HMM related use-after-free with amdgpu

[Kuehling, Felix]

On 2019-07-16 1:04 p.m., Michel Dänzer wrote:
> On 2019-07-16 6:35 p.m., Jason Gunthorpe wrote:
>> 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 can't, due to the issue pointed out by Linus in the "drm pull for
> 5.3-rc1" thread: DRM_AMDGPU_USERPTR still depends on ARCH_HAS_HMM, which
> no longer exists, so it can't be enabled.

As far as I can tell, Linus fixed this up in his merge commit 
be8454afc50f43016ca8b6130d9673bdd0bd56ec. Jason, is hmm.git going to get 
rebased or merge to pick up the amdgpu changes for HMM from master?

Regards,
   Felix


>
> Fixing that up manually, it successfully finished a piglit run with that
> functionality enabled as well.
>
>