This patch fixes the argument length checking in sched_setaffinity.

Previously it would error out when the length passed was smaller than
sizeof(cpumask_t).  And any bits beyond cpumask_s would be silently
ignored.

First this assumes that the user application knows the size of cpumask_t,
which should be kernel internal.  When you increase cpumask_t old
applications break and there is no good way for the application to find out
the cpumask_t size the kernel uses.

This patch changes it to do similar checking to the NUMA API calls:

- Any length is ok as long as all online CPUs are covered (this could
  still cause application breakage with more CPUs, but there is no good way
  around it)

- When the user passes more than cpumask_t bytes the excess bytes are
  checked to be zero.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>