On Fri, Feb 17, 2017 at 12:30 AM, Cyrill Gorcunov <gorcunov@xxxxxxxxxx> wrote: > When we checkpoint a process we look into /proc/<pid>/fdinfo/<fd> of eventpoll > file and parse target files list from there. In most situations this is fine > because target file is present in the /proc/<pid>/fd/ list. But in case if file > descriptor was dup'ed or transferred via unix socket and closed after, > it might not be in the list and we can't figure out which file descriptor > to pass into epoll_ctl call. > > To resolve this tie lets add EPOLL_CTL_DUP operation which simply takes > target file descriptor number and installs it into a caller's file table, > thus we can use kcmp() syscall and figure out which exactly file to be > added into eventpoll on restore procedure. This is a scary thing to let an unprivileged process do. I'm wondering if there might be a nicer way to address this using a better interface in /proc.
