Re: [PATCH] mm/gup: disallow GUP writing to file-backed mappings by default

[Jason Gunthorpe]

On Mon, Apr 24, 2023 at 06:09:52PM +0200, Jan Kara wrote:

> So I'm maybe missing a bigger picture why we would like a change like this.
> Because we still need to teach filesystems to handle pinned pages for the
> usecases you don't forbid and for which we know there are users and then
> what's the benefit of this patch?

It immediately closes a security hole we have been talking about
fixing for years already and still don't have a full fix for.

An acknowledgment that this is not going to go away and starting to
clamp down on the insecurity may motivate some investment in the
proper fix. :)

Jason