[PATCH] irq: ipi: fix NULL pointer deref in irq_data_get_affinity_mask()

[Sergey Shtylyov <s.shtylyov@omp.ru>]

Iff ipi_send_{mask|single}() get called with e.g. an invalid IRQ #, all the
local variables there will be NULL -- the problem is that ipi_send_verify()
(that's called first thing) doesn't 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 check in ipi_send_verify()...

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

Fixes: 3b8e29a82dd1 ("genirq: Implement ipi_send_mask/single()")
Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>

---
The patch is against the 'tip.git' repo's 'master' branch...

 kernel/irq/ipi.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Index: tip/kernel/irq/ipi.c
===================================================================
--- tip.orig/kernel/irq/ipi.c
+++ tip/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_ch
 	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;