[systemd-devel] [RFC PATCH 1/2] Replace mkostemp+unlink with open(O_TMPFILE)

[Zbigniew Jędrzejewski-Szmek]

On Mon, Jan 27, 2014 at 06:40:39PM +0100, Zbigniew Jędrzejewski-Szmek wrote:
> On Mon, Jan 27, 2014 at 05:54:58PM +0100, Kay Sievers wrote:
> > On Mon, Jan 27, 2014 at 5:35 PM, Zbigniew Jędrzejewski-Szmek
> > <zbyszek at in.waw.pl> wrote:
> > > On Mon, Jan 27, 2014 at 03:14:28PM +0100, Lennart Poettering wrote:
> > >> Yupp, it's certainly a good idea to make our logging functions safe for
> > >> execution in any context.
> > >>
> > >> What I don't understands though is why mkostemp() would not be safe here?
> > > mkostemp is not on the list of "safe" functions. I looked at the
> > > implementation, and it actually has a static variable, so it really
> > > cannot be called.
> > 
> > But does this matter here? The static var is still mixed with random.
> > It seems it will work just fine, at least with the next iteration?
> I guess it's a question whether we want to rely on a specific
> implementation, or on the promises made by standards/documentation.
> mkostemp might call the random number generator, which might modify some
> global state, etc, which could be visible from outside of the signal handler.
> It just feels risky to make promises about this.
Yeah, it's hard to tell because of all the ifdefs, but it might call
gettimeofday, which rules it out.

> writev should probably be safe... OTOH, it's trivial to reimplement.

Zbyszek