irqchip/gic-v3-its: Fix potential race condition in its_vlpi_prop_update()

its_vlpi_prop_update() calls lpi_write_config() which obtains the
mapping information for a VLPI without lock held. So it could race
with its_vlpi_unmap().

Since all calls from its_irq_set_vcpu_affinity() require the same
lock to be held, hoist the locking there instead of sprinkling the
locking all over the place.

This bug was discovered using Coverity Static Analysis Security Testing
(SAST) by Synopsys, Inc.

[ tglx: Use guard() instead of goto ]

Fixes: 015ec038 ("irqchip/gic-v3-its: Add VLPI configuration handling")
Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Hagar Hemdan <hagarhem@amazon.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240531162144.28650-1-hagarhem@amazon.com

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

@@ -1846,28 +1846,22 @@ static int its_vlpi_map(struct irq_data *d, struct its_cmd_info *info)
 {
 	struct its_device *its_dev = irq_data_get_irq_chip_data(d);
 	u32 event = its_get_event_id(d);
-	int ret = 0;
 
 	if (!info->map)
 		return -EINVAL;
 
-	raw_spin_lock(&its_dev->event_map.vlpi_lock);
-
 	if (!its_dev->event_map.vm) {
 		struct its_vlpi_map *maps;
 
 		maps = kcalloc(its_dev->event_map.nr_lpis, sizeof(*maps),
 			       GFP_ATOMIC);
-		if (!maps) {
-			ret = -ENOMEM;
-			goto out;
-		}
+		if (!maps)
+			return -ENOMEM;
 
 		its_dev->event_map.vm = info->map->vm;
 		its_dev->event_map.vlpi_maps = maps;
 	} else if (its_dev->event_map.vm != info->map->vm) {
-		ret = -EINVAL;
-		goto out;
+		return -EINVAL;
 	}
 
 	/* Get our private copy of the mapping information */
@@ -1899,46 +1893,32 @@ static int its_vlpi_map(struct irq_data *d, struct its_cmd_info *info)
 		its_dev->event_map.nr_vlpis++;
 	}
 
-out:
-	raw_spin_unlock(&its_dev->event_map.vlpi_lock);
-	return ret;
+	return 0;
 }
 
 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;
-	int ret = 0;
-
-	raw_spin_lock(&its_dev->event_map.vlpi_lock);
 
 	map = get_vlpi_map(d);
 
-	if (!its_dev->event_map.vm || !map) {
-		ret = -EINVAL;
-		goto out;
-	}
+	if (!its_dev->event_map.vm || !map)
+		return -EINVAL;
 
 	/* Copy our mapping information to the incoming request */
 	*info->map = *map;
 
-out:
-	raw_spin_unlock(&its_dev->event_map.vlpi_lock);
-	return ret;
+	return 0;
 }
 
 static int its_vlpi_unmap(struct irq_data *d)
 {
 	struct its_device *its_dev = irq_data_get_irq_chip_data(d);
 	u32 event = its_get_event_id(d);
-	int ret = 0;
-
-	raw_spin_lock(&its_dev->event_map.vlpi_lock);
 
-	if (!its_dev->event_map.vm || !irqd_is_forwarded_to_vcpu(d)) {
-		ret = -EINVAL;
-		goto out;
-	}
+	if (!its_dev->event_map.vm || !irqd_is_forwarded_to_vcpu(d))
+		return -EINVAL;
 
 	/* Drop the virtual mapping */
 	its_send_discard(its_dev, event);
@@ -1962,9 +1942,7 @@ static int its_vlpi_unmap(struct irq_data *d)
 		kfree(its_dev->event_map.vlpi_maps);
 	}
 
-out:
-	raw_spin_unlock(&its_dev->event_map.vlpi_lock);
-	return ret;
+	return 0;
 }
 
 static int its_vlpi_prop_update(struct irq_data *d, struct its_cmd_info *info)
@@ -1992,6 +1970,8 @@ static int its_irq_set_vcpu_affinity(struct irq_data *d, void *vcpu_info)
 	if (!is_v4(its_dev->its))
 		return -EINVAL;
 
+	guard(raw_spinlock_irq)(&its_dev->event_map.vlpi_lock);
+
 	/* Unmap request? */
 	if (!info)
 		return its_vlpi_unmap(d);