fix create_new_namespaces() return value

fix create_new_namespaces() return value

dup_mnt_ns() and clone_uts_ns() return NULL on failure.  This is wrong,
create_new_namespaces() uses ERR_PTR() to catch an error.  This means that the
subsequent create_new_namespaces() will hit BUG_ON() in copy_mnt_ns() or
copy_utsname().

Modify create_new_namespaces() to also use the errors returned by the
copy_*_ns routines and not to systematically return ENOMEM.

[[email protected]: better changelog]
Signed-off-by: Cedric Le Goater <[email protected]>
Cc: Serge E. Hallyn <[email protected]>
Cc: Badari Pulavarty <[email protected]>
Cc: Pavel Emelianov <[email protected]>
Cc: Herbert Poetzl <[email protected]>
Cc: Eric W. Biederman <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>