irqchip/gic-v3-its: Lock VLPI map array before translating it

Obtaining the mapping ivformation for a VLPI should always be
done with the vlpi_lock for this device held. Otherwise, we
expose ourselves to races against a concurrent unmap.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20191108165805.3071-11-maz@kernel.org

drivers/irqchip/irq-gic-v3-its.c

@@ -1492,12 +1492,14 @@ static int its_vlpi_map(struct irq_data *d, struct its_cmd_info *info)
 static int its_vlpi_get(struct irq_data *d, struct its_cmd_info *info)
 {
 	struct its_device *its_dev = irq_data_get_irq_chip_data(d);
-	struct its_vlpi_map *map = get_vlpi_map(d);
+	struct its_vlpi_map *map;
 	int ret = 0;
 
 	mutex_lock(&its_dev->event_map.vlpi_lock);
 
-	if (!its_dev->event_map.vm || !map->vm) {
+	map = get_vlpi_map(d);
+
+	if (!its_dev->event_map.vm || !map) {
 		ret = -EINVAL;
 		goto out;
 	}