We open a boost shared memory that was created by another process like this
boost::interprocess::managed_shared_memory segment(boost::interprocess::open_on
If you look at the shared_memory constructor, it takes a permissions object. boost::interprocess::permissions::set_unrestricted
is probably what you are looking for
void set_unrestricted();
//Sets permissions to unrestricted access:
// A null DACL for windows or 0666 for UNIX.
According to this, it was added in 1.45 version