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

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: 121f80ba68f1 ("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>

diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
index e99a147..c4b606f 100644 (file)
--- a/arch/powerpc/kvm/book3s_64_vio.c
+++ b/arch/powerpc/kvm/book3s_64_vio.c
@@ -660,8 +660,10 @@ long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
                }
                tce = be64_to_cpu(tce);
 
-               if (kvmppc_tce_to_ua(vcpu->kvm, tce, &ua))
-                       return H_PARAMETER;
+               if (kvmppc_tce_to_ua(vcpu->kvm, tce, &ua)) {
+                       ret = H_PARAMETER;
+                       goto unlock_exit;
+               }
 
                list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
                        ret = kvmppc_tce_iommu_map(vcpu->kvm, stt,

diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c
index f50bbee..b4f20f1 100644 (file)
--- a/arch/powerpc/kvm/book3s_64_vio_hv.c
+++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
@@ -556,8 +556,10 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
                unsigned long tce = be64_to_cpu(((u64 *)tces)[i]);
 
                ua = 0;
-               if (kvmppc_rm_tce_to_ua(vcpu->kvm, tce, &ua, NULL))
-                       return H_PARAMETER;
+               if (kvmppc_rm_tce_to_ua(vcpu->kvm, tce, &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,