Re: [Xen-devel] [PATCH] xl: close nullfd after dup2'ing it to stdin

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Tue, 2016-02-16 at 17:45 +0000, Ian Jackson wrote:
> Ian Campbell writes ("[PATCH] xl: close nullfd after dup2'ing it to
> stdin"):
> > Taking care not to do so if nullfd happens (somehow) to have the
> same
> > fd number as stdin/out/err.
> 
> I think that can only happen if the program (the process) has a
> serious problem: ie, fd 0 1 or 2 would have to be closed.

Yes, that was my thought and what I wanted to guard against.

> If that happens many other things can go badly wrong.

Indeed. I've seen this happen in other scenarios with non-C programs
forking and execing stuff with stdio fds closed.

> If this is causing Coverity to complain I would suggest adding
>    assert(nullfd >= 3);
>    assert(logfile >= 3);
> instead.

Coverity wasn't complaining about this particular aspect, it was only
complaining about the leak of nullfd, avoiding stdin/out/err was just
me being belt and braces about the possibility of nullfd being one of
the stdio fds. I'm happy with the assert approach too.

Ian

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