[PATCH] irqdomain: Fix mapping-creation race

[Johan Hovold]

Parallel probing (e.g. due to asynchronous probing) of devices that share
interrupts can currently result in two mappings for the same hardware
interrupt to be created.

Add a serialising mapping mutex so that looking for an existing mapping
before creating a new one is done atomically.

Note that serialising the lookup and creation in
irq_create_mapping_affinity() would have been enough to prevent the
duplicate mapping, but that could instead cause
irq_create_fwspec_mapping() to fail when there is a race.

Fixes: 765230b5f084 ("driver-core: add asynchronous probing support for drivers")
Fixes: b62b2cf5759b ("irqdomain: Fix handling of type settings for existing mappings")
Cc: Dmitry Torokhov <dtor@xxxxxxxxxxxx>
Cc: Jon Hunter <jonathanh@xxxxxxxxxx>
Signed-off-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
---
 kernel/irq/irqdomain.c | 46 +++++++++++++++++++++++++++++++-----------
 1 file changed, 34 insertions(+), 12 deletions(-)

diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 8fe1da9614ee..d263a7dd4170 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -22,6 +22,7 @@
 
 static LIST_HEAD(irq_domain_list);
 static DEFINE_MUTEX(irq_domain_mutex);
+static DEFINE_MUTEX(irq_mapping_mutex);
 
 static struct irq_domain *irq_default_domain;
 
@@ -669,7 +670,7 @@ EXPORT_SYMBOL_GPL(irq_create_direct_mapping);
 #endif
 
 /**
- * irq_create_mapping_affinity() - Map a hardware interrupt into linux irq space
+ * __irq_create_mapping_affinity() - Map a hardware interrupt into linux irq space
  * @domain: domain owning this hardware interrupt or NULL for default domain
  * @hwirq: hardware irq number in that domain space
  * @affinity: irq affinity
@@ -679,9 +680,9 @@ EXPORT_SYMBOL_GPL(irq_create_direct_mapping);
  * If the sense/trigger is to be specified, set_irq_type() should be called
  * on the number returned from that call.
  */
-unsigned int irq_create_mapping_affinity(struct irq_domain *domain,
-				       irq_hw_number_t hwirq,
-				       const struct irq_affinity_desc *affinity)
+static unsigned int __irq_create_mapping_affinity(struct irq_domain *domain,
+						  irq_hw_number_t hwirq,
+						  const struct irq_affinity_desc *affinity)
 {
 	struct device_node *of_node;
 	int virq;
@@ -724,6 +725,19 @@ unsigned int irq_create_mapping_affinity(struct irq_domain *domain,
 
 	return virq;
 }
+
+unsigned int irq_create_mapping_affinity(struct irq_domain *domain,
+					 irq_hw_number_t hwirq,
+					 const struct irq_affinity_desc *affinity)
+{
+	unsigned int virq;
+
+	mutex_lock(&irq_mapping_mutex);
+	virq = __irq_create_mapping_affinity(domain, hwirq, affinity);
+	mutex_unlock(&irq_mapping_mutex);
+
+	return virq;
+}
 EXPORT_SYMBOL_GPL(irq_create_mapping_affinity);
 
 static int irq_domain_translate(struct irq_domain *d,
@@ -789,6 +803,8 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
 	if (WARN_ON(type & ~IRQ_TYPE_SENSE_MASK))
 		type &= IRQ_TYPE_SENSE_MASK;
 
+	mutex_lock(&irq_mapping_mutex);
+
 	/*
 	 * If we've already configured this interrupt,
 	 * don't do it again, or hell will break loose.
@@ -801,7 +817,7 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
 		 * interrupt number.
 		 */
 		if (type == IRQ_TYPE_NONE || type == irq_get_trigger_type(virq))
-			return virq;
+			goto out;
 
 		/*
 		 * If the trigger type has not been set yet, then set
@@ -810,26 +826,26 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
 		if (irq_get_trigger_type(virq) == IRQ_TYPE_NONE) {
 			irq_data = irq_get_irq_data(virq);
 			if (!irq_data)
-				return 0;
+				goto err;
 
 			irqd_set_trigger_type(irq_data, type);
-			return virq;
+			goto out;
 		}
 
 		pr_warn("type mismatch, failed to map hwirq-%lu for %s!\n",
 			hwirq, of_node_full_name(to_of_node(fwspec->fwnode)));
-		return 0;
+		goto err;
 	}
 
 	if (irq_domain_is_hierarchy(domain)) {
 		virq = irq_domain_alloc_irqs(domain, 1, NUMA_NO_NODE, fwspec);
 		if (virq <= 0)
-			return 0;
+			goto err;
 	} else {
 		/* Create mapping */
-		virq = irq_create_mapping(domain, hwirq);
+		virq = __irq_create_mapping_affinity(domain, hwirq, NULL);
 		if (!virq)
-			return virq;
+			goto err;
 	}
 
 	irq_data = irq_get_irq_data(virq);
@@ -838,13 +854,19 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
 			irq_domain_free_irqs(virq, 1);
 		else
 			irq_dispose_mapping(virq);
-		return 0;
+		goto err;
 	}
 
 	/* Store trigger type */
 	irqd_set_trigger_type(irq_data, type);
+out:
+	mutex_unlock(&irq_mapping_mutex);
 
 	return virq;
+err:
+	mutex_unlock(&irq_mapping_mutex);
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(irq_create_fwspec_mapping);
 
-- 
2.35.1