Re: [GIT PULL] VFIO fix for v6.0-rc5

[David Hildenbrand]

On 09.09.22 13:53, Linus Torvalds wrote:
> On Fri, Sep 9, 2022 at 6:52 AM Alex Williamson
> <alex.williamson@xxxxxxxxxx> wrote:
> > VFIO fix for v6.0-rc5
> >
> >   - Fix zero page refcount leak (Alex Williamson)
>
> Ugh. This is disgusting.
>
> Don't get me wrong - I've pulled this, but I think there's some deeper
> problem that made this patch required.
>
> Why is pin_user_pages_remote() taking a reference to a reserved page?
> Maybe it just shouldn't (and then obviously we should fix the unpin
> case to match too).
>
> Adding a few GUP people to the participants for comments.
>
> Anybody?

I mentioned in an offline discussion to Alex that we should teach the 
pin/unpin interface to not mess with the zeropage at all (i.e., not 
adjust the refcount and eventually overflow it).

We decided that the unbalanced pin/unpin should be fixed independently, 
such that the refcount handling change on pin/unpin stays GUP internal.


--
Thanks,

David / dhildenb