Messages in this thread | | | From | Andy Lutomirski <> | Date | Fri, 17 Feb 2017 08:52:59 -0800 | Subject | Re: [RFC 1/2] fs,eventpoll: Add ability to install target file by its number |
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On Fri, Feb 17, 2017 at 12:30 AM, Cyrill Gorcunov <gorcunov@openvz.org> 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.
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