linux-kernel - [PATCH 5.2 088/143] KVM: PPC: Book3S: Fix incorrect guest-to-user-translation error handling

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Message-Id: <20190904175317.528542156@linuxfoundation.org>
Date:   Wed,  4 Sep 2019 19:53:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alexey Kardashevskiy <aik@...abs.ru>,
        Paul Mackerras <paulus@...abs.org>
Subject: [PATCH 5.2 088/143] KVM: PPC: Book3S: Fix incorrect guest-to-user-translation error handling

From: Alexey Kardashevskiy <aik@...abs.ru>

commit ddfd151f3def9258397fcde7a372205a2d661903 upstream.

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@...r.kernel.org # v4.11+
Fixes: 121f80ba68f1 ("KVM: PPC: VFIO: Add in-kernel acceleration for VFIO")
Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
Signed-off-by: Paul Mackerras <paulus@...abs.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/kvm/book3s_64_vio.c    |    6 ++++--
 arch/powerpc/kvm/book3s_64_vio_hv.c |    6 ++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

--- a/arch/powerpc/kvm/book3s_64_vio.c
+++ b/arch/powerpc/kvm/book3s_64_vio.c
@@ -696,8 +696,10 @@ long kvmppc_h_put_tce_indirect(struct kv
 		}
 		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,
--- 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
 		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,