[PATCH v1] KVM: arm64: nv: Use kvm_phys_size() for VNCR invalidation range

[Fuad Tabba]

KVM: arm64: nv: Use kvm_phys_size() for VNCR invalidation range

Protected mode uses `pkvm_mappings` of the union inside `struct kvm_pgtable`.
This aliases `ia_bits`, which is used in non-protected mode.

Attempting to use `pgt->ia_bits` in kvm_nested_s2_unmap() and
kvm_nested_s2_wp() results in reading mapping pointers or state as a
shift amount. This triggers a UBSAN shift-out-of-bounds error:

    UBSAN: shift-out-of-bounds in arch/arm64/kvm/nested.c:1127:34
    shift exponent 174565952 is too large for 64-bit type 'unsigned long'
    Call trace:
     __ubsan_handle_shift_out_of_bounds+0x28c/0x2c0
     kvm_nested_s2_unmap+0x228/0x248
     kvm_arch_flush_shadow_memslot+0x98/0xc0
     kvm_set_memslot+0x248/0xce0

Fix this by using kvm_phys_size() to determine the IPA size. This helper
is independent of the software page table representation and works
correctly for both protected and non-protected modes, as it derives the
size directly from VTCR_EL2.

Fixes: 7270cc9157f47 ("KVM: arm64: nv: Handle VNCR_EL2 invalidation from MMU notifiers")
Signed-off-by: Fuad Tabba <tabba at google.com>
---
Based on Linux 6.19-rc8
---
 arch/arm64/kvm/nested.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index cdeeb8f09e72..eb9666ba15b4 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -1108,7 +1108,7 @@ void kvm_nested_s2_wp(struct kvm *kvm)
 			kvm_stage2_wp_range(mmu, 0, kvm_phys_size(mmu));
 	}
 
-	kvm_invalidate_vncr_ipa(kvm, 0, BIT(kvm->arch.mmu.pgt->ia_bits));
+	kvm_invalidate_vncr_ipa(kvm, 0, kvm_phys_size(&kvm->arch.mmu));
 }
 
 void kvm_nested_s2_unmap(struct kvm *kvm, bool may_block)
@@ -1124,7 +1124,7 @@ void kvm_nested_s2_unmap(struct kvm *kvm, bool may_block)
 			kvm_stage2_unmap_range(mmu, 0, kvm_phys_size(mmu), may_block);
 	}
 
-	kvm_invalidate_vncr_ipa(kvm, 0, BIT(kvm->arch.mmu.pgt->ia_bits));
+	kvm_invalidate_vncr_ipa(kvm, 0, kvm_phys_size(&kvm->arch.mmu));
 }
 
 void kvm_nested_s2_flush(struct kvm *kvm)

base-commit: 18f7fcd5e69a04df57b563360b88be72471d6b62
-- 
2.53.0.rc1.225.gd81095ad13-goog