KVM supports mapping VM_IO and VM_PFNMAP memory into the guest by using follow_pte in gfn_to_pfn. However, the resolved pfns may not have assoicated struct pages, so they should not be passed to pfn_to_page. This series removes such calls from the x86 and arm64 secondary MMU. To do this, this series introduces gfn_to_pfn_page functions that parallel the gfn_to_pfn functions. These functions take an extra out parameter which contains the page if the hva was resovled by gup. This allows the caller to call put_page only when necessated by gup.
The gfn_to_pfn functions are depreciated. For now the functions remain with identical behavior to before, but callers should be migrated to the new gfn_to_pfn_page functions. I added new functions instead of simply adding another parameter to the existing functions to make it easier to track down users of the deprecated functions.
I have migrated the x86 and arm64 secondary MMUs to the new gfn_to_pfn_page functions.
This addresses CVE-2021-22543 on x86 and arm64.
v1 -> v2: - Introduce new gfn_to_pfn_page functions instead of modifying the behavior of existing gfn_to_pfn functions, to make the change less invasive. - Drop changes to mmu_audit.c - Include Nicholas Piggin's patch to avoid corrupting refcount in the follow_pte case, and use it in depreciated gfn_to_pfn functions. - Rebase on kvm/next
David Stevens (4): KVM: mmu: introduce new gfn_to_pfn_page functions KVM: x86/mmu: use gfn_to_pfn_page KVM: arm64/mmu: use gfn_to_pfn_page KVM: mmu: remove over-aggressive warnings
Nicholas Piggin (1): KVM: do not allow mapping valid but non-refcounted pages
arch/arm64/kvm/mmu.c | 26 +++-- arch/x86/kvm/mmu/mmu.c | 50 ++++----- arch/x86/kvm/mmu/mmu_internal.h | 3 +- arch/x86/kvm/mmu/paging_tmpl.h | 23 +++-- arch/x86/kvm/mmu/tdp_mmu.c | 6 +- arch/x86/kvm/mmu/tdp_mmu.h | 4 +- arch/x86/kvm/x86.c | 6 +- include/linux/kvm_host.h | 17 +++ virt/kvm/kvm_main.c | 177 +++++++++++++++++++++++++------- 9 files changed, 222 insertions(+), 90 deletions(-)