multiple vulnerabilities exist in both linux-source-2.6.10 and linux-source-2.6.8. These include race conditions and denial of service flaws.