MFC r227485:

MFC r227485:
To limit amount of the kernel memory allocated, and to optimize the
iteration over the fdsets, kern_select() limits the length of the
fdsets copied in by the last valid file descriptor index. If any bit
is set in a mask above the limit, current implementation ignores the
filedescriptor, instead of returning EBADF.

Fix the issue by scanning the tails of fdset before entering the
select loop and returning EBADF if any bit above last valid
filedescriptor index is set. The performance impact of the additional
check is only imposed on the (somewhat) buggy applications that pass
bad file descriptors to select(2) or pselect(2).

PR:	kern/155606, kern/162379

git-svn-id: svn://svn.freebsd.org/base/stable/8@228038 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f