[PATCH] avoid multiplication overflows and signedness issues for max_fds

Limit sysctl_nr_open - we don't want ->max_fds to exceed MAX_INT and
we don't want size calculation for ->fd[] to overflow.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc fs/file.c
Simple merge

diff --cc kernel/sysctl.c
Simple merge