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>

1 files changed, 4 insertions, 2 deletions

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 6eb3c7952b64..0ad02d76a0c4 100644
--- 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.*/