Re: [PATCH v9] pidfd: add ioctl to retrieve pid info

[Jonathan Corbet <corbet@lwn.net>]

Christian Brauner <brauner@kernel.org> writes:

> pidfd_info overwrites the request_mask with what is supported by the
> kernel. I don't think userspace setting random stuff in the request_mask
> is a problem. It would already be a problem with statx() and we haven't
> seen that so far.
>
> If userspace happens to set a some random bit in the request_mask and
> that bit ends up being used a few kernel releases later to e.g.,
> retrieve additional information then all that happens is that userspace
> would now receive information they didn't need. That's not a problem.

That, of course, assumes that there will never be a request_mask bit
that affects the information gathering in some other way -- say looking
in the parent namespace or such (a random example that just popped into
my undercaffeinated brain and is unlikely to be anything we actually
do).

But then, as I said, I'm bad at this :)

jon