[PATCH] KVM: arm64: Fix uninitialized memcache pointer in user_mem_abort()

[Sebastian Ott]

Commit fce886a60207 ("KVM: arm64: Plumb the pKVM MMU in KVM") made the
initialization of the local memcache variable in user_mem_abort()
conditional, leaving a codepath where it is used uninitialized via
kvm_pgtable_stage2_map().

This can fail on any path that requires a stage-2 allocation
without transition via a permission fault or dirty logging.

Fix this by making sure that memcache is always valid.

Fixes: fce886a60207 ("KVM: arm64: Plumb the pKVM MMU in KVM")
Signed-off-by: Sebastian Ott <sebott at redhat.com>
Reviewed-by: Marc Zyngier <maz at kernel.org>
Cc: stable at vger.kernel.org
Link: https://lore.kernel.org/kvmarm/3f5db4c7-ccce-fb95-595c-692fa7aad227@redhat.com/
---
 arch/arm64/kvm/mmu.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 754f2fe0cc67..eeda92330ade 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1501,6 +1501,11 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 		return -EFAULT;
 	}
 
+	if (!is_protected_kvm_enabled())
+		memcache = &vcpu->arch.mmu_page_cache;
+	else
+		memcache = &vcpu->arch.pkvm_memcache;
+
 	/*
 	 * Permission faults just need to update the existing leaf entry,
 	 * and so normally don't require allocations from the memcache. The
@@ -1510,13 +1515,11 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (!fault_is_perm || (logging_active && write_fault)) {
 		int min_pages = kvm_mmu_cache_min_pages(vcpu->arch.hw_mmu);
 
-		if (!is_protected_kvm_enabled()) {
-			memcache = &vcpu->arch.mmu_page_cache;
+		if (!is_protected_kvm_enabled())
 			ret = kvm_mmu_topup_memory_cache(memcache, min_pages);
-		} else {
-			memcache = &vcpu->arch.pkvm_memcache;
+		else
 			ret = topup_hyp_memcache(memcache, min_pages);
-		}
+
 		if (ret)
 			return ret;
 	}

base-commit: 92a09c47464d040866cf2b4cd052bc60555185fb
-- 
2.49.0