Re: [PATCH v10 0/5] Introduce mseal

Theo de Raadt
2024-05-14T22:55:27Z

Matthew Wilcox <willy@infradead.org> wrote:

> > Not taking a position on merging, but I have to ask: are we convinced at
> > this point that mseal() isn't a chrome-only system call? Did we ever
> > see the glibc patches that were promised?
>
> I think _this_ version of mseal() is OpenBSD's mimmutable() with a
> basically unused extra 'flags' argument. As such, we have an existance
> proof that it's useful beyond Chrome.

Yes, it is close enough.

> I think Liam still had concerns around the
> walk-the-vmas-twice-to-error-out-early part of the implementation?
> Although we can always fix the implementation later; changing the API
> is hard.

Yes I am a bit worried about the point Liam brings up -- we've discussed
it privately at length. Matthew, to keep it short I have a different
viewpoint:

Some of the Linux m* system calls have non-conforming, partial-work-then-return-error
behaviour. I cannot find anything like this in any system call in any other
operating system, and I believe there is a defacto rule against doing this, and
Linux has an optimization which violating this, and I think it could be fixed
with fairly minor expense, and can't imagine it affecting a single application.

I worry that the non-atomicity will one day be used by an attacker.