Felix Kuehling

The issue is related to the drm/amdkfd module in the Linux kernel, where mapping the MMIO HDP page with large pages is not allowed due to incorrect offset handling. This can expose PAGE SIZE of MMIO space on systems with page sizes greater than 4K. The GPU has an unused 4K area in the register BAR space where registers can be remapped, including HDP flush registers, to allow userspace to flush the HDP when updating VRAM.

The issue is related to a possible null pointer dereference in the `amdgpu vm bo update` function of the Linux kernel's `drm/amdgpu` component. This could allow a remote attacker to cause a denial of service. The problem occurs because `abo->tbo.resource` may be `NULL` in `amdgpu vm bo update`.