Re: [Libevent-users] [PATCH] Make evutil_read_file() close-on-exec safe.

[Nick Mathewson <nickm@xxxxxxxxxxxxx>]

On Sat, Feb 11, 2012 at 10:34 AM, Ross Lagerwall
<rosslagerwall@xxxxxxxxx> wrote:
> In a multi-process/threaded environment, ev_util_read_file()
> could leak fds to child processes when not using O_CLOEXEC/FD_CLOEXEC.

Hm.  I'm not sure I trust "#ifdef O_CLOEXEC" as a test for whether
open() supports O_CLOEXEC.  Generally, I'd prefer a solution that
falls back gracefully if Libevent is built with headers from a newer
libc/kernel and then run on an older kernel.  (This is a real concern:
it seems to happen to RHEL/Centos users pretty often.)

Unfortunately, it seems we can't just do a pattern of
   if ((fd = open(path, flags|O_CLOEXEC)) == -1) {
      fd = open(path, flags);
      if (fd == -1) return -1;
      fcntl(fd,...)
  }
because (if my tests are right) at least some implementations of
open() ignore unrecognized flags.

So given that, maybe the solution you suggest is the best we can do?


Additionally, I see 3 other open()s: two in arc4random.c and one in
devpoll.c.  Maybe this means we want an evutil_* wrapper function to
set CLOEXEC on fds.

thoughts?
-- 
Nick
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