[tor-bugs] #8795 [Tor]: Make #2077 survivable

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#8795: Make #2077 survivable
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 Reporter:  cypherpunks                                |          Owner:                     
     Type:  defect                                     |         Status:  needs_review       
 Priority:  normal                                     |      Milestone:  Tor: 0.2.4.x-final 
Component:  Tor                                        |        Version:  Tor: 0.2.4.12-alpha
 Keywords:  Tor, Permisson denied, getinfo_helper_dir  |         Parent:                     
   Points:                                             |   Actualpoints:                     
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Comment(by rransom):

 Replying to [comment:13 nickm]:
 > Except, start_writing_to_file opens an fd.

 `start_writing_to_file` as called by `microdesc_cache_rebuild` opens an fd
 for a non-existent file, so calling `chown` or `chmod` on the destination
 file wouldn't work either.

 To cause `finish_writing_to_file` to fail on Unix, one would have to
 change the containing directory's permissions at exactly the right time.
 On Windows NT, it's much easier to make DeleteFile fail: just keep the
 file ‘open for normal I/O or as a memory-mapped file’ -- as
 `microdesc_cache_rebuild` does.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/8795#comment:15>
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