Re: [PATCH v2 04/18] KVM: x86/mmu: avoid NULL-pointer dereference on page freeing bugs

[Sean Christopherson]

On Thu, Feb 17, 2022, Paolo Bonzini wrote:
> WARN and bail if KVM attempts to free a root that isn't backed by a shadow
> page.  KVM allocates a bare page for "special" roots, e.g. when using PAE
> paging or shadowing 2/3/4-level page tables with 4/5-level, and so root_hpa
> will be valid but won't be backed by a shadow page.  It's all too easy to
> blindly call mmu_free_root_page() on root_hpa, be nice and WARN instead of
> crashing KVM and possibly the kernel.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---

Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>