[PATCH v2 0/5] Remove uses of struct page from x86 and arm64 MMU

David Stevens
2021-06-25T07:37:21Z

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(-)

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2.32.0.93.g670b81a890-goog