[tor-bugs] #2029 [Tor Relay]: Set FD_CLOEXEC on all open file descriptors so that they are closed on exec()

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#2029: Set FD_CLOEXEC on all open file descriptors so that they are closed on
exec()
-----------------------+----------------------------------------------------
 Reporter:  sjmurdoch  |       Owner:  sjmurdoch
     Type:  defect     |      Status:  new      
 Priority:  normal     |   Milestone:           
Component:  Tor Relay  |     Version:           
 Keywords:             |      Parent:  #1775    
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 Tor currently does not set FD_CLOEXEC on files it opens, so any child
 processes (e.g. tor-fw-helper) inherit open files. This is bad, so
 currently we try to guess the largest open file handle and close
 everything up to it, but this is icky and probably not reliable.

 We should call fcntl(fd, F_SETFD, FD_CLOEXEC) on any files we open to
 avoid needing to do this. This will require finding all the cases where
 Tor and its libraries create a file descriptor, so not just open but also
 pipe, dup/dup2, socket, etc...

 Tor currently does not exec anything except tor-fw-helper, so this should
 not affect anything else.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/2029>
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