The NV stage-2 manipulation functions kvm_nested_s2_unmap(), kvm_nested_s2_wp(), and others, are being called for any stage-2 manipulation regardless of whether nested virtualization is supported or enabled for the VM. For protected KVM (pKVM), `struct kvm_pgtable` uses the `pkvm_mappings` member of the union. This member aliases `ia_bits`, which is used by the non-protected NV code paths. Attempting to read `pgt->ia_bits` in these functions results in treating protected mapping pointers or state values as bit-shift amounts. 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 Since pKVM and NV are mutually exclusive, prevent entry into these NV handling functions if the VM has not allocated any nested MMUs (i.e., `kvm->arch.nested_mmus_size` is 0). Fixes: 7270cc9157f47 ("KVM: arm64: nv: Handle VNCR_EL2 invalidation from MMU notifiers") Suggested-by: Marc Zyngier Signed-off-by: Fuad Tabba --- Based on Linux 6.19-rc8 --- arch/arm64/kvm/nested.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index cdeeb8f09e72..d03e9b71bf6c 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -1101,6 +1101,9 @@ void kvm_nested_s2_wp(struct kvm *kvm) lockdep_assert_held_write(&kvm->mmu_lock); + if (!kvm->arch.nested_mmus_size) + return; + for (i = 0; i < kvm->arch.nested_mmus_size; i++) { struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i]; @@ -1117,6 +1120,9 @@ void kvm_nested_s2_unmap(struct kvm *kvm, bool may_block) lockdep_assert_held_write(&kvm->mmu_lock); + if (!kvm->arch.nested_mmus_size) + return; + for (i = 0; i < kvm->arch.nested_mmus_size; i++) { struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i]; @@ -1133,6 +1139,9 @@ void kvm_nested_s2_flush(struct kvm *kvm) lockdep_assert_held_write(&kvm->mmu_lock); + if (!kvm->arch.nested_mmus_size) + return; + for (i = 0; i < kvm->arch.nested_mmus_size; i++) { struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i]; @@ -1145,6 +1154,9 @@ void kvm_arch_flush_shadow_all(struct kvm *kvm) { int i; + if (!kvm->arch.nested_mmus_size) + return; + for (i = 0; i < kvm->arch.nested_mmus_size; i++) { struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i]; base-commit: 18f7fcd5e69a04df57b563360b88be72471d6b62 -- 2.53.0.rc1.225.gd81095ad13-goog