In the function, setup_irq(), we don't check that the descriptor
returned from irq_to_desc() is valid before we start using it. For
example chip_bus_lock() called from setup_irq(), assumes that the
descriptor pointer is valid and doesn't check before dereferencing it.

In many other functions including setup/free_percpu_irq() we do check
that the descriptor returned is not NULL and therefore add the same test
to setup_irq() to ensure the descriptor returned is valid.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
---
 kernel/irq/manage.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index b2a93a37f772..eaedeb74b49d 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c

@@ -1414,7 +1414,7 @@ int setup_irq(unsigned int irq, struct irqaction *act)
 	int retval;
 	struct irq_desc *desc = irq_to_desc(irq);
 
-	if (WARN_ON(irq_settings_is_per_cpu_devid(desc)))
+	if (!desc || WARN_ON(irq_settings_is_per_cpu_devid(desc)))
 		return -EINVAL;
 	chip_bus_lock(desc);
 	retval = __setup_irq(irq, desc, act);

-- 
2.1.4