On Fri, Feb 17, 2017 at 08:52:59AM -0800, Andy Lutomirski wrote: > > > > 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. Well, I tend to agree. Need to add security checking if the target file is accessable by a caller. As to better interface to procfs nothing comes to mind immediately. Another potential problem is that since it is never guaranteed that target file number listed in fdinfo matching existing /proc/pid/fd/N, so that I think we will have to use this dup functionality for every target file, which of course not that fast. Probably need to think more if I manage to invent some better and faster interface to find where exactly target file belong in the whole process tree of a container. Thanks for pointing about this security problem, Andy!
