KVM: PPC: Book3S: Fix incorrect guest-to-user-translation error handling

[ Upstream commit ddfd151f ]

H_PUT_TCE_INDIRECT handlers receive a page with up to 512 TCEs from
a guest. Although we verify correctness of TCEs before we do anything
with the existing tables, there is a small window when a check in
kvmppc_tce_validate might pass and right after that the guest alters
the page of TCEs, causing an early exit from the handler and leaving
srcu_read_lock(&vcpu->kvm->srcu) (virtual mode) or lock_rmap(rmap)
(real mode) locked.

This fixes the bug by jumping to the common exit code with an appropriate
unlock.

Cc: stable@vger.kernel.org # v4.11+
Fixes: 121f80ba ("KVM: PPC: VFIO: Add in-kernel acceleration for VFIO")
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

arch/powerpc/kvm/book3s_64_vio.c

@@ -602,8 +602,10 @@ long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
 
 		if (kvmppc_gpa_to_ua(vcpu->kvm,
 				tce & ~(TCE_PCI_READ | TCE_PCI_WRITE),
-				&ua, NULL))
-			return H_PARAMETER;
+				&ua, NULL)) {
+			ret = H_PARAMETER;
+			goto unlock_exit;
+		}
 
 		list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
 			ret = kvmppc_tce_iommu_map(vcpu->kvm, stt,

arch/powerpc/kvm/book3s_64_vio_hv.c

@@ -528,8 +528,10 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
 		ua = 0;
 		if (kvmppc_gpa_to_ua(vcpu->kvm,
 				tce & ~(TCE_PCI_READ | TCE_PCI_WRITE),
-				&ua, NULL))
-			return H_PARAMETER;
+				&ua, NULL)) {
+			ret = H_PARAMETER;
+			goto unlock_exit;
+		}
 
 		list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
 			ret = kvmppc_rm_tce_iommu_map(vcpu->kvm, stt,