genirq: check chip->ack before calling

Impact: fix theoretical NULL dereference

The generic irq layer doesn't know whether irq_chip has ack routine on some
architectures or not. Upon that, before calling chip->ack, we should check
that it's not NULL.

Signed-off-by: Wang Chen <wangchen@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 6eb3c79..0ad02d7 100644 (file)
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -290,7 +290,8 @@ static inline void mask_ack_irq(struct irq_desc *desc, int irq)
                desc->chip->mask_ack(irq);
        else {
                desc->chip->mask(irq);
-               desc->chip->ack(irq);
+               if (desc->chip->ack)
+                       desc->chip->ack(irq);
        }
 }
 
@@ -475,7 +476,8 @@ handle_edge_irq(unsigned int irq, struct irq_desc *desc)
        kstat_incr_irqs_this_cpu(irq, desc);
 
        /* Start handling the irq */
-       desc->chip->ack(irq);
+       if (desc->chip->ack)
+               desc->chip->ack(irq);
        desc = irq_remap_to_desc(irq, desc);
 
        /* Mark the IRQ currently in progress.*/