[PATCH 3/4] KVM: arm64: vgic: Do not ignore vgic_its_restore_cte failures

[Ricardo Koller <ricarkol@google.com>]

Restoring a corrupted collection entry is being ignored: a
vgic_its_restore_cte failure is treated as success by
vgic_its_restore_collection_table.  vgic_its_restore_cte uses a positive
number to return ITS error codes, and +1 to return success.  The caller
then uses "ret > 0" to check for success. An additional issue is that
invalid entries return 0 and although that doesn't fail the restore, it
leads to skipping all the next entries.

Fix this by having vgic_its_restore_cte return negative numbers on
error, and 0 on success (which includes skipping an invalid entry).
While doing that, also fix alloc_collection return codes to not mix ITS
error codes (positive numbers) and generic error codes (negative
numbers).

Signed-off-by: Ricardo Koller <ricarkol@google.com>
---
 arch/arm64/kvm/vgic/vgic-its.c | 31 +++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
index dfd73fa1ed43..4ece649e2493 100644
--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -1013,9 +1013,6 @@ static int vgic_its_alloc_collection(struct vgic_its *its,
 {
 	struct its_collection *collection;
 
-	if (!vgic_its_check_id(its, its->baser_coll_table, coll_id, NULL))
-		return E_ITS_MAPC_COLLECTION_OOR;
-
 	collection = kzalloc(sizeof(*collection), GFP_KERNEL_ACCOUNT);
 	if (!collection)
 		return -ENOMEM;
@@ -1112,7 +1109,12 @@ static int vgic_its_cmd_handle_mapi(struct kvm *kvm, struct vgic_its *its,
 
 	collection = find_collection(its, coll_id);
 	if (!collection) {
-		int ret = vgic_its_alloc_collection(its, &collection, coll_id);
+		int ret;
+
+		if (!vgic_its_check_id(its, its->baser_coll_table, coll_id, NULL))
+			return E_ITS_MAPC_COLLECTION_OOR;
+
+		ret = vgic_its_alloc_collection(its, &collection, coll_id);
 		if (ret)
 			return ret;
 		new_coll = collection;
@@ -1267,6 +1269,10 @@ static int vgic_its_cmd_handle_mapc(struct kvm *kvm, struct vgic_its *its,
 		if (!collection) {
 			int ret;
 
+			if (!vgic_its_check_id(its, its->baser_coll_table,
+						coll_id, NULL))
+				return E_ITS_MAPC_COLLECTION_OOR;
+
 			ret = vgic_its_alloc_collection(its, &collection,
 							coll_id);
 			if (ret)
@@ -2508,6 +2514,10 @@ static int vgic_its_save_cte(struct vgic_its *its,
 	return kvm_write_guest_lock(its->dev->kvm, gpa, &val, esz);
 }
 
+/*
+ * Restores a collection entry into the ITS collection table.
+ * Returns 0 on success, and a negative error value for generic errors.
+ */
 static int vgic_its_restore_cte(struct vgic_its *its, gpa_t gpa, int esz)
 {
 	struct its_collection *collection;
@@ -2522,7 +2532,7 @@ static int vgic_its_restore_cte(struct vgic_its *its, gpa_t gpa, int esz)
 		return ret;
 	val = le64_to_cpu(val);
 	if (!(val & KVM_ITS_CTE_VALID_MASK))
-		return 0;
+		return 0; /* invalid entry, skip it */
 
 	target_addr = (u32)(val >> KVM_ITS_CTE_RDBASE_SHIFT);
 	coll_id = val & KVM_ITS_CTE_ICID_MASK;
@@ -2534,11 +2544,15 @@ static int vgic_its_restore_cte(struct vgic_its *its, gpa_t gpa, int esz)
 	collection = find_collection(its, coll_id);
 	if (collection)
 		return -EEXIST;
+
+	if (!vgic_its_check_id(its, its->baser_coll_table, coll_id, NULL))
+		return -EINVAL;
+
 	ret = vgic_its_alloc_collection(its, &collection, coll_id);
 	if (ret)
 		return ret;
 	collection->target_addr = target_addr;
-	return 1;
+	return 0;
 }
 
 /**
@@ -2604,15 +2618,12 @@ static int vgic_its_restore_collection_table(struct vgic_its *its)
 
 	while (read < max_size) {
 		ret = vgic_its_restore_cte(its, gpa, cte_esz);
-		if (ret <= 0)
+		if (ret < 0)
 			break;
 		gpa += cte_esz;
 		read += cte_esz;
 	}
 
-	if (ret > 0)
-		return 0;
-
 	return ret;
 }
 
-- 
2.36.0.rc2.479.g8af0fa9b8e-goog