KVM: arm/arm64: vgic-its: Check result of allocation before use

We miss a test against NULL after allocation.

Fixes: 6d03a68f ("KVM: arm64: vgic-its: Turn device_id validation into generic ID validation")
Cc: stable@vger.kernel.org # 4.8
Reported-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

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

@@ -821,6 +821,8 @@ static int vgic_its_alloc_collection(struct vgic_its *its,
 		return E_ITS_MAPC_COLLECTION_OOR;
 
 	collection = kzalloc(sizeof(*collection), GFP_KERNEL);
+	if (!collection)
+		return -ENOMEM;
 
 	collection->collection_id = coll_id;
 	collection->target_addr = COLLECTION_NOT_MAPPED;