kernel: ptrace: Crash on PTRACE_{ATTACH,DETACH} race

Race condition in the ptrace and utrace support in the Linux kernel 2.6.9 through 2.6.25, as used in Red Hat Enterprise Linux RHEL 4, allows local users to cause a denial of service oops via a long series of PTRACEATTACH ptrace calls to another user's process that trigger a conflict between...