KVM: arm64: vgic-its: Fix memory leak on the error path of vgic_add_lpi()

If we're going to fail out the vgic_add_lpi(), let's make sure the
allocated vgic_irq memory is also freed. Though it seems that both
cases are unlikely to fail.
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200414030349.625-3-yuzenghui@huawei.com

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

@@ -96,14 +96,21 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid,
 	 * We "cache" the configuration table entries in our struct vgic_irq's.
 	 * However we only have those structs for mapped IRQs, so we read in
 	 * the respective config data from memory here upon mapping the LPI.
+	 *
+	 * Should any of these fail, behave as if we couldn't create the LPI
+	 * by dropping the refcount and returning the error.
 	 */
 	ret = update_lpi_config(kvm, irq, NULL, false);
-	if (ret)
+	if (ret) {
+		vgic_put_irq(kvm, irq);
 		return ERR_PTR(ret);
+	}
 
 	ret = vgic_v3_lpi_sync_pending_status(kvm, irq);
-	if (ret)
+	if (ret) {
+		vgic_put_irq(kvm, irq);
 		return ERR_PTR(ret);
+	}
 
 	return irq;
 }