c/r: prctl: add minimal address test to PR_SET_MM

c/r: prctl: add minimal address test to PR_SET_MM

Make sure the address being set is greater than mmap_min_addr (as
suggested by Kees Cook).

Signed-off-by: Cyrill Gorcunov <[email protected]>
Acked-by: Kees Cook <[email protected]>
Cc: Serge Hallyn <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>