Re: [PATCH v5 1/6] mm/gup: remove unused vmas parameter from get_user_pages()

[David Hildenbrand]

On 16.05.23 16:30, Sean Christopherson wrote:
> On Tue, May 16, 2023, David Hildenbrand wrote:
> > On 15.05.23 21:07, Sean Christopherson wrote:
> > > On Sun, May 14, 2023, Lorenzo Stoakes wrote:
> > > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > > > index cb5c13eee193..eaa5bb8dbadc 100644
> > > > --- a/virt/kvm/kvm_main.c
> > > > +++ b/virt/kvm/kvm_main.c
> > > > @@ -2477,7 +2477,7 @@ static inline int check_user_page_hwpoison(unsigned long addr)
> > > >    {
> > > >    	int rc, flags = FOLL_HWPOISON | FOLL_WRITE;
> > > > -	rc = get_user_pages(addr, 1, flags, NULL, NULL);
> > > > +	rc = get_user_pages(addr, 1, flags, NULL);
> > > >    	return rc == -EHWPOISON;
> > >
> > > Unrelated to this patch, I think there's a pre-existing bug here.  If gup() returns
> > > a valid page, KVM will leak the refcount and unintentionally pin the page.  That's
> >
> > When passing NULL as "pages" to get_user_pages(), __get_user_pages_locked()
> > won't set FOLL_GET. As FOLL_PIN is also not set, we won't be messing with
> > the mapcount of the page.

For completeness: s/mapcount/refcount/ :)

> Ah, that's what I'm missing.



--
Thanks,

David / dhildenb