Re: [PATCH v4 0/1] Use HMM for ODP v4

Jerome Glisse
2019-05-23T19:40:06Z

On Thu, May 23, 2019 at 04:10:38PM -0300, Jason Gunthorpe wrote:
>
> On Thu, May 23, 2019 at 02:24:58PM -0400, Jerome Glisse wrote:
> > I can not take mmap_sem in range_register, the READ_ONCE is fine and
> > they are no race as we do take a reference on the hmm struct thus
>
> Of course there are use after free races with a READ_ONCE scheme, I
> shouldn't have to explain this.

Well i can not think of anything again here the mm->hmm can not
change while driver is calling hmm_range_register() so if you
want i can remove the READ_ONCE() this does not change anything.

> If you cannot take the read mmap sem (why not?), then please use my
> version and push the update to the driver through -mm..

Please see previous threads on why it was a failure.

Cheers,
Jérôme