genirq/ipi: Fix NULL pointer deref in irq_data_get_affinity_mask()

If ipi_send_{mask|single}() is called with an invalid interrupt number, all
the local variables there will be NULL. ipi_send_verify() which is invoked
from these functions does verify its 'data' parameter, resulting in a
kernel oops in irq_data_get_affinity_mask() as the passed NULL pointer gets
dereferenced.

Add a missing NULL pointer check in ipi_send_verify()...

Found by Linux Verification Center (linuxtesting.org) with the SVACE static
analysis tool.

Fixes: 3b8e29a ("genirq: Implement ipi_send_mask/single()")
Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/b541232d-c2b6-1fe9-79b4-a7129459e4d0@omp.ru

Author: Sergey Shtylyov

kernel/irq/ipi.c

@@ -188,9 +188,9 @@ EXPORT_SYMBOL_GPL(ipi_get_hwirq);
 static int ipi_send_verify(struct irq_chip *chip, struct irq_data *data,
 			   const struct cpumask *dest, unsigned int cpu)
 {
-	const struct cpumask *ipimask = irq_data_get_affinity_mask(data);
+	const struct cpumask *ipimask;
 
-	if (!chip || !ipimask)
+	if (!chip || !data)
 		return -EINVAL;
 
 	if (!chip->ipi_send_single && !chip->ipi_send_mask)
@@ -199,6 +199,10 @@ static int ipi_send_verify(struct irq_chip *chip, struct irq_data *data,
 	if (cpu >= nr_cpu_ids)
 		return -EINVAL;
 
+	ipimask = irq_data_get_affinity_mask(data);
+	if (!ipimask)
+		return -EINVAL;
+
 	if (dest) {
 		if (!cpumask_subset(dest, ipimask))
 			return -EINVAL;