Re: [PATCH v17 18/23] platform/x86: Intel SGX driver

[Dave Hansen]

On 12/17/18 10:48 AM, Sean Christopherson wrote:
> We can't set mm to NULL as we need it to unregister the notifier, and
> I'm fairly certain attempting to unregister in the release callback
> will deadlock.

Suggestion:

It looks like you only expect one VMA per enclave.  Things go bonkers if
this is not true.  So, instead of storing encl->mm, don't.  You can get
the mm from vma->vm_mm and you could just store encl->vma instead.

Doing that, you could even axe encl->base and encl->size, I think
because you just get those from the VMA itself.

That makes the relationship clearer: 1 VMA per enclave.  We also
implicitly understand that if you have a VMA, you implicitly have a ref
to the mm *and* the VMA is immutable.

If there were ever a path where encl->vma wasn't immutable, we'd have a
bug (or load of bugs) somewhere, right?