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

[Alex Williamson]

On Fri, 9 Sep 2022 07:53:17 -0400
Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> 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?

Yes, David is working on allocating pages rather than pinning the zero
page, however that's going to have some user visible locked memory
accounting changes.  This isn't the long term solution, it's only meant
to close the shared zero page refcount holes we have currently.  Thanks,

Alex