On Fri, Oct 9, 2020 at 11:27 PM Bart Schaefer <schaefer@brasslantern.com> wrote:
>
> The document linked by Matthew asserts that "mkdir -m mode" should behave "as if" chmod() is called after creating the directory.

This applies only when mkdir creates a directory but not when the
directory already existed prior to the call. Here's the relevant part:

   Each dir operand that names an existing directory shall be ignored
without error.

On Fri, Oct 9, 2020 at 11:40 PM Matthew Martin <phy1729@gmail.com> wrote:
>
> For a sufficiently well timed attacker, the target could be created and
> deleted so that this loop never exits.  Even if pathological, I don't
> think it should be possible for mkdir to loop forever.

Perhaps try N times instead of forever? The patch you've posted uses N
= 1 (which is already better than the existing code) but it can be any
other number.

Roman.