x86: Unify copy_to_user() and add size checking to it

x86: Unify copy_to_user() and add size checking to it

Similarly to copy_from_user(), where the range check is to
protect against kernel memory corruption, copy_to_user() can
benefit from such checking too: Here it protects against kernel
information leaks.

Signed-off-by: Jan Beulich <[email protected]>
Cc: <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
Cc: Arjan van de Ven <[email protected]>