Re: [PATCH v3 2/2] KVM: arm64: nv: Fix null ptr deref on nested wp/unmap, teardown race

[Jonathan Davies]

On Tue, 01 Sep 2026, "Lorenzo Stoakes (ARM)" <ljs@xxxxxxxxxx> wrote:
> This means that stage2_apply_range() can drop the kvm->mmu_lock and
> thus concurrent progress can be made in lockstep with
> kvm_arch_flush_shadow_all().
>
> If kvm_arch_flush_shadow_all() advances ahead of stage2_apply_range()
> and completes its operation it guarantees a NULL pointer deref.

I've reproducibly hit exactly this problem when running nested guests
with concurrent memory compaction on the L0 host. This patch fixes it
for me perfectly (applied to a 6.18 kernel).

So, for what it's worth:

Tested-by: Jonathan Davies <jonathan.davies@xxxxxxxxxxx>