KVM: arm/arm64: vgic-its: Check GITS_BASER Valid bit before saving tables

At the moment we don't properly check the GITS_BASER<n>.Valid
bit before saving the collection and device tables.

On vgic_its_save_collection_table() we use the GITS_BASER gpa
field whereas the Valid bit should be used.

On vgic_its_save_device_tables() there is no check. This can
cause various bugs, among which a subsequent fault when accessing
the table in guest memory.

Let's systematically check the Valid bit before doing anything.

We also uniformize the code between save and restore.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

virt/kvm/arm/vgic/vgic-its.c

@@ -2067,11 +2067,12 @@ static int vgic_its_device_cmp(void *priv, struct list_head *a,
 static int vgic_its_save_device_tables(struct vgic_its *its)
 {
 	const struct vgic_its_abi *abi = vgic_its_get_abi(its);
+	u64 baser = its->baser_device_table;
 	struct its_device *dev;
 	int dte_esz = abi->dte_esz;
-	u64 baser;
 
-	baser = its->baser_device_table;
+	if (!(baser & GITS_BASER_VALID))
+		return 0;
 
 	list_sort(NULL, &its->device_list, vgic_its_device_cmp);
 
@@ -2215,17 +2216,17 @@ static int vgic_its_restore_cte(struct vgic_its *its, gpa_t gpa, int esz)
 static int vgic_its_save_collection_table(struct vgic_its *its)
 {
 	const struct vgic_its_abi *abi = vgic_its_get_abi(its);
+	u64 baser = its->baser_coll_table;
+	gpa_t gpa = BASER_ADDRESS(baser);
 	struct its_collection *collection;
 	u64 val;
-	gpa_t gpa;
 	size_t max_size, filled = 0;
 	int ret, cte_esz = abi->cte_esz;
 
-	gpa = BASER_ADDRESS(its->baser_coll_table);
-	if (!gpa)
+	if (!(baser & GITS_BASER_VALID))
 		return 0;
 
-	max_size = GITS_BASER_NR_PAGES(its->baser_coll_table) * SZ_64K;
+	max_size = GITS_BASER_NR_PAGES(baser) * SZ_64K;
 
 	list_for_each_entry(collection, &its->collection_list, coll_list) {
 		ret = vgic_its_save_cte(its, collection, gpa, cte_esz);
@@ -2256,17 +2257,18 @@ static int vgic_its_save_collection_table(struct vgic_its *its)
 static int vgic_its_restore_collection_table(struct vgic_its *its)
 {
 	const struct vgic_its_abi *abi = vgic_its_get_abi(its);
+	u64 baser = its->baser_coll_table;
 	int cte_esz = abi->cte_esz;
 	size_t max_size, read = 0;
 	gpa_t gpa;
 	int ret;
 
-	if (!(its->baser_coll_table & GITS_BASER_VALID))
+	if (!(baser & GITS_BASER_VALID))
 		return 0;
 
-	gpa = BASER_ADDRESS(its->baser_coll_table);
+	gpa = BASER_ADDRESS(baser);
 
-	max_size = GITS_BASER_NR_PAGES(its->baser_coll_table) * SZ_64K;
+	max_size = GITS_BASER_NR_PAGES(baser) * SZ_64K;
 
 	while (read < max_size) {
 		ret = vgic_its_restore_cte(its, gpa, cte_esz);