[PATCH 05/26] vfio: KVM: Pass get/put helpers from KVM to VFIO, don't do circular lookup

[Jason Gunthorpe]

On Fri, Dec 01, 2023 at 04:51:55PM -0800, Sean Christopherson wrote:

> There's one more wrinkle: this patch is buggy in that it doesn't ensure the liveliness
> of KVM-the-module, i.e. nothing prevents userspace from unloading kvm.ko while VFIO
> still holds a reference to a kvm structure, and so invoking ->put_kvm() could jump
> into freed code.  To fix that, KVM would also need to pass along a module pointer :-(

Maybe we should be refcounting the struct file not the struct kvm?

Then we don't need special helpers and it keeps the module alive correctly.

Jason