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Subject[PATCH v2 2/4] irqdomain: Fix mapping-creation race
Date
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.

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@chromium.org>
Cc: Jon Hunter <jonathanh@nvidia.com>
Link: https://lore.kernel.org/r/YuJXMHoT4ijUxnRb@hovoldconsulting.com
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
---
include/linux/irqdomain.h | 2 ++
kernel/irq/irqdomain.c | 33 ++++++++++++++++++++++++---------
2 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index 00d577f90883..8df9b9586e29 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -144,6 +144,7 @@ struct irq_domain_chip_generic;
* core code.
* @flags: host per irq_domain flags
* @mapcount: The number of mapped interrupts
+ * @map_mutex: Mapping lock
*
* Optional elements
* @fwnode: Pointer to firmware node associated with the irq_domain. Pretty easy
@@ -168,6 +169,7 @@ struct irq_domain {
void *host_data;
unsigned int flags;
unsigned int mapcount;
+ struct mutex map_mutex;

/* Optional data */
struct fwnode_handle *fwnode;
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 24ddd8d9b597..1af1d141e165 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -215,6 +215,7 @@ struct irq_domain *__irq_domain_add(struct fwnode_handle *fwnode, unsigned int s
/* Fill structure */
INIT_RADIX_TREE(&domain->revmap_tree, GFP_KERNEL);
mutex_init(&domain->revmap_mutex);
+ mutex_init(&domain->map_mutex);
domain->ops = ops;
domain->host_data = host_data;
domain->hwirq_max = hwirq_max;
@@ -721,14 +722,20 @@ unsigned int irq_create_mapping_affinity(struct irq_domain *domain,
return 0;
}

+ mutex_lock(&domain->map_mutex);
+
/* Check if mapping already exists */
virq = irq_find_mapping(domain, hwirq);
if (virq) {
pr_debug("existing mapping on virq %d\n", virq);
- return virq;
+ goto out;
}

- return __irq_create_mapping_affinity(domain, hwirq, affinity);
+ virq = __irq_create_mapping_affinity(domain, hwirq, affinity);
+out:
+ mutex_unlock(&domain->map_mutex);
+
+ return virq;
}
EXPORT_SYMBOL_GPL(irq_create_mapping_affinity);

@@ -795,6 +802,8 @@ 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(&domain->map_mutex);
+
/*
* If we've already configured this interrupt,
* don't do it again, or hell will break loose.
@@ -807,7 +816,7 @@ 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
@@ -816,26 +825,26 @@ 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_affinity(domain, hwirq, NULL);
if (!virq)
- return virq;
+ goto err;
}

irq_data = irq_get_irq_data(virq);
@@ -844,13 +853,19 @@ 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(&domain->map_mutex);

return virq;
+err:
+ mutex_unlock(&domain->map_mutex);
+
+ return 0;
}
EXPORT_SYMBOL_GPL(irq_create_fwspec_mapping);

--
2.35.1
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