HMM related use-after-free with amdgpu

[Jason Gunthorpe]

On Tue, Jul 16, 2019 at 06:31:09PM +0200, Michel Dänzer wrote:
> On 2019-07-15 7:25 p.m., Jason Gunthorpe wrote:
> > On Mon, Jul 15, 2019 at 06:51:06PM +0200, Michel Dänzer wrote:
> >>
> >> With a KASAN enabled kernel built from amd-staging-drm-next, the
> >> attached use-after-free is pretty reliably detected during a piglit gpu run.
> > 
> > Does this branch you are testing have the hmm.git merged? I think from
> > the name it does not?
> 
> Indeed, no.
> 
> 
> > Use after free's of this nature were something that was fixed in
> > hmm.git..
> > 
> > I don't see an obvious way you can hit something like this with the
> > new code arrangement..
> 
> I tried merging the hmm-devmem-cleanup.4 changes[0] into my 5.2.y +
> drm-next for 5.3 kernel. While the result didn't hit the problem, all
> GL_AMD_pinned_memory piglit tests failed, so I suspect the problem was
> simply avoided by not actually hitting the HMM related functionality.
> 
> It's possible that I made a mistake in merging the changes, or that I
> missed some other required changes. But it's also possible that the HMM
> changes broke the corresponding user-pointer functionality in amdgpu.

Not sure, this was all Tested by the AMD team so it should work, I
hope.

It should all be sorted out in rc1, try again then?

Jason