Re: [PATCH v1 1/1] KVM: s390: VSIE: fix virtual/physical address in unpin_scb()

[Nico Boehr]

On Tue Dec 10, 2024 at 9:39 AM CET, Claudio Imbrenda wrote:
> In commit 77b533411595 ("KVM: s390: VSIE: sort out virtual/physical
> address in pin_guest_page"), only pin_scb() has been updated. This
> means that in unpin_scb() a virtual address was still used directly as
> physical address without conversion. The resulting physical address is
> obviously wrong and most of the time also invalid.
>
> Since commit d0ef8d9fbebe ("KVM: s390: Use kvm_release_page_dirty() to
> unpin "struct page" memory"), unpin_guest_page() will directly use
> kvm_release_page_dirty(), instead of kvm_release_pfn_dirty(), which has
> since been removed.
>
> One of the checks that were performed by kvm_release_pfn_dirty() was to
> verify whether the page was valid at all, and silently return
> successfully without doing anything if the page was invalid.
>
> When kvm_release_pfn_dirty() was still used, the invalid page was thus
> silently ignored. Now the check is gone and the result is an Oops.
> This also means that when running with a V!=R kernel, the page was not
> released, causing a leak.
>
> The solution is simply to add the missing virt_to_phys().
>
> Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
> Fixes: 77b533411595 ("KVM: s390: VSIE: sort out virtual/physical address in pin_guest_page")

Reviewed-by: Nico Boehr <nrb@xxxxxxxxxxxxx>