[Haskell-cafe] Discussion: The CLOEXEC problem

David Turner dct25-561bs at mythic-beasts.com
Mon Aug 31 07:28:19 UTC 2015

Exactly. As I said earlier, if you forget to clear FD_CLOEXEC when you
meant to then your program breaks loudly and obviously; if you forget to
*set* FD_CLOEXEC then the bug is much quieter and more subtle.

I asked for a specific example of some existing code that would be broken
by this, but none was forthcoming. I understand why, in theory, changing
this would be a problem (indeed, changing anything is similarly
problematic) but in practice the pros enormously outweigh the cons here.
On 30 Aug 2015 11:17 pm, "Niklas Hambüchen" <mail at nh2.me> wrote:

> On 30/08/15 16:59, Donn Cave wrote:
> > Quoth Niklas Hambüchen <mail at nh2.me>,
> > ... and you go on to demonstrate that you didn't really take the point
> > I was trying to make.  How did you find out about this flock(2) scenario?
> > Do you suppose that this is the only one, because you and I don't know
> > of any more?
> No, I do take your point, and I admit that more things may break when
> changing the default.
> What I'm saying is that such cases are relatively easy to find. When you
> rely on inheriting FDs, you know it.
> It is exotic enough that when you've built something that needs it,
> you'll remember it.
> This leads me to think that the damage done / cost to fix introduced by
> breaking the backwards compatibility here might be smaller than the
> damage / fixing that will arise in the future from surprising behaviour
> and security/privilege problems through leaked FDs in all non-exotic
> programs that want to exec() something. I'd assume the Python and Perl
> people came to this conclusion.
> Further, our community is small, and if you announce something loud and
> long-term via mailing list and Reddit, it will go a long way and make it
> unlikely that somebody will be unaware of such a change. Your point that
> we may break things that we don't know of / understand still stands though.
> Regarding pipes and sockets, pipe()/socket() accept CLOEXEC as well.
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