When mapping a page in a shadow stage-2, special care must be
taken not to be more permissive than the guest is (writable or
readable page when the guest hasn't set that permission).
Reviewed-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
arch/arm64/include/asm/kvm_nested.h | 15 +++++++++++++++
arch/arm64/kvm/mmu.c | 14 +++++++++++++-
arch/arm64/kvm/nested.c | 2 +-
3 files changed, 29 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index d2cee4faa387..f20d272fcd6d 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -91,6 +91,21 @@ static inline u32 kvm_s2_trans_esr(struct kvm_s2_trans *trans)
return trans->esr;
}
+static inline bool kvm_s2_trans_readable(struct kvm_s2_trans *trans)
+{
+ return trans->readable;
+}
+
+static inline bool kvm_s2_trans_writable(struct kvm_s2_trans *trans)
+{
+ return trans->writable;
+}
+
+static inline bool kvm_s2_trans_executable(struct kvm_s2_trans *trans)
+{
+ return !(trans->upper_attr & BIT(54));
+}
+
extern int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, phys_addr_t gipa,
struct kvm_s2_trans *result);
extern int kvm_s2_handle_perm_fault(struct kvm_vcpu *vcpu,
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index bc6f004d4ffb..1e19c59b8235 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1427,6 +1427,17 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (exec_fault && device)
return -ENOEXEC;
+ /*
+ * Potentially reduce shadow S2 permissions to match the guest's own
+ * S2. For exec faults, we'd only reach this point if the guest
+ * actually allowed it (see kvm_s2_handle_perm_fault).
+ */
+ if (nested) {
+ writable &= kvm_s2_trans_writable(nested);
+ if (!kvm_s2_trans_readable(nested))
+ prot &= ~KVM_PGTABLE_PROT_R;
+ }
+
read_lock(&kvm->mmu_lock);
pgt = vcpu->arch.hw_mmu->pgt;
if (mmu_invalidate_retry(kvm, mmu_seq))
@@ -1469,7 +1480,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (device)
prot |= KVM_PGTABLE_PROT_DEVICE;
- else if (cpus_have_const_cap(ARM64_HAS_CACHE_DIC))
+ else if (cpus_have_const_cap(ARM64_HAS_CACHE_DIC) &&
+ (!nested || kvm_s2_trans_executable(nested)))
prot |= KVM_PGTABLE_PROT_X;
/*
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 2538e0c632f2..73c0be25345a 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -499,7 +499,7 @@ int kvm_s2_handle_perm_fault(struct kvm_vcpu *vcpu, struct kvm_s2_trans *trans)
return 0;
if (kvm_vcpu_trap_is_iabt(vcpu)) {
- forward_fault = (trans->upper_attr & BIT(54));
+ forward_fault = !kvm_s2_trans_executable(trans);
} else {
bool write_fault = kvm_is_write_fault(vcpu);
--
2.34.1
