The Linux kernel stack is a tempting target for attack. This is because the kernel needs to keep track of where it is. If a function gets called, which then calls another, which then calls another, the kernel needs to remember the order they were all called, so that each function can return to the function that called it. To do that, the kernel keeps a "stack" of values representing the history of its current context.
LinuxJournal: The Linux kernel stack is a tempting target for attack.